Coax Switching

[Ron Pollack]

I also have multiple setups, mostly boatanchor but some solid state.  I did have a case once where a "fuse" type of thing blew out from rf in the front end of a 757.  I don't remember if I had a switch thrown wrong or there was inadequate attenuation in the switch.

I solved the problem:  I physically take the coax from the antenna tuner and manual connect it to the rig I am preparing to use.  For the ones where the coax doesn't reach, I've provided a short length of coax with a PL259 and double female (barrel connector) long enough to meet the coax from the antenna tuner.  This only takes a few seconds, and removes all danger to the receiver front ends, whether on, off, set to same band, or whatever.

This is an attempt to circumvent Mr. Murphy!  It only takes once forgetting to change the switch!

Long live Murphy's Law and Cole's Law.

Ron K2RP


---- Don Melcher <don at HFRADIO.COM> wrote: 
> 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.
> >>
> 
> -----------------------------------------------------------
> Products bought, sold or traded here is the responsibility of the
> parties involved.  This list and the City of Tempe are not responsible
> for losses or misrepresentations of any kind.  Buyer beware!
> 
> -----------------------------------------------------------
> This list is a public service of the City of Tempe, Arizona
> -----------------------------------------------------------
> 
> Subscription control - http://www.tempe.gov/lists/control.asp?list=HEATH
> To post - HEATH at LISTSERV.TEMPE.GOV
> Archives - http://listserv.tempe.gov/archives/HEATH.html

-----------------------------------------------------------
Products bought, sold or traded here is the responsibility of the
parties involved.  This list and the City of Tempe are not responsible
for losses or misrepresentations of any kind.  Buyer beware!

-----------------------------------------------------------
This list is a public service of the City of Tempe, Arizona
-----------------------------------------------------------

Subscription control - http://www.tempe.gov/lists/control.asp?list=HEATH
To post - HEATH at LISTSERV.TEMPE.GOV
Archives - http://listserv.tempe.gov/archives/HEATH.html