Conventional VHF

[N8NCX]

Am I correct in assuming that all conventional VHF systems for law/fire operate in a narrow band (12.5khz)
mode these days? It would explain why these systems all sound weak audio-wise having only half the deviation of say ham radio. Is there anything that can help increase the volume besides turing it up? Some of the cars in our local conventional law system have so little modulation it's impossible to hear the traffic but dispatch always seems to be able to.

[Ed_Azalea]

A lot of them already are but all will be 1-1-2013. Narrowbanding - The RadioReference Wiki

[cabletech]

Yes in narrow band mode, the audio is 'lower' then what everyone has been used too. Most newer scanners will allow you to set each frequency to either WB FM or NFM.

Check your settings and change the frequecy to NFM.

[Ed_Azalea]

Actually I didn't read the link completely and "narrowbanding" doesn't just create new frequencies between the existing ones, but also reduces the modulation deviation in half. That's why the audio is not as loud on a normal "wideband" setting on your scanner.

[N8NCX]

Originally Posted by cabletech

Yes in narrow band mode, the audio is 'lower' then what everyone has been used too. Most newer scanners will allow you to set each frequency to either WB FM or NFM.

Check your settings and change the frequecy to NFM.

So setting the listening device say a GRE PSR-600 to Narrow will increase the volume? I'll give it a try.

[budevans]

Originally Posted by N8NCX

So setting the listening device say a GRE PSR-600 to Narrow will increase the volume? I'll give it a try.

I have a PSR 500, setting to NFM did not increase the volume. But, you can select Audio Boost for each freq. I did that in one pass by using WIN500 to select the VHF freq's and then clicked on Audio Boost.

[N8NCX]

Originally Posted by budevans

I have a PSR 500, setting to NFM did not increase the volume. But, you can select Audio Boost for each freq. I did that in one pass by using WIN500 to select the VHF freq's and then clicked on Audio Boost.

I've set the audio boost and it helps on the GRE. The dispatch seems to be much louder than the cars. And in a small city where there are only 4 cars on the road there is one in particular that most times you have to put the radio right up to your ear to hear his voice. Not sure if this officer uses the same car all the time but he is really hard to hear. Like he holds his mic a couple feet away from his mouth. But overall the deviation is quite thin except dispatch. I think it's more of a problem with their gear.

[mdulrich]

If it is this one officer, he most likely has poor radio habits. I've seen officers who don't even remove the mic from the holder when they talk or have the mic laying on the seat and talk from there. Sometimes officers use portable radios with lapel mics that aren't anywhere close to their mouths.

Mike

[N8NCX]

Originally Posted by mdulrich

If it is this one officer, he most likely has poor radio habits. I've seen officers who don't even remove the mic from the holder when they talk or have the mic laying on the seat and talk from there. Sometimes officers use portable radios with lapel mics that aren't anywhere close to their mouths.

Mike

One in particular is horrible. And yes it sounds like he is using a portable with external mic clipped to his shoulder and looks straight ahead while talking. It exacerbates a system where the cars deviation is already lacking. I think I'm going to go to the FCC site and see what freq the repeater input is and listen
to the cars direct. Maybe it's the repeater output that is under modulated.

[Ed_Azalea]

Originally Posted by N8NCX

. Maybe it's the repeater output that is under modulated.

The repeater only sends what it hears. If the unit's audio is low it's not going to get boosted when retransmitted. I really don't know but there may be something like AGC is some repeater systems that could do that.

[N8NCX]

Originally Posted by Ed_Azalea

The repeater only sends what it hears. If the unit's audio is low it's not going to get boosted when retransmitted. I really don't know but there may be something like AGC is some repeater systems that could do that.

A repeater has a transmit deviation setting. It's not like a linear amp. However if the repeater's receiver isn't demodulating the audio properly and passing low deviation to to the exciter the problem could be
in the repeater's receiver. As I mentioned dispatch seems to be properly modulated so if they are sending directly from the repeater which they may be because the repeater is located at the PD, then it could be an issue of what the repeater receiver passes on to the exciter.

[Ed_Azalea]

Yep, I'm quite familiar with repeater operation. I spent the better part of 50 years in the LMR field. But you are right in that if the dispatcher is hardwired in, the audio setting may differ from the receiver audio.

[N8NCX]

Originally Posted by Ed_Azalea

Yep, I'm quite familiar with repeater operation. I spent the better part of 50 years in the LMR field. But you are right in that if the dispatcher is hardwired in, the audio setting may differ from the receiver audio.

Something else very odd about the repeater output. When my PSR-600 is set to decode conventional PL tone, it won't stop on the channel. I've narrowed it down to the signal strength. Being a mile away from the repeater when I use a rooftop antenna, the 600 won't stop when the channel is active. Use the telescoping indoor antenna and it stops. But it only does it with this repeater. I can take the 600 mobile to another conventional repeater using PL tone and sit right under the tower and the 600 will stop. Wish I didn't have to sell my old Aeroflex test set, I might have been able to see what if anything was riding along with the signal or tone itself that causes the PSR-600 to act up. My old Uniden isn't bothered and stops with PL on. Same with all my amateur gear. So for now I turn the PL off. I liked to use PL so I didn't hear the station ID.

[jim202]

Originally Posted by N8NCX

Something else very odd about the repeater output. When my PSR-600 is set to decode conventional PL tone, it won't stop on the channel. I've narrowed it down to the signal strength. Being a mile away from the repeater when I use a rooftop antenna, the 600 won't stop when the channel is active. Use the telescoping indoor antenna and it stops. But it only does it with this repeater. I can take the 600 mobile to another conventional repeater using PL tone and sit right under the tower and the 600 will stop. Wish I didn't have to sell my old Aeroflex test set, I might have been able to see what if anything was riding along with the signal or tone itself that causes the PSR-600 to act up. My old Uniden isn't bothered and stops with PL on. Same with all my amateur gear. So for now I turn the PL off. I liked to use PL so I didn't hear the station ID.

Let me inject some comments here that may lend to understanding some of the issues.

There are few good radio techs out there today that still understand just how to set repeater audio today. In many cases they set the audio too hot and you hear a bunch of background noise when no one is talking, like long pauses between words. This just compresses the passed through audio and starts to distort what you hear going through the repeater.

With narrow banding just about complete, many of the repeaters now have too low of audio being passed through. Again the radio techs don't seem to know just what level to set the repeaters at.

The PL decode has been mentioned. In the process of narrow banding, the PL level also gets lowered. If the basic radio adjustment is not correct, the PL encode will be low. This is common on many of the newer Motorola radios. Seems like the boys at the plant never took the time to set the test system up correctly and this is the results. I have seen radios where the max deviation on the old +/- 5.0 KHz setting barely make audio at 4.0 Khz. This is way on the low side, but that is the way the manual says to set it. I don't agree, but unless you ignore the recommended settings, that is what you end up with.

Many of the scanners on the market today were not designed for the narrow banding that is taking place today. The issues are just what your talking about. Low audio recovery, problems with trying to use PL decode to mute the receiver and strong signal overload.

With the amount being charged for these scanners, you would expect better results. But they are pushing off a poor front end design that results in overload from strong signals not even near the frequency your trying to listen to. As long as people put up with the poor performance and keep buying this kind of crap, the companies supplying this poor product won't change the design. As the old saying goes, you get what you pay for. Only in this case, your not getting what you pay for.

[N8NCX]

Originally Posted by jim202

Let me inject some comments here that may lend to understanding some of the issues.

There are few good radio techs out there today that still understand just how to set repeater audio today. In many cases they set the audio too hot and you hear a bunch of background noise when no one is talking, like long pauses between words. This just compresses the passed through audio and starts to distort what you hear going through the repeater.

With narrow banding just about complete, many of the repeaters now have too low of audio being passed through. Again the radio techs don't seem to know just what level to set the repeaters at.

The PL decode has been mentioned. In the process of narrow banding, the PL level also gets lowered. If the basic radio adjustment is not correct, the PL encode will be low. This is common on many of the newer Motorola radios. Seems like the boys at the plant never took the time to set the test system up correctly and this is the results. I have seen radios where the max deviation on the old +/- 5.0 KHz setting barely make audio at 4.0 Khz. This is way on the low side, but that is the way the manual says to set it. I don't agree, but unless you ignore the recommended settings, that is what you end up with.

Many of the scanners on the market today were not designed for the narrow banding that is taking place today. The issues are just what your talking about. Low audio recovery, problems with trying to use PL decode to mute the receiver and strong signal overload.

With the amount being charged for these scanners, you would expect better results. But they are pushing off a poor front end design that results in overload from strong signals not even near the frequency your trying to listen to. As long as people put up with the poor performance and keep buying this kind of crap, the companies supplying this poor product won't change the design. As the old saying goes, you get what you pay for. Only in this case, your not getting what you pay for.

The problem with today's scanning receivers is the manufacture is trying to do too much. People want a radio that will do everything but cook your dinner in the $350 dollar range. So there has to be a compromise in performance to keep costs out of the thousands of dollar range. The GRE 500/600 is a good radio for all it covers. It just doesn't do anything superbly, it can't. But it beats the hell out of buying a Motorola Astro 1500, Icom R9500, EF Johnson Ascend. I think most of our local conventional system's problems are just the poor technical service provided.