Buffer/Slave relay for keying

  • 1
  • Question
  • Updated 1 year ago

I want to use this simple circuit as a buffer/slave relay to key
my RF amplifier from the Flex 6300. I have used this many time before on
various rigs with success, but not the 6300. 

The relay will key when just the
tip of the RCA connector is inserted into the key jack on the 6300 on receive.

Is there a software setting I am missing that controls this? 

This circuit works
fine on my Elecraft K2.
Photo of aaron brio

aaron brio

  • 2 Posts
  • 0 Reply Likes

Posted 1 year ago

  • 1
Photo of Dennis Terry W4SG

Dennis Terry W4SG

  • 70 Posts
  • 9 Reply Likes
Perhaps it is just the wording you used but did you mean the key jack or the TX jack?  The TX jack  or the accessory TX pin is the proper one to connect to for what you are trying to do.  It needs to be enabled in the software transmit profile.  Not sure of the default state if it is not enabled.
Photo of Clay N9IO

Clay N9IO

  • 638 Posts
  • 172 Reply Likes

The TX jack is preferred and must be enabled in the menu under Transmit.

It's good you're using a separate 12 volt supply.

A more accepted practice if you must have an outboard relay for a dry pair is to introduce an NPN saturated transistor switch to buffer the current draw on your TX port. Very simple to build. For a transistor switch pretty much anyone will work.

Curious what amplifier you are driving, many modern amps work perfectly with an RCA m-m cable from the 6300 to the amplifier. My Acom 1000 is one that does.
When I had my L4B and TL922a I too built a transistor switch driven relay.
Photo of Michael Walker

Michael Walker, Employee

  • 1097 Posts
  • 325 Reply Likes
I am curious as to why you need one as Clay asked?

There is no need for one unless you are using a Heathkit amp or something like a TL922A.

Photo of aaron brio

aaron brio

  • 2 Posts
  • 0 Reply Likes
Hi Mike....The 6300 only has one RCA jack to key an amplifier.  I would like to use a 4pdt relay to key other equipment in the shack.  
Photo of Michael Walker

Michael Walker, Employee

  • 1061 Posts
  • 316 Reply Likes
Yep, that would be a good reason.   Make sure that you have that TX turned on as Clay mentioned.  It is off by default.

Photo of Neal Pollack, N6YFM

Neal Pollack, N6YFM

  • 260 Posts
  • 137 Reply Likes
Make sure that the current draw for the 4 pole relay coil does not exceed what the TX port on your 6300 can handle.  If unsure, or if it is near the limit, use a transistor to switch your relay coil.

Here is a good primer on adding a transistor to switch the relay coil.
You probably want PNP, so it turns on when the rig's TX output shorts to ground;

But you might also want a capacitor to debounce the circuit, just be aware that this
may add some delay in keying an amp, so you want to add a much smaller capacitor
than they suggest in the below circuit, and you want to measure that switching delay
with an oscilloscope and add some keying delay on your rig so you don't "Hot Switch"
the amp;

Again, if you find the specifications for how much current in milliamps that your Flex 6300
can switch on the TX out port, and if your relay coil is less, you are fine without anything
extra.   For me, just for added idiot proofing, I added an external key circuit like you want to,
so I could key on multiple things like the amp, a transmit sign, etc.


Photo of John  - W8AGS

John - W8AGS

  • 48 Posts
  • 13 Reply Likes

You can find the max current the TX port can sink in the Flex 6000 Harfdware Reference Manual. My 6600 max is
140ma. Not sure for the 6300.

Photo of Greg - N8GD

Greg - N8GD

  • 239 Posts
  • 88 Reply Likes
The 6300 TX Output is also 140 mA @ +40 VDC maximum.  This is from the original FLEX-6000 Hardware Reference Manual, V1.2, dated 5/11/2014, which was published when the 6300 came out just prior to the 2014 Hamvention.
Photo of Roberto EA2CNU

Roberto EA2CNU

  • 11 Posts
  • 1 Reply Like
These diagrams that I attach would be correct?
The data of the solid state relay are:

The data of the miniature relay are:

Thank you very much for the help.

Roberto EA2CNU