[TowerTalk] TH7 puzzle

[K4SAV]

Sounds like you have a bad connection somewhere in the antenna or coax 
to the antenna.  Probably some oxidation.  Your amp is putting out 
enough voltage to clear the oxidation and "weld" a connection, much the 
same kind of thing you see happen with Christmas lights. Same thing will 
happen with open frame relays used for antenna switching. After you make 
a good connection using the amp, it is OK for a while until the 
oxidation builds up again, and everything starts over.

Jerry, K4SAV

Steve Lawrence wrote:

>TH7 Puzzle:
>
>I have an FT1000D driving a legal limit amp to a TH7DX. The FT1KD  
>tuner is left off when driving the amp. Occasionally, the FT's Hi SWR  
>light will flicker or stay on but only when the amp is off line. The  
>FT's power setting can be anywhere from the 3 watt minimum to full.  
>This happens only on 20m, not 15m or 10m and not all of the time. If  
>I put the amp on, the antenna takes the full legal limit without any  
>problems. Immediately after that, if I put the amp on standby, the  
>rig's Hi SWR light no longer reacts and there is no indication of  
>reflected power.
>
>I can make the light go out when I have the Hi SWR indication and the  
>amp is off line by switching the FT's tuner in but I'll still see the  
>same reflected power as if the Hi SWR light is on.
>
>I have connected the FT directly to a dummy load and the Hi SWR light  
>remains off. Connecting the TH7 directly - no switches, power meters,  
>coax elbows, no amp in standby - and the light comes on. This is  
>repeatable. Unless I run the amp and then everything is normal until  
>some time passes - hours, days or not for some time.
>
>Best guess is that there something going on with the TH7. Loose  
>hardware? Critters in traps? But why only 20m and why would high  
>power clear it but not blow it out.
>
>Experiences and thoughts appreciated.
>
>73 - Steve WB6RSE
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