If you have an ohm meter, you can clip one lead to the chassis, and the
other lead to one of the leads of the DC cable.  Usually, one lead will
give you a reading of 0 ohms, and the other one will be somewhat higher,
and maybe even infinite if the radio is turned off.  The lead that gives
you a 0 reading is the negative one.  Then, you just have to know which one
on the power supply is negative, which you can determine with a volt
meter.  Incidentally, don't assume that all radios have diode
protection.  The TM-G707A does, but others may not.  I once had a Uniden
PCS5000 that blew the fuse when I connected it up the wrong way, which was
lucky but annoying since it didn't use a standard length fuse.  The worst
case is that you might cook the radio or burn out the supply.

Steve

On Friday 1/7/05 08:05 John Miller wrote:

>Well, both are good radios.  As for the power supply, I either get sighted
>help to figure out which wire is which and go from there, or I look at
>another radio with the same cord and figure out which side of the plug is
>which and then I follow the cord out, then I put a piece of electrical tape
>on the negative wire so I don't have to trace all the time.
>----- Original Message -----
>From: "Eric Patterson" <[log in to unmask]>
>To: <[log in to unmask]>
>Sent: Thursday, January 06, 2005 11:33 PM
>Subject: accessible VHF equipment
>
>
> > Hi all, I am a new member on this list and have a question about VHF
> > equipment.  My name is Eric Patterson and my call is kb7vfr.  I have been
> > an
> > amateur radio operator since 1993.
> >        Currently, I have an old FT-470 portable radio, whose battery does
> > not
> > maintain a charge anymore.  I am looking at getting a new VHF/UHF radio.
> > Here are the options I am considering:
> > 1.  getting a portable such as the Icom IC-t90 or Kenwood TH-f6a.
> > 2.  getting a mobile unit like the Kenwood Tm-g707.  The advantage to
> > going
> > this route is that it might allow me to install a voice synthesizer for
> > checking the frequency.  However, because I have no useable vision, I
> > would
> > have trouble hooking up the power supply.  Please send recommendations on
> > accessible mobile or portable VHF radios and instructions for hooking up
> > power supplies.  Thanks in advance.
> >
> > Eric Patterson
> >