Batboard

What is the best way to accomplish this for the purpose of broadcasting dispatch as a live audio feed?

try a Audio ground loop isolator. Can be found all over the online auction sites fairly cheap.

birminghamWILDCAT wrote:What is the best way to accomplish this for the purpose of broadcasting dispatch as a live audio feed?

There is a low level squelched filtered audio output on the Spectra. This output is independent of the volume control. You have to add a capacitor inside the radio.

XTL I do not have a clue... But a small 600 ohms coupling transformer to isolate the bridge speaker amplifier would give you good isolation.

Will that isolate everything in the spectra audio output from being grounded when he plugs into the computer.

Well, here's what were thinking of doing. We want to use a desktop model left over from a station that got combined with another station to hook to a PC here at Fire Alarm for the sole purpose of broadcasting F1 DISP or dispatch on a live feed either on our website or another.As Fire Alarm is a noise sensitive area, we will not require a speaker for this unit. I was thinking along the lines of somehow rigging the speaker wire to an audio imput wire. However the Motorola Speaker wire is a two lead and is probably too large to attempt to splice into a standard 3.5mm input cord. So i am faced with a true dilemma. And the chief doesn't want us spending city money to get the local Motorola people involved but he does like the idea.

If you ground either side of that audio output on a spectra, your going to ruin the audio Circuits. That is why you need something like a ground loop isolator. The cabinet on a computer is grounded.

You didn't mention if the radios were all front mount or not. Also you didn't mention if the radios were not
the high power versions. The reason I bring this up is the cable connections are different on the high
powered units.

On the Spectra low and med front mount, you can get fixed audio out on pin 11. Use pin 8 as the ground.
You will need to add a 1.0 mf cap in series with the pin 11 audio to prevent an issue with the DC bias
voltage on the line.

On the XTL5000, you have the same issue. You need to be cautious of where and how you make the
connections. On the low and mid power XTL mobiles, there is this funky 26 pin connector on the rear.
Pin 21 is the RX audio out at a fixed level. It is not controlled by the volume control. Again measure the
voltage on this pin to make sure there is no DC bias. It is a good move to couple this pin through a 1.0
uf cap. The radio will let you use the rear connector for a mic input on pin 23. You may have to use a
cap on this pin depending on the type of mic you use.

The PTT is on pin 16. You can get the connector from Motorola with part number HLN6863A. Extra pins
are part number 3980034F01, I think for a pack of 10. Pin 15 is the emergency and needs to be tied to
pin 14 which is ground.

On a second note, depending on the mic you use, there is a software external mic gain that you might
have to raise up in the XTL mobile. There are 2 places that come into play here. One is in the
"ADVANCED" tab. Go to the "AUX PTT AUDIO SOURCE" and there are 2 options. One is "AUX_MIC" and
forget the other selection. Depending on the mood of the programmer at Motorola, this selection has
flip flopped back and forth. If you don't get mic audio, go back and make the other selection. This is
one area that has been a moving target with the different versions of the CPS. The other area to go
into is the "TX AUDIO CONTROL PER MODE". Down about the middle of the page you will see some gain
settings. Here is where you have the external mic gain adjustment. It will not effect the normal mic
of the front panel. The exact number you need will depend on the mic your using. Bear in mind that the
radio from the plant will not do much more than 4.2 KHz deviation. That's just the way Motorola is
setting up the radios these days. Can't help you on a narrow band deviation setting. Haven't had to
cross that road yet.

Jim

Jim,
As far as the power goes I am not sure, I will have to find one that isn't currently tied down to something and match the serials. I do know that the system is set up as such:
Most radios are either Motorcycle or Dash mount XTL5000's. However some stations and the unit we've picked for this is a modified dash mount Astro Spectra for desktop use (AC to DC inverter, speaker, and desktop mic) As of right now it has a connector from the radio that went to a station control unit, i.e. intercom, lights, and this nifty light switch that each unit has to flip when going out of service, on a call, or for the nightly 8pm test response. This is not hooked to anything, we simply have the radio in a desktop mount next to the PC we intend to use for the broadcast. The radio is off as of right now. The only remote mount units we use are in the newer rescue ambulances (dual head) and in some Engines and Trucks (single head).
As for other factors, I know this:
Fire Alarm is licensed to 155.17500, KNIH899, however, without digital scanners you can only hear the dispatcher. This is likely because (and I'm venturing here because I haven't been the communications director for very long and I have no idea) either we have a trunked system on that frequency or this is a simulcast of the trunked system in the 800's. I know someone told me that these 5k's were on 800something based on the serial, but when the dispatcher calls "Time now is 8pm central standard time, this is KNIH899 testing with all stations, the alert level is yellow", this leads me to believe that the system is at the 155.17500, the frequency that call sign is issued to. The city's trunked system has the call sign of WPZE311, all in 800mhz band. This is all extremely confusing to me and every time I ask Allcomm exactly what all this means they tell me ask the chief if I can tell you and the chief is like why do you need to know your job is to make sure we have what we need not to make sure it works right. So I don't know. The city of Birmingham has been in a bit of a tumble since Mayor Langford was convicted. The new mayor, Mayor Bell, has everybody going huh? and hes even started buying Kenworths like crazy to replace the city's nearly brand new fleet of International heavy duty public works trucks. This is all so confusing and I'm starting to miss riding the engine. But it also looks like fun if i learn enough.

BikerScout wrote:If you ground either side of that audio output on a spectra, your going to ruin the audio Circuits. That is why you need something like a ground loop isolator. The cabinet on a computer is grounded.

Something like this?
How would I go about connecting my radio to this?

I have used an astro spectra to provide an online feed. I just connected a 3.5mm jack to an old speaker wire i had left over from a spectra, used a ground loop isolator exactly like the one in the photo, and plugged it into my computer input. Works perfect. I have since switched to a kenwood that i had left over for my feed but either way i've had no problems with either one for a feed.

hope this helps!