[TowerTalk] Crossover Transfer Relay

[Roger (K8RI)]

jimlux wrote:
> W5KI at aol.com wrote:
>   
>> Jim,
>>  
>> Agree.  And thanks for your later comments about failure of one  of the ABSS. 
>>  Something I didn't consider for Ken, since I use a  single transfer switch 
>> here (the 300-11002-2 you mentioned [below],  good to 1 Ghz.)
>>  
>> Steve, W5KI
>>
>>     
>
> The recent reference to KK1L's switch is interesting. He uses 3 SPDT 
> relays per "antenna port", which makes it fail safe, at least as far as 
> not connecting two radios together accidentally.
>   
I'm not sure of this particular circuit, but it only takes a pair of 
DPDT relays to make an antenna A/B selector fail safe.  The coil for 
each relay in the pair is fed through the normally closed contact of the 
other relay.  So when one relay is energized the other can not be 
energized.  One set of contacts for the RF and one set for the coils.

73

Roger (K8RI)
> There's also an HP ap note, AN332, which I don't think is online, which 
> is a good summary of all sorts of rf switching. I see it's not marked 
> with a copyright, so maybe I can put it online. I'll write to Agilent 
> and ask.
>
>
>
> Jim, W6RMK
>
>
> BTW
> http://www.hpmemory.org/ressources/resrc_an_01.htm is a useful resource 
> in general
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