My problem with all of this is the issues with Motorola (and other
commercial radios as well) hookup.
Depends on the radio. Maxtracs (16 pin), GTXs, Spectras are so simple to interface that it's almost a non-issue. All the signals are on the back...discriminator audio out, audio in, ptt, and ground. And, unlike most if not all ham-grade equipment, are can handle the rigors of constant duty cycle rather than the ICAS rated ham equipment.
The speaker isn't a speaker and ground it's a floating set of two wires and
they bias it with voltage, and the PTT and Mic interconnection aren't that
obvious either, as you may need to put resistors and caps in line to filter
and cause the radio to see the correct voltage so that the PTT enables.
Audio floats above ground in a balanced system so as to minimize common mode interference. On the radios I've worked on, especially Batwings, I've noticed no bias voltages on speaker leads. Besides, you really should not be using speaker audio to drive a URI anyway. Find the discriminator output, and use that. Friends don't let friends use VOX on asterisk; it makes it simple to interface, because, in the end, you only need 3 leads plus a ground to get the thing to work if you use the DSP processing to derive your COS and PL decode.
You may, and I say may, depending on how you send audio back in (flat vs mic), have to use a 47 puff in the mic line IF there is bias voltage on it for a condensor mic. Otherwise, put a pull up on to the PTT pin, and ground it for PTT. The URI can handle push to 5v or pull to ground as the signal for PTT; it's looking for the voltage transition to determine (as best I can tell) whether or not it's a valid state change and act accordingly. Heck, I even have some dry contacts on a broadcast studio audio console muting relay that can properly signal a URI to turn on the cluster transmitters.
It's not hard, nor complicated, if you're using the right equipment.
On the GP300's, I don't think you need that adapter as they have a 2 jack
location already provided.
I think what I'm going to try, just because I have one and all the parts is
my TH-F6A, you can put it in 9600 baud packet mode and get to the
discriminator and mod input directly, and it has COR (but alas, it's just
connected to the meter, not really to a valid COR on CTCSS). but I also have
a TS-32 laying around so I may make something really small. The radio is
way over kill, but hey I have it and it's straight forward to connect up.
If you have a discriminator output, you don't need to have a hardware COS. That's what the DSP is for, as well as CTCSS decoding. A lot easier to interface.
···
On 6/18/12 12:09 PM, Alan Adamson wrote:
--
Bryan
In this world, you must be oh so smart or oh so pleasant.
Well, for years I was smart. I recommend pleasant.
You may quote me.
Sent from my MacBook Pro.