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Vintage Amateur and Military Radio Amateur/military receivers and transmitters, morse, and any other related vintage comms equipment.

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Old 30th Mar 2016, 6:06 am   #1
echelon
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Default CTCSS modules for retrofit into 30+ yr old TXs: recommendations?

I have a small collection of Icom VHF/UHF hand-held transceivers, dating back to around 30 years ago.

Although hardly as flexible as modern current cheap Chinese keypad radios, rigs such as the classic IC-2E / IC-4E (or the IC-02E family) have a rugged charm and good sensitivity on RX that fully-justifies them being kept warm and working.

Therein lies the problem. Whilst being able to produce the now-obsolete 1750Hz traditional access tones, these rigs have no integral means of generating the now-mandatory CTCSS 'tone squelch' for repeater access.

Any recommendations/experiences/sources of small inexpensive modules that can be shoehorned into these venerable radios, to allow them to again irradiate the UK's amateur radio FM repeater 'network'?
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Old 30th Mar 2016, 7:51 am   #2
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Default Re: CTCSS modules for retrofit into 30+ yr old TXs: recommendations?

CTCSS is only really needed for repeater access, but many of the repeaters will refuse a signal with wider deviation than the 12.5kHz channel spacing (introduced since their day) dictates. So you'll need to turn the deviation down as well. On the receive side the IF filters will be too wide in theory to to do a good job of excluding adjacent channels in the new scheme, in practice, with the reduced amount of traffic on the bands this won't often be noticed.

It's a bit of a shame that the change in band planning sidelined so much still functional equipment. The reduction in active population in recent years has meant that there was never any need for the increased capacity. Right now, at prime drive-time there is one QSO on 2 metres and none on 70cm. As a compromise, at lest a few 25kHz channels could have been kept.

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Old 30th Mar 2016, 6:22 pm   #3
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Default Re: CTCSS modules for retrofit into 30+ yr old TXs: recommendations?

To the best of my knowledge at least one of our long-established local repeaters no longer responds to 1750Hz toneburst - only to CTCSS - following the most recent update to its control logic. If this pattern is being repeated elsewhere it suggests that CTCSS is becoming difficult to be without. I noticed a request for an original or third-party CTCSS module for an FT690 in these forums just a few days ago.

In the old days if your radio didn't have 1750Hz toneburst built in you could 'whistle up' the repeater, but now it seems we're going to have to practice humming and talking at the same time. A good baritone voice may help...
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Old 30th Mar 2016, 7:50 pm   #4
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Default Re: CTCSS modules for retrofit into 30+ yr old TXs: recommendations?

I used one of these FX465 chips in the past.
 
Old 31st Mar 2016, 7:21 pm   #5
Jon_G4MDC
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Default Re: CTCSS modules for retrofit into 30+ yr old TXs: recommendations?

I was absolutely against CTCSS when it was first introduced. Looking back on it now I can't explain why. It is far superior to the 1750 system with the only nuisance being that not only do you have to have the correct channel, you have to have the right tone.

For old times sake I recently bought an FT202 - crystal controlled 6ch 2m portable. Getting the R6 crystal to R5.5 for the local 12.5kHz box was easy enough but it is CTCSS access only. The FT202 had the usual 1750 gen fitted in the base just above the charging terminals. That came out and in went a CTCSS board found in early Tait base stations. Part Number is now unsure - Selectone or Norcomm possibly.

These are just op-amp based. They can decode if you can be bothered to wire it up (which I can't). The beauty of them - they are tuned by a pot. Setting to 77Hz for the local box was easy.

The fun bit came on a trip away to Herefordshire where, unexpectedly, the local box is on the same RF channel but it runs a different CTCSS. That was a nice surprise.

Not a problem! Off came the bottom panel and after a few minutes of pot twiddling we were in business there by trial and error. Naturally I had to tweak back again on coming back home.

All part of the fun. Yes I could have used an FX335/365 based board ex PF85/PFX or similar. This is about 1"x1.5" overall so smaller than most.

Last edited by Jon_G4MDC; 31st Mar 2016 at 7:38 pm.
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Old 31st Mar 2016, 11:15 pm   #6
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Default Re: CTCSS modules for retrofit into 30+ yr old TXs: recommendations?

Quote:
Originally Posted by Jon_G4MDC View Post
I was absolutely against CTCSS when it was first introduced. Looking back on it now I can't explain why
I still only approve of it for repeater access - whenever there was a good 'lift' on it used to be mayhem with people opening up three or more repeaters when trying to access their own local repeater using 1750Hz. At least CTCSS allows you to target a repeater by area - you might even want to target a distant repeater during a 'lift' without waking up your own local repeater on the same frequency. With CTCSS, you can do that.

When used in the 'channel privacy' sense (ie, using CTCSS gated receive squelch) for amateur simplex operation, CTCSS is just a menace. It just makes it even easier for amateurs to ignore each other than it already is, and can lead to people who are using it not hearing you when you enquire if their frequency is in use.

It is however genuinely useful on other 'public' radio systems where there are a limited number of frequencies and potentially a lot of unrelated groups using them, most notably on PMR446 (Europe) and FRS (USA).
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Old 1st Apr 2016, 9:22 am   #7
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Default Re: CTCSS modules for retrofit into 30+ yr old TXs: recommendations?

Agreed - as I said I never bother to wire the decode side.

I found a pic of the module I used for the FT202. Does anyone recognise it perhaps?
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Old 2nd Apr 2016, 6:36 pm   #8
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Default Re: CTCSS modules for retrofit into 30+ yr old TXs: recommendations?

Have a look at www.cstech.co.uk. I recently bought a CTCSS encoder module from them to install in a KM450 ex PMR set. They do a comprehensive range of encode/decode modules and DTMF also.
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