Dave, et al:
My thoughts, exactly. Perhaps the center conductor of the coax is not
making good contact until warmed.
73
Don
N8DE
Quoting David Gilbert <xdavid@cis-broadband.com>:
>
> I'd suspect some kind of bad connection due to thermal expansion.
> Moisture is not likely to make that kind of dramatic shift in SWR, and
> certainly not that consistently from day to day.
>
> 73,
> Dave AB7E
>
>
>
> On 4/1/2012 8:01 AM, Richard Thorne wrote:
>> I finished my tower/antenna install Friday. 77' of 45g with 15' of mast
>> out the top. I have a F12 D240 mounted 10' up the mast and a F12 C31 at
>> about 1' up the mast. The swr is where they are supposed to be on both
>> antennas.
>>
>> Now for the strange part.
>>
>> Some time after dark my D240 becomes attenuated and the swr is very very
>> high. But after the sun comes up for about 2 to 3 hours, the
>> attenuation goes away and the swr is right where its suppose to be and
>> signals are clear and strong.
>>
>> Its been clear with no rain since the antenna has was put up Friday
>> morning. There must be some moisture in the air as dew does form on the
>> grass and the roof of my steel building/shop.
>>
>> So I'm scratching my head on this one. I've switched out coax cables at
>> the shack, bypassed the polyphaser lightning suppressors, used the
>> different antenna inputs to my Elecraft K3, checked to be sure I didn't
>> have a receive antenna selected on the K3 etc.
>>
>> I have a single 158' run of coax from my entrance panel to the top of
>> the tower and have it terminated with one of these
>> http://www.dxengineering.com/Parts.asp?ID=3320&PLID=105&SecID=94&DeptID={DBD52E00-E4FA-4BB0-A7B9-1EDCD8FCDE17}&PartNo=DXE-CGB-150
>> then another length of coax that forms the rotor loop, goes up the mast
>> then to the f12 balun (f12 B1) at the feed point of the D240. I have
>> the same setup via another coax cable going to the C31XR which doesn't
>> exhibit this strange problem
>>
>> I have two weep holes drilled in the bottom of each trap cover for
>> moisture to escape.
>>
>> All connection points are weatherized using 3m rubber splicing tape
>> which is then wrapped with Scotch Super 33. All coax, connectors etc
>> are brand spanking new.
>>
>> The next step is to climb the tower and check the connections at the top
>> of the tower, if that's not the problem it will be time to bring out the
>> crane again and check the connections at the feed point.
>>
>> Before I get to far into this I'd like to know if any else has run into
>> this symptom and what the final resolution was.
>>
>> Thanks
>>
>> Rich - N5ZC
>>
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