From: crh@hpcvaac.cv.hp.com (Ron Henderson)
Subject: Re: Using the FT47 for packet
Organization: Hewlett-Packard Company, Corvallis, Oregon USA
Date: Fri, 2 Oct 1992 18:38:00 GMT

In article <1ag916INNq8d@usenet.INS.CWRU.Edu>, au297@cleveland.Freenet.Edu (Jim Evers) writes:
|> 
|> In a previous article, johna@icsbelf.co.uk (John Agnew) says:
|> 
|> >Hi all,
|> >
|> >I have an FT 470 which I wish to use with my PacComm Tiny-2 for packet

For those that may have missed it Sept of last year :-) :

>In article <1991Sep27.033057.22510@agate.berkeley.edu> ajk@garnet.berkeley.edu (Adam Jacobs N2LAW) writes:
>>
>>1.  Does anyone have the exact wiring specifications for the Yaesu
>>side of the cable to the TNC?  Is "where do I plug it in" a stupid
>>question?  Presumably the MIC and EAR jacks, but how is the MIC jack
>>configured -- if it's (as the manual specifies) a 2-conductor
>>micro-mini phone jack, then what do I do with the PTT signal?  Or is
>>there something else I should know?  I can wire the cable all right,
>>but I have no appetite for blindly trying configurations on an
>>expensive piece of equipment.  Do I have to open the unit up?
>
>The FT470 is wired like an Icom. You connect the audio from the TNC
>to the tip of the mike plug through a capacitor and connect the PTT
>to the tip with a resistor. The Icoms and Yaesus use a "leaky ground"
>to generate PTT. The problem with this approach is there is a tradeoff
>between rapid PTT and audio level and response. Typical values are
>.1 ufd and 2.2 k ohms. The RC time constant limits TR turnaround.
>
>A better scheme is to use a tiny audio transformer sideways like so,
>
>
>TNC PTT----------))))))))))))------------> radio tip (audio)
>                 ============
>TNC AF OUT-------))))))))))))----X--------> radio sleeve (gnd)
>                                 |
>TNC GND--------------------------|
>
>You can rip a suitable transformer out of an old transistor radio or
>buy one from Radio Shack.
>
>>2.  Suppose I want to run the HT off a 12V external power supply.
>>Where do I feed the power?  Not the battery terminals, I hope.  I
>>would have expected a DC power jack somewhere on the unit, but again I
>>don't see anything except a mysterious looking rubber plug-which-might-
>>hide-a-jack-but-I'm-afraid-to-pull-it-and-look.  The manual, again,
>>says nothing about this.
>
>The 2 meter only model does have a power jack under the rubber plug, but
>the 470 doesn't. There's a place on the board for one, but Yaesu recomends
>that you use a PA-6 module instead. This is a module that mounts in place
>of the battery and contains regulators for running the radio and charging
>a battery connected to the bottom of the PA-6. This is a really nice
>accessory and well worth the price.
>
>>3.  Anything else (useful modifications, hints, caveats) I should know
>>about the FT-470 (or PK-88?)
>
>Just the standard remarks that you should carefully set the audio level
>so you wind up with a 3 khz deviation for your tones. Don't exceed that
>level or many units will have trouble decoding your packets. Make sure
>you have the power saver on the 470 turned off when you run packet or
>you'll miss the first part of every packet. This can drive you nuts
>because everything seems to be working but nothing prints.
>
>One last note. Use a separate antenna and use shielded cables on your
>TNC. Otherwise the RFI and RF feedback will ruin your packet operation.
>
>Gary KE4ZV

Ron WA7TAS
crh@cv.hp.com