Batboard

Hi
My County is in the process of narrowbanding. We were planning on programming mobiles and portables in advance of our programming the repeaters etc and for a while going narrowband into wideband receivers. We don't have a lot of conventional radio channels. We are mostly Motorola digital, trunked, simulcast. We have a handful of conventional TAC channels and all the city PD's are conventional. Other than the volume issue our initial testing using several city PD repeaters and simplex showed good results and minimal problems. Then we did some testing on our TAC channels which have voted receivers and comparators. With some models of radios ( specifically Motorola XTS3000 portables and Astro Specta mobiles) we are having trouble opening and/or voting receivers. We do not have this problem with XTS5000's, XTL series mobiles or the new APX radios. Turns out that in narrowband, the XTS3000 puts out about 350 Hz of PL while the other radios are closer to 450 Hz PL when in narrowband. Motorola says there is no way to up the PL in XTS3000's. Is there anything in the CPS that Moto hasn't told us about that might help or have you heard of anyone solving this problem coming from the Astro-Tac receiver / comparator end?

turn your deviation down from 5 khz to 2 khz on the transmitting units that are wideband.. the more you deviate on wideband into a narrowband voter, the voter will sense and cutoff the audio passing through it.. This will solve your problem and scream as loud as you can into a wideband radio while adjusting the deviation to avoid clipping

With modern microprocessor/DSP based equipment there probably isn't much you can do to increase the PL deviation of the sending units or the PL decode sensitivity of the voting receivers.

I would consider connecting an external third-party PL decoder to the receivers. Adjust it to respond down to about 250 Hz PL deviation which would be the lowest value a narrow-band radio would be expected to transmit.

Connect the decoder output to a receiver wildcard input. Reprogram your receivers so that input becomes the aux detect signal and change your receiver qualifiers accordingly.

I'd go through the alignment procedures of the XTS3K and Astro Spectras to increase PL dev.

Are the voting receivers narrow band? When they are set for narrow band the receivers will open with the standard PL or DPL deviation from the mobiles and portables.

In my city we are changing from PL to DPL and adding narrow zones. That way when we convert next year only the narrow zones will work since the wide PL zones will not work. We will have a massive infrastructure change out and we will only have to tell the users to change zones. All of the sites and voter sites will change at the same time.

I haven't seen a working Motorola radio that wouldn't decode down to about 100hz of PL/DPL before failing. Are your voters some other type of receiver other than Motorola?

I would just create a seperate zone in all the radios for the wide band stuff... and replace the current zone with narrow band channels.. have them operate in the wide band zone as needed until they get everything in place and then tell everyone to go back to the old channels (which are actually the new narrow channels)
As you repair or PM the radios, replace the codeplug with one that doesn't have the wideband channels after the conversion.

The XTS3000 and Astro spectra were turned down to narrowband - 2.5K. Can't adjust PL levels in CPS, as far as I can tell, and Moto says it can't be done. Are they right? We already confirmed that the mobiles and portables decode at as low as 100Hz.
Problem doesn't seem to be there on the City's repeaters
On our much more expansive system the receivers are taking too long to select, resulting in an over the air clicking noise.
The voters are currently wideband and made by Moto
Looking for a prime site fix. We will be going out to all the sites, eventually, to change the bases and receivers to narrowband. However our annual maintenance cycle is starting and the templates will be modified at that time. It's a real pain getting the officers to bring their units in and if we are trying to avoid having to call them in twice for just a handfull of channels

the voters aren't wide or narrow band, it's the receiver that is one or the other.
issue is if your RECEIVERS are set wide and you are talking into them narrow, you are sending only half the signal they are expecting.
Second issue is if you crank up the audio out on the receivers so the levels are correct, you crank up the noise floor levels as well. This signal to noise levels are what the voters
operate on. It's seeing more noise floor and less audio intelligence. Basically they have gone from voting the best signal to what we do at the polls for president. Choosing the lessor of to bad choices.

Proving this is easy too, as far as troubleshooting. If you are using a narrow band programmed radio, set one receiver that can hear your portable but not the one at the site you are at.
Program it to narrow band receive and then do a couple over the air checks. Chances are that you will vote that site every time even though you are standing under the local receive antenna.

Here's why it's doing all this. Radios have an AGC (automatic gain control) in the receiver audio circuit. It boosts weak audio signals to intelligible levels and brings those with a wreak voice up to the same level that a standard persons voice would be. Problem with AGC is that it's all or noting. When it boosts the intelligible voice audio it also boosts the noise floor level.
Say you have an audio level on wide band (subscriber and receiver set wide) of -10 db and the noise floor is -40 db. At these levels the voter system can see a clear difference in the two and vote quickly and correctly. It's based on a sinad test more or less, but it's not done at -12. The AGC is happy and a strong signal gets NO additional gain added to it in the receiver.

Now if you program the subscriber unit to narrow band and leave the receiver in wide band the signal level is -20 and the noise floor is still -40
this math is a bit off but it shows how it all works.
a strong signal is now -20, the AGC boosts it to -10. Problem is that it boosts the -40 noise floor to -20. The original seperation in wide band was signal at -10 noise at -40 or 30 db differece.
now you have boosted signal of -10 with a doubling of signal... noise floor is doubled as well it went from -40 to -20 seperation went from 30 db to 10 db. and the voter thinks it's a crap signal and looks at other signals. It see's crap on all the inputs and round robins the vote trying to track a better S/N (signal to noise) ratio to vote. The clicking you hear is the voting taking place. This also indicates that you have some levels out of whack on the voters from the receivers.
To address that, you need two techs. One at the receiver sites and one at the voter with an audio voltmeter. have them inject a signal on the receiver with a fixed level and then set the output to match all sites as you read them on the audio volt meter.

All that being said. You are asking too much of the voter. It votes on S/N ratio and yours are all out of whack because you are running wide band receivers with narrow band subscribers.
Only way around it is what I mentioned above, program a new zone in the radios. Add the current wide channels in it. Go into the current zone and set the channels to narrow. (I think you did this already.) Have the users operate in the newly created zone until you have the infrastructure changed over to narrow band. Then thy simply go back to the current zone with the narrow band channels.
Once narrowbanding is complete you can take the zone out of the radios at your leisure.