Date   

Frequency Calibration

KD
 

I've run through the frequency calibration process in WSJT-X and up until the past week or so felt good about my rigs frequency.  However, I've worked a few stations that report I'm off frequency on 2M by anywhere from +1500 Hz to -600 Hz.  The -600 Hz report was from an op running with a GPSDO as was the +1500 Hz report.  I've had a couple of reports in the -200 to + 200 Hz arena from ops that have "calibrated" rigs.  So my question revolves around how to really determine if I am off frequency and if so, by how much.  I had my rig, a TS-2000, serviced in August, and the tech said it was now off at 10 MHz by 0.3 Hz.  The WSJT-X calibration process adjusts my 2M frequency by approximately 12 Hz, and I really question if I am off frequency.

KD - N5KS DM95be


Re: [VHFcontesting] Digital and Q arrangement contesting

Doug Gilliam
 

Well put Lew!  

Those of us who put a lot of expense, time, and skill into our stations, and who appreciate a hard fought cw contact, get frustrated with being thoroughly beaten by an operator sitting in his easy chair with a laptop and a good 6 meter opening.

BUT, I understand the value of these modes in bringing dx communication to those with smaller stations. It would have been great fun to have had FT8 when I was in a college apartment in the early 70s.

Having been continuously licensed for 52 years, I also remember the AM guys griping about the SSB guys in the 60s. I guess I will grumpily add FT8 to my efforts until such time that there are separate contests. 

Doug   WA7XX  DM42jh


From: nmvhf@groups.io <nmvhf@groups.io> on behalf of Keith Morehouse <w9rm@...>
Sent: Tuesday, September 24, 2019 7:53 AM
To: vhfcontesting@... <VHFcontesting@...>
Cc: GMCC <gmc@...>; nmvhf@groups.io <nmvhf@groups.io>
Subject: Re: [nmvhf] [VHFcontesting] Digital and Q arrangement contesting
 
... for what it's worth, Lew has nailed down my exact feelings and opinion of the current state of VHF contesting in this new world of FT8.  I approve of his post !

-W9RM

Keith Morehouse
via MotoG

On Mon, Sep 23, 2019, 9:41 PM Lew Sayre <w7ew@...> wrote:
     Greetings to all Contesters,
K5QE has written up a fine article about VHF contesting and why we should
leave the contest rules alone. It is clear that K5QE cares deeply about the
subject. So do I. I have a different opinion on some of his assumptions so
I'm sharing them with you. My opinions may be worth exactly what it costs
you to read them but they may be representative of a significant number of
operators

K5QE wrote, "HF contesting is all about how you find stations not about how
you work stations".  I'd like him to explain more fully that statement to
Ops like KL9A, N6MJ, W2SC,CT1BOH and others who are  performing mutant like
operating by interleaving QSOs from 2 radios. Why do they do this?  I'd
guess that by developing their operating skills and winning contests they
are having fun. I'll get back to this idea of fun.

The ARRL did remove rules pertaining to the use of internet chat rooms and
telephones during contests a few years ago. Why did they do that?  It was
aimed at making it easier for stations to find other stations to work and
diminish slow times.  After reading K5QE's note it is clear that by making
VHF contesting easier it has been a great success with everybody having
more fun.

Then along comes Dr. Taylor with his brilliant weak signal modes in WSJT-X.
Now not only do the operators not worry about looking for stations but they
really don't need to know how to operate to the same extent as a CW, SSB or
RTTY operator. The FT-modes now allows minimally equipped stations to see
and work real DX. It is a whole lot easier and a whole lot of fun which
explains the runaway popularity of the FT-modes.

What we are experiencing is amateur radio evolution right in front of us.
Operators are voting with their computer mice over the other modes because
the FT-modes are easier than CQ or SSB or RTTY, and a lot of fun.

But there is a rub. There is a significant number of operators who have
developed contesting skills and derive their fun from exercising those
skills like the 4 stalwarts mentioned in the second paragraph. We have
already seen that by combining the FT-modes in a VHF contest with CW and
SSB that the pool of operators for the legacy modes is diminished. Since it
is not much fun for the CW or SSB Ops they'll find other ways to enjoy
their recreational time in the future such as SOTA, IOTA, golf or moving to
a state where recreational cannabis is legal.

The WWROF (World Wide Radio Operators Foundation) has the correct outlook
here. A few weeks ago they sponsored the first FT8/FT4 only HF contest
which was well attended.  The VHF contesting world needs to do the same
thing, which is to delete digital modes in the current VHF contests and
develop a separate FT8/FT4 only VHF contest.  This would provide a pool of
operators who would be having FT fun with a percentage of them becoming
bitten by the contesting bug and then developing the other skills necessary
to compete in CQ and SSB contests.

We do radio to exercise our radio skills which is rewarding and fun. The
contests we do should emphasize those rewards and, not by their very
nature, lead to conflict, malaise and unhappiness..The old VHF rules are
broken by the success of the FT modes. Separate contests will rectify the
situation.

73 and I remain,
  Lew       w7ew
_______________________________________________
VHFcontesting mailing list
VHFcontesting@...
http://lists.contesting.com/mailman/listinfo/vhfcontesting


Re: [VHFcontesting] Digital and Q arrangement contesting

Keith Morehouse
 

... for what it's worth, Lew has nailed down my exact feelings and opinion of the current state of VHF contesting in this new world of FT8.  I approve of his post !

-W9RM

Keith Morehouse
via MotoG

On Mon, Sep 23, 2019, 9:41 PM Lew Sayre <w7ew@...> wrote:
     Greetings to all Contesters,
K5QE has written up a fine article about VHF contesting and why we should
leave the contest rules alone. It is clear that K5QE cares deeply about the
subject. So do I. I have a different opinion on some of his assumptions so
I'm sharing them with you. My opinions may be worth exactly what it costs
you to read them but they may be representative of a significant number of
operators

K5QE wrote, "HF contesting is all about how you find stations not about how
you work stations".  I'd like him to explain more fully that statement to
Ops like KL9A, N6MJ, W2SC,CT1BOH and others who are  performing mutant like
operating by interleaving QSOs from 2 radios. Why do they do this?  I'd
guess that by developing their operating skills and winning contests they
are having fun. I'll get back to this idea of fun.

The ARRL did remove rules pertaining to the use of internet chat rooms and
telephones during contests a few years ago. Why did they do that?  It was
aimed at making it easier for stations to find other stations to work and
diminish slow times.  After reading K5QE's note it is clear that by making
VHF contesting easier it has been a great success with everybody having
more fun.

Then along comes Dr. Taylor with his brilliant weak signal modes in WSJT-X.
Now not only do the operators not worry about looking for stations but they
really don't need to know how to operate to the same extent as a CW, SSB or
RTTY operator. The FT-modes now allows minimally equipped stations to see
and work real DX. It is a whole lot easier and a whole lot of fun which
explains the runaway popularity of the FT-modes.

What we are experiencing is amateur radio evolution right in front of us.
Operators are voting with their computer mice over the other modes because
the FT-modes are easier than CQ or SSB or RTTY, and a lot of fun.

But there is a rub. There is a significant number of operators who have
developed contesting skills and derive their fun from exercising those
skills like the 4 stalwarts mentioned in the second paragraph. We have
already seen that by combining the FT-modes in a VHF contest with CW and
SSB that the pool of operators for the legacy modes is diminished. Since it
is not much fun for the CW or SSB Ops they'll find other ways to enjoy
their recreational time in the future such as SOTA, IOTA, golf or moving to
a state where recreational cannabis is legal.

The WWROF (World Wide Radio Operators Foundation) has the correct outlook
here. A few weeks ago they sponsored the first FT8/FT4 only HF contest
which was well attended.  The VHF contesting world needs to do the same
thing, which is to delete digital modes in the current VHF contests and
develop a separate FT8/FT4 only VHF contest.  This would provide a pool of
operators who would be having FT fun with a percentage of them becoming
bitten by the contesting bug and then developing the other skills necessary
to compete in CQ and SSB contests.

We do radio to exercise our radio skills which is rewarding and fun. The
contests we do should emphasize those rewards and, not by their very
nature, lead to conflict, malaise and unhappiness..The old VHF rules are
broken by the success of the FT modes. Separate contests will rectify the
situation.

73 and I remain,
  Lew       w7ew
_______________________________________________
VHFcontesting mailing list
VHFcontesting@...
http://lists.contesting.com/mailman/listinfo/vhfcontesting


Slack invite

Mike WB2FKO
 

This is a reminder that the NM VHF Society has a slack channel in addition to this mailing list.  Activity can get pretty high during contests. Anyone interested is free to join at this link:

https://tinyurl.com/y43ol665

that can also be found on the CHAT page of nmvhf.org.

Mike WB2FKO


2 meter Sprint tonight

Tom
 

To All..
I will be active from Home QTH, DM42DW, tonight all 4 hours,, IF MOTHER NATURE does not upset my plans,, Storm and HEAVY rain predicted,,
I will be on 144.200 looking and calling and 144.210.also,,PLUS msk SH on, contest mode, me first looking east , North east way..call freq... or skeds..
If you want to make a sked,, My cell IS 419-370-8802..
Looking for ANY and ALL!!
See you Tropo and Ping Jockeys TONIGHT!!
Tom
N7GP
EX WA8WZG


2M fall Sprint tonight

Keith Morehouse
 

W7QQ DM75ao will be active in tonight's 2M Sprint starting at 7pm.  We will be watching the various Slack channels and listening and occasionally CQing on 144.200 or 144.150 meteor scatter using MSK144.  We can also run on FT8.

W7QQ & W9RM 

Keith Morehouse
via MotoG


Re: Our rove for the 2019 September VHF contest was in turn, rewarding…

dclark9225@...
 

Hi Duffey, 
Sorry to hear about your mishap, but I'm glad that you and Mike are OK.  Have a nice day. 
73 
David 
K5PHF 


On Wednesday, September 18, 2019, 11:49:54 AM MDT, James Duffey <JamesDuffey@...> wrote:


Our rove for the 2019 September VHF contest was in turn, rewarding, frustrating, educational, and catastrophic. I roved with WB2FKO In this contest in part to learn WSJT and in part to have two operators, which is a big help in roving. I will deal with the catastrophic first; near the end of the contest, on our way back to Albuquerque we hit a horse with the rover just west of Whippoorwill, AZ. It was dark and the horse was black. We were not in open range, that is, the range in that area is fenced with gates and livestock is not supposed to be on the road, so it was unexpected. The horse is dead and the rover is likely totaled, although that is still up to the insurance company. It was (is) undrivable. Mike and I were examined by EMTs at the scene and other than a few scrapes and light bruises appear to be OK. Olivia’s brother Alex came up on Monday to pick us up and empty gear from the rover. We ended up back home about 1630 Monday.

This was to be a trip to learn how to use WSJT in the rover. Lots learned in that area. We spent the Thursday before the contest in my driveway doing a dry run. After a few issues we finally got everything working and made an FT8 QSO and an MSK144 QSO, so things appeared to be OK.

We started in DM64 and things went well, working a number of stations on SSB and CW. Signals seemed down from what I expected. We then switched to FT8 and picked up an Es opening and worked several stations. Signals were strong so we went to SSB and CW, but there was nothing. Calling CQ did not raise anyone. There were lots of looky-loos there, so we got in some good PR for ham radio. WW6V was among them and he stayed for a while to chat and watch us work. We got on the road and Mike worked several stations from DM65 while in motion.

The next stop was DM55 and we started having problems with the interface sending continuous dahs, no matter which mode we were in. It was intermittent, but the next day I discovered the paddle cord was frayed, so we solved that problem, too late, by carefully positioning the cord.

We then moved to DM44 in Holbrook, AZ, but couldn’t raise anyone on the way. We decided to have dinner before getting on the air. Denny’s seemed like a good choice, but it turned out to have a dysfunctional kitchen. We got on the air from the motel semi parking lot, which was pretty nice with clear horizons and low noise. The IsoPwr battery charger/isolator failed, so we had to hook up directly to the car battery and run the car. The battery booster also blew a fuse. I think there is something in the setup that draws more current than it should. When I disconnected the 222 gear it seemed to go away, so there may be a problem there. We worked some down into Phoenix, but signals were never strong.

After charging the battery overnight, We got up the next morning, with the purpose of working meteor scatter in the morning. For reasons that are still not clear to us, we didn’t work anyone in over an hour. PSK reporter indicates we were heard over a wide area, and we had lots of solid decodes. Nobody came back to us. I am sure it wasn’t a multipath problem. After a morning of this, we got back on the road to DM45 and set up in a nice spot with clear horizons. We got on the air and worked a few SSB/CW QSOs. With not much in the way of expectations, we switched to MSK144. Here, unlike in DM44, we had success immediately and put a half dozen stations in the log in half an hour, including some good grids. We then conducted the infamous “multipath” experiments with W9RM using a variety of WSJT modes and beam headings. 45 minutes later we decided to bag the WSJT modes and worked on CW. Too many scientists/engineers involved and not enough sense of contest urgency.

We then got on the road to DM45. I decided to take a BIA road through and above Keams canyon to avoid an extra hour on paved roads and that turned out to be a mistake. Never take an unpaved BIA Road! It had started to rain, which made the road muddy and slippery, but that wasn’t a problem until we had to descend down the other side of the canyon. It got steep and very slippery, similar to driving on ice. There were no guardrails and a very steep and high drop off, so we decided to stop until the road dried off. Despite not being able to point the antennas, which were pointed straight into the mountain, we got on the air, but I don’t think we worked anyone. We were still in DM44. After three hours it stopped raining and 45 minutes after that the road dried enough to travel and, although the sun had set, it was light enough for us to continue down the mountain. It was late by then so we decided to head back to Albuquerque.

About a half hour after that disaster struck and we hit the horse. This, from talking to people there, is a fairly common occurrence in this area. One of the EMTs said it was her third day on the job and this was the third time she had to deal with people in cars hitting livestock. No one seemed surprised that we had hit livestock and almost everyone had a story to tell of them or someone in their family hitting livestock.

With many (most?)people working WSJT modes, it seems like the VHF contests seem to have shifted from rate-oriented to activity-oriented events. Although many times rates could have been higher on SSB/CW, there was no activity to support them.

Not sure why, but it seemed after DM64 we never developed a rhythm. Some of this may have been due to having to shift from WSJT to the analog modes and some of it may have been that Mike and I weren’t familiar with each other’s operation styles. Anyway, I learned much about operating the digital modes that I can use going forward.



James Duffey KK6MC
Cedar Crest NM



Re: AA5PR/R Sept VHF contest rove

Jay
 

John,
Glad we were able to make it happen during the contest! 

Jay N1AV

On Sep 18, 2019, at 8:33 PM, John Klem <klemjf@...> wrote:

I spent early Saturday afternoon in DM55 in the Cibola National Forest south of Thoreau, NM.  In the couple of hours I had there, I enjoyed the 6m opening that stretched as far east as EM64 from my location.  Later that afternoon, I drove to the Bisti / De-Na-Zin Wilderness Area in DM56 and set up long enough to make a few contacts and check out the terrain for a return Sunday morning.  I spent the night in Farmington.

On Sunday morning, I returned to Bisti and concentrated on making 6 m meteor scatter contacts, and that was reasonably successful.  In the late morning I set out for DM66, traveling through Farmington after some backtracking to avoid what I was surprised to learn was probably going to be a 4WD trip across tribal land.  In DM66, I was again surprised that my intended operating spot was apparently on tribal land (not sure how I missed that) behind a locked gate, so I had to settle for a large pullout on NM 550 northwest of Cuba, NM.  By the time I got there, the worst of the rain had stopped, so I set up.  Then the silent petition, "Please don't make me use meteors here," which was not granted.

Over the contest period, I made more contacts via meteor scatter than any other mode, followed by roughly equal numbers of SSB and FT8 contacts, and a few via CW.  I made two non-digital contacts with anyone outside CO/NM on 6 m SSB.  None into AZ on 2 m tropo scatter from DM55, despite decent power and antenna, which was disappointing.  Perhaps I was just too distracted by the 6 m action to have given it a proper effort, or maybe everyone on 2 m there is now on FT8, which I didn't check.  I'd be interested in knowing what it takes to work anyone via tropo scatter in AZ, particularly in terms of coordination.

I had the usual number of equipment, software, and mental failures:  two cables, one brand new; several laptop reboots required; and you know the contest is almost over when you start to say things on Slack like, "Let's keep trying for a couple more minutes because for the last several I haven't actually been transmitting," instead of, "Guess the rocks are gone."

Anyway, final score 2204: 58 QSO points x 38 mults

John AA5PR


AA5PR/R Sept VHF contest rove

John Klem
 

I spent early Saturday afternoon in DM55 in the Cibola National Forest south of Thoreau, NM.  In the couple of hours I had there, I enjoyed the 6m opening that stretched as far east as EM64 from my location.  Later that afternoon, I drove to the Bisti / De-Na-Zin Wilderness Area in DM56 and set up long enough to make a few contacts and check out the terrain for a return Sunday morning.  I spent the night in Farmington.

On Sunday morning, I returned to Bisti and concentrated on making 6 m meteor scatter contacts, and that was reasonably successful.  In the late morning I set out for DM66, traveling through Farmington after some backtracking to avoid what I was surprised to learn was probably going to be a 4WD trip across tribal land.  In DM66, I was again surprised that my intended operating spot was apparently on tribal land (not sure how I missed that) behind a locked gate, so I had to settle for a large pullout on NM 550 northwest of Cuba, NM.  By the time I got there, the worst of the rain had stopped, so I set up.  Then the silent petition, "Please don't make me use meteors here," which was not granted.

Over the contest period, I made more contacts via meteor scatter than any other mode, followed by roughly equal numbers of SSB and FT8 contacts, and a few via CW.  I made two non-digital contacts with anyone outside CO/NM on 6 m SSB.  None into AZ on 2 m tropo scatter from DM55, despite decent power and antenna, which was disappointing.  Perhaps I was just too distracted by the 6 m action to have given it a proper effort, or maybe everyone on 2 m there is now on FT8, which I didn't check.  I'd be interested in knowing what it takes to work anyone via tropo scatter in AZ, particularly in terms of coordination.

I had the usual number of equipment, software, and mental failures:  two cables, one brand new; several laptop reboots required; and you know the contest is almost over when you start to say things on Slack like, "Let's keep trying for a couple more minutes because for the last several I haven't actually been transmitting," instead of, "Guess the rocks are gone."

Anyway, final score 2204: 58 QSO points x 38 mults

John AA5PR


Re: Our rove for the 2019 September VHF contest was in turn, rewarding…

Bill Mader
 

Glad to read you guys are OK!  

This will make an "interesting" article for the NCJ or other publication and a "great" presentation for the ADXA, once you fully recover.  While not in a contest, we wiped out a deer near the IL/IN border on the way to HamVention some years ago.  The truck survived after $4,500 State Farm paid, but didn't make it through the next wreck in 2005 when a guy ran a red light in front of me at the corner just beyond which I would have turned into the parking lot.

I look forward to seeing some of you at the convention this weekend.  We and our bags arrived in ABQ last night from PEI.  Our WAE SSB Contest was not quite the disaster, but less than it could have been.  Still, it was a great team-building exercise/experience and the girls had great fun touring the island.  There was some damage from hurricane Dorian, but at least the power was on at VY2TT when we arrived.

73, Bill Mader, K8TE
W6H NM Coordinator, Route 66 On-the-Air 4-13 Sep 2020
ARRL New Mexico Section Manager
ARRL - The national association for Amateur Radio
Duke City Hamfest BoD www.dukecityhamfest.org 20-22 Sep 2019
President, Albuquerque DX Association 


On Wed, Sep 18, 2019 at 1:01 PM Mike WB2FKO <mph@...> wrote:
Her are some photos of the rover, taken at the wrecking yard in Chinle,
Arizona on Monday morning. WB2FKO

On 9/18/19 11:49 AM, James Duffey wrote:
> Our rove for the 2019 September VHF contest was in turn, rewarding, frustrating, educational, and catastrophic. I roved with WB2FKO In this contest in part to learn WSJT and in part to have two operators, which is a big help in roving. I will deal with the catastrophic first; near the end of the contest, on our way back to Albuquerque we hit a horse with the rover just west of Whippoorwill, AZ. It was dark and the horse was black. We were not in open range, that is, the range in that area is fenced with gates and livestock is not supposed to be on the road, so it was unexpected. The horse is dead and the rover is likely totaled, although that is still up to the insurance company. It was (is) undrivable. Mike and I were examined by EMTs at the scene and other than a few scrapes and light bruises appear to be OK. Olivia’s brother Alex came up on Monday to pick us up and empty gear from the rover. We ended up back home about 1630 Monday.
>
> This was to be a trip to learn how to use WSJT in the rover. Lots learned in that area. We spent the Thursday before the contest in my driveway doing a dry run. After a few issues we finally got everything working and made an FT8 QSO and an MSK144 QSO, so things appeared to be OK.
>
> We started in DM64 and things went well, working a number of stations on SSB and CW. Signals seemed down from what I expected. We then switched to FT8 and picked up an Es opening and worked several stations. Signals were strong so we went to SSB and CW, but there was nothing. Calling CQ did not raise anyone. There were lots of looky-loos there, so we got in some good PR for ham radio. WW6V was among them and he stayed for a while to chat and watch us work. We got on the road and Mike worked several stations from DM65 while in motion.
>
> The next stop was DM55 and we started having problems with the interface sending continuous dahs, no matter which mode we were in. It was intermittent, but the next day I discovered the paddle cord was frayed, so we solved that problem, too late, by carefully positioning the cord.
>
> We then moved to DM44 in Holbrook, AZ, but couldn’t raise anyone on the way. We decided to have dinner before getting on the air. Denny’s seemed like a good choice, but it turned out to have a dysfunctional kitchen. We got on the air from the motel semi parking lot, which was pretty nice with clear horizons and low noise. The IsoPwr battery charger/isolator failed, so we had to hook up directly to the car battery and run the car. The battery booster also blew a fuse. I think there is something in the setup that draws more current than it should. When I disconnected the 222 gear it seemed to go away, so there may be a problem there. We worked some down into Phoenix, but signals were never strong.
>
> After charging the battery overnight, We got up the next morning, with the purpose of working meteor scatter in the morning. For reasons that are still not clear to us, we didn’t work anyone in over an hour. PSK reporter indicates we were heard over a wide area, and we had lots of solid decodes. Nobody came back to us. I am sure it wasn’t a multipath problem. After a morning of this, we got back on the road to DM45 and set up in a nice spot with clear horizons. We got on the air and worked a few SSB/CW QSOs. With not much in the way of expectations, we switched to MSK144. Here, unlike in DM44, we had success immediately and put a half dozen stations in the log in half an hour, including some good grids. We then conducted the infamous “multipath” experiments with W9RM using a variety of WSJT modes and beam headings. 45 minutes later we decided to bag the WSJT modes and worked on CW. Too many scientists/engineers involved and not enough sense of contest urgency.
>
> We then got on the road to DM45. I decided to take a BIA road through and above Keams canyon to avoid an extra hour on paved roads and that turned out to be a mistake. Never take an unpaved BIA Road! It had started to rain, which made the road muddy and slippery, but that wasn’t a problem until we had to descend down the other side of the canyon. It got steep and very slippery, similar to driving on ice. There were no guardrails and a very steep and high drop off, so we decided to stop until the road dried off. Despite not being able to point the antennas, which were pointed straight into the mountain, we got on the air, but I don’t think we worked anyone. We were still in DM44. After three hours it stopped raining and 45 minutes after that the road dried enough to travel and, although the sun had set, it was light enough for us to continue down the mountain. It was late by then so we decided to head back to Albuquerque.
>
> About a half hour after that disaster struck and we hit the horse. This, from talking to people there, is a fairly common occurrence in this area. One of the EMTs said it was her third day on the job and this was the third time she had to deal with people in cars hitting livestock. No one seemed surprised that we had hit livestock and almost everyone had a story to tell of them or someone in their family hitting livestock.
>
> With many (most?)people working WSJT modes, it seems like the VHF contests seem to have shifted from rate-oriented to activity-oriented events. Although many times rates could have been higher on SSB/CW, there was no activity to support them.
>
> Not sure why, but it seemed after DM64 we never developed a rhythm. Some of this may have been due to having to shift from WSJT to the analog modes and some of it may have been that Mike and I weren’t familiar with each other’s operation styles. Anyway, I learned much about operating the digital modes that I can use going forward.
>
>
>
> James Duffey KK6MC
> Cedar Crest NM
>
>
>




Re: multipath

Mike WB2FKO
 

John's explanation has cleared up the physical picture I have of what is happening.  Two or more coherent signals traveling over different static paths and interfering at the receiver can't produce new frequencies.  All they can do is enhance or reduce signal strength, but there won't be any new harmonic content.  The path length has to be changing/moving to induce a Doppler shift.

If I assume a steady 10mph wind, pushing an air mass that can somehow reflect/scatter RF, I estimate a Doppler shift of about 7 Hz at 432 MHz. Stronger winds and higher carrier frequencies induce bigger frequency shifts. I am unsure if atmospherics can do this, but such a shift is consistent with the fuzz I remember seeing on the FT8 waterfall.  If the wind is steady, the signals should still decode. If the air mass is not moving steady, then the Doppler shift will fluctuate and and decodes may not happen. FT8 is not tolerant of frequency instability beyond ± 1 Hz. 

This problem should have been reciprocal, however, and Jay seemed to be decoding us just fine. This makes me suspect there was a problem in our setup.  I'm quite sure the audio level coming into WSJT was set below the point of clipping, although it might have been getting close. The indicator on the GUI turns red to warn the op of this condition, but I don't recall seeing that.

Didn't save any traces, so just going by memory.  I think the JT65 ghost signals (yes, they were weaker) were spaced at periodic intervals in frequency, suggesting a nonlinearity like clipping somewhere in the demodulation or decoding.

Mike

On 9/17/19 11:02 PM, John Klem wrote:
Actually, I'm saying the multipath you describe (time-invariant coherent interference) should not produce what you saw.  If I understand the physics correctly... 

If you consider a signal transmitted at a single frequency, you can scatter it however many times from however many static (not changing in any way with time) scatterers, but when you recombine all those linearly at any point (specifically the receiver), the sum will have the same frequency as the signal originally transmitted.  Only the amplitude and phase will be different in the final sum signal.  I think you can effectively consider any of the low-symbol-rate modes single-frequency for this purpose.  So I don't think time-invariant multipath explains what is happening here.

If your scatterers start changing slowly, you will see the sum signal at the receiver slowly changing in phase and amplitude, which would be typical fading.  The frequency remains essentially constant.  Again, not what you saw.

If the scatterers change rapidly, you could modulate the sum signal fast enough to create obvious sidebands.  It seems unlikely there would be anything like a natural modulator generating carrier plus one sideband, which is similar to what we've seen, but I don't know the math behind that.

I suspect there's some sort of moving atmospheric refractor creating a Doppler-shifted version of the original signal, but what is it and what is its path?  Maybe some sort of moving density boundary?  Maybe a big blob of something that is expanding or contracting?  Waves of some sort in the troposphere?Beats me, but I imagine someone with a good understanding of atmospheric science would have some ideas.

Do you remember, in the case where you saw four signals, were they equally spaced in frequency?

John AA5PR


Re: Our rove for the 2019 September VHF contest was in turn, rewarding…

Mike WB2FKO
 

Her are some photos of the rover, taken at the wrecking yard in Chinle, Arizona on Monday morning. WB2FKO

On 9/18/19 11:49 AM, James Duffey wrote:
Our rove for the 2019 September VHF contest was in turn, rewarding, frustrating, educational, and catastrophic. I roved with WB2FKO In this contest in part to learn WSJT and in part to have two operators, which is a big help in roving. I will deal with the catastrophic first; near the end of the contest, on our way back to Albuquerque we hit a horse with the rover just west of Whippoorwill, AZ. It was dark and the horse was black. We were not in open range, that is, the range in that area is fenced with gates and livestock is not supposed to be on the road, so it was unexpected. The horse is dead and the rover is likely totaled, although that is still up to the insurance company. It was (is) undrivable. Mike and I were examined by EMTs at the scene and other than a few scrapes and light bruises appear to be OK. Olivia’s brother Alex came up on Monday to pick us up and empty gear from the rover. We ended up back home about 1630 Monday.

This was to be a trip to learn how to use WSJT in the rover. Lots learned in that area. We spent the Thursday before the contest in my driveway doing a dry run. After a few issues we finally got everything working and made an FT8 QSO and an MSK144 QSO, so things appeared to be OK.

We started in DM64 and things went well, working a number of stations on SSB and CW. Signals seemed down from what I expected. We then switched to FT8 and picked up an Es opening and worked several stations. Signals were strong so we went to SSB and CW, but there was nothing. Calling CQ did not raise anyone. There were lots of looky-loos there, so we got in some good PR for ham radio. WW6V was among them and he stayed for a while to chat and watch us work. We got on the road and Mike worked several stations from DM65 while in motion.

The next stop was DM55 and we started having problems with the interface sending continuous dahs, no matter which mode we were in. It was intermittent, but the next day I discovered the paddle cord was frayed, so we solved that problem, too late, by carefully positioning the cord.

We then moved to DM44 in Holbrook, AZ, but couldn’t raise anyone on the way. We decided to have dinner before getting on the air. Denny’s seemed like a good choice, but it turned out to have a dysfunctional kitchen. We got on the air from the motel semi parking lot, which was pretty nice with clear horizons and low noise. The IsoPwr battery charger/isolator failed, so we had to hook up directly to the car battery and run the car. The battery booster also blew a fuse. I think there is something in the setup that draws more current than it should. When I disconnected the 222 gear it seemed to go away, so there may be a problem there. We worked some down into Phoenix, but signals were never strong.

After charging the battery overnight, We got up the next morning, with the purpose of working meteor scatter in the morning. For reasons that are still not clear to us, we didn’t work anyone in over an hour. PSK reporter indicates we were heard over a wide area, and we had lots of solid decodes. Nobody came back to us. I am sure it wasn’t a multipath problem. After a morning of this, we got back on the road to DM45 and set up in a nice spot with clear horizons. We got on the air and worked a few SSB/CW QSOs. With not much in the way of expectations, we switched to MSK144. Here, unlike in DM44, we had success immediately and put a half dozen stations in the log in half an hour, including some good grids. We then conducted the infamous “multipath” experiments with W9RM using a variety of WSJT modes and beam headings. 45 minutes later we decided to bag the WSJT modes and worked on CW. Too many scientists/engineers involved and not enough sense of contest urgency.

We then got on the road to DM45. I decided to take a BIA road through and above Keams canyon to avoid an extra hour on paved roads and that turned out to be a mistake. Never take an unpaved BIA Road! It had started to rain, which made the road muddy and slippery, but that wasn’t a problem until we had to descend down the other side of the canyon. It got steep and very slippery, similar to driving on ice. There were no guardrails and a very steep and high drop off, so we decided to stop until the road dried off. Despite not being able to point the antennas, which were pointed straight into the mountain, we got on the air, but I don’t think we worked anyone. We were still in DM44. After three hours it stopped raining and 45 minutes after that the road dried enough to travel and, although the sun had set, it was light enough for us to continue down the mountain. It was late by then so we decided to head back to Albuquerque.

About a half hour after that disaster struck and we hit the horse. This, from talking to people there, is a fairly common occurrence in this area. One of the EMTs said it was her third day on the job and this was the third time she had to deal with people in cars hitting livestock. No one seemed surprised that we had hit livestock and almost everyone had a story to tell of them or someone in their family hitting livestock.

With many (most?)people working WSJT modes, it seems like the VHF contests seem to have shifted from rate-oriented to activity-oriented events. Although many times rates could have been higher on SSB/CW, there was no activity to support them.

Not sure why, but it seemed after DM64 we never developed a rhythm. Some of this may have been due to having to shift from WSJT to the analog modes and some of it may have been that Mike and I weren’t familiar with each other’s operation styles. Anyway, I learned much about operating the digital modes that I can use going forward.



James Duffey KK6MC
Cedar Crest NM


Re: Our rove for the 2019 September VHF contest was in turn, rewarding…

Steve London
 

Glad to hear that you and Mike had only minor injuries.

Thanks for the FT8 QSO from DM55. One of the few times I was on during the 18 continuous hours of rain on Saturday/Sunday. You were weak (around -18, if I recall), but there was Es to southern CA, so you may have been strong, but 18 dB weaker than the strong Es signals.

73,
Steve, N2IC

On 09/18/2019 11:49 AM, James Duffey wrote:
Our rove for the 2019 September VHF contest was in turn, rewarding, frustrating, educational, and catastrophic. I roved with WB2FKO In this contest in part to learn WSJT and in part to have two operators, which is a big help in roving. I will deal with the catastrophic first; near the end of the contest, on our way back to Albuquerque we hit a horse with the rover just west of Whippoorwill, AZ. It was dark and the horse was black. We were not in open range, that is, the range in that area is fenced with gates and livestock is not supposed to be on the road, so it was unexpected. The horse is dead and the rover is likely totaled, although that is still up to the insurance company. It was (is) undrivable. Mike and I were examined by EMTs at the scene and other than a few scrapes and light bruises appear to be OK. Olivia’s brother Alex came up on Monday to pick us up and empty gear from the rover. We ended up back home about 1630 Monday.
This was to be a trip to learn how to use WSJT in the rover. Lots learned in that area. We spent the Thursday before the contest in my driveway doing a dry run. After a few issues we finally got everything working and made an FT8 QSO and an MSK144 QSO, so things appeared to be OK.
We started in DM64 and things went well, working a number of stations on SSB and CW. Signals seemed down from what I expected. We then switched to FT8 and picked up an Es opening and worked several stations. Signals were strong so we went to SSB and CW, but there was nothing. Calling CQ did not raise anyone. There were lots of looky-loos there, so we got in some good PR for ham radio. WW6V was among them and he stayed for a while to chat and watch us work. We got on the road and Mike worked several stations from DM65 while in motion.
The next stop was DM55 and we started having problems with the interface sending continuous dahs, no matter which mode we were in. It was intermittent, but the next day I discovered the paddle cord was frayed, so we solved that problem, too late, by carefully positioning the cord.
We then moved to DM44 in Holbrook, AZ, but couldn’t raise anyone on the way. We decided to have dinner before getting on the air. Denny’s seemed like a good choice, but it turned out to have a dysfunctional kitchen. We got on the air from the motel semi parking lot, which was pretty nice with clear horizons and low noise. The IsoPwr battery charger/isolator failed, so we had to hook up directly to the car battery and run the car. The battery booster also blew a fuse. I think there is something in the setup that draws more current than it should. When I disconnected the 222 gear it seemed to go away, so there may be a problem there. We worked some down into Phoenix, but signals were never strong.
After charging the battery overnight, We got up the next morning, with the purpose of working meteor scatter in the morning. For reasons that are still not clear to us, we didn’t work anyone in over an hour. PSK reporter indicates we were heard over a wide area, and we had lots of solid decodes. Nobody came back to us. I am sure it wasn’t a multipath problem. After a morning of this, we got back on the road to DM45 and set up in a nice spot with clear horizons. We got on the air and worked a few SSB/CW QSOs. With not much in the way of expectations, we switched to MSK144. Here, unlike in DM44, we had success immediately and put a half dozen stations in the log in half an hour, including some good grids. We then conducted the infamous “multipath” experiments with W9RM using a variety of WSJT modes and beam headings. 45 minutes later we decided to bag the WSJT modes and worked on CW. Too many scientists/engineers involved and not enough sense of contest urgency.
We then got on the road to DM45. I decided to take a BIA road through and above Keams canyon to avoid an extra hour on paved roads and that turned out to be a mistake. Never take an unpaved BIA Road! It had started to rain, which made the road muddy and slippery, but that wasn’t a problem until we had to descend down the other side of the canyon. It got steep and very slippery, similar to driving on ice. There were no guardrails and a very steep and high drop off, so we decided to stop until the road dried off. Despite not being able to point the antennas, which were pointed straight into the mountain, we got on the air, but I don’t think we worked anyone. We were still in DM44. After three hours it stopped raining and 45 minutes after that the road dried enough to travel and, although the sun had set, it was light enough for us to continue down the mountain. It was late by then so we decided to head back to Albuquerque.
About a half hour after that disaster struck and we hit the horse. This, from talking to people there, is a fairly common occurrence in this area. One of the EMTs said it was her third day on the job and this was the third time she had to deal with people in cars hitting livestock. No one seemed surprised that we had hit livestock and almost everyone had a story to tell of them or someone in their family hitting livestock.
With many (most?)people working WSJT modes, it seems like the VHF contests seem to have shifted from rate-oriented to activity-oriented events. Although many times rates could have been higher on SSB/CW, there was no activity to support them.
Not sure why, but it seemed after DM64 we never developed a rhythm. Some of this may have been due to having to shift from WSJT to the analog modes and some of it may have been that Mike and I weren’t familiar with each other’s operation styles. Anyway, I learned much about operating the digital modes that I can use going forward.
James Duffey KK6MC
Cedar Crest NM


Our rove for the 2019 September VHF contest was in turn, rewarding…

James Duffey
 

Our rove for the 2019 September VHF contest was in turn, rewarding, frustrating, educational, and catastrophic. I roved with WB2FKO In this contest in part to learn WSJT and in part to have two operators, which is a big help in roving. I will deal with the catastrophic first; near the end of the contest, on our way back to Albuquerque we hit a horse with the rover just west of Whippoorwill, AZ. It was dark and the horse was black. We were not in open range, that is, the range in that area is fenced with gates and livestock is not supposed to be on the road, so it was unexpected. The horse is dead and the rover is likely totaled, although that is still up to the insurance company. It was (is) undrivable. Mike and I were examined by EMTs at the scene and other than a few scrapes and light bruises appear to be OK. Olivia’s brother Alex came up on Monday to pick us up and empty gear from the rover. We ended up back home about 1630 Monday.

This was to be a trip to learn how to use WSJT in the rover. Lots learned in that area. We spent the Thursday before the contest in my driveway doing a dry run. After a few issues we finally got everything working and made an FT8 QSO and an MSK144 QSO, so things appeared to be OK.

We started in DM64 and things went well, working a number of stations on SSB and CW. Signals seemed down from what I expected. We then switched to FT8 and picked up an Es opening and worked several stations. Signals were strong so we went to SSB and CW, but there was nothing. Calling CQ did not raise anyone. There were lots of looky-loos there, so we got in some good PR for ham radio. WW6V was among them and he stayed for a while to chat and watch us work. We got on the road and Mike worked several stations from DM65 while in motion.

The next stop was DM55 and we started having problems with the interface sending continuous dahs, no matter which mode we were in. It was intermittent, but the next day I discovered the paddle cord was frayed, so we solved that problem, too late, by carefully positioning the cord.

We then moved to DM44 in Holbrook, AZ, but couldn’t raise anyone on the way. We decided to have dinner before getting on the air. Denny’s seemed like a good choice, but it turned out to have a dysfunctional kitchen. We got on the air from the motel semi parking lot, which was pretty nice with clear horizons and low noise. The IsoPwr battery charger/isolator failed, so we had to hook up directly to the car battery and run the car. The battery booster also blew a fuse. I think there is something in the setup that draws more current than it should. When I disconnected the 222 gear it seemed to go away, so there may be a problem there. We worked some down into Phoenix, but signals were never strong.

After charging the battery overnight, We got up the next morning, with the purpose of working meteor scatter in the morning. For reasons that are still not clear to us, we didn’t work anyone in over an hour. PSK reporter indicates we were heard over a wide area, and we had lots of solid decodes. Nobody came back to us. I am sure it wasn’t a multipath problem. After a morning of this, we got back on the road to DM45 and set up in a nice spot with clear horizons. We got on the air and worked a few SSB/CW QSOs. With not much in the way of expectations, we switched to MSK144. Here, unlike in DM44, we had success immediately and put a half dozen stations in the log in half an hour, including some good grids. We then conducted the infamous “multipath” experiments with W9RM using a variety of WSJT modes and beam headings. 45 minutes later we decided to bag the WSJT modes and worked on CW. Too many scientists/engineers involved and not enough sense of contest urgency.

We then got on the road to DM45. I decided to take a BIA road through and above Keams canyon to avoid an extra hour on paved roads and that turned out to be a mistake. Never take an unpaved BIA Road! It had started to rain, which made the road muddy and slippery, but that wasn’t a problem until we had to descend down the other side of the canyon. It got steep and very slippery, similar to driving on ice. There were no guardrails and a very steep and high drop off, so we decided to stop until the road dried off. Despite not being able to point the antennas, which were pointed straight into the mountain, we got on the air, but I don’t think we worked anyone. We were still in DM44. After three hours it stopped raining and 45 minutes after that the road dried enough to travel and, although the sun had set, it was light enough for us to continue down the mountain. It was late by then so we decided to head back to Albuquerque.

About a half hour after that disaster struck and we hit the horse. This, from talking to people there, is a fairly common occurrence in this area. One of the EMTs said it was her third day on the job and this was the third time she had to deal with people in cars hitting livestock. No one seemed surprised that we had hit livestock and almost everyone had a story to tell of them or someone in their family hitting livestock.

With many (most?)people working WSJT modes, it seems like the VHF contests seem to have shifted from rate-oriented to activity-oriented events. Although many times rates could have been higher on SSB/CW, there was no activity to support them.

Not sure why, but it seemed after DM64 we never developed a rhythm. Some of this may have been due to having to shift from WSJT to the analog modes and some of it may have been that Mike and I weren’t familiar with each other’s operation styles. Anyway, I learned much about operating the digital modes that I can use going forward.



James Duffey KK6MC
Cedar Crest NM


Re: multipath

Scott K5TA
 

Just got around to reading these messages —

A couple of questions come to mind:

Is there any noticeable difference in the appearance of the waterfall traces between the fundamental signal and the ghosts?  Signal strength?  Freq stability?

Was the only available spectrum display at audio?  It would be neat to look at an RF panadapter display alongside of the WSJT audio waterfall to compare.  A local RX issue could be in play, which would also provide a possible explanation for the non-reciprocal observations.

-TA


On Sep 18, 2019, at 8:34 AM, Keith Morehouse <w9rm@...> wrote:

There are, most certainly, two different phenomenon with regard to "multi-path" (I'll put that in quotation marks).

Bruce describes one, which is heard frequently.  Rapid fading due to out of phase paths mixing at the receive end.  There is another, which manifests itself as multiple coherent signals.  I see both, although the latter is much more obvious on CW or FT8.

-W9RM

Keith Morehouse
via MotoG

On Wed, Sep 18, 2019, 6:36 AM Bruce Draper <bruceaa5b@...> wrote:
What I saw -- and heard -- a few times was multipath fading of the single-frequency type described by John. It was plenty strong enough to be decoded, but failed. There was a single trace on the waterfall, but visibly a little different than normal. In the headphones, there was the sound of phase-shifted signals interfering with each other (hear this occasionally on DX signals on 20 CW, too).

Could've completed a CW or SSB QSO. Just sayin'.

    -Bruce AA5B

On Tue, Sep 17, 2019 at 11:02 PM John Klem <klemjf@...> wrote:
Actually, I'm saying the multipath you describe (time-invariant coherent interference) should not produce what you saw.  If I understand the physics correctly... 

If you consider a signal transmitted at a single frequency, you can scatter it however many times from however many static (not changing in any way with time) scatterers, but when you recombine all those linearly at any point (specifically the receiver), the sum will have the same frequency as the signal originally transmitted.  Only the amplitude and phase will be different in the final sum signal.  I think you can effectively consider any of the low-symbol-rate modes single-frequency for this purpose.  So I don't think time-invariant multipath explains what is happening here.

If your scatterers start changing slowly, you will see the sum signal at the receiver slowly changing in phase and amplitude, which would be typical fading.  The frequency remains essentially constant.  Again, not what you saw.

If the scatterers change rapidly, you could modulate the sum signal fast enough to create obvious sidebands.  It seems unlikely there would be anything like a natural modulator generating carrier plus one sideband, which is similar to what we've seen, but I don't know the math behind that.

I suspect there's some sort of moving atmospheric refractor creating a Doppler-shifted version of the original signal, but what is it and what is its path?  Maybe some sort of moving density boundary?  Maybe a big blob of something that is expanding or contracting?  Waves of some sort in the troposphere?Beats me, but I imagine someone with a good understanding of atmospheric science would have some ideas.

Do you remember, in the case where you saw four signals, were they equally spaced in frequency?

John AA5PR


Re: multipath

Keith Morehouse
 

There are, most certainly, two different phenomenon with regard to "multi-path" (I'll put that in quotation marks).

Bruce describes one, which is heard frequently.  Rapid fading due to out of phase paths mixing at the receive end.  There is another, which manifests itself as multiple coherent signals.  I see both, although the latter is much more obvious on CW or FT8.

-W9RM

Keith Morehouse
via MotoG


On Wed, Sep 18, 2019, 6:36 AM Bruce Draper <bruceaa5b@...> wrote:
What I saw -- and heard -- a few times was multipath fading of the single-frequency type described by John. It was plenty strong enough to be decoded, but failed. There was a single trace on the waterfall, but visibly a little different than normal. In the headphones, there was the sound of phase-shifted signals interfering with each other (hear this occasionally on DX signals on 20 CW, too).

Could've completed a CW or SSB QSO. Just sayin'.

    -Bruce AA5B

On Tue, Sep 17, 2019 at 11:02 PM John Klem <klemjf@...> wrote:
Actually, I'm saying the multipath you describe (time-invariant coherent interference) should not produce what you saw.  If I understand the physics correctly... 

If you consider a signal transmitted at a single frequency, you can scatter it however many times from however many static (not changing in any way with time) scatterers, but when you recombine all those linearly at any point (specifically the receiver), the sum will have the same frequency as the signal originally transmitted.  Only the amplitude and phase will be different in the final sum signal.  I think you can effectively consider any of the low-symbol-rate modes single-frequency for this purpose.  So I don't think time-invariant multipath explains what is happening here.

If your scatterers start changing slowly, you will see the sum signal at the receiver slowly changing in phase and amplitude, which would be typical fading.  The frequency remains essentially constant.  Again, not what you saw.

If the scatterers change rapidly, you could modulate the sum signal fast enough to create obvious sidebands.  It seems unlikely there would be anything like a natural modulator generating carrier plus one sideband, which is similar to what we've seen, but I don't know the math behind that.

I suspect there's some sort of moving atmospheric refractor creating a Doppler-shifted version of the original signal, but what is it and what is its path?  Maybe some sort of moving density boundary?  Maybe a big blob of something that is expanding or contracting?  Waves of some sort in the troposphere?Beats me, but I imagine someone with a good understanding of atmospheric science would have some ideas.

Do you remember, in the case where you saw four signals, were they equally spaced in frequency?

John AA5PR


Re: multipath

Bruce Draper
 

What I saw -- and heard -- a few times was multipath fading of the single-frequency type described by John. It was plenty strong enough to be decoded, but failed. There was a single trace on the waterfall, but visibly a little different than normal. In the headphones, there was the sound of phase-shifted signals interfering with each other (hear this occasionally on DX signals on 20 CW, too).

Could've completed a CW or SSB QSO. Just sayin'.

    -Bruce AA5B

On Tue, Sep 17, 2019 at 11:02 PM John Klem <klemjf@...> wrote:
Actually, I'm saying the multipath you describe (time-invariant coherent interference) should not produce what you saw.  If I understand the physics correctly... 

If you consider a signal transmitted at a single frequency, you can scatter it however many times from however many static (not changing in any way with time) scatterers, but when you recombine all those linearly at any point (specifically the receiver), the sum will have the same frequency as the signal originally transmitted.  Only the amplitude and phase will be different in the final sum signal.  I think you can effectively consider any of the low-symbol-rate modes single-frequency for this purpose.  So I don't think time-invariant multipath explains what is happening here.

If your scatterers start changing slowly, you will see the sum signal at the receiver slowly changing in phase and amplitude, which would be typical fading.  The frequency remains essentially constant.  Again, not what you saw.

If the scatterers change rapidly, you could modulate the sum signal fast enough to create obvious sidebands.  It seems unlikely there would be anything like a natural modulator generating carrier plus one sideband, which is similar to what we've seen, but I don't know the math behind that.

I suspect there's some sort of moving atmospheric refractor creating a Doppler-shifted version of the original signal, but what is it and what is its path?  Maybe some sort of moving density boundary?  Maybe a big blob of something that is expanding or contracting?  Waves of some sort in the troposphere?Beats me, but I imagine someone with a good understanding of atmospheric science would have some ideas.

Do you remember, in the case where you saw four signals, were they equally spaced in frequency?

John AA5PR


Re: multipath

John Klem
 

Actually, I'm saying the multipath you describe (time-invariant coherent interference) should not produce what you saw.  If I understand the physics correctly... 

If you consider a signal transmitted at a single frequency, you can scatter it however many times from however many static (not changing in any way with time) scatterers, but when you recombine all those linearly at any point (specifically the receiver), the sum will have the same frequency as the signal originally transmitted.  Only the amplitude and phase will be different in the final sum signal.  I think you can effectively consider any of the low-symbol-rate modes single-frequency for this purpose.  So I don't think time-invariant multipath explains what is happening here.

If your scatterers start changing slowly, you will see the sum signal at the receiver slowly changing in phase and amplitude, which would be typical fading.  The frequency remains essentially constant.  Again, not what you saw.

If the scatterers change rapidly, you could modulate the sum signal fast enough to create obvious sidebands.  It seems unlikely there would be anything like a natural modulator generating carrier plus one sideband, which is similar to what we've seen, but I don't know the math behind that.

I suspect there's some sort of moving atmospheric refractor creating a Doppler-shifted version of the original signal, but what is it and what is its path?  Maybe some sort of moving density boundary?  Maybe a big blob of something that is expanding or contracting?  Waves of some sort in the troposphere?Beats me, but I imagine someone with a good understanding of atmospheric science would have some ideas.

Do you remember, in the case where you saw four signals, were they equally spaced in frequency?

John AA5PR


Re: [AOCC] ARRL Sep VHF K7HP Single Op LP

Mike WB2FKO
 

Yes, offsets in frequency in the waterfall.  To confuse the FT8 decoder would require two signals offset in time by more than 40ms.  If my math is right, this corresponds to a path length difference of 12,000 km.  That's why I think it's multipath coherent interference, which only requires a path length difference on the order of a wavelength.  I suspect greater phase difference (multiple wavelengths) would make it worse and also explains why it would be more problematic as the radio frequency goes up.

If I understand you correctly, multiple static paths would produce multiple ghost traces that should still all decode.  It's the dynamic path difference that causes sufficient signal distortion to prevent decoding.

I should mention that in the ~30 minutes of trying various things with W9RM on 432, I did actually get one FT8 decode.  But we had already agreed to switch modes at that point and start over.

Mike WB2FKO

On 9/17/19 6:14 PM, John Klem wrote:
If I correctly understand, you saw multiple traces offset in frequency, not time?  I think many people have now seen this on 6 m (I'm among them), and it's not hard to believe the effect could be worse on 432.

In order to produce this frequency offset, I believe you must have some sort of dynamics in your path to induce Doppler or something similar.  Multiple static paths shouldn't do it.  I trust your receiver is linear enough that you shouldn't have observable mixing products (unless you have multiple strong signals already on different frequencies and an FT-817 like mine).  As Keith suggested, aircraft would do it, but the shift would vary with time (which I presume you didn't see).  I suppose some sort of atmospheric dynamics could produce this effect as well, and someone invoked that explanation in something I read recently.

I did a quick search on nonreciprocal propagation, and it appears this is generally recognized for ionospheric paths, but not obviously so for tropospheric paths.

Really interesting stuff.  It would be fun to do comparisons on different bands when you observe this, to see if the frequency offset scales with carrier frequency.

John AA5PR



Re: [AOCC] ARRL Sep VHF K7HP Single Op LP

John Klem
 

If I correctly understand, you saw multiple traces offset in frequency, not time?  I think many people have now seen this on 6 m (I'm among them), and it's not hard to believe the effect could be worse on 432.

In order to produce this frequency offset, I believe you must have some sort of dynamics in your path to induce Doppler or something similar.  Multiple static paths shouldn't do it.  I trust your receiver is linear enough that you shouldn't have observable mixing products (unless you have multiple strong signals already on different frequencies and an FT-817 like mine).  As Keith suggested, aircraft would do it, but the shift would vary with time (which I presume you didn't see).  I suppose some sort of atmospheric dynamics could produce this effect as well, and someone invoked that explanation in something I read recently.

I did a quick search on nonreciprocal propagation, and it appears this is generally recognized for ionospheric paths, but not obviously so for tropospheric paths.

Really interesting stuff.  It would be fun to do comparisons on different bands when you observe this, to see if the frequency offset scales with carrier frequency.

John AA5PR

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