[TowerTalk] 6M Beam being weird

[Ian White GM3SEK]

Scott MacKenzie wrote:
>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.
>
>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.
>
>The only thing I can think of left is to replace the coax less shield 
>inside the gamma.
>
>What else can it be?

1. Check the SWR with an antenna analyser connected directly to the 
antenna. The DC measurements were a good place to start, but they don't 
tell you everything.

2. If there are N connectors involved, it's possible that a centre pin 
may have pulled back inside the cable. N connectors don't have a lot of 
tolerance for axial movement, and very occasionally you find a pair of 
connectors where each one works fine with the test equipment, but they 
still don't connect to each other.


-- 

73 from Ian GM3SEK         'In Practice' columnist for RadCom (RSGB)
http://www.ifwtech.co.uk/g3sek