Batboard

Hello all!

I'm looking at setting up a VHF-based POCSAG paging transmitter sometime in the near future. I had planned on using a 50w Maxtrac for starters, but then I read this on http://www.qsl.net/kb9mwr/projects/pager/plan.html:

...must be capable of transmitting +/- 4.5 Khz FSK data. The transmitter must have a low audio responce, around 20 to 50 hertz. You will need a direct (varactor or varacap) drive to transmit pages, and a discriminator output to monitor pages. Most 9600 baud "data ready" radios will work. The following radios are capable of being FSK'ed real hard:
...
Motorola Mitrek, Maxar
...

I don't want to run an old rock-bound radio for this.

I did read the Batlabs page describing a 9600 packet modification for the Maxtrac, but I'm not knowledgeable enough to determine if the hacked radio would be usable in this case. How would I find out if the Maxtrac meets the spec?

Also, what other synthesized Moto rigs would work well for this sort of thing?

Feel free to point out anything I forgot (or didn't know)


Keith

16-pin Maxtrac is no problem. Use the "flat TX input" on the 16-pin connector.

A Maxtrac/GM300 will work just fine, using the flat audio input. Seen several commercial paging systems set up using GM300s with a power amplifier (and quite a few of them broken and throwing spurs everywhere... )

I've also used SM50 & CDM series radios for Pocsag paging with good results (flat TX input, as was mentioned). Radios which most certainly won't do it are MCS2000 & Astro Spectra...at least I haven't been able to get them to do it.

Todd

I've recently had success using a 40 watt M1225 for an in-house system...(Flat tx audio) and 4.3 kc Good luck!

Those of you that are doing this already, what kind of encoder are you running / would you recommend?


Keith

I know this is an old post but here goes:

I'm looking at doing something very similar shortly with a GM350 (4CH).

What's the best way to connect sound coming from the speaker out jack (3.5mm) of a PC to the accessory port of a GM350.

Thanks.

Use a 2.2uF capacitor and a 2k resistor in series with the Mic hi, + of the capacitor to the Mic input on radio. This matches the input and blocks the DC on the mic line.