Mod to add PL Tones

Add CTCSS PL Tones to Your Old VHF Rig

Last week I gladly accepted a free Azden 2m FM transceiver model number PCS-4000 that was offered to me.  You have to love the old free stuff!  The only capability this 25W rig was missing is the ability to transmit CTCSS PL tones or sub audible tones to activate a repeater.

I found the manual and schematics online and found that this rig was built to accept a tone generator as an add-on. See below.

PL Tone Mod Circuit

Below is a photo showing the jumper locations for the tone input.  I soldered some leads with a home brew disconnect to easily remove the cover in the future.PL Tone Mods

Below is a photo showing an added 1/8″ mono jack for the input tone.

PL Tone Mods

For an input tone, I used an Android cell phone with a frequency generator App to generate the PL tone.

PL Tone Generator

I can experiment with other ways to generate the tone such as an Arduino with RC filters etc.  I can also try to insert a 700 Hz tone with my Arduino keyer for MCW.

Below is a photo of the rig set up for a local repeater.

Completed Mod to add PL Tones

So now to quote Pete Juliano “Bob’s your uncle”!!!


Mike, AB1YK

If you have found a spelling error, please, notify us by selecting that text and pressing Ctrl+Enter.

Follow or Contact Us: