Local P25 problem solved for BCD436HP?

[kc5igh]

I may have solved a problem I've been experiencing while trying to monitor a local P25 system with my BCD436HP.

For several months now, I've been complaining about how poorly my 436 tracks a nearby P25 system that comes through loud and clear on my other digital-capable scanners. The 436 had been missing 40% to 50% of these transmissions, which was a real mystery to me because it does well with other P25 systems and channels. Turning on the attenuator helped quite a bit (I still don't understand why), but the results were still pretty far south of what I was experiencing with the other radios.

This is a Harris system that uses frequencies in the federal government UHF trunked frequency range (406 to 420 MHz), and it's undergoing a conversion from EDACS to P25. When I programmed the 436, it seems that the radio must have decided this was a Motorola site that needed a custom band plan, so it gave itself a generic 406/12.5 kHz base/step plan. Deleting the generic custom band plan seems to have cleared up the problem.

Now, if I cam only get the 436 to perform even half as well on VHF analog as it generally does on digital, I'll really be a really happy camper! It's still practically deaf on VHF analog compared to its BCD396T and BCD396XT sisters and its GRE-designed cousins. Unfortunately, most of the agencies I monitor are analog VHF and will probably remain so for a long time.

I hope this comes as helpful news to others out there who may be having similar problems.

Thanks for listening.

-Johnnie

 

[kc5igh]

I may have solved a problem I've been experiencing while trying to monitor a local P25 system with my BCD436HP.

For several months now, I've been complaining about how poorly my 436 tracks a nearby P25 system that comes through loud and clear on my other digital-capable scanners. The 436 had been missing 40% to 50% of these transmissions, which was a real mystery to me because it does well with other P25 systems and channels. Turning on the attenuator helped quite a bit (I still don't understand why), but the results were still pretty far south of what I was experiencing with the other radios.

This is a Harris system that uses frequencies in the federal government UHF trunked frequency range (406 to 420 MHz), and it's undergoing a conversion from EDACS to P25. When I programmed the 436, it seems that the radio must have decided this was a Motorola site that needed a custom band plan, so it gave itself a generic 406/12.5 kHz base/step plan. Deleting the generic custom band plan seems to have cleared up the problem.

Now, if I cam only get the 436 to perform even half as well on VHF analog as it generally does on digital, I'll really be a really happy camper! It's still practically deaf on VHF analog compared to its BCD396T and BCD396XT sisters and its GRE-designed cousins. Unfortunately, most of the agencies I monitor are analog VHF and will probably remain so for a long time.

I hope this comes as helpful news to others out there who may be having similar problems.

Thanks for listening.

-Johnnie

Hello, it's me again.

I just noticed that my 436 reverts to a custom bandplan (406.0/12.5) for the Harris P25 system I referenced above every time I turn the radio off and back on again. It seems that the 406-420 MHz federal trunked frequency range I'm trying to monitor has got the radio believing it needs a custom bandplan.

Would those of you who understand this radio better than I do answer a couple of questions, please?

1. What, if anything, can be done to keep it in "P25 Trunk" mode, rather than let it default to what I suspect must be "Motorola/P25" mode?

2. Should being in Motorola/P25 mode (if that's where I am) really make a difference while monitoring this Harris P25 radio system?

Any help would be deeply appreciated.

Thanks!

-Johnnie

 

[UPMan]

All VHF/UHF trunked systems require a custom band plan. For most P25 systems, that band plan is sent over the control channel. The scanner stores the band plan, when received.

 

[KevinC]

Which other radios do you have that are successfully tracking this system?

I suspect the system isn't sending the bandplan OTA.

 

[kc5igh]

All VHF/UHF trunked systems require a custom band plan. For most P25 systems, that band plan is sent over the control channel. The scanner stores the band plan, when received.

Thanks, Paul, I'm sure that's what's happening.

I thought turning the radio off and back on caused it to reset to some sort of default band plan, but if I'm following what you're saying correctly, the 406.0/12.5 base frequency/step band plan that reappears is "real," not some kind of default setting driven by the fact it's a UHF (406-420 MHz, not 800 MHz) system.

I appreciate the help!

-Johnnie

 

[kc5igh]

Which other radios do you have that are successfully tracking this system?

I suspect the system isn't sending the bandplan OTA.

Hello, Kevin.

I'm running a PRO-106 alongside the 436 as I write this, and the 106 "seems" to have an edge on the 436 in terms of fewer missed replies and picking up the beginning of transmissions more quickly. I say the 106 "seems" to have an edge on the 436 because once in a great while, the 436 will catch a transmission that the 106 skips. I've tried to program them as much alike as possible (e.g., same delay times) to make any comparisons a little more objective.

Paul Opitz' response above tells me that the system is indeed sending the band plan OTA (OTA = over the air?), and that's why I see the 406.0/12.5 band plan pop up again in the 436 after I've deleted it.

The PRO-106 and my other GRE-made scanners can be programmed in something GRE calls "P25 Auto" mode, which results in a "default" band plan setting, so it seems to me that they're doing essentially the same thing that the Uniden radios do when it comes to VHF/UHF trunked systems.

The fact that the system I'm trying to monitor is still in its infancy may also have something to do with all this.

Thanks for responding!

-Johnnie

 

[Ghstwolf62]

Could changing your default bandwidth for those frequencies help with it possibly? I remember something from a long time ago about changing them to 6.25 from default 12.5 to improve trunking on a system out here. There are multiple choices.

 

[kc5igh]

Hello, Ghstwolf62.

I doubt that changing the default bandwidth would help, but I may give it a try just for the heck of it.

With the trunked radio system itself providing the band plan information, as Paul Opitz pointed out above, I'm now thinking this is as good as it's going to get for the time being. My other radios (e.g., the PRO-106 and BCD396XT) are tracking this system pretty well, and I'm sure they're all working with the same band plan and default band width settings.

There may be some other settings in the 436 that could be tweaked to improve its reception, which I will explore more thoroughly (e.g., delay time, hold time, FM, NFM, etc.).

Thanks for the suggestion.

-Johnnie

 

[scanman1958]

Thought I would ask a nagging question about custom band plans.

I am gathering from Paul's response that 'most' P25 trunked systems 'automatically' send the band plan information on and through the control channel. My assumption is that the scanner decodes it properly and all is well. I actually did not know that.

Why would some systems (according to Paul most VHF-UHF systems) need a 'custom' band plan? Why don't all trunked systems send the info automatically? I remember having lots of problems trying to monitor Scott AFB in metro east IL (St Louis) and I was told (I think) I needed a custom band plan for that system. To figure it out I was pulling my hair our thinking I needed a calculus major to do the math. Is that the same kind of band plan that is being talked about here? The problems that kc5igh was having is similar to mine until I figured it out.

Thanks for any reply.

 

[kc5igh]

Hi, scanman.

That's a good question.

Like yourself, I thought that new P25 systems, like the Harris system I'm trying to monitor, relied on the system computer and control channel to automatically assign frequencies (essentially like the "control channel only" option we have on the BCD396XT for 800 MHz trunked radio systems).

I knew that other VHF and UHF (e.g., 406-420 MHz) systems require custom band plans, which can really be a challenge to calculate, especially with large systems that have multiple custom band plans, and I've been able to successfully work those out using the custom band plan table Uniden provides.

The BCD436HP owner's manual led me to believe (mistakenly) that the only time I needed to worry about editing the band plan in the radio was for "Motorola/P25" systems, not for other non-Motorola P25 systems, so I was surprised to see a 406.0/12.5 band plan pop up in the 436 (which, by the way, also happens in the 396).

The GRE-made radios have a "P25 auto" setting that apparently also receives and inserts custom band plans as necessary, but I don't believe you can see what the base frequency and step are the way you can in Uniden radios (I'll have to look into this).

All this is probably my mistaken interpretation of the owner's manual. I haven't had a chance to do any independent research on how the various P25 systems out there manage themselves.

-Johnnie

 

[scanman1958]

Where can you find the Uniden band plan table you mentioned?

Glad to see we all (well most of us) are still learning how things work in the scanning hobby. Just wish it wasn't so hard to figure them out. Ha.

 

[kc5igh]

Here you go, scanman:

CalculatingUpperBaseFrequencies < UnidenMan4 < TWiki

Good luck!

-Johnnie

 

[Ghstwolf62]

Hello, Ghstwolf62.

I doubt that changing the default bandwidth would help, but I may give it a try just for the heck of it.

With the trunked radio system itself providing the band plan information, as Paul Opitz pointed out above, I'm now thinking this is as good as it's going to get for the time being. My other radios (e.g., the PRO-106 and BCD396XT) are tracking this system pretty well, and I'm sure they're all working with the same band plan and default band width settings.

There may be some other settings in the 436 that could be tweaked to improve its reception, which I will explore more thoroughly (e.g., delay time, hold time, FM, NFM, etc.).

Thanks for the suggestion.

-Johnnie

That may well be true. It seems often the tweaks are specific to the system the user is needing help with. Some for instance say changing to manual from auto and setting 11-13 dramatically increases P25 decode yet out here on the statewide VHF system its manual and 7 that does the job. Setting it 11-13 kills all reception.

Some as you mention have had luck with NFM vs FM on reception while others have said it makes no difference. Rolling back firmware for some seems to help while others it does not. Its pretty much going to be experimentation to hopefully find something that does work.

I know there is that default bandplan that everything operates from which is what I was talking about. I hope it does help you. It made a difference for a lot of people in Virginia I know with the statewide system. It defaults to 12.5 and it needed to default to 6.25 to completely decode the system from what I understand of it.

Good luck with it. Be interested to know what you hopefully find to work for your system out there.

 

[kc5igh]

Hello again, Ghstwolf!

I've been on the road and unable to try tweaking any of the settings we've been discussing. Before I left the office, I was running my PSR-800 alongside the 436 on this system, and the 800 was tracking everything loud and clear. The 436 was skipping the very first part of some of the transmissions, particularly those that were quick responses to a previous transmission, almost as though the radio was hung up somehow on the first transmission and couldn't receive the next signal until it had a chance to resume scanning again.

This was all happening on the same talkgroup, so I couldn't chalk it up to the delay setting (or hold setting, since I was only monitoring one system). It's been hard to understand because all my other P25-capable scanners (Uniden and GRE) track this system much more effectively.

Today is Saturday, and the system is not being used, so I'll have to wait until Monday when it comes back to life.

Thanks for checking in on me, and have a good weekend!

-Johnnie

 

[Ghstwolf62]

That is something that has been commented about before. Cutting off the first part of transmissions and stopping on a TG and there is no audio.

I found for me the latter was it stopping as the audio on the TG ended. So nothing was coming through.

The other I think has to do with the scan speed. As you said it takes time to get back around to it and misses first part of transmissions. Scan speed could sure stand to be increased on these. Locking them down onto the system with the P25 alone does wonders but once you add other stuff then it has noticeable delays.

Another trick others found was to put everything into one favorite lists rather than multiple ones. Don't know if that applies to you or not but if it does it might help.

I still keep my 600 around and between the two I get everything covered. Plus it allows for different TGs to show up at same time. Its funny when I have RTL added in and get three different conversations going at once off the same site.

 

[budevans]

Hi, scanman.

That's a good question.

Like yourself, I thought that new P25 systems, like the Harris system I'm trying to monitor, relied on the system computer and control channel to automatically assign frequencies (essentially like the "control channel only" option we have on the BCD396XT for 800 MHz trunked radio systems).

I knew that other VHF and UHF (e.g., 406-420 MHz) systems require custom band plans, which can really be a challenge to calculate, especially with large systems that have multiple custom band plans, and I've been able to successfully work those out using the custom band plan table Uniden provides.

The BCD436HP owner's manual led me to believe (mistakenly) that the only time I needed to worry about editing the band plan in the radio was for "Motorola/P25" systems, not for other non-Motorola P25 systems, so I was surprised to see a 406.0/12.5 band plan pop up in the 436 (which, by the way, also happens in the 396).

The GRE-made radios have a "P25 auto" setting that apparently also receives and inserts custom band plans as necessary, but I don't believe you can see what the base frequency and step are the way you can in Uniden radios (I'll have to look into this).

All this is probably my mistaken interpretation of the owner's manual. I haven't had a chance to do any independent research on how the various P25 systems out there manage themselves.

-Johnnie

There are several older trunking systems that require a manual band plan. The Motorola Type II trunking system is one. It's also the trunking system that is most often confused for a Project 25 system. Since most Moto type II systems use P25 (cai) for audio.

All (certified) P25 Trunking systems adhere to the P25 Trunking standards, one of which is to transmit the band plan on the Control Channel.

Regarding the GRE radio's, you can view the P25 band plan that the Control Channel has downloaded with the appropriate software. In my case Win500.

Bottom line P25 trunk systems send the band plan for what ever band they are setup to run on, 800 Mhz, 700 Mhz, UHF, VHF.

Regarding Delay Time settings, try reducing it. If your scanner holds on a TG/channel after a transmission ends then it won't be scanning for the next active TG/channel. The three P25 systems I monitor all have there own delays, about 1 to 1.5 seconds from when the MIC is unkeyed. Adding additional delays would most likely cause you to miss other transmissions.

FYI, in some parts of the country (down south) the speech pattern is slower, so adding a delay can help to keep your scanner from missing a reply.

I look forward to hearing how your experimenting with the delay settings works out.

 

[kc5igh]

Hello, Ghstwolf and Bud.

The following is a quick update on my experiences with the tweaks and adjustments to the BCD436HP you suggested for the P25 system I'm trying to monitor:

-Modulation - toggling between FM and NFM seems to make no difference.

-Default bandwidth - moving from 12.5 to 6.25 may have negatively impacted reception, but I need to experiment a little more with this. The system wasn't experiencing much traffic when I tried this, and I need to spend a little time listening at the 6.25 setting.

-Hold time setting - changing from zero to two seconds seemed to make no difference. I'm generally only trying to monitor this system by itself, so there's not much point in messing with this setting since the scanner isn't trying to move on to another system most of the time.

-Delay time setting - I'm not finding a delay time adjustment for the 436's trunked system menus (systems/sites/departments) that would allow me to change "hang time" after transmissions. I'm guessing that delay times may be programmed by the trunked system itself. Any ideas?

-P25 threshold mode (and P25 adjustment mode) - the auto setting (level 8) seems to be pretty close to optimum (but so does manual level 5 - see below), but I'm not certain I'm following the manual correctly when I try to let the threshold levels adjust automatically. Should I leave the radio in manual or auto when I turn on the P25 adjustment mode? The instructions call for the radio to be in manual mode, but the adjustment levels don't seem to change from any manual setting I start with (5, 8, or 11). Am I doing something wrong?

-P25 adjustment level - moving the level to 11 and 12 seemed to negatively impact signal reception. Level 8 and 5 both seemed to be much better, but as I note above, I'm not certain I'm employing the P25 adjustment mode correctly.

-Automatic gain control - turning the AGC on or off seemed to make no difference.

Bottom line? I'd appreciate some advice about the P25 adjustment mode, but I'm beginning to think that the 436's apparent lower levels of signal sensitivity may have something to do with the difference between how well it tracks this system in comparison to my other digital-capable scanners (GRE and Uniden).

Thanks!

-Johnnie

 

[Ghstwolf62]

Set it on manual and 8 to start then set the visible decode monitor to activate. Once its showing change the levels while its receiving transmissions and look for best decode rate which would be closest to zero.

That's how I did it and found seven to be best for most all. Occasionally eight and six worked as well. I'm stumped about nothing helping you. These scanners generally decode really well. I've also found if the antenna is turned wrong it can get a signal and stop yet nothing will come through. (Base antenna) I imagine its got a signal but not a good enough one. I can turn the antenna so it decodes everything but changing it leaves me missing a lot.

They love P25 from what I can see. Picks up great and only had a slight problem with one system out here. Still not sure the rubber duck didn't work better than a mobile antenna to decode that one. You might try switching to just a 77A or Condor and see if reception picks up for this system.

They can be strange though. I've picked up a couple of systems better with a 77 or Condor duck than with a nice mobile antenna attached. One was P25 and the other was EDACS analog. The statewide system comes out great though.

The 6.25 is based on what you're system is using. Some say theirs are 7.5 while others say 2.5 and 12.5 so you may have to check to find band width that works on yours.

Still hoping some random ramble helps you.

Ron

 

[kc5igh]

Hello again, Ghstwolf.

Could you please explain a little more about what you mean by the second sentence in your message above: "Once its showing change the levels while its receiving transmissions and look for best decode rate which would be closest to zero."?

Do you mean that I should somehow change the levels manually while the P25 adjustment mode display is showing? I thought the levels are supposed to change automatically in the display as the radio receives traffic.

Thanks for the help!

 

[smokchsr]

Turning on the attenuator helped quite a bit (I still don't understand why), but the results were still pretty far south of what I was experiencing with the other radios.
/QUOTE]

Do you know if this is a simulcast system? If it is, the reason turning on the attenuator helps is that you are receiving multiple signals from different towers. Due to differences in propagating the different signals will arrive at your antenna at slightly different times. When this happens it tends to confuse the decoder a bit.
By turning on the attenuator you sometimes lower the signal level from the distant towers where the decoder doesn't see them well enough to interfere with the decoding process.

Since the arrival of a fancy new p25 simulcast system in my area I've often had to break the news to people that invested in fancy receive antennas, that they are too good and often a simple paperclip works better.