How to mute Hammarlund SP-600

[iw5ci]

I would like to interface my Hammarlund SP-600 with a Geloso G-222 trasmitter. The trasmitter has no relay, when in tx , the receiver antenna is disconnected and shorted to ground. There is also the mute output but the SP-600 has no mute connection on the rear panel, so what i have to do to mute the sp-600?

[KC4VWU]

I use a DPDT relay to switch the speaker in and out with PTT. Use between a 1.5K and 2K 2W resistor to keep an appearant load on the output when the speaker is disconnected.

Phil

[iw5ci]

I am worried about RF... just disconnecting the speaker does not solve the problem of RF from tx entering in the SP-600. Even with receiver antenna connector shorted is it possible to damage the sp-600 frontend?

[Steve - WB3HUZ]

How is the receiver antenna disconnected and shorted to ground? If you are using an external relay, it's very unlikely you could get enough power into the front-end of the SP600 to cause any damage.

I would like to interface my Hammarlund SP-600 with a Geloso G-222 trasmitter. The trasmitter has no relay, when in tx , the receiver antenna is disconnected and shorted to ground. There is also the mute output but the SP-600 has no mute connection on the rear panel, so what i have to do to mute the sp-600?

[Todd, KA1KAQ]

Right, using something like a Dow Key relay with the external contacts to switch the antenna as well as muting the receiver should work if there is no circuitry provided between the two for muting.

[ke7trp]

My SP600 has no "relay" socket on the back.  Some do and some dont.

If yours has this socket, THen get a plug that fits into it.  There is voltage on that line so be carefull.. I know,  My right hand and arm hurt for about a week after getting across those lines on this project!

If your radio DOES NOT have this relay socket on the back, Simply open up the radio and solder on two conductor wire to the back of the Send, recieve switch.  If you look at the schematic, This is exactly how the relay socket is wired. Off the back of that switch.  Now run the wires up the top and out the back of the radio. 

You now have MUTE.  When the radio is in SEND, These wires are hooked up for RX.  When you unhook them, the Reciever mutes.  TO override this feature (when tuning) just place switch in receive position.

On my T368 Transmitter,  It has two output terminals for muting.  They where normaly OPEN so they would not work with the SP600. 

I Purchased a small 12 Volt DC relay at radio shack.  DPDT.  I also picked up the socket and some connectors while I was there. 

I wired the SP600's new mute line to the relay on the normly CLOSED position.

I then got a 12 volt DC wall transformer that was used to power an old Clock radio. I cut the end off and wired it to the relay coil.  The T368s two relay terminals then where inserted on the negative side of this Coil. 

Now, When I key the T368, Its contacts CLOSE, sending 12 volts DC to the relay coil. This then breaks the contact on the SP600 mute line. 

Very simple.  Cost about $10.  Been working for about a week with no issues.  Its nice becuase on the Sp600, it only kills a stage of the IF, So you still have a little RX even when muted to hear yourself speak. Works FB

Clark