USFS Programming

[RobertW1]

I appologize if this question is not in the proper forum... When programming the USFS frequencies for ANG or BNF how important is it that you use the Narrow FM band mode on the scanner. Will you receive the signal as well if it is under FM or WFM mode? How important is it to have the proper mode selected when dealing with FM?

 

[oregontreehugger]

I believe programming them as narrowband boosts the audio output due to the fact that narrowband isn't as strong of a signal.

I have programmed narrowband USFS frequencies in a scanner without narrowband capability -- all that I've noticed is the audio is lower when folks are talking.

I'm sure there is someone who can lend a little more detail about it...

 

[SCPD]

I appologize if this question is not in the proper forum... When programming the USFS frequencies for ANG or BNF how important is it that you use the Narrow FM band mode on the scanner. Will you receive the signal as well if it is under FM or WFM mode? How important is it to have the proper mode selected when dealing with FM?

I assume by ANG and BNF you mean the Angeles and San Bernardino National Forests. Not ot be too technical but the official Incident Command System (ICS) identifiiers for them are ANF and BDF. You can look up almost every fire department likely to be involved in wildland fire (depending on the state) in the U.S. here:

http://www.nifc.blm.gov/nsdu/unit_id/Publish.html

Now for your question. I don't know how the narrowband function works on the newest Uniden scanners. The switch to narrowband by the federal government in January 2005 is causing problems for scanner owners such as oregontreehugger related. Narrowband means the channel spacing and bandwidth has been cut in half. The receiver puts out a given volume for the older maximum 20 kHz wide signal and now is receiving those with a maximum 10 kHz signal also accounting for the difference.

Beyond that someone with a lot more technical know-how needs to explain this futher because I've never used one of the new narrowband radios and don't know if they have varying volumes depending on the bandwidth of the signal being received. Since the new radios must both transmit and receive on non-narrowband systems for quite some time to come, I dont' have first hand knowledge of whether they receive the wider signals at an increased volume. Maybe someone can shed some light on this. I suspect the newer narrowband radios automatically compensate between 10 and 20 kHz signals so different volumes don't result.

I've also wondered why their isn't a notable difference between VHF and UHF on scanners as most scanners have been capable of tuning in 12.5 kHz steps for decades now. When I look through licenses in the UHF band I see they have a 20 kHz maximum bandwidth specified just like the VHF licenses do (20K0F3E) so apparently channels are not licensed with a true 12.5 Khz spacing, or were not at the time of license issuance. Again, someone with more technical knowledge should be able to answer this.

 

[digitaljim6]

Narrowband means the channel spacing and bandwidth has been cut in half. The receiver puts out a given volume for the older maximum 20 kHz wide signal and now is receiving those with a maximum 10 kHz signal also accounting for the difference.

There are two factors at work. One is the channel spacing and the other is the bandwidth. On 450-470 MHz for example, the channels were spaced 25KHz apart and now are mostly 12.5KHz apart. The 20.0KHz bandwidth that the signal can occupy (as shown by 20K0F3E) has gone down to a little more than 11Khz (11K2F3E). This provides a little "guardband" between adjacent signals so the risk of adjacent channel interference is reduced or eliminated. Within 450-470 MHz, new licenses or modifications generally require changing the bandwidth from 20K0 to something narrower like 11K2.

In VHF (like 150-160), channel spacings vary but are generally 15KHz for wide and 7.5 for narrow. For example, the new CDF Air Tactics 21 (151.2725) and 22 (151.2875) frequencies are 7.5 KHz below and above Air Tactics 4 (151.280) to split the 15KHz channel spacing previously used. The licensed bandwidth for these channels is 11.2KHz (11K2F3E). If they haven't done so already, they need to get Air Tactics 4 and 5 narrowbanded so they can use them along side of 21 and 22. The big deal will be getting CDF Command 2 (151.265) narrowbanded so that 21 will be usable.

I suspect the newer narrowband radios automatically compensate between 10 and 20 kHz signals so different volumes don't result.

My experience is that they generally do. Selecting the right "mode" changes the receiver's filters and somewhat adjusts the volume to make it sound the same between the different bandwidths. Some radio systems may be set for lower than licensed deviation so they will appear to have lower than expected volume.

I've also wondered why their isn't a notable difference between VHF and UHF on scanners as most scanners have been capable of tuning in 12.5 kHz steps for decades now. When I look through licenses in the UHF band I see they have a 20 kHz maximum bandwidth specified just like the VHF licenses do (20K0F3E) so apparently channels are not licensed with a true 12.5 Khz spacing, or were not at the time of license issuance. Again, someone with more technical knowledge should be able to answer this.

My experience has been that the 12.5 steps in older scanners took care of the spectrum pieces where the spacing was still 25 but the channels started on a 12.5 boundary (perhaps like 452.0125 then 452.0375 then 452.0625 instead of 452.000, 452.025, 452.050). My older scanners thought in terms of 25 KHz boundaries so 452.0375 was not possible without a 12.5 step.

Not sure what licenses you are looking at but the narrow ones are there. By the way, the info that RR displays when using its links to see license info displays the emission designators incorrectly in many cases. I reported it to Lindsay and it's on the list of things to fix - an SQL query problem. The designators will be correct but their relationship to what frequency uses them may not be.

Here are some UHF systems that have other than 20K0 emissions in Mono County. You can retrieve the license info on the FCC website at http://wireless2.fcc.gov/UlsApp/UlsSearch/searchLicense.jsp
and enter the callsign. Easiest thing to do is click on the callsign after the search returns and then select "Reference Copy" above the four blue tabs. This gives you a license "lookalike" that probably has the most useful info.

WNKU887 - Mono County - look at the 453/458 freqs - 11K0F3E.
WPGY991 - Mammoth Mountain Ski Area - 15K0F2D (data)
WPNU512 - State of CA - 11K3F3E - possibly a point-to-point link to a remote transmitter. One end is probably on Crestview. I'd guess either CHP or CalTrans.
WQAQ850 - Neal & Neal Foods in Bishop - 11K2F3E

 

[SCPD]

I didn't think to click on those licenses when I looked up some of the emission data on the FCC sites. Trying to post quickly and off the top of my head again.

The link you mentioned is to link the Caltrans repeater on Queen Bee Hill near Bodie to the microwave site east of the Crestview Maintenance Station on 395. The new Caltrans radios are labeled with the mountain top site or the area a particular frequency/tone combination works the appropriate repeater. So in this area there is a channel labeled "Conway" because everyone knows where that is, but Queen Bee is actually shown as "June Lake" on the display because that is the area the Queen Bee repeater was put in to serve and not many people know where Queen Bee Hill is.

Thanks for the explanation of bandwidth and its affect on volume. None of the older UHF scanners I used, which would have been unable to tune in the 12.5 spacing, are currently being used in my shack. I still have them in the dark spaces of my loft, but they don't get turned on more than once per 5 years. I had forgotten that they would not tune in the 12.5 spacing in UHF.

 

[digitaljim6]

I still have a very old handheld scanner that I occasionally use. There are many things it cannot do compared to current units. One is modes. It has "AM" and "FM". "FM" doesn't quite cut it now that there are narrow systems next to other narrow systems in the same area. It has no menu, only buttons. I keep looking for a button to do a common function that current units have and it doesn't exist.

I didn't think to click on those licenses when I looked up some of the emission data on the FCC sites. Trying to post quickly and off the top of my head again.

The link you mentioned is to link the Caltrans repeater on Queen Bee Hill near Bodie to the microwave site east of the Crestview Maintenance Station on 395. The new Caltrans radios are labeled with the mountain top site or the area a particular frequency/tone combination works the appropriate repeater. So in this area there is a channel labeled "Conway" because everyone knows where that is, but Queen Bee is actually shown as "June Lake" on the display because that is the area the Queen Bee repeater was put in to serve and not many people know where Queen Bee Hill is.

Thanks for the explanation of bandwidth and its affect on volume. None of the older UHF scanners I used, which would have been unable to tune in the 12.5 spacing, are currently being used in my shack. I still have them in the dark spaces of my loft, but they don't get turned on more than once per 5 years. I had forgotten that they would not tune in the 12.5 spacing in UHF.