The AM Forum

Does anyone have plans or a schematic for a carrier operated relay circuit I can use with my 5 watt Nouveau 75 QRP rig to key an amplifier. Unfortunately there is no provision for keying an external device the the N-75. Thanks.

Rich  K1ETP

Rich,

I would just pick off the TX switch or PTT switch and use that point in the circuit to drive a transistor acting as a switch.  I can't give you the exact circuit, since I do not have the schematic along with not knowing what you want to switch.

Joe-GMS 

In my QST article from back in 1990 "A compact Brick for Six" I used a COR circuit that worked very well with the 100 watt amplifier

It pulls in the T/R relay very quickly at the first hint of RF. Several hundred of these amps were built and the COR circuit never was a problem that I heard about. It was a pretty good zCOR with both SSB and CW.

Pat
N4LTA

  Another suggestion: on the MFJ website you can download the manual - which includes the full schematic - for their MFJ-1708B-SDR T/R switch.  In addition to using wired "hard" keying, this box also has an RF "sniffer" circuit to actuate the relays upon sensing RF.  Using that schematic it should be easy to build your own.

http://www.qrpkits.com/ezseries.html#eztrsw

It’s a kit..  ;)

Looks just about right

Lichaloni,

Just in case you are able to do this:  Do you use a MASTER station 24VDC PTT keying line for all your rigs?  (controlled by a handheld switch)

On the back of every rig here I have an RCA jack that is the PTT input. It connects to an internal 24VDC relay which in turn keys the rig and swiches the antennna. I have a switch on each rig front panel to turn the 24VDC loop on for each rig.

This same 24VDC keying line can then key any linear, exciter or whatever rig combo you want to key once it is organized like this.  The Nouveau is just another rig that gets keyed like the rest when its own PTT panel switch is on.

T

I run boat anchors of most all makes and models, and there were a variety of interface schemes used.   In an attempt to make life simple, I installed CORs in all my amplifiers.  Doing this requires me to only switch the Key line, and Mic audio to the desired transmitter/exciter, and at the R.F. patch panel, connect to the desired amplifier.  

I use a set of SPDT relay contacts for the key line so I can configure it as needed by a particular transmitter.  

This is the basic circuit.   Some amps also have antenna relays and some don't, so I jumper Anetnna relay contacts, and use an electronic T/R antenna switch.  

With this combination, mixing and matching boxes is pretty much a plug and play affair, and, the antenna is always connected, so the amp doesn't start up without a proper load.

This circuit will work down to a Watt or two of drive.

(https://photos.smugmug.com/Dentron-Clipperton-L-Amp/Rework-and-repair/i-vsnkBfD/0/7d101163/L/Schematic-L.jpg)

If you feel the need for more info, go here. (https://mikeharrison.smugmug.com/)

Thanks, everyone for the input. Tom, I do use a common keying loop for all my rigs except I use 12VDC. With a COR I'll just add the little Nouveau to that loop. I might try the kit Jeff, NBC, suggested only because Jeff knows how much I love building mini-kits. A shot of Jack keeps the soldering hand from shaking.

Rich  K1ETP

Lich,

I don't understand....  if you are already able to key the Nova with the master PTT loop and also key any linear amp it may drive the same way, why do you need another PTT line activated by a carrier?

Or maybe you are keying the Nova alone with its own hand mike  - in that case I get it.
   
T