Batboard

Our county is currently operating on Low Band. Due to circumstances outside of our control (geography and lack of maintenance in the com center), the low band really doesnt work in our area (especially in buildings). My fire company set up a VHF to lowband repeater on our base station. Its basically just two CDMs RICK'd together. Coverage is awesome, a vhf portable ANYWHERE in our first due can hit the repeater (not surprising, the antennas are on top of a 150' monopole...).

Anyway, the problem we're having is that the repeater is not keying up fast enough, and when the impatient dispatcher keys up (outside our control), they talk right away and fast, and in the .5 seconds it takes the repeater to recognize a PL, send out the signal, key the PTT, and Tx, part of the message is clipped. I realize this is an inherent problem with the sytem (using 2 mobiles instead of a real repeater), but I can't help but wonder if there isn't a way around it.

Any thoughts?

Jon

I've encountered this problem and the only practical answer is to instruct users to wait two seconds after hitting the PTT before they begin speaking. With larger systems with voting receivers, inter-site tielines, etc. it seems especially to be a common occurrence/problem.

[quote="Tom in D.C."]I've encountered this problem and the only practical answer is to instruct users to wait two seconds after hitting the PTT before they begin speaking. With larger systems with voting receivers, inter-site tielines, etc. it seems especially to be a common occurrence/problem.[/quote]

Like Tom has said, your hitting the limits of the equipment functionality. You can't get it to work much faster. Some brands do decode just a tad faster, but in general, what you see is what your going to end up with.

Your stuck with retraning the untrainable. Ever tried to ask a dispatcher to change their ways? Best way to work through the problem is keep asking them to repeat the message. Tell them after a couple of tries to talk slower. They will ether get the hint or will stop talking all together.

Jim

We did the same with lowband and UHF.

Set up the VHF radios with an MDC1200 "pre" ID and set up the PTT "wait" tone so the radio will beep when they key it up.

It doesn't matter what ID# you use, since you are just using MDC to create a PTT delay tone.

I don't like applying hardware solutions to fix personnel issues but, that said:

You can install a "Delay Line" in transmit audio between the two mobiles. One example of the product is listed below:

http://www.simulcastsolutions.com/audio ... remote.htm
(Tell Ed that Bob J. sent you)

The delay line can be set to delay the audio up to 1 second; shorter is much better.

Be aware that if you have VHF and Low Band both in use at the scene and you have siren-radio or pump-panel speakers on, there will be an audible illusion that sounds like an echo due to the delay line.

I agree with the others though, teach the dispatchers to PTT, then Talk. It's a good practice to observe.

Good Luck

We replaced our Motorola tone remote consoles some years back with Zetron's Model 280 digital remote units. One of the really slick features of these tone remotes is that they automatically digitize the dispatcher’s voice (using full rate Telco PCM) and delays it momentarily before the voice is actually sent out. The dispatcher can slam the PTT and start yakin' immediately, but lo and behold, her voice doesn't go out until after the delay time. Zetron did this to take into account all sorts of parameters that must be met before actual Transmitter key-up occurs in complex systems. It takes into account the fact that the (old time) dispatchers are typically used to the Motorola T-1600 series Tone Remotes, where they could start talking instantaneously without having to worry about all the modern complex systems' momentary delay times.

We use it in connection with our DIU 3000 in mixed mode (analog FM and IMBE). It has every single function imaginable, including all the standard stuff, such as Set-up/Knock-down, Encryption ON/OFF, FM vs/ P25 IMBE, PL ON/OFF, MRTI ACCESS Enable/Disable, and list goes on and on. The M-280 has a built in internal mic, as well as its handset, of course. You can also hook up an external mic. It has a good internal speaker, with tons of crisp and loud audio, but you can also hook up external speaker(s).

All functions are software programmable on your PC, and its default settings use the exact same tone frequencies and tone ON/OFF and inter tone timings as the standard Motorola scheme. All of these can be custom programmed to your heart's content, if you don't want to use standard Motorola tone sets and timings.

http://www.zetron.com/pages/english/products/m280.html

Make sure to click on the "Spec Sheet" button at the upper right hand corner of the quick preview sheet so you can bring up all of the specs of the M-280, as well as a good picture of the unit.

Sorry to be so emphatic in my support of the M-280, but we have several of 'em, and they are the best Digital Tone Remote desk set on the market today, IMHO.

Hope this helps.

larry