Duplex systems on Pro-96

[feta92]

Is there any way to program a duplex system into the Pro-96 so you can hear both sides of the conversation.

I live near Detroit, MI and have a hard time monitoring EMS to Hospital coms due to the duplex system.

Any help would be greatful

Thanks
Jason

 

[nmfire10]

If your asking if you can monitor two frequencies with radio traffic at the same time, no. Best thing you can do is find another cheapo scanner and listen to both at once.

 

[rdale]

"I live near Detroit, MI and have a hard time monitoring EMS to Hospital coms due to the duplex system"

Since the ambulance and hospital don't talk at the same time - can you explain a little better what the problem is?

 

[AZScanner]

"I live near Detroit, MI and have a hard time monitoring EMS to Hospital coms due to the duplex system"

Since the ambulance and hospital don't talk at the same time - can you explain a little better what the problem is?

Well, if it is a true duplex system, then both frequencies will stay keyed up at the same time. So you'd have to use two scanners. I'd put the base freq's in one scanner and the mobiles in the other.

-AZ

 

[rdale]

How about pressing the UP/DOWN buttons to alternate between the two freqs as they alternate?

 

[RolnCode3]

This sounds like CHP as well. Base station is on one frequency, and the mobiles are on a different one. The radios they use can follow the base freq and the mobile freq so they can follow a conversation. Those of us who listen with scanner have to switch channels. I was wondering if there was a way to do this with the 785, but obviously the answer is no.

 

[nmfire10]

How about pressing the UP/DOWN buttons to alternate between the two freqs as they alternate?

A true duplex system has no alternating. They are both transmitting at the same time on diifferent frequencies. You will need two scanners to follow that.

 

[Pro-95]

From what I gather the 160Mhz railroad frequencies are the same way. The train xmits on "x" frequency then recieves on a different "y" frequency. The radios in trains display a 4 digit number the first 2 are the transmit freq and the last 2 are the receive frequency, in an order set by AAR. AAR train radio frequency list. If I was to listen to trains I think I'd set a bank with all the 96 frequencies then scan only that bank. The speed of scanners should allow you to hear most if not all the conversation.

2cents.

 

[nd5y]

From what I gather the 160Mhz railroad frequencies are the same way. The train xmits on "x" frequency then recieves on a different "y" frequency. The radios in trains display a 4 digit number the first 2 are the transmit freq and the last 2 are the receive frequency, in an order set by AAR. AAR train radio frequency list. If I was to listen to trains I think I'd set a bank with all the 96 frequencies then scan only that bank. The speed of scanners should allow you to hear most if not all the conversation.

2cents.

That is only if they are on a repeater. Most RR traffic is simplex on 1 frequency and the AAR channel will be the same for both like 1616.

Tom

 

[Pro-95]

Cool! Thanks for the clarification Tom.

 

[KT4HX]

Maybe I'm off base here, but something about this scenario seems strange. I would be under the assumption that the system he is monitoring was utilizing a repeater. Therefore, the mobiles would be transmitting on the input frequency and may or may not be heard on that frequency depending upon their location. However, I would think they could be heard on the output frequency of the repeater, in the same way the dispatcher would be. I agree with others that a true duplex circuit would entail two full time frequencies, but is any local jurisdiction, anywhere, using such a beast? If so, that would seem an awkward way to conduct business. :?

 

[nmfire10]

KT4HX, your assumption is just that. The person who started this thread has not stated that it is or isn't a repeater. I would think if it was as simple as a repeater, he wouldn't be asking this question to begin with.

 

[ChrisP]

Maybe I'm off base here, but something about this scenario seems strange. I would be under the assumption that the system he is monitoring was utilizing a repeater.

Not always. In the original post he mentioned wanting to listen to EMS to hospital communications. In several areas I have lived, the UHF Medcom channels are not repeated, and are run in half-duplex. The hospitals listen to the EMS units on the 467 Mhz frequencies, and they respond on the 462 Mhz frequencies.

I don't know of anything you can do programming wise to help montior this other than make sure you have both the 462 Mhz and 467 Mhz Medcom channels in the scanner and a good antenna to pick up the mobile units...

- Chris

 

[rdale]

"A true duplex system has no alternating. They are both transmitting at the same time on diifferent frequencies. You will need two scanners to follow that."

I don't follow... If the hospital is talking, the ambulance wouldn't be talking at the exact same time. If the ambulance is talking, the hospital would be listening. I have no problem following those conversations by alternating between the 462 and 467 freq's...

- Rob

 

[nmfire10]

"A true duplex system has no alternating. They are both transmitting at the same time on diifferent frequencies. You will need two scanners to follow that."

I don't follow... If the hospital is talking, the ambulance wouldn't be talking at the exact same time. If the ambulance is talking, the hospital would be listening. I have no problem following those conversations by alternating between the 462 and 467 freq's...

Well thats what they do.

 

[N_Jay]

"A true duplex system has no alternating. They are both transmitting at the same time on diifferent frequencies. You will need two scanners to follow that."

I don't follow... If the hospital is talking, the ambulance wouldn't be talking at the exact same time. If the ambulance is talking, the hospital would be listening. I have no problem following those conversations by alternating between the 462 and 467 freq's...

- Rob

THis goes back to the design of the original MED/EMS system from teh 1970's.
The system, at the insistance of the Drs, was FULL DUPLEX with the ability for the DR/Hospital to interupt the EMT/Paramedic.

The system was also able to send telemetry inbound without loosing the interupt capability.
There were also ambulance mounted repeaters that enabled a portable near the ambulance to repeat through the vehicle. This was also full duplex by using a thrid set of frequencies.

Kind of a cool system (and fun to design )

 

[rdale]

"was FULL DUPLEX with the ability for the DR/Hospital to interupt the EMT/Paramedic."

I understand they have the ability to - I just have never heard that utilized. Guess nm lives in an area where they often break in - what sort of things do they interrupt for?

 

[loumaag]

A full duplex system is easy to understand. And, as N_Jay points out, this is how the MED channels were originally supposed to work. Just think of it kind of like a telephone. Both sides are receiving and both sides are transmitting at the same time. It is pretty easy to do at 460 MHz when the TX/RX channel spacing is 5 MHz.

 

[qoatzecotl]

This is all very interesting to me, because I have been listening to the MED channels for 7 years in the Fort Wayne, Indiana and Cleveland, Ohio areas and have yet to hear them used in full-duplex, only semi...

 

[nmfire10]

"was FULL DUPLEX with the ability for the DR/Hospital to interupt the EMT/Paramedic."

I understand they have the ability to - I just have never heard that utilized. Guess nm lives in an area where they often break in - what sort of things do they interrupt for?

No. I never said that this is what they use here. It is all normal repeaters around here for med channels.

It isn't just "Interupting". It allows you to have basicly a telephone conversation. Both parties can talk at the same time and listen at the same time.