Posted by
Stewart Baker on
Feb 12, 2006; 12:24pm
URL: http://elecraft.85.s1.nabble.com/K2-Relay-contact-resistance-tp386534.html
Having decided to join the melee trying to work 3Y0X on Peter One Island, I
dusted off my FT1000MP. The only time that I use it are on occasions such as
this when a separate receiver is useful when working split.
I noticed that the receive sensitivity was varying on 20 & 40m, and traced this
to the HPF board at the front of the receiver. This board contains 8 miniature
relays which do the filter switching. If I tapped the board the received signal
strength varied. From notes I found on the web this is a known problem where the
solution is to change all 8 relays. I didn't fancy changing these small relays
if there was a better solution.
I remembered that the FT102 had big problems with people were changing relays by
the bucket full. Yaesu don't seemed to have learned the lesson of the FT102 !
A local amateur came up with a fix which consisted of running a small DC current
through the contacts to break down any oxide layer that had formed over time.
This morning I modified the HPF board to run about 1mA through the contacts.
10 resistors and 2 caps later - End of problem - Fixed....
The big relays in the KAT100 should not have a problem, but what about the
smaller ones in the K2, KAT2 ? As far a I can tell a number of these have only
very small AC signals passing through them. None have any DC current flow.
It took about 7 years before the problem surfaced with my FT1000MP, I would be
interested in comments on whether in the same time scale I might expect to get
similar problems with my Elecraft gear.
73
Stewart G3RXQ
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