Date   

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


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

Keith Morehouse
 

Mike gave a good explanation of what our problem was.  The multi-path really became obvious when we tried JT65 and KK6MC was seeing two synch tones.  I moved my antenna 10 degrees west and the result on the paths south end was FOUR synch tones.  Your question about reciprocity is valid.  I don't know why I wasn't being affected - the signal strength explanation put forward by Mike is certainly possible.  When we went to CW, I could detect a slight buzz or beat-note on his signal that was probably multi-path induced.

I have terrible multi-path problems on 2M when working rovers from a couple of commonly used locations to the south of me.  There is one place in particular were signals are very loud but the distortion is so bad on the direct path I need to turn the antenna 20-30 degrees east or west to copy anything on SSB.  On CW, it sounds like a DX pileup on 20M.  The 14,000' peaks of the San Juan range lay just 40 miles south of here.

On 6M, it is very common at this QTH to see multiple FT8 traces on 6M from 'local' stations (50-60 miles away).  The are usually offset by at least 1/2 of the FT8 signal bandwidth (so, maybe 15-20 Hz).  Sometimes, depending on who I'm hearing and where the respective antennas are pointed, they are far enough apart to see two distinct signals.  The result is usually TWO decodes of the same station, reported on two discreet frequencies, not a total failure.  It appears signals offset a smaller amount at much higher frequencies can cause problems.

A good example of multi-path can be viewed if you're near a major airport and can hear a CW beacon on 432 that's out a way - maybe 100 miles.  If the air traffic flow is correct, and the incoming or outbound traffic passes across your path to the beacon, you can watch a spectrum display and see the multiple signals caused by the aircraft reflections.  When I lived in Illinois, I used to monitor a 432 beacon in Michigan, northeast across the lake about 200 miles.  The direct path was right across the traffic flow in and out of O'Hare airport in Chicago.  The patterns of multi-path and Doppler shifted signals caused by the aircraft was amazing.  This is also a good demonstration of a technique called 'passive bi-static radar' that can be used to detect stealth aircraft without having to emit a signal of your own.

-W9RM

Keith Morehouse
via MotoG


On Mon, Sep 16, 2019, 9:40 PM John Klem <klemjf@...> wrote:
I am very curious - what characteristics of these signals led you to conclude multipath was the problem?  What was painfully obvious about it?
Should multipath be non-reciprocal?

Getting an audio recording of this kind of signal for analysis would be really interesting.

John AA5PR


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

Bill
 

Nicely done guys.

Bill


On Sep 16, 2019, at 10:54 PM, Mike WB2FKO <mph@...> wrote:

Duffey and I discussed this on the long ride home today.  Thinking about it some more, the idea of multipath is that two or more (coherent) signals from the same source travel by slightly different paths to the receiver.  This path difference only has to be a fraction of a wavelength. This causes interference and mixing in the detection circuit, producing ghosts of the digital signal in the audio waterfall.  This is exactly what I saw when we were running FT8 and especially JT65 (the synch signal is very obvious in the traces).  Seems this would be become a greater issue as the frequency goes up into UHF. All that said, FT8 should have been able to successfully decode the baseline signal and any harmonics.  Or maybe the frequency separation of the ghost signals was not sufficient and confused the decoder.

I am convinced the equipment was not at fault, as we had been working very successfully with various digital modes throughout the weekend.

The question of reciprocity is a good one.  W9RM's signal was very up and down, but his digital signals refused to decode independent of the widely varying receive level.  My hunch is that the reflection(s) occurred closer -- much closer -- to our QTH than his.  Beam divergence and diffraction would substantially weaken the reflected/scattered signal by the point they reached him, allowing decodes there.  Also the lower gain, wider aperture of the rover antenna may make us more susceptible.  But we were at an ideal location with almost nothing on the near horizon that suggested a reflection source. We experimented over the course of about 30 minutes with different digital modes and especially beam headings to no avail.  I would have wagered that moving the beam around would have fixed it.  And lost.

I have never had this problem (that I can remember anyway) on 6 or 2.  My experience with FT8 on UHF has been entirely this past weekend, or about 3-4 QSOs total.

Mike WB2FKO


On 9/16/19 9:40 PM, John Klem wrote:
I am very curious - what characteristics of these signals led you to conclude multipath was the problem?  What was painfully obvious about it?
Should multipath be non-reciprocal?

Getting an audio recording of this kind of signal for analysis would be really interesting.

John AA5PR


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

Mike WB2FKO
 

Duffey and I discussed this on the long ride home today.  Thinking about it some more, the idea of multipath is that two or more (coherent) signals from the same source travel by slightly different paths to the receiver.  This path difference only has to be a fraction of a wavelength. This causes interference and mixing in the detection circuit, producing ghosts of the digital signal in the audio waterfall.  This is exactly what I saw when we were running FT8 and especially JT65 (the synch signal is very obvious in the traces).  Seems this would be become a greater issue as the frequency goes up into UHF. All that said, FT8 should have been able to successfully decode the baseline signal and any harmonics.  Or maybe the frequency separation of the ghost signals was not sufficient and confused the decoder.

I am convinced the equipment was not at fault, as we had been working very successfully with various digital modes throughout the weekend.

The question of reciprocity is a good one.  W9RM's signal was very up and down, but his digital signals refused to decode independent of the widely varying receive level.  My hunch is that the reflection(s) occurred closer -- much closer -- to our QTH than his.  Beam divergence and diffraction would substantially weaken the reflected/scattered signal by the point they reached him, allowing decodes there.  Also the lower gain, wider aperture of the rover antenna may make us more susceptible.  But we were at an ideal location with almost nothing on the near horizon that suggested a reflection source. We experimented over the course of about 30 minutes with different digital modes and especially beam headings to no avail.  I would have wagered that moving the beam around would have fixed it.  And lost.

I have never had this problem (that I can remember anyway) on 6 or 2.  My experience with FT8 on UHF has been entirely this past weekend, or about 3-4 QSOs total.

Mike WB2FKO


On 9/16/19 9:40 PM, John Klem wrote:
I am very curious - what characteristics of these signals led you to conclude multipath was the problem?  What was painfully obvious about it?
Should multipath be non-reciprocal?

Getting an audio recording of this kind of signal for analysis would be really interesting.

John AA5PR

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