Topband: tree losses

[Bruce]

Another way of looking at it:

There is loss in vegetation that goes up as the frequency goes up.  At low 
frequencies, in a seconds time, only a small amount of wavelengths pass 
through a given bit of vegetation.

As the frequency goes up to UHF, and into gigahertz range,  for a given 
second, many many more wavelengths pass through.  Each pass  contributing 
heat to this (slightly re-radiating) "dummy load".

They give the gigahertz range, a name of ionization waves, but this post is 
trying for an alternate way of looking at it.

Microwave oven= hot dummy load= Lunch. ( ; - ))

73
Bruce-K1FZ




----- Original Message ----- 
From: "jim rogers" <jdrog at bellsouth.net>
To: "ZR" <zr at jeremy.mv.com>
Cc: "Topband" <topband at contesting.com>; "Rudy Severns" <rseverns at gmail.com>
Sent: Monday, August 05, 2013 6:03 AM
Subject: Re: Topband: tree losses


> Carl et al,
>
> Interesting, my 80M full size (66') sloper comes within about 5 ft of a 
> dogwood tree and it is dying. The sloped is fed 8' AGL with 2 full size 
> elevated radials and about 500w and the dogwood is dying from that 
> height(8') to the top of the tree at about 15'. Unfortunately for me, my 
> XYL pointed this out to me - not good. The sloper has been in that 
> position for about 1 year, before that the tree was doing fine.
>
> Coincidence?
>
> Jim N4DU
>
>
> On 8/4/13 9:42 PM, ZR wrote:
>> I cant think of anyone claiming a tree is resonant on any particular 
>> frequency but that doesnt mean it cant be used as an antenna. Anyone 
>> disagreeing with that should discuss it with the military who have been 
>> loading trees for decades for emergency communications; in the 3-8MHz 
>> range if I remember and going back as far as the 50's. Read the old CQ 
>> and QST's.
>>
>> On another note I spent most of today outside doing tree trimming and 
>> other sweaty exercises. I noted that my best producing Bartlett pear tree 
>> was dead at the top and also a bit down on one side. Now it may be just 
>> coincidence but the 80M sloper passes about 5' from the farthest out 
>> branches and the end is exactly at the same height as the tree top.
>> This antenna is used at the vintage gear bench and also on the one for 
>> amp repairs where Ive been hitting it rather hard this year with AM with 
>> serious carrier power; the most recent being an Alpha 77SX.
>>
>> I also remember wilting the top of a sugar maple about 20 years ago with 
>> 1200W on 6M to a 6/6 yagi array. After I moved the antenna to another 
>> tower the tree recovered the following year.
>> Another coincidence?
>>
>> Carl
>> KM1H
>>
>>
>> ----- Original Message ----- From: "Rudy Severns" <rseverns at gmail.com>
>> To: "Topband" <topband at contesting.com>
>> Sent: Sunday, August 04, 2013 5:39 PM
>> Subject: Topband: tree losses
>>
>>
>>> Tom's correct, the issue is not "resonance" but rather what, if 
>>> anything,
>>> happens when you have a so-so conductor/insulator (a tree) in the 
>>> near-field and/or further out. Do the losses matter?
>>>
>>> Performing a definitive set of experiments would be a serious 
>>> undertaking. I've fiddled around a bit but not much more than the tree 
>>> conductivity work mentioned earlier.
>>>
>>> At this point I'm an agnostic: we really don't have good data. There are 
>>> a number of Vietnam era papers on trees as antennas and propagation 
>>> through jungle but most of that was at frequencies well above 160m.
>>>
>>> Here's a challenge for experimenters that'll keep you busy and out of 
>>> the
>>> bars.
>>>
>>> 73, Rudy N6LF
>>>
>>>
>>> _________________
>>> Topband Reflector
>>>
>>>
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>>
>> _________________
>> Topband Reflector
>>
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> Topband Reflector
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