CALFIRE Air Tac question
- Thread starter kma371
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That is odd. I'm surprised the equipment he used allowed transmissions on AM on the Cal Fire freqs. The only AM transmissions should be ATC related (118-136 mhz).
Yeah I thought it was strange. I originally had it in NFM mode but switched to FM thinking they hadnt made narrow band switch yet. Still kinda garbled like he was off frequency. Switched to AM mode and heard it perfect.
He was the only one I could hear so I couldn't compare the other guys.
techman210
Member
This is why we refer to our simplest-to-operate equipment in the inventory as "fireman proof"!
R1VINCE
Member
im listening right now on a PRO2045 switching modes back and forth-
sounds as if they are somehow in both modes as they sound clear in either
also sounds the same on my 2042 and 2006 and AR8200
weird
update: i dont know their exact location but it sounds that the weaker the signal, the NFM mode on some of my radios will still pick up but on AM it drops off, yet I can still hear it in both modes
sounds as if they are somehow in both modes as they sound clear in either
also sounds the same on my 2042 and 2006 and AR8200
weird
update: i dont know their exact location but it sounds that the weaker the signal, the NFM mode on some of my radios will still pick up but on AM it drops off, yet I can still hear it in both modes
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I think they are working a TCU area fire.
Retired911Guy
Member
Now, Now, in my 32yrs in Public Safety I've seen plenty of Tech errors, so lets not sling mud around.
Definitely not bleedover. Definitely AM.
I'll second Brandon's reply as the most likely cause for your distortion. If your scanner can work with the new narrowband 7.5KHz steps try tuning to either of those two frequencies (151.2725MHz or 151.2875MHz) as he suggested and see if the signal is clearer. If you can only do 5KHz steps then try tuning off by +/- 5KHz and see what you get (i.e. 151.275MHz or 151.285MHz); if you find that one of those is best then try tuning off another 5Khz to "zero in" on the likely new narrowband frequency. For example, if you find that 151.285MHz is best then try going higher by another 5KHz. If the actual frequency is 151.2875MHz then, assuming your scanner's local oscillator is tuned correctly and assuming your IF filter is symmetrical (not always the case in consumer scanner radios especially if they are more than a few years old and/or have been used in varying temperatures) then you should notice little or no difference between 151.285MHz and 151.290MHz because they are equally distant frequency-wise from the true center frequency of 151.2875MHz (by 2.5KHz) - the actual frequency being used. Likewise, if you find that the signal sounds best at 151.275MHz, then try tuning down another 5KHz to 151.270MHz and you should then find the signal quality about the same as what you get at 151.275MHz which likely means, in this case, that the actual frequency is most likely 151.2725MHz.
-Mike
-Mike
Bill, can you ID which assets you are listening to?
I'm only hearing activity on Tac 4. I have all the other air tacs programmed and they are the only ones I'm hearing.
I was away from the scanner since I last posted about hearing them. Next time I will try to ID. But based on their signal strength, it's probably they were in the sierra foothills, (Amador/Calaveras/Tuolumne Counties, most likely).
You probably did hear AM in that range.
The air units use some of the Wulfsberg electronics RT5000 wide band radio which is capable of AM, all modes of FM and P25 digital from 29.7 to 400 MHz and FM and P25 digital from 400 to 960 MHz.
The extended range AM comm band is 118 to 151.9875 MHz and when I was working on some of the transmitter designs for Wulfsbergs comm lines a few years back we would frequently get customer eval or loaner radios back from CDF in our engineering lab that had AM comm channels with alpha tags that were set to frequencies between 137 and 151.9875 MHz plus even some AM channels down in the 30 to 36 MHz range along with numerous ones in the 225 to 384 MHz band.
Customs and Border protection would also use AM throughout the entire operating range of the radio as did Air Force, Air national guard and some of the other govt agencies that use the RT5000 series radios.
Frequently I would hear Air force instructors out of Luke AFB flying over the Bagdad Arizona area operating around 151 to 152 MHz AM.
If they were working with federal firefighting agencies then it's very possible that they were operating AM where you heard them.
Mike
The air units use some of the Wulfsberg electronics RT5000 wide band radio which is capable of AM, all modes of FM and P25 digital from 29.7 to 400 MHz and FM and P25 digital from 400 to 960 MHz.
The extended range AM comm band is 118 to 151.9875 MHz and when I was working on some of the transmitter designs for Wulfsbergs comm lines a few years back we would frequently get customer eval or loaner radios back from CDF in our engineering lab that had AM comm channels with alpha tags that were set to frequencies between 137 and 151.9875 MHz plus even some AM channels down in the 30 to 36 MHz range along with numerous ones in the 225 to 384 MHz band.
Customs and Border protection would also use AM throughout the entire operating range of the radio as did Air Force, Air national guard and some of the other govt agencies that use the RT5000 series radios.
Frequently I would hear Air force instructors out of Luke AFB flying over the Bagdad Arizona area operating around 151 to 152 MHz AM.
If they were working with federal firefighting agencies then it's very possible that they were operating AM where you heard them.
Mike
tomasG
Member
It is more likely than not that although you are hearing the units in AM mode they are using FM. You are hearing what is called "slope detection" which has been around for many, many years. For the units to truly be using AM would mean a complete and unapproved departure from the CALFIRE/Firescope/USFS agreement. In contrast I can use my Kenwood commercial radio and hear AM down to 134MHz but programmed as FM. That when when a contractor comes up on 135.xxx I can still hear them without a scanner. Garbled at times but completely readable.
Interesting! I've never heard of the "extended range AM comm band" before (well, at least not going all the way up to 151.9875MHz as you stated, only up to 144MHz on occasion) but then I've never worked professionally on military or government communications equipment (with one vaguely indirect exception). One of my old college friends used to work for Global Wulfsberg in Prescott, AZ (back when they had a place in Prescott). I recall his telling me about the wide range multi-mode transceivers used by civilian and government helicopters involved in fire and law enforcement mutual aid operations. When I first read this thread my initial thought was that something like this was being used and that either it was pre-programmed incorrectly with the wrong mode for the air attack memory channels or that the operator accidentally dialed up the air attack channel frequency with the mode set to AM. However, Brandon's post made more sense to me and seemed more likely but now, given your info, I wonder. Maybe so...maybe so...
I do know that USAF and other military air assets use AM in the 136MHz to 144MHz range, though, as I understand it, less frequently now then in the past. I agree with tomasG, however, in that it would not be normal accepted practice on the CDF air attack 151MHz frequencies.
Out of curiosity, kma371, what radio are you using when you hear this traffic? Another possibility is some strong nearby AM traffic from either the 118MHz-136MHz or the 225MHz-400MHz band is creating a "false" signal in your radio on the air attack 151MHz (supposedly FM) frequency but proving that would take some knowledge of the receiving radio's frequency plan (RF-to-IF up/down conversion, etc.) which varies by manufacturer and model and establishing a credible mathematical link back to the actual "real" source frequency.
-Mike
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Understand. With the actual asset numbers it can be determined if it is a state aircraft or a contracted one.
nd5y
Member
Back in the late 70's and early 80's before digital displays I remember messing with military arcraft radios on static displays at airshows and they went up to 152 MHz
There are several AM milair channels used here in the DFW area between 148-150 MHz.
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