Thanks Roger. The DS50-4 uses a gamma match, but the DS50-5 now uses a
T-Match. Apparently this is an older beam (I picked it up used at a
Downeast Microwave garage sale) that used a gamma match.
I think you are right - it is probably a moisture issue. I am replacing the
dielectric and investigating the cost of the T-Match for this antenna (and
will water/moisture proof it). It was not moisture proof - or water proof
by any stretch of the imagination.
Scott
-----Original Message-----
From: Roger (K8RI) [mailto:K8RI-on-TowerTalk@tm.net]
Sent: Sunday, April 26, 2009 4:31 PM
To: Scott MacKenzie
Cc: towertalk@contesting.com
Subject: Re: [TowerTalk] 6M Beam being weird
Scott MacKenzie wrote:
> All:
>
> I have a 6M beam that is showing high SWR (10:1). I checked each
> connector to the antenna by disconnecting and placing a dummy load.
> Finally up at the antenna, I disconnected the antenna, and placed the
> dummy load as the antenna. Readings were 1:1 SWR. I then clean up
> the connector at the antenna, and retest. SWR is still high.
>
> I then pull down the antenna (K1FO or similar - not M2) and check it out.
>
> With the coax disconnected, I check the connector - good continuity
> from the center pin to the otherside of the connector (where the gamma
> match is attached.
>
Ian already had some good comments on this.
In addition, make sure the center pin is ALL the way in. It's possible to
assemble a connector and not get the center pin fully forward.
>
> I check from center pin to ground on the conductor to see if shorted -
> Circuit is open.
>
> I check to make sure I have continuity between outside of gamma and
> rest of antenna. Circuit is fine - and shows continuity.
>
>
I thought the DS50-4 used a T-match?
If using a sleeve balun and it's properly connected to the braid, how is the
braid waterproofed?
If the sleeve is either clamped or soldered to the braid it needs to be
thoroughly moisture proofed. Although as hams we tend to use a lot of RTV
and I too use a lot of Silastic RTV (TM) it is water proof, not moisture
proof. However for an open sleeve it shouldn't make a difference, BUT it is
very difficult to waterproof braid with any of the RTVs as they are so thick
it makes thourough penetration of the braid difficult. Something with a much
lower viscosity such as "Liquid Electrical Tape" would be a better choice
and is available at most hardware stores. It's also available in several
colors. As it's in the open there is little need to worry about which RTV is
used.
> The only thing I can think of left is to replace the coax less shield
> inside the gamma.
>
> What else can it be?
>
> I was hoping to get this up higher in the air for the summer Es season.
>
> Thanks
>
> Scott
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