[Boatanchors] WTB: Coax relay, 110VAC, aux contacts

[RAY FRIESS]

are these cube relays similar to those youd see in older cb radio base stations and the power amps for cb that were illegal to use? when my friend closed his cb repair shop I was given a bunch of his junkers that I thought I would keep in my junk box for parts like the so239s and discrete components. I often wondered if the relays would handle enough power to be useful .. But I guess in the case of the illegal power amps, they carried 100 or 200 watts of rf on their antenna contacts. some of those big amps he got as junk were as much as 300 or 400 watt amps. he would never sell them but would bench check them and often if they were toast the owner never came back for them. I rebuilt one tube model for 10 meters, adding harmonic filters and basically using all the usable parts to build an amp from scratch. kind of like the old days when we would cannabalize old tv sets. ---------- Sent from my Verizon Wireless mobile phone


-----Original Message-----
From: WQ9E at btsnetworks.net
Sent: 11/14/2011 3:44:11 PM
To: wa1rkt at arrl.net
Cc: boatanchors at mailman.qth.net
Subject: Re: [Boatanchors] WTB: Coax relay, 110VAC, aux contacts
Hi Rick,

A lot of the old coax relays are showing their age.  A friend just went through this issue with the one used with his Collins 32V-3.  If you don't mind doing a little soldering you can easily construct a more reliable relay using any of the standard "cube" relays such as this one available at your local Radio Shack:  http://www.radioshack.com/product/index.jsp?productId=2049721

I use these relays for all of my low and medium powered gear (and I have a lot of transmitter and receiver pairs).  For neatness mount the relay in a small box although they can be left exposed as long as you cover the exposed terminals with shrink wrap.  I set them up by soldering short lengths of coax with a PL-259 on one end and tie the center conductor of one to the NC contact (receiver) and the other to the NO contact (transmitter).  Solder a third coax cable center conductor to the common contact and solder all three ground braids together.  The third coax cable should have a SO-239 (or whatever matches the antenna feedline you are using).  Most vintage receivers use a short across the standby terminals for receive so attach a short length of two conductor wire (shielding not needed) to the remaining pair of contacts, one to the common and the other to the NC contact, if you use a more modern receiver that requires an open to receive then connect one lead to the NO cont
 act instead of the NC.

The relay I linked to at RS is a 2 pole (DPDT) unit but 4PDT units are also common and useful.  For example the Johnson Viking 1 or 2 with the external VFO tends to chirp on CW.  If you are not using full break-in you can set this combination up where an additional set of relay contacts is used to keep the VFO active whenever you are in transmit mode so that keying is only done in the transmitter and this provides a very clean stable signal.

Cube type relays are used in the remote Ameritron antenna switches along with doing T/R switching in most linear amplifiers.  I am using an older coax relay with my Viking 500 / Pierson KP-81 setup but last week I had to tap the relay a couple of times because it is becoming intermittent on receive.  It will soon be replaced with a new cube style relay.  I use a vacuum relay with my Johnson Desk KW because of its power rating and I would not trust an older relay with it.

If you do find an older coax relay, note that most of them have exposed auxiliary contacts.  Be careful to provide some protection of these because many vintage receivers provide standby switching through opening the B+ circuit and this will leave high voltage accessible on the relay.

Rodger WQ9E


-------- Original Message --------
> From: Rick Poole <wa1rkt at arrl.net>
> Sent: Monday, November 14, 2011 9:02 AM
> To: boatanchors at mailman.qth.net
> Subject: [Boatanchors] WTB: Coax relay, 110VAC, aux contacts
>
> Looking to buy a coax relay in good condition, 110VAC coil, with aux
> contacts to control a receiver mute.  It's the last thing I need to
> complete my AM station.  Strongly prefer SO-239 connectors but can
> adapt something else.  Only ones I've been able to find are 12 VDC
> coils, or else they don't have the aux contacts.  Please reply
> off-list to wa1rkt at arrl.net with price including shipping to NH 03053.
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