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Question: foliage, vhf

Bruce Draper
 

I put up my 6-mtr yagi antenna this morning, but now I’m thinking about moving it. It’s on a tripod on my roof, about 30 feet off the ground (good) but only 15 feet from and directly pointed into dense cottonwood trees (bad?). I don’t think it matters much on HF, but I’m guessing that it’s not great on 6 meters (and much worse on UHF). There are a couple other places on the flat roof where I could put it, but the best one is directly above the radio room and I bet there will be RFI problems on both RX and TX. 

My question to you VHF experts: Is the absorption on 50 MHz by trees bad enough to make me want to move the antenna? 

   -Bruce AA5B

Keith Morehouse
 

Look up document ITU-R P.833-9 for the actual numbers, but, IMO, it's really bad at 432, of some concern at 222 & 144 and not much of a worry at 50 MHz unless you're literally buried in foliage.

BTW, below 100 MHz, it's considerable worse with vertical polarization then horizontal, but still negligible

-W9RM

Keith Morehouse
via MotoG


On Fri, May 3, 2019, 1:20 PM Bruce Draper <bruceaa5b@...> wrote:
I put up my 6-mtr yagi antenna this morning, but now I’m thinking about moving it. It’s on a tripod on my roof, about 30 feet off the ground (good) but only 15 feet from and directly pointed into dense cottonwood trees (bad?). I don’t think it matters much on HF, but I’m guessing that it’s not great on 6 meters (and much worse on UHF). There are a couple other places on the flat roof where I could put it, but the best one is directly above the radio room and I bet there will be RFI problems on both RX and TX. 

My question to you VHF experts: Is the absorption on 50 MHz by trees bad enough to make me want to move the antenna? 

   -Bruce AA5B

lewisre@...
 

I would suggest a series of tests with other 6 meter stations first.  Also if possible you might compare performance  with 10 and 2 meters. 

Dick, K5RHR, DM65uv


 

On 2019-05-03 13:20, Bruce Draper wrote:

I put up my 6-mtr yagi antenna this morning, but now I'm thinking about moving it. It's on a tripod on my roof, about 30 feet off the ground (good) but only 15 feet from and directly pointed into dense cottonwood trees (bad?). I don't think it matters much on HF, but I'm guessing that it's not great on 6 meters (and much worse on UHF). There are a couple other places on the flat roof where I could put it, but the best one is directly above the radio room and I bet there will be RFI problems on both RX and TX. 

 
My question to you VHF experts: Is the absorption on 50 MHz by trees bad enough to make me want to move the antenna? 
 
   -Bruce AA5B
 

Mike WB2FKO
 

Interesting to note that W7GJ has carved out a patch of Montana forest for his VHF aluminum:


Lots of foliage there.

On May 4, 2019, at 10:49 AM, lewisre@... wrote:

I would suggest a series of tests with other 6 meter stations first.  Also if possible you might compare performance  with 10 and 2 meters. 

Dick, K5RHR, DM65uv


 

On 2019-05-03 13:20, Bruce Draper wrote:

I put up my 6-mtr yagi antenna this morning, but now I'm thinking about moving it. It's on a tripod on my roof, about 30 feet off the ground (good) but only 15 feet from and directly pointed into dense cottonwood trees (bad?). I don't think it matters much on HF, but I'm guessing that it's not great on 6 meters (and much worse on UHF). There are a couple other places on the flat roof where I could put it, but the best one is directly above the radio room and I bet there will be RFI problems on both RX and TX. 

 
My question to you VHF experts: Is the absorption on 50 MHz by trees bad enough to make me want to move the antenna? 
 
   -Bruce AA5B
 

K Chapman
 


Do a digi-mode with a S/N readout.  Then, compare with a known antenna with the directionality of the yagi.

Kyle AK5Z

On 2019-05-05 04:25, Mike WB2FKO wrote:
Interesting to note that W7GJ has carved out a patch of Montana forest for his VHF aluminum:


Lots of foliage there.

On May 4, 2019, at 10:49 AM, lewisre@... wrote:

I would suggest a series of tests with other 6 meter stations first.  Also if possible you might compare performance  with 10 and 2 meters. 

Dick, K5RHR, DM65uv


 

On 2019-05-03 13:20, Bruce Draper wrote:

I put up my 6-mtr yagi antenna this morning, but now I'm thinking about moving it. It's on a tripod on my roof, about 30 feet off the ground (good) but only 15 feet from and directly pointed into dense cottonwood trees (bad?). I don't think it matters much on HF, but I'm guessing that it's not great on 6 meters (and much worse on UHF). There are a couple other places on the flat roof where I could put it, but the best one is directly above the radio room and I bet there will be RFI problems on both RX and TX. 

 
My question to you VHF experts: Is the absorption on 50 MHz by trees bad enough to make me want to move the antenna? 
 
   -Bruce AA5B
 


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Kyle Chapman
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Universität Heidelberg
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