rebanding

[a23051coug]

Recently our county rebanned/narrowbanded our 158.760 chanel. Since then my scanner Pro106 will not pickup this chanel. I called the radio people and they said it shouldn't affect it. One other person is having the same problem. I am located in Miner County, SD. Any suggestions. Thanks

 

[ka3jjz]

There are simply too many variables here to even begin to analyze this issue. The antenna pattern at the transmitter site has changed (did they lower the antenna, or move it entirely?), the power has been reduced, something wrong with the antenna at your end (you didn't say what you are using)...there are probably other things I can't think of at the moment.

If you're just using the antenna that comes with the scanner, most of these duckies, as they're called, are about as good as a wet noodle at VHF hi frequencies. There are much better ones - even those that are tuned for the 2 meter ham band would be an improvement here.

A bit more homework is needed, I think. If you sit on the frequency and open the squelch, and you can hear it (perhaps a good deal weaker than you used to), then any of the above is a possibility.

As an aside, rebanding has nothing to do with VHF hi freqs, but narrowbanding certainly does....

best regards..Mike

 

[W8RMH]

As part of the FCC's requirement to narrowband, it may have also required a reduction of transmitter power, to only what is actually needed. This may affect your reception.

 

[RKG]

Another possibility has to do with the signal level of PLs or DPLs that your receiver sends to its decoder.

Narrowbanding involves reducing the maximum allowed frequency deviation from 5 KHz to 2.5 KHz. Your receiver translates deviation into amplitude of the audio signal, so if you use a wideband receiver to listen to a narrowbanded channel, the voice volume will sound low.

To some extent, a listener can compensate for reduced voice volume by manipulating the volume control. However, the deviation at which the sending station sends PL or DPL tones is also reduced by half, and the effect is the same as if a wideband channel reduced its PL or DPL from 500-750 Hz to 250-375 Hz (resulting in a reduction of signalling level from, say, -20 dBm to -23 dBm). This may put the PL or DPL below the level at which your receiver's decoder will detect it.

The test for this is to program the same channel CSQ and see if you hear transmissions.

By the way, "rebanding" and "narrowbanding" are not synonymous. Narrowbanding refers to the aforesaid reduction in maximum allowed FM deviation for certain Part 90 licensees. Rebanding refers to the de-allocation of a portion of the 800 MHz spectrum formerly used by other Part 90 licensees. The two phenomena have no relation to one another.

 

[N8IAA]

Recently our county rebanned/narrowbanded our 158.760 chanel. Since then my scanner Pro106 will not pickup this chanel. I called the radio people and they said it shouldn't affect it. One other person is having the same problem. I am located in Miner County, SD. Any suggestions. Thanks

Could it be that they went onto the SD statewide system? There are a lot of TGID's for the SO dept. They may use the conventional frequency for backup. You may want to ask in the SD state forum further down the forums page
HTH,
Larry

 

[a23051coug]

Thank you all for the answers. I found out they narrow banded. I hate to say it but I don't understand the responses I received except that there is no easy answer, or better yet, no answer I understand. Can anyone give me a step by step way of testing on the pro 106. Please don't be offended by my post. I'm just not very radio smart. Thanks

 

[ka3jjz]

Be more specific about what you don't understand and we'll try to clarify.

There are a couple of things to understand about narrowbanding - not only is the deviation (you can think of this as the amount of space the freq takes - and before I get flamed, yes that is a vast oversimplification) reduced, but if the power or the height of the antenna is reduced, it's going to be harder to hear. Think of a flashlight with a Krypton bulb - these burn quite brightly and can be seen for a great distance. Take that flashlight and put it near the ground, and the distance you can 'see' the light is vastly reduced. The concept is not all that different for radio.

If you are using this frequency with a tone (either a PL - otherwise known as Private Line - and perhaps more complex as CTCSS - or Digital Coded Squelch, which is somewhat different), it's possible that the deviation for the tone has been reduced too far for your scanner to pick it up reliably. That is why it was suggested that you try listening without a tone. Or as I had suggested, just sit on the frequency with no squelch and see what develops.

Incidentally I've put some links in here - they're in blue - from our online wiki glossary to help explain the terminology.

In any case it would seem, at least at first blush, that reprogramming the frequency as a narrow band FM mode would solve the issue. I'm not up on the RS object oriented scanners, but it shouldn't be all that hard. You didn't say if you were programming this with software or doing this by hand...that is assuming that the issue isn't being caused by a power reduction (just as likely) or an antenna change at the transmit site.

best regards...Mike

 

[a23051coug]

Thanks Mike, I appreciate your thoughts and time. I will try it out. I used the RS software to program it. May try a different antenna.

 

[a23051coug]

Mike I think our new system is using DCS since there is a telegraph type code that comes across when someone transmits.

 

[ka3jjz]

You should not be hearing anything insofar as PL or DCS is concerned (and the database lists 158.76 with a PL of 100.0). Most likely there's some MDC1200 type signaling going on. Mike