[TowerTalk] Strange happening with 10 Meter Beam

[Herbert Schoenbohm]

Thanks Barry for the suggestions....I took the beam down and replace the 
deteriorating cup insulators that seems to have turned into a carbon 
resistor.  This is what gave me the low VSWR but also acted like a dummy 
load, thus low signals but good VSWR.  I did not know that the cup 
insulators could turn to carbon resistors but apparently they 
did.....but the beam was bought in the states near an industrial zone 
and I guess anything could happen as it did.



Herb, KV4FZ

On 10/28/2015 1:32 PM, W5GN wrote:
> I'd start by either replacing the coax or putting dummy load
> at the antenna end - all symptoms sound like a discontinuity
> in the coas or connectors in spite of newness.
>
> You could even just run twisted pair to replace the coax for
> a quick verification that there is resonance even at a little
> higher SWR.
>
> It's almost always the electro-mechanical interface that fails
> in my experience in things electronid.
>
> 73
>
> Barry, W5GN
>
> -----Original Message-----
> From: TowerTalk [mailto:towertalk-bounces at contesting.com] On Behalf Of
> Herbert Schoenbohm
> Sent: Wednesday, October 28, 2015 12:12 PM
> To: towertalk at contesting.com
> Subject: Re: [TowerTalk] Strange happening with 10 Meter Beam
>
> John,  The the problem was neither VSWR (very low) or Beam Direction (any
> direction) even on the ground no signals were apparent except very very weak
> ones were heard on ten in any direction.  It appeared that a
> dummy load was at the end of the feed line.  The   beam is one the
> ground at 10 feet and the insulator cup were changed and the beta rods
> installed.  Immediately the signals started to come in and the rig came to
> life on 10 meters. It appears the cups were acting more like a resistive
> element and took out the signals but provided a good load for VSWR
> measurements.  I installed the beta rods which the manual said are
> 36 inches long....but no where in the book does it give me the distance from
> the Driven Element for the shorting bar on the boom and I looked at every
> page....... The manual just refers to it as "L" but does not say the
> distance of "L".....Do you have nay idea?.\
>
>
> Herb, KV4FZ
>
> On 10/28/2015 12:39 PM, john at kk9a.com wrote:
>> Low SWR is not a bad thing. My homebrew 6el 10m beams have 1.1:1 SWR
>> 28-29 MHz and they work very well.  Does the SWR increase outside the 10m
> band?
>> Is the antenna pointing the correct direction?
>>
>> John KK9A
>>
>>
>> To:	towertalk at contesting.com, Yuri <n2tta at yahoo.com>
>> Subject:	[TowerTalk] Strange happening with 10 Meter Beam
>> From:	Herbert Schoenbohm <herbert.schoenbohm at gmail.com>
>> Date:	Wed, 28 Oct 2015 09:30:21 -0400
>>
>> For the CQ WW I put up a 5 Element HyGain 10 meter beam(LJ-105CA) I
>> double and triple checked all the element lengths and the VSWR is so
>> low across the band it really excited me. It also scares me a bit as
>> up in the air the VSWR is never above 1.3 to 1 from 28.0 to 29.5. The
>> problem is that signals are very weak on non existent when compared to
>> my 3 element quad at 80 feet which was the only antenna that worked on
>> ten during the contest and after.. ( The yagi is one a separate tower
>> at 50 feet)
>>
>> Here is what I have on it.
>> New piece of LMR-400 with good connectors fed directly to the
>> insulated (Hy Gain cup type) director. The beta rods were missing so I
>> use the direct feed to each director. (OWA type matching idea) I moved
>> the first director slightly closer to the driven element to obtain the
>> correct match at 28.4 Mhz Everything looks good but the 10 meter
>> antenna is about as good as a dummy load.
>>
>>
>> I have been building yagi's for over 50 years and have never had such
>> a strange problem. Even a beam with half the driven element missing
>> after a hurricane could hear something but what I have up can't.
>>
>> Before I take it down I ask if anyone else had experiences with this
>> problem. It must be something very simple but I have checked
>> everything I can think of and still no joy here.
>>
>>
>> Please let me know
>> Herb Schoenbohm, KV4FZ
>> ________________________
>>
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