Coax Switching

[Don Melcher]

There is a pass-band filter that is in the circuit in receive as well as
transmit on a radio like a 430 - I am not sure what the state is when the
radio is off - though I am sure the relays that select that filter are not
latching, so the receiver may be effectively disconnected from the antenna
when the radio is off (though may not have much isolation due to capacitive
coupling across the relay contacts). On the 830 - I think the problem is
ahead of any filtering. I'd have to look at the schematics. I mainly
remember people bringing 830's in for repair of a deaf receiver in the weeks
after field day every year. There is no way your 430 should be "hot"
compared to the 830, though the noise floor may be higher so you perceive
that to be the case.



-----Original Message-----
From: Heathkit Owners and Collectors List [mailto:HEATH at LISTSERV.TEMPE.GOV]
On Behalf Of DavidGriffin
Sent: Monday, January 08, 2007 8:47 PM
To: HEATH at LISTSERV.TEMPE.GOV
Subject: Re: [HEATH-TEMPE] Coax Switching

You know, I always do that but I'm unsure it if helps because I don't 
think the first FET cares what band the rest of the radio is tuned to.  
What do  you think?
Dave

Dick KF4NS wrote:
> One thing that was not mentioned here but would help considerably is, 
> in addition to the level  of  isolation, tune the unused radios to  
> another band or at least detune them (if  boatanchors) or select the 
> opposite end of the band.
>
> 73, Dick KF4NS
> St Petersburg, FL 33714
> Keep The Glow!
>
>> -----Original Message-----
>> From: Heathkit Owners and Collectors List
>> [mailto:HEATH at LISTSERV.TEMPE.GOV]On Behalf Of Bernie Arcand
>> Sent: Saturday, January 06, 2007 5:20 PM
>> To: HEATH at LISTSERV.TEMPE.GOV
>> Subject: Coax Switching
>>
>>
>> Hi guys...
>> I have a Heathkit Coax switch that I built decades ago, and now
>> that I have two rigs, I have the output of both of these rigs
>> into the switch, with the common port the output to the
>> tuner/antenna.  Question:  Is there a possibility or potential or
>> likelyhood that by transmitting on one radio, that I can damage
>> the receive on the other radio when it is turned off?  Would I
>> decrease the likelyhood of damage if I turn on the RF attenuator
>> on the unused rig before I turn it off?  I realize the safest way
>> is to disconnect the coax and terminate it into a 50 ohm
>> load...but don't want to do that.  Simply want to switch between rigs.
>>

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