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From: brian@sdcsvax.UUCP (Brian Kantor)
Newsgroups: net.ham-radio
Subject: Re: ICOM 22S mods
Message-ID: <842@sdcsvax.UUCP>
Date: Fri, 3-May-85 10:06:57 EDT
Article-I.D.: sdcsvax.842
Posted: Fri May  3 10:06:57 1985
Date-Received: Mon, 6-May-85 00:20:35 EDT
References: <16846@mgweed.UUCP>
Reply-To: brian@sdcsvax.UUCP (Brian Kantor)
Organization: UCSD beer & pizza society
Lines: 24

Since the synthesizer in an IC22S uses 8 bits to set the frequency, it
is quite easy to drive it with a microprocessor.  I use exactly this
scheme in a remote base, where the touch-tone commands are converted
by the Z80 system controller into the synthesizer input to put the radio
on any frequency in the band.

But a more practical idea:  since the endings of all frequencies at .015
spacings are unique in the top two MHZ of two meters, you can easily use
something like a 2716 to translate 9 bits (two BCD thumbwheels and a 0/5
toggle) into the synthesizer input.  That way you can dial up any
frequency the radio will do directly.  There are 11 address bits on a
2716, so you can even use the other 3 512 word partitions for special
effects - or (this is nifty), switch one of the address lines with the
transmit line, which gives you the ability to have custom offsets for
repeaters and such - since the transmit and receive frequencies are
separately stored and separately loaded into the synthesizer from the
prom.  At about $6 for the switches, and $3 for the chips, its a cheap
mod!

	Brian Kantor, WB6CYT	UC San Diego

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