Signal 652 About Radio Interference and Switching Frequencies
- Thread starter jlab
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6:00PM EST
NEW YORK CITY IS CURRENTLY EXPERIENCING INTERFERENCE FROM TROPOSPHERIC DUCTING. ALL UNITS MUST SWITCH RADIOS TO 8 FIRE DISPATCH BACK UP ZONE AND CHANGE CHANNEL TO YOUR DESIGNATED BORO. DEPARTMENT CELL PHONES SHOULD BE USED AS A LAST RESORT TO CONTACT THE DISPATCHER, SIGNED ASSISTANT CHIEF MICHAEL V MYERS
So 8 FIRE DISPATCH BACKUP is a zone on the 800 trunking system. Unfortunately all of the trunking talkgroups are encrypted. However it should pass back thru the regular conventional dispatch channels.
So 8 FIRE DISPATCH BACKUP is a zone on the 800 trunking system. Unfortunately all of the trunking talkgroups are encrypted. However it should pass back thru the regular conventional dispatch channels.
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Yes, It Is Encrypted.
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Thanks. I was still able to listen to Staten Island on the normal 482.04375.
Yes, so those backup talkgroups are all patched to the regular UHF frequencies so even though those talkgroups are encrypted the get unencrypted with the patch. If there was no patch you would not hear them on the 800 talkgroups if that makes sense to you.
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Ok.But if there was atmospheric interference on the 400 mhz channels, and they are still used, how does the 800 Mhz system solvbe the problem ?
They actually did. I know some of the old frequencies have come back on line. Unfortunately VHF frequencies can be affected just as bad as UHF with tropospheric ducting.
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What was peculiar in Queens, you could hear clearly a field unit calling the Queens CO; but once the carrier was turned on, you lost the field unit and only heard the console acknowledging.
Someone said that theyb may be testing the encrypting of transmissions. The only problem with that would be that units would be stepping all over each other once the carrier is turned on.
Someone said that theyb may be testing the encrypting of transmissions. The only problem with that would be that units would be stepping all over each other once the carrier is turned on.
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NYPD Freq's are only about 5 mHz above ours; yet, there was no problems with any of the PD division transmissions in Queens - unless it has to do with there's being a simplex system, and we use a duplex/rebroadcast system.
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Eh, sort of. Both are really semi-duplex, meaning both rely on repeaters and only one side (the dispatcher) can transmit and receive at the same time. Simplex means both sides can only transmit or receive at one time. The difference between NYPD and FDNY is PD's "mixer" is on all the time, inserting audio received on the input frequency by portables in the field into the dispatcher's output (and scanner listeners) automatically.
I also didn't notice any interference on the PD freqs. PD is still "wideband", meaning they have 25KHz spacing, while FDNY UHF is "Narrowband", meaning half of that. That is a possible reason.
Also, PD is generally in the 476 MHz range, and FD is in 482 MHz area. The input frequencies (units in the field) have a standard offset for both systems.
If I have this wrong, please let me know. Thanks!