CTCSS Tones For Older Radios
88.5Hz Tone Generator
From my bad location deep in the pits of Sandton I can just reach the Sandton repeater (145.700) up on the water tower near Wm Nicol Drive if I look north, and if I look south I can definitely reach the ZS6TJ repeater (145.650) on the Carlton Centre. The latter is a very convenient repeater for me to use as it will put me in contact with most of the people I need to talk to from my home QTH. The only problem is they were forced to put a 88.5Hz CTCSS sub-tone on the repeater because otherwise it was prone to false triggering.
And the problem is that my old FT-480R was built in the early 80’s, before the days of CTCSS. However Yaesu had the foresight to put a little connector at the back of the radio where a 35mV signal can be injected (in addition to a burst, but the two signals are paralleled) together with a convenient PTT signal marked 13.6volt. So the search was on for a CTCSS tone generator. I didn’t even bother to look for an original part as the radio is very old, although Yaesu makes mention of a FTS-63E device that should fit the radio.
It didn’t take me long to discover that OM Thys Maree ZS6MJM in Pretoria is building some excellent tone generator boards for the Magalies Club ZS6MRK. Very small and compact, it requires a 5-12v in and puts out a perfect tone that can be level-adjusted. On the bench it immediately gave me a beautiful tone, I adjusted the level and proceeded to install it in an open space in the radio cabinet. Fortunately the FT-480R has a bump on the bottom for the speaker, and there in the corner was a perfect hiding spot for the board.
I haven’t been able to trigger the repeater yet because I soon discovered that the power to the board was not 13.6v as the diagram says, and I suspect a loose connection or something. Nevertheless, I can highly recommend this little board as an add-on to an older rig as it has all the ingredients of a “Life-Extender” for older radios.
Comment sent by e-mail from Thys:
Dankie vir die terugvoering so gou. Baie netjiese installasie en terugvoering! Hoop net jy kry die probleem en dat dit nie ‘n droë las op die bordjie self is nie.
Miskien net hoe die ouens reken om die vlak van die toon te stel:
1. As jy nie ‘n deviasiemeter het nie gebruik dan ‘n ander radio op simpleks waar die toon ook op ontvangs aan is. Stel dan maar die vlak totdat die ander radio aanskakel.
2. Sou jy wel ‘n deviasiemeter tot jou beskikking het – die mense praat van +-500 tot +-600 KHz deviasie net vir die toon alleen op ‘n 12.5 kHz kanaalstelsel.
Hoop jy kom reg.
Thanks Thys for the good advice. I agree with what you say and I took my radio in to have the deviation measured. It seems to be working well now.