Batboard

I am trying to use a VHF GM300 hooked to our UHF GR1225 to transmit QCII alerts over our repeater. My plan is to use a 555 circuit triggered by External Alarm PIN on the GM300 set to active low. The 555 would then open a relay that connects the PL Dect pin on the GM300 with the PTT pin on the GR1225 for about 30 seconds. First off, is this the easiest/cheapest way to do this? I only want transmit our calls and the GM300 does not auto reset.

I have very little experience building circuits so I need a little help. I went to Radio Shack with a lot of help from the internet built a 555 circuit on a breadboard. It worked great with a 9v battery. As soon as I hooked up the radios power (PINs 7 and 13) to the breadboard the circuit stopped working and I can’t get it to work again with the 9v battery. Is the radio too much for the 555 chip to handle? Should I be using something between the radio and the 555 chip?

Any help would be greatly appreciated!

The 555 was originally developed for a 5v supply. But, most modern versions now tolerate higher voltages up to 15v if you incorporate a 100 ohm limiter resistor in your design. Some of it depends on the quality of the 555 you purchase. RS sells "reasonable" quality, but you can expect variations. If the circuit is on a breadboard, it is simple enough to drop in a new timer, and try again.

Is your goal to set up a crossband repeater that is only active when you xmit QCII on VHF? Do you intend to alert the GM300 with the first set of QCII and then xmit a second set of QCII tones through UHF?

The plan is to open up a one way crossband (vhf->uhf) repeater for about 30 seconds. So we can hear the voice message of the page on the uhf repeater. No second set of tones.

Thanks.

Joes,

You can do this already with the GR1225,

The 16 pin on the GR1225 is the same as the GM300 as long as you program the pins in the software.

Programming pin 8 on the GM300 to go active low when the proper paging transmission is sent the active low tied to pin 3 on the GR1225 will key the station. Pin 11 on the GM300 tied to pin 2 on the GR1225 will pass the RX audio from the gm300 to the Mic high TX in the GR1225 which can include the tones.

This will probably only work as planned if the GM300 only receives transmissions when there are paging tones sent as this will also key the 1225 on every transmission unless there is a specific PL/DPL tone used when only paging tones are sent.

CoM

What Chart pointed out is where I was going. However, I also wondered if you were going to QCII protect the link AND attempt to pass the same tones through. The tones won't pass, but the voice will until the timer dekeys the radio. If that's all you're interested, it should work. You may want to consider adding ADD logic to the PTT so that the repeater dekeys at the end of the voice message instead of waiting for the timer to count down. The timer will set the window. CSQ or PL det will force the PTT.

Thank you for your help guys!

If I set pin 8 to "External Alarm", it only goes low for about 5 seconds. Is there anyway to adjust it so it goes low for about 30 seconds? If you can, then your idea will work.

Use ext alm to trigger your timer. The timer will qualify one input of the AND logic (setting the xmit allowed window), and COR will qualify the other causing PTT.