Ive found over the years, going back to using a RCS-4 in the 80's to switch
Beverages, that a tiny drop of DeOxit D-100 eliminates the receiving
problem. It also works on amp bypass path contacts.
Since the common TX/RX path in an antenna/stack switch is always getting
wiped I havent noticed any problem there and wouldnt want to use DeOxit at
more than 100W or so anyway.
Just a tiny as possible drop applied with a pointy implement does the job. I
use a face magnifier to be sure it goes where it should.
The vacuum relay in my 1986 LK-500ZC gets a low current in the RX path every
5 years or so; only the first time did it really need it, the rest is PM.
Carl
KM1H
On Fri, 10 Oct 2014 11:13:14 -0700
Paul Baldock <pbaldock@frontier.com> wrote:
One solution to the receiving problem when using high current relays may
be to have dc current (eg 100mA) pass through the contact in RX.
1. In all my antenna systems I always use some wetting current. I feed
from 24 V about 2 mA of DC wetting current via a 1 mH choke and a 4k7
resistor at each end. I used to have receive problems with all kinds of
relays, including vacuum relays, before I added the wetting current. Since
then, all relays have been working perfectly in RX (via the normally
closed contacts).
2. For TX above 500 W I use vacuum relays. Where the SWR is low I use RJ1A
(HC-1) or RF1D ((K45C) or similar types and where the SWR could be high I
use RJ4 (KC-2, KC8 or H-8) types. Overkill? Maybe. But...
73,
George
AA7JV
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