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Originally Posted by upthesaukee
What you are hearing from dispatch is VHF frequency talk from an antenna that your unit can receive direct line-of-sight transmission from. The remote unit's transmissions are received by the antenna and then back to the dispatch center via landline.
Perhaps "Al from the Sea que" can enlighten us both.  |
What UptheSaukee is referring to is called a Remote Base System.
Remote Base means that the 2-way radio (transceiver or transmitter and receiver) and antenna are located in a prime (usually high up, often isolated) location some distance away from the business, office, agency or dispatcher. The desk console the dispatcher uses connects to the remote 2-way radio at the Remote Base site via special phone line or by other methods. This allows use of the Remote Base as if the dispatcher were at that “high up” remote spot where the 2-way radio is located – it’s just remote controlled. The received audio gets to the dispatcher from the off premises Remote Base receiver while the dispatcher’s voice is sent from his desk (when they push their talk button) to be broadcast from the remote base transmitter. Remote Base systems usually operate on the same transmit and receive frequency.
So, Scanner listeners may always hear the Remote Base dispatcher (transmitting from the high antenna of the remote base). The dispatcher will hear the mobile units because they “hear” with the Remote Base receiver and antenna. The scanner listener does not have that listening advantage. Your antenna is probably mounted right on top of your scanner – not as efficient as an antenna mounted high on a hill and/or tower. With this system your scanner can only hear mobiles that are CLOSE enough for direct pick-up (signal path from the mobile to your scanner). All that said, the list below shows fire “dispatch” on it’s own frequency and maybe that’s why you hear only dispatch. (ask DRH).
Note: With NH Marine Patrol, scanner listeners could hear the dispatcher on one frequency but most of the units used a separate frequency (and system) to reply. Their units were using digital (APCO-25) protocol, which can not be decoded by the average (analog) scanner. There are a few newer scanners on the market that receive digital systems.
By comparison to remote base, many systems use REPEATERS at the prime antenna location. These 2-way radios listen to one frequency and automatically transmit what they hear on a different frequency – all from a “prime” location. As the name suggests, it REPEATS what it hears. This allows everyone in the system the ability to hear everyone else on that repeater. The repeater hears the mobile units on the “input frequency” and the mobiles hear the repeater on the repeater “output” frequency. It ties up 2 frequencies to do this but is a very popular method for VHF and UHF 2-way radio systems. If the scanner user can hear the repeater (output) then they hear the dispatcher and the mobile units. The dispatcher is using a 2-way radio to talk through the repeater. I won’t delve into shared repeater systems or other derivations of the basic systems.
From the Fordyce.org web site:
Fire
159.900 - Lakes Region Mutual Fire Aid Association - F-1 (Dispatch)
160.110 - Lakes Region Mutual Fire Aid Association - F-2 (Fireground/Operations)
160.155 - Lakes Region Mutual Fire Aid Association - F-3 (Fireground/Operations)
154.280 - Lakes Region Mutual Fire Aid Association - F-4 (Statewide Fireground)
154.3025- Lakes Region Mutual Fire Aid Association - F-5 (Fireground - Mobile Only)
154.9875- Lakes Region Mutual Fire Aid Association - F-6 (Fireground/Repeater Direct)
154.9875- Lakes Region Mutual Fire Aid Association - F-7 - F9 (A,B,C Operations Repeaters)
For a complete list of Fire and EMS frequencies and their functions see the following web page.
http://www.fordyce.org/cgi-bin/yabb1...num=1047860842
DRH has much more experience scanning in the Lakes Region area than I do – I suggest you take him up on his offer to exchange e-mail. I programmed a bank of channels in my digital capable, trunk tracking scanner based on info from DRH and another well known forum member for my Lake scanning. There are many more public service agencies in NH that use Digital 2-way radio than we have around here in MA.
Good luck.