[Elecraft] Output power being eaten

[Bob McGraw]

I doubt that ice on the antenna would have any effect in terms of 
increased loss.   However, I would expect the resonant frequency to 
change and thus the need to adjust the tuner.   If it is and ATU / 
automated tuner, then perhaps a bit too low power may cause the SWR 
bridge to read incorrectly.

I use a KAT500 and my TUNE power is 20 watts.  This assures the ATU and 
SWR circuits have adequate signal to perform the desired function.   As 
to the SPE 1.3K amp, as fussy as they are, I'm surprised it didn't trip 
off line.

My experience with antenna's changing due to moisture is with my 
balanced center fed wire which uses window line for the feed.  It 
accumulates moisture, frost, rain, snow, and ice.  The change I do see 
is due to the velocity change of the balanced feed.  My measurements of 
a couple of years back indicated the length of the line changed 
electrically thus a velocity factor change.  Any loss, wet or dry, under 
matched conditions was not measurable over a length of 100 ft on 20M.   
Therefore, I would expect the mis-matched loss to be about as the book 
say.  Again, either wet or dry.

73

Bob, K4TAX

On 12/27/2021 4:10 PM, elecraft-request at mailman.qth.net wrote:
> Message: 21
> Date: Mon, 27 Dec 2021 14:10:25 -0800
> From: Fred Jensen<k6dgwnv at gmail.com>
> To: Elecraft Reflector<elecraft at mailman.qth.net>
> Subject: Re: [Elecraft] Output power being eaten
> Message-ID:<8c012d97-f62d-b342-4ec3-20db2e8f51d8 at gmail.com>
> Content-Type: text/plain; charset=utf-8; format=flowed
>
> I doubt that pogonip or even solid ice on your antenna would have major
> effects [well, except for weight].? Ice forming from water directly from
> the sky is a pretty good insulator.? We had a very large Log-Periodic on
> the roof of the hangar at my first USAF assignment in the remote
> northern interior of KL7.? Lots of ice fog creating rime ice on the
> elements in the dead of winter, much of which was -35 C or below.? In
> the so-called spring, solid ice would form on them, and there was
> essentially no perceptible change in the antenna performance.? If your
> ATU wasn't getting enough power to tune, it was probably "eating your
> power" rather than the ice on the antenna.
>
> At home, I have an HOA "WOOF" antenna [Wire On Organic Fence] at about 2
> m AGL.? We've been having a series of snowstorms, the top of the fence,
> including the wire, was encased in snow yesterday for the 40 m ECN, and
> it worked as good as it ever does.
>
> 73 & HNY,
>
> Fred ["Skip"] K6DGW
> Sparks NV DM09dn
> Washoe County
>
> Bill Frantz wrote on 12/27/2021 11:48 AM:
>> I didn't have a good night in the K1USN Slow Speed Test. I started
>> more-or-less on time and tried to answer CQs. None of the stations I
>> tried
>> could hear me. My SPE 1.3K amp said I was putting out about a kilowatt,
>> although the antenna tuning on my normally low SWR 40M dipole needed
>> to be
>> redone. I was receiving many stations, at normal levels.
>>
>> After a few minutes, I started searching for causes, since operators
>> calling CQ weren't hearing me and sending CQ again. Some of these
>> operators had worked other stations, so I knew their radios were
>> basically working. I tried maybe a half a dozen stations.
>>
>> Finally, in desperation, I raised the tune power in my K3 exciter to 15W
>> and retuned the dipole yet again. Things started working and I managed to
>> check into the Elecraft 40M CW net via KD5ONS in OR at 0050z. With only 5
>> minutes in the contest left, I managed QSOs with W6SX and VE5MX.
>> Thanks to
>> both of them.
>>
>> My current theory about what was happening is that ice on the antenna was
>> eating transmit power, although receive seemed normal. Does ice seem a
>> reasonable explanation? What else could be the cause? I'd love to come up
>> with a believable answer. Even more so, avoid the situation in the
>> future.
>>
>> 73 Bill AE6JV