CTCSS add on for old rigs- has anybody done this?

[G0LQU]

Basically, the CTCSS tone is inserted on the wiper of the deviation control. You definitely do NOT want to insert the tone in the microphone circuit.

Glen, K9STH

Thanks for that Glen - well I did insert a CTCSS tone into the mike (generated on my laptop) and it did open my local repeater. (GB3PO). I assume the tones are filtered out on the repeater output as they are of course audible! The problem is the repeater needs a continuous CTCSS tone to hold it open even with audio present. I need to get at that deviation control wiper to narrow the deviation (as that's another problem with this repeater - its based on PMR equipment which has a much tighter spec. that amateur gear). So if the prject progresses, that's where I will insert it! Thanks again. Peter G0LQU

[G0LQU]

In a word...
ComSpec...
They are cheap and easy to install in just about any radio.

That reminds me...
I need to get an encoder for my Kenwood Brick.

Thanks for that Sue - I did take a look at the ComSpec units but they are too large to fit inside the FT290 case(!). So i will try for a homebrew miniature project as suggested by others here. Thanks for taking the time to respond.
Peter G0LQU

[G0LQU]

If you only need 1 tone you can build a simple 555 and network for sine-wave encoding. 567s are good also.

The Communication Specialists are about the best ready built on the market.

You can buy the chip that Communication Specialists uses if you did need to build your own, but it would be cheaper to buy the "ready to go board".

Thanks for that Don - I'll quite probably go down a similar route!
Best
Peter G0LQU

[G0LQU]

With an FT290 Mk1,you can insert the CTCSS tone at the same place the 1750 Hz tone goes in.
I was lucky enough to have access to a Deviation Monitor at work,& I found that with my homebrew CTCSS generator,I could obtain sufficient deviation with ease,using that input.

I built a 567 CTCSS source from a circuit in "AR" magazine,by Will, VK6UU.
If you Google you will probably find it.

I added an emitter follower to it,if I remember correctly,---it was ages ago.


All noted thank you! I will certainly look into the 567-based unit. Never come across the FT290 frequency drift problem though, but will watch out for it now!
Many thanks
Peter G0LQU

At the time, the only thing we had which needed a CTCSS tone was a 2m to 10mFM "gateway",so I only needed one frequency.
I made it very small,as there isn't much room in those radios.

It worked OK,but when I spoke to VK6IQ through the "gateway",he reported that I sounded a bit off frequency.
We went to 2m Simplex & checked,with the CTCSS board removed--still the same.

The work frequency counter verified it.

Yep! the FT290 had developed the magic "slightly off frequency" disease,so I had more to worry about than CTCSS tones.
When I pulled the radio to pieces,the CTCSS board was chucked in the toolbox.

I never really sorted the '290 out,but I found the CTCSS board early this year,& fired it up,--still works!

73,VK6ZGO

All noted thank you! I will certainly look into the 567-based unit. Never come across the FT290 frequency drift problem though, but will watch out for it now!
Many thanks
Peter G0LQU

[G0LQU]

Don't forget u may want to add a 10-20k siries resistor for isolation between the encoder output and dev pot arm so you don't inadvertantly load down the mic audio. Those ComSpecs modules have plenty of output.

OK thanks for the warning! duly noted!

Peter G0LQU

[N6VLH]

The Azden PCS-3000 just uses a 74c00 IC. it then goes into a 100k resistor which meets just after the mic output volume control. Uses a couple of diodes for switching and a regulated power source at one of the inputs. can use a simple regulator IC in place of the reg. supply. All you do is dial in the frequency you want. need a way to readout the frequency. can just buy a simple frequency meter for about 15 bucks. here is where the user manual is located http://www.rigpix.com/azden/pcs3000.htm I am sure a 555 timer circuit would work too. better yet would be to make your circuit using a cmos device rather than a TTL type. That way you don't have to worry about having exactly 5 volts to make it work.

[VK6ZGO]

I Googled & found the following two sites:

The first one shows the correct connections on the FT290R for CTCSS,plus a PIC based gen,
The second is Will,VK6UU's 567 gen.

http://www.spikey-mike.com/radio/ctcss.html
http://www.vk2bv.org/wars-files/p_fig2a.gif

I haven't included it,but vk2bv has a PCB for Will's gadget.


73,VK6ZGO

[G0LQU]

The Azden PCS-3000 just uses a 74c00 IC. it then goes into a 100k resistor which meets just after the mic output volume control. Uses a couple of diodes for switching and a regulated power source at one of the inputs. can use a simple regulator IC in place of the reg. supply. All you do is dial in the frequency you want. need a way to readout the frequency. can just buy a simple frequency meter for about 15 bucks. here is where the user manual is located http://www.rigpix.com/azden/pcs3000.htm I am sure a 555 timer circuit would work too. better yet would be to make your circuit using a cmos device rather than a TTL type. That way you don't have to worry about having exactly 5 volts to make it work.

Hi and thanks for the info and link. I had thought about a simple astable multivibrator using a CMOS logic chip with a crystal oscillator control. I hadn't realised how helpful all you guys and galls were. Thank you!
Peter G0LQU

[G0LQU]

I Googled & found the following two sites:

The first one shows the correct connections on the FT290R for CTCSS,plus a PIC based gen,
The second is Will,VK6UU's 567 gen.

http://www.spikey-mike.com/radio/ctcss.html
http://www.vk2bv.org/wars-files/p_fig2a.gif

I haven't included it,but vk2bv has a PCB for Will's gadget.


73,VK6ZGO

Thanks for that - much closer to what I had in mind. I need a few hours to digest it all! Thank you so much one and all - I've gone from zero info to an embarassment of riches in 36 hours. A great resource.
Peter G0LQU

[K7JEM]

One thing to remember about CTCSS is that the tone frequency has to be pretty close, like +-1% or so. If your tone is supposed to be 100Hz, and your encoder has drifted to 102Hz, it probably won't work. Drift on free running oscillators is going to be a problem, unless you use very tight specs on the caps, and keep the thing at a fairly constant temperature. Normal caps will easily drift 5% over a 20 degree temperature change, so as the unit warms up, it might require continuous adjustment.

Your best bet is to get a commercial unit, some are very small. I had one years ago that readily fit in an Icom 2AT, there should be no problem finding one for the larger radio.

Joe