Batboard

Hello all,

We have a large need here locally to take a low band dispatch signal QC and voice and re broadcast them on UHF. We currently use a low band federal informer to do this function connected to a UHF mobile radio. The low band dispatch sends out DTMF to open the informer and then dispatches the QC tones and voice which play over the uhf mobile. THis works great however the informer leaves alot to be desired about reliability. Any thoughts on what to use? I know the zetron model 25 can be prgrammed to decode and activate relays but is cost prohibitive for a simple function. Is the model 15 able to encode and activate internal relays for PTT? Is anyone else doing this and what are you using?

Thanks, Rob

Use a Maxtrac low band radio, they are available. You can get a RUS, receiver un-squelched, signal out of the radio's 16 pin connector.

Will,

Ill bite. I agree with the use of a maxtrac (what a great radio), but what would I use for a decoder and relay module to toggle PTT of the UHF radio?

Thanks, Rob

Zetron model 25 is a multi-format ENCODER (sends DTMF, paging tones etc). The Model 15 is also an ENCODER.

Where are you thinking of using the model 25 or model 15?

The Maxtrac can decode a DTMF and set a relay. The relay can provide a PTT to the UHF radio.

You can also use the RUS, receiver un-squelch, PL and Un-Mute, to hold the PTT till the LB RX carrier drops.

Will - yes, those are great ideas! I am going to experiment.

RFGUY - sheer cost. The 25 is something like 8-9K, which far exceeds a reasonable cost for just a paging translation from low band to high band. I was looking to see what the 15 costs and to see if they have similar functions and programmability.

Thanks, Rob

FMROB wrote: RFGUY - sheer cost. The 25 is something like 8-9K, which far exceeds a reasonable cost for just a paging translation from low band to high band. I was looking to see what the 15 costs and to see if they have similar functions and programmability.

I guess I'm still not understanding where you plan to use the Model 25 or Model 15. These are paging encoders. Does your dispatch center not already have the ability to send pages?

RF Guy,

Basically looking for a (professional, high grade) replacement for the federal informer - which acts as a low band receiver, decoder, and relay board. Instead, we were looking at using a low band mobile, UHF mobile, and decoder with relay board to perform the exact funtion of the federal informer.

Bascially, how things operate around here is that primary activations are on low band and we need to translate that to UHF. The dipatcher(s) have no capability to go on UHF (and never will) as it is a county level function. We do the translation within the respective district to their own UHF system.

PM sent

Correct me if I'm wrong, but doesn't the MaxTrac need an option board for DTMF decode?

The CDM should be able to decode an MDC call?

FMROB wrote:The CDM should be able to decode an MDC call?

Yes, the CDM can activate the external alarm PIN 4 by decoding either a Selcall, Call Alert, or MDC call. It can be programmed to be active from 1 to 20 seconds and reset automatically. It can also be set to delay the external alarm from 0 to 30 seconds.

From what I read it sounds like county dispatch sends a dtmf string to open up the informer which keys the uhf radio then they send the quick call tones and message. The informer then resets after a pre determined time and unkeys the uhf radio.

If this is correct a CDM repeater would be the easiest way to go. Lowband cdm1250 or 750 which I believe does dtmf decode. ricked to a uhf cdm. The dtmf string gets sent to open the lowband radio then when they key up to send the quick call the uhf radio will key up and repeat the audio. The lowband receive radio would reset after a pre determined time for next call. To me a ricked one-way cross band repeater is the easiest setup.

kd9suy, you do not even need a R.I.C.K. as it just needs a couple of wires to the UHF radio's TX mic or accy jack.

I know you don't need a rick. I wouldn't build it though without some type of controller for public safety use.

kb9suy wrote:I know you don't need a rick. I wouldn't build it though without some type of controller for public safety use.

A R.I.C.K. is NOT a controller. I think the term 'controller' is being used in place of interface.

We are talking about an interface between the low band receiver and the UHF transmitter to pass the paging tones.

KBSUY, you hit the nail on the head. However the 20 second time frame for pin 4 may be a bit to short, specifically when dispatch needs to activate two departments at once and sends a long QC tone string.

My quest is no a timer circuit. I can use cdm pin 4 to maybe activate a adjustable timer circuit?

Thanks, Rob

Some simple timer circuits using the 555 chip are on the web.

Yes the CDM radio pin 4 would start a timer that would allow the RUS signal from the CDM to key the UHF radio. If the 'page out' is shorter than the timer, the RUS goes away and the UHF radio is no longer keyed.