Local frequency problems.. need help!

seagravebuff60 · Feb 9, 2017

Hi All,

So my School District Busses Seem to be operation on 2 separate frequencies.

From what I've gathered when listening to my scanner it seems that the handheld radios (Dispatchers, Boss, Yard Manager, Bus Manager, mechanic, ECT) are using their own frequency while the radios in the busses are using a separate frequency. So when listening to my scanner the dispatcher will make a call to one of the bus drivers on one frequency, and then the bus driver will start talking on another frequency. But then when I am in the bus listing to the conversation on the radio, it all sounds like there all talking on one frequency.

I have never heard of anything like this, and when listing in to other busses with other school districts the all operate on one frequency, but my school district operates on two.

Again, I have never heard of this, I am looking to see if any of you have heard of this?

Thanks,
Nickthequick0

ThePagerGeek · Feb 9, 2017

I'm going to guess they are using a repeater to provide a wide area coverage.

Which School District?

WA0CBW · Feb 9, 2017

Sounds like what taxi cabs used. It keeps the busses from hearing each other. Everyone talks on one frequency but receives on another.
BB

seagravebuff60 · Feb 9, 2017

WA0CBW said:
Sounds like what taxi cabs used. It keeps the busses from hearing each other. Everyone talks on one frequency but receives on another.
BB

Kind of like a trunked system?

seagravebuff60 · Feb 9, 2017

ThePagerGeek said:
I'm going to guess they are using a repeater to provide a wide area coverage.

Which School District?

Ok yea that looks like it make sense because the one of the is VHF and the other is a UHF. Maybe, idk i just never heard of this before.

As for the school district it is located in Weschester county.. it not listed on the Radio Reference Database if your looking for it. i had to find the 2 frequencies myself.

WA0CBW · Feb 9, 2017

Works like this:. The two frequencies are in the same band. Mobiles and portables transmit on frequency 1 and receive on frequenciy 2. The base station or dispatch transmits on frequency 2 and receives on frequency 1. Everyone hears dispatch and dispatch hears all the units. All the units can't hear each other because they are transmitting on one frequency and listening to another. This keeps the units from chit-chatting with each other.
BB

ecps92 · Feb 9, 2017

Rather Odd, being in two bands.

How about this, what two Frequencies and Tones have you discovered.??

nickthequick0 said:
Ok yea that looks like it make sense because the one of the is VHF and the other is a UHF. Maybe, idk i just never heard of this before.

As for the school district it is located in Weschester county.. it not listed on the Radio Reference Database if your looking for it. i had to find the 2 frequencies myself.

WA0CBW · Feb 9, 2017

Good question "ecps92"!
BB

seagravebuff60 · Feb 9, 2017

ecps92 said:
Rather Odd, being in two bands.

How about this, what two Frequencies and Tones have you discovered.??

One of the frequencies is 33.1000 MHz with no tone and the other frequency of 467.7875 MHz and also with no tone. Do you think maybe the tone is affecting it, because other neighboring schools use no tone as well but don't have this problem. .

seagravebuff60 · Feb 9, 2017

WA0CBW said:
Works like this:. The two frequencies are in the same band. Mobiles and portables transmit on frequency 1 and receive on frequenciy 2. The base station or dispatch transmits on frequency 2 and receives on frequency 1. Everyone hears dispatch and dispatch hears all the units. All the units can't hear each other because they are transmitting on one frequency and listening to another. This keeps the units from chit-chatting with each other.
BB

Ok this look like this might be whats happening, but the frequencies are on different bands one being VHF and the other being UHF, and all the busses can talk to each other for example bus 1 can talk to bus 2 no problem.

ThePagerGeek · Feb 9, 2017

Somers Central School District?

Based on the itinerant UHF frequency, sounds like they have a patch between the LowBand VHF and UHF.

Talk on one, heard on the other...

seagravebuff60 · Feb 9, 2017

ThePagerGeek said:
Somers Central School District?

Based on the itinerant UHF frequency, sounds like they have a patch between the LowBand VHF and UHF.

Talk on one, heard on the other...

Yea it is Somers, sound like this is probably the issue. Just very weird they would do this. Thanks

RKG · Feb 9, 2017

I don't know anything about the particular situation the OP refers to, but radio systems where subscribers transmit on one frequency and the dispatcher transmits on a different one, with Rx freqs reversed, is known as Two-Frequency Simplex. At one time it was widely used in public safety, and is still common in certain geographic areas.

The advantage of Two-Frequency Simplex over single frequency simplex is that it allows the use of multiple voted receivers to extend talk-in range. In terms of equipment Two-Frequency Simplex uses essentially the same hardware as a voted receiver repeater system, except that the repeater controller is disabled.

One issue that is (or was) presented is that, because one mobile couldn't tell when other mobiles were transmitting, they risked talking over one another. To deal with this, the system would emit a signal, usually a series of beeps, over the talk-out frequency whenever the comparator voted audio line was true. These are known collogquially as "California Beeps."

For what it is worth, I've never heard of a Two-Frequency Simplex system that cross-banded.

wtp · Feb 9, 2017

nick

check for a personal message.

seagravebuff60 · Feb 9, 2017

nickthequick0 said:
Hi All,

So my School District Busses Seem to be operation on 2 separate frequencies.

From what I've gathered when listening to my scanner it seems that the handheld radios (Dispatchers, Boss, Yard Manager, Bus Manager, mechanic, ECT) are using their own frequency while the radios in the busses are using a separate frequency. So when listening to my scanner the dispatcher will make a call to one of the bus drivers on one frequency, and then the bus driver will start talking on another frequency. But then when I am in the bus listing to the conversation on the radio, it all sounds like there all talking on one frequency.

I have never heard of anything like this, and when listing in to other busses with other school districts the all operate on one frequency, but my school district operates on two.

Again, I have never heard of this, I am looking to see if any of you have heard of this?

Thanks,
Nickthequick0

Just kind of an update,

So to give you a example When i am listing on my scanner i hear a conversation that takes place like this: Dispatcher starts talking to a bus driver on one frequency (33.1000 MHz) then when the Dispatchers is done talking, the bus driver responds on the other (467.7875 MHz). Then the Dispatchers replies on 33.1000 MHz.

I don't think that the UHF (467.7875) is a repeater frequency. Because only the busses are talking on this frequency not the Dispatchers on 33.1000 MHz. Now everyone can hear each other (The Dispatchers can hear the busses, the busses can hear the Dispatchers, the busses can hear the other busses, the handheld radios can hear the busses and the other handhelds can talk to the busses).

But then when you hear the conversation in the bus it sounds perfict, like everyone is talking on the same frequency.

Thunderknight · Feb 9, 2017

Here is Somer's UHF license
ULS License - Industrial/Business Pool, Conventional License - WPML482 - SOMERS CENTRAL SCHOOL DISTRICT
And the low band
ULS License - Public Safety Pool, Conventional License - KNGL645 - SOMERS CENTRAL SCHOOL DISTRICT

Try listening to 462.7875 MHz to see if you hear anything. If there was a UHF repeater, traditionally the low side would be the output...although they are not licensed for a repeater.

ai8o · Feb 9, 2017

To get an idea of how this works, go to my webpage on how repeaters work.

HTTP://www.yemiola.net/rptrwork/rptrwork.htm

Go to figure #4, Hemi-Duplex, on that webpage.

In the Somers SD system
33.100 Base output frequency, would be the BLACK waves (F1)
467.7875 Mobiles frequency, would be the RED waves (F2)

Usually the two frequencies are in the same frequency band (UHF-UHF, VHF-VHF).

Hemi-Duplex is a very old concept.
Lots of police radio systems worked this way in the 1930s, 40s and fifties.
Base station on a MF (1700Khz) output frequency and mobiles on VHF low band (39 Mhz)
About the only comms handled this way today are Marine HF; for example 6316Khz Coast station output frequency, 6366 Ship frequency.

seagravebuff60 · Feb 10, 2017

Thunderknight said:
Here is Somer's UHF license
ULS License - Industrial/Business Pool, Conventional License - WPML482 - SOMERS CENTRAL SCHOOL DISTRICT
And the low band
ULS License - Public Safety Pool, Conventional License - KNGL645 - SOMERS CENTRAL SCHOOL DISTRICT

Try listening to 462.7875 MHz to see if you hear anything. If there was a UHF repeater, traditionally the low side would be the output...although they are not licensed for a repeater.

I have tried listing to 462.7875 MHz and i heard nothing.

seagravebuff60 · Feb 10, 2017

Thunderknight said:
Here is Somer's UHF license
ULS License - Industrial/Business Pool, Conventional License - WPML482 - SOMERS CENTRAL SCHOOL DISTRICT
And the low band
ULS License - Public Safety Pool, Conventional License - KNGL645 - SOMERS CENTRAL SCHOOL DISTRICT

Try listening to 462.7875 MHz to see if you hear anything. If there was a UHF repeater, traditionally the low side would be the output...although they are not licensed for a repeater.

I have tried listing to 462.7875 MHz and i heard nothing.

Mtnrider · Feb 10, 2017

Looks to me that there using the UHF Freq to operate the VHF low freq...(UHF LINK) .and vice versa....not uncommon...but most times the Low VHF is parked on top of a mountain or other high structure ..but than again the JR HS might be high enough..But this is my far away opinion

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