Specifications

and error. Things such as CTCSS, DCS and the modulation mode make programming even conventional channels a
challenge sometimes.
If you just want to listen to these basic analog channels then high-end models such as the PSR500 are not for you. It’s like
buying a Ferrari to drive two streets to pick up milk. It’s far too complicated and costly when a simple low-cost model will
work equally as well for basic channels. In much of the country nowadays though you must have the Ferrari or otherwise you
can’t listen any longer. There’s no such thing as a simple (and low-cost) scanner that can monitor advanced radio systems.
The PSR310 is a great radio for those who just don’t need a more expensive digital scanner.
FM vs. NFM vs. WFM
When you program in a conventional channel you need to know the proper Modulation Mode. If you are listening to aircraft
in the 108-136 or 225 thru 400 MHz. bands then AM is the proper mode. Beyond that most communications are either
regular FM or Narrow FM (NFM). Since the PSR310 does not include the FM broadcast band it also does not include the
WFM mode.
Over the last few years, and continuing until the end of 2012, most conventional channels have been or will be converted
from what scanners usually call “FM” to a narrower format called Narrow FM. This allows additional channels to be
squeezed into the same amount of spectrum.
Until recently most VHF High Band (150 to 162 MHz) channels have been 15 KHz. apart, for example, the next frequency
used after 155.250 was 155.265, then 155.280. With the Narrowband initiative the channels are now closer together, 7.5
KHz. apart. 155.250 is followed by 155.2575, then 155.265, then 155.2725 and followed by 155.280. All users of the new
channels in-between older channels must use NFM, and users of the existing older channels must convert to NFM by the end
of 2012.
UHF is affected the same way, but some of the rules are different. Originally regular channels were 25 KHz. apart, for
example, 460.275 was followed by 460.300 and then 460.325. The in-between channels (called “Interstitials”) 12.5 KHz.
apart from the main channels (460.275, 460.2875, 460.3000, 460.3125, 460.325) were restricted to low power use only. With
the new rules these “12.5 KHz. Channels” or Interstitials were allowed to use the same power levels as the original main
channels (subject to certain rules of course) and new 6.25 KHz. offset channels were allowed for use at low power.
In many areas the available pool of original VHF and UHF channels were used up and this method of refarming the available
spectrum allows more channels to be squeezed in. It is not without precedent, the same thing has been done several times in
the past, when VHF channels were changed to 15 KHz. separation from 30, and 60 was the norm before that.
How will I know whether to use FM or NFM?
While the new channels are almost always going to be using the NFM mode, older channels could use either, at least for now.
Unless you know for sure you may have to try both methods and see which works best. If you select FM now, your local
agency might switch over any time, requiring you to adjust your programming. If you chose the wrong mode you will still
hear the communication, but at a reduced volume or with distortion. If the volume is low compared to other nearby stations,
then you are likely programmed to FM on a NFM channel. If the conversation sounds distorted or over-driven (like many CB
operations) then you may have a channel programmed in narrow mode still using regular FM.
Since many channels are shared among many users, some may have switched over to NFM while others have not, at least not
yet. If listening to both NFM and FM users on the same scanner channel is not working for you then you could use the
CTCSS or DCS feature and program in a separate channel for each.
PL, DPL, CTCSS, DCS, etc.
Years ago radio manufactures hit on a great idea. Transmit a low level tone on a radio channel so that radios equipped with a
special decoder would only hear radios transmitting that tone. This way users would not have to listen to all the rest of the
users of the channel, either local or when “Skip” comes in. Eventually dozens of different tones were developed by
manufacturers and 38 of them were more or less standardized. The various manufacturers had different trade names for this
feature, Motorola’s “PL” (Private Line) was the most used. It kind of became a generic name for the feature even though it
was offered by GE, Kenwood and many other vendors, much like Kleenex has become a generic name for facial tissue. The
scanner manufacturers call the feature by its technical name of Continuous Tone Coded Signal Squelch, or more succinctly,
CTCSS. These are expressed in Hz., with one digit right of the decimal point, ranging from 67.0 to 254.1 Hz.