Topband: TX relays

[Carl]

 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 at 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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