I learned long ago that I was missing quite a bit of traffic by monitoring just the 170.55 (old Los Padres Forest forest net output frequency) and added its input of 169.9 to the line-up. I continued the practice with the new frequencies.
As you can see below, my scanner checks the output (170.4625) before the input (164.9125) yet the input still collects transmissions that the output does not. I am within 20 miles of both the Santa Ynez repeater and Goleta headquarters yet I will receive transmissions off Frazier (110.9) and Sissar (123.0) on input and not on output.
During the morning status report on the forest net, my first catch will be on 164.9125 with open tone search bringing in 77.0 or 77.9 tones. I lock-out that channel and immediately pick-up the UHF repeater (406.325 103.5) channel. I lock-out that channel and I will not hear anything on 170.4625 even though the status report is still being transmitted.
I don't know if there is an easy explanation (beyond my question about opening all repeaters with 77.0/77.9) for these occurrences. I just thought you might be interested in what is being heard in this forest system.
Thank you for the time you've taken on this and all the information you provide to this site.
The transmissions on the input that you are hearing all originate from the Santa Ynez remote base. You very likely cannot hear Frazier or Sisar from your location because you hear nothing on the output. You are hearing transmissions off of Santa Ynez with the correct tones to bring up those other sites. Where I live in Santa Ynez, I can hear the outputs from La Cumbre, Tepuquet and Plowshare. I long ago stopped listening on the inputs and just listen to the links (if I want lots of traffic) or the output when I only want to hear local traffic.
The 77 and 77.9 tones are not part of the standard set of sixteen tones. I have not seen any forest in California using non-standard tones. Also, you will find that most systems (commercial, government or amateur) use tones above 100Hz for technical reasons.
Listening to the input will sometimes give you information that you would not otherwise hear, but that's what the link frequencies are for. All important traffic is sent out multiple times on multiple repeaters so you won't miss a fire dispatch, for example. Local traffic is obviously not repeated this way, but again you will hear both sides of the conversation on the link.
As I said in an earlier post, they did try simulcasting, but it creates so much phase distortion that they don't do it anymore.
I done with this obsessive interest in input tones. They don't matter.