Greetings All,

I'm working on designing/building a new PCL (Pilot Controlled Lighting) controller for our airfield (Simsbury Airport). For those of you not familiar, pilots are able to key their mic (over VHF radio) a predesignated number of times (3, 5 or 7 times - sometimes with different brightnesses at each level, sometimes not depending on the airport) within a short timespan (5-10 seconds) to turn on lights at untowered/unattended airports.

Basically, from a very simple standpoint, the signal pathway goes: VHF Receiver > IDEC SmartRelay with timing programming > Larger Relay that can handle the full power load

I've got the SmartRelay programmed up with my code to receive in an analog voltage from a VHF receiver then trigger its various sequences to turn on/off the larger relay (and thus the lights).

What I need help with is figuring out the best solution for the VHF receiver where I can generate some sort of analog voltage (anywhere in the 3-10v range, 4-20ma range) whenever there is a squelch break. Not afraid of soldering something myself or just getting something (economical) from off the shelf.

FWIW, I am aware of the threads here: https://forum.allaboutcircuits.com/threads/designing-a-lights-controller.151275/
and here: https://forum.allaboutcircuits.com/...ling-the-lights-at-a-private-airfield.148305/ but there wasn't anything I found that seemed to answer my question.

Appreciate any help anyone can provide!
-Brad

 

Need to know what the squelch signal looks like and what output you want from that.
Do you have an oscilloscope?

 

What is your receiver model, ? the service manual will help you better...

 

Need to know what the squelch signal looks like and what output you want from that.
Do you have an oscilloscope?

I could pretty easily acquire a simple oscilloscope but don't have one currently. I'm starting a little more basic on the receiver side as well. While I have a handheld airband VHF radio, I'm ok working with any receiver. I wasn't sure if there was any type of purpose built VHF airband receiver that can trigger those voltages rather than reverse engineering an existing one.

 

Can you not use Ctcss boards??

 

Can you not use Ctcss boards??

I guess I had a misunderstanding of what CTCSS was - I thought it was a decoder board detecting the introduced tone to prevent interference between users on the same channel. Airband VHF doesn't utilize CTCSS (That I'm aware of). Can you recommend any specific hardware?

 

I could pretty easily acquire a simple oscilloscope but don't have one currently

Well, we can't really design a circuit until we know what the signal looks like.

 

I read in a reference that the typical squelch delay time is 50-150ms for the squelch to operate after a transmission ends.
So, if that generates a burst of random noise at the audio output for that length of time, then I would think you could rectify the noise to get a DC pulse, and the run that to a comparator with an adjustable trigger level to respond to the high amplitude noise, but not to lower level audio.
You could add discrimination at the comparator output (if needed ) to ignore signals longer that the longest squelch noise burst (which are likely audio).

 

The idea of ctcss is a sub tone over the carrier, then the receiver will pick it up and you can use this to switch on a relay, to put the lights on , . Yes they are used normally for multi use on one frequency like pmr radio, to prevent other users from listening in, the ctcss has an output that can operate a relay or open the squelch circuit.