BM82557
Member
Just a better screen grab to show the difference between an typical P25 CC on the left (171.5375 site 1.88) and a non-decodable P25 CC on the right (171.6125 site 1.96) --
IWN National Capital Region System Changes
- Thread starter BM82557
- Start date
- Status
The one on the left looks like a smartnet control channel. In any event, it's weaker than the signal on the right.
BM82557
Member
It is weaker but is decodes fine, it is P25, site 1.88's CC on 171.5375, post # 40
- Joined
- Dec 19, 2002
- Messages
- 2,418
Paris Mtn. was (is?) transmitting that signal simultaneously on 168.4875, 170.3875, 170.9125, and 171.6125--so I do not think we can label it as a control channel transmission. At the same time, nearby Bull Run was using the same 171.6125 as its normal control channel! I think this is a test signal.
Right - it's possible that 171.6125 is being used for coverage testing. I saw something similar last week in the PG area, and I've seen it during MontCo PA coverage testing - the waveform looks P25, decodes as P25, but no control channel data. I have a document somewhere that describes the process and the signal that is typically used in coverage testing Motorola systems.
BM82557
Member
Here I posted my P25Data file awhile back and forgot to go back and cross-check it out! If I had done that I would have realized that all 4 freqs are on the same site so you guys are most likely correct as to it being a test signal. Sorry for the confusion I have caused.
Here's my contribution to MontCo PA thread that talked about the signal, lol:
forums.radioreference.com
forums.radioreference.com
Montgomery County P25 system update
The county has stated that their new 700 MHz system will start testing during the summer of 2020. I would monitor 769.30625 for control channel activity.
Montgomery County P25 system update
The county has stated that their new 700 MHz system will start testing during the summer of 2020. I would monitor 769.30625 for control channel activity.
BM82557
Member
Finally had a chance to look at this some more, from the received signal strength at my location it appears 170.9125 is not at the same location as 168.4875, 170.3875 and 171.6125 but it doesn't change the fact that all 4 are transmitting a test signal --
- Joined
- Dec 19, 2002
- Messages
- 2,418
I was at the transmitter site--shouting distance to the tower. I had to back off down the mountain as it swamped the receiver. They were all from there but you are correct, the signal levels were not equal. It is also possible that making measurements at a different time might have see different sites. Real odd how 171.6125 was coming from there and Bull Run was using that as its control at the same time. I checked signal level at each while there rather than just the sound. Note that the frequencies previously know for the site are 170.625, 170.8375, and 170.9125 leaving the 170.9125 the only one in both lists--maybe it is an older lower powered transmitter or the others were set to new different frequencies and power increased (or forgottne to turn down) when doing that. Would be worth watching--I cannot see the site from home.
Last edited:
BM82557
Member
Good conditions this morning, this is what I am getting for site 1.90 --
BM82557
Member
169.6625 P25 NAC 717 today, not a control channel
- Joined
- Dec 19, 2002
- Messages
- 2,418
Site not known?
palmerjrusa
Member
Not able to monitor the Fort Detrick channels any more on JCNR here in Frederick.
Does anyone know what's happening?
Does anyone know what's happening?
Shooting related ENC?
palmerjrusa
Member
Don't know...
Last edited:
palmerjrusa
Member
.
palmerjrusa
Member
freqhopping
Member
- Joined
- Jan 5, 2004
- Messages
- 7,096
The Ft Detrick site is working just fine for me. Current CC is 387.5375. Hearing channels not in the database.
- Status
Similar threads
