Okay, since you did not provide a specific example I will utilize one of the ones you mentioned to see if I can understand it exactly.
Let's take the
Salinas PD Car-to-Car. The PD units use a repeater on 460.500/465.500 (Op/Ip) and apparently this traffic is also carried on 153.815. 153.815 is licensed as a repeater (
KBJ220 -- I added it to DB page), what is the input? Is it picking up the mobiles directly (465.500), is it picking up the mobiles after being repeated (460.500) or is it a direct audio link from the C2C repeater controller?
I'm sorry I thought I had here with Salinas PD apparently my rushing out the door I might have missed something.
SPD operates on the 460 band for all of it's units. The Monterey SO operates on the VHF Hi Band (hi band) as does the SFD. SPD has repeaters set up on UHF for normal in-house ops for channels 1, 2, and 3. To comply with interoperability they added a radio, for each of those channels, at the repeater site that while acts much like a remote link would, is designed to function as a cross band repeater. The radio repeats all traffic coming out of the repeater and will provide the repeater with radio traffic input from a high band user (MSO). As such this is not a Fixed or Control station but rather a repeater. Being a repeater, a causal data base user can see the "R" designation and try to extrapolate the non-existing input frequency. That is why I was suggesting the addition of something like "C" for Cross-Band Repeater.
There are cases as in Sonoma County where the repeaters that are on different bands are (or will be) linked. In this case the "R" is proper.
In most cases linking a repeater is done with a repeater controller. This is normally an external box that adjusts levels and in some cases can filter traffic. Controllers can also be used for time outs, ID'ers, phone patches, and an abundance of other features. These controllers can be from very simple and basic to extremely complex.
Still, without knowing, how the 153.815 repeater is getting the input signal, the more important question is, who is listening to the output? Presuming since it is car to car traffic, some other law enforcement agency has access to this to hear, how do they talk back? We are not talking about monitoring a dispatch channel where it is possible that only one way monitoring is desirable and done (like one county listening to an adjacent county dispatch so they are aware of what is happening), with no means of doing the reverse (in other words talking back to the units on Salinas PD C2C) on the surface it appears to have no purpose.
So, sticking to this link, who is listening and for what purpose? (I am not referring to scanner hobbyists.)
Now as to the reason why are these links are out in the world? Different agencies use various bands to fulfill their agency's needs. Low band users normally need to cover a vase area with not the need to populate the hills with repeaters and do need to get into the shadowed areas of what would not be covered by a repeater. High band users do not get the only a slightly reduced range of low band, but get some penetration and as such are considered to be a good all round band. UHF has better penetration and are great for metro applications, where with one or two repeaters they are in business. (High band users would have to look at having a voting system to make up for this with the loss of the penetration.) Many use 800 because of the trunking systems built into these products. This was a new band when trunking was introduced to the masses and it's rather difficult to put trunking in an existing band (note difficult NOT impossible).
In California most fire departments use the high band. Those departments that do not, will equip their mutual aid units with high band radio capability. Those agencies that use 800 like Sacramento may have high band channel(s) that is linked into the 800 system for use by allied agencies. This maybe always on or may be controlled on an as needed bases. This also may be just for monitoring or may include two way communications ala cross band repeating.
I know in one case where two counties had a UHF repeater that repeated one county's high band traffic for the second one. They would interrupt the relayed traffic with communication between the two dispatchers and occasionally various fire chiefs from the districts within the two counties. This was used more as a dispatchers command channel as opposed to the incident command channels of today.
As you can see from some of the data base entries, California has been in the lead of interoperability with many agencies throughout the state, Some agencies more than others, but none the less we have had various forms of inter-op for a good many years. Seeing the need, as well as the requirements to expand on inter-op communication, cross band repeaters are cropping up in various forms and designs, as they fit the needs of the locality they serve. (This is also being federally mandated as a result of events like WTC and Katrina as well as in California where we have something called earthquakes.)
Who makes use of these frequencies besides the day to day system user?
Those who travel through an area.
Those of us who are called into an area from a mutual aid or strike team or disaster request.
Causal listener and in some cases a system user who may not be able to have one band but can hear the other band when at home.
In the case of SPD, I know of officers who live locally and work there. UHF is not reachable from there but high band is (at least currently) as such this might not have been a design feature, I think you can see how it can be of an advantage in this case.
Reading between the lines, I see the question, "Should they be listed?" Yes, not only for the above reasons, but who or how is one to tell which frequency is primary and which frequency is the back up. These change as an agency changes its radio configuration grows. Communication priorities can and will change, changing an agency use of frequencies. Thus having them all listed makes finding move and changes easier.
If you are still awake, let me know if clears the muddy water.
