Trying to setup a BCD536 for a P25 system...

[ke4gbe]

I've been trying to figure out how to get my new 536 to receive a P25 system, but... nothing.

I have set up a favorites list with a P25 Phase II system in a nearby country (Cobb Co, GA). I've used Sentinel to add the proper agencies, and can scan them - but no audio. I can pick up conventional traffic, from non-trunked agencies, I have plenty of signal from an outside antenna.
But when the 536 scans the trunked freqs, I see "ID Searching" but never hear any traffic. What am I missing??

Thanks for the help, I've spent a week trying to figure this out from the manual !

 

[tvengr]

If it says ID Searching, it should receive all talkgroups on the system whether programmed or not. If it says ID Scanning, it will only receive the talkgroups you programmed. Does the scanner stop on talkgroups? Do you have all of the appropriate service types enabled in the profile? If you export a hpe file of your favorites list, I will check it for problems. You will need to right click on the file and Send to Compressed (zipped) folder to be able to attach it. Click on Attach files and Open the zipped folder.

 

[Whiskey3JMC]

Hi & welcome to the RR forums!
I'll put my money down and say simulcast distortion is the real issue at hand here, it's one of the most discussed issues on these forums. I'd be willing to bet if you programmed it into an SDS100 or 200 you'd be able to receive the system without a hitch



73!

 

[bchappuie]

Edit profile and make sure all are checked in Service Types tab.

 

[ke4gbe]

Thank you everyone, and especially the advice about Services - some EMS stuff wasn't defaulted in my Profile.

Woo Hoo! I'm getting some traffic now, and learned something I should have known - a preamp is not your friend. Even the better ones have a higher noise floor than the 536 has, so you are just ADDING noise in the digital realm. Here, I have about a 35 foot run of cable. I had been using RG-58 since I had it handy but replaced that with a double shielded, better cable and saved a Db or two. Running straight from the discone antenna, I'm getting readable traffic - not 100% but enough to let me know I'm on the right track.

I have a couple of questions though...

Digital AGC - good or bad for marginal signals?

Digital Threshold - I'm assuming it's for sensitivity adjustment, and the default is 8. Is a 9 more sensitive? Or is a 7 (or lower) more sensitive?

Again, truly appreciate the help !

 

[bchappuie]

Take a look at this page. kinda long, but explains everything
Easier to Read BCD436/536HP Digital Scanner Manual

 

[Ubbe]

Digital AGC - good or bad for marginal signals?

That's audio AGC and it doesn't hurt to enable both digital and analog AGC as it tries to even out different audio levels from different users.

Digital Threshold - I'm assuming it's for sensitivity adjustment, and the default is 8. Is a 9 more sensitive? Or is a 7 (or lower) more sensitive?

Lower values are more sensitive and will start decoding more easily but will also have more bit errors that could make the sound more choppy. If the signal are really weak and has a lot of noise in it then going down to 7 or even 6 might produce some voice compared to a 8 that might not even start to decode anything. Most systems seems to have the least distorsion between setting 8-10 if the signal strength are good.

/Ubbe

 

[ke4gbe]

That's audio AGC and it doesn't hurt to enable both digital and analog AGC as it tries to even out different audio levels from different users.Lower values are more sensitive and will start decoding more easily but will also have more bit errors that could make the sound more choppy. If the signal are really weak and has a lot of noise in it then going down to 7 or even 6 might produce some voice compared to a 8 that might not even start to decode anything. Most systems seems to have the least distorsion between setting 8-10 if the signal strength are good.

/Ubbe

Thanks for the explanation. You guys have been a big help.

 

[maus92]

You mention that you are trying to receive an "nearby county" which makes it sound like your monitoring location is not within the intended service area of the Cobb County system. Newer P25 systems are typically designed to provide coverage only a few miles outside of the jurisdiction's borders to limit interference and promote frequency reuse. I see that you enabled some Service types and that helped your situation, so at least you are getting a usable signal. You *might* be able to improve your situation by using a Yagi antenna aimed at one of Cobb County system towers which *could* increase your RSSI and attenuate interfering simulcast signalling for other transmit sites.

 

[ke4gbe]

You've got a good idea, maus92, about using a directional antenna. My location has terrain issues and I'm pretty sure the signals I'm getting are reflections - line of sight is poor in that direction.

Thanks to bchappuie for suggesting the online manual (link above). It details how to set for manual threshold for P25 systems and with that you can not only see the error rate in real time, but can easily adjust the threshold to see the results.

I hadn't thought about how with a networked system you could give reliable coverage where needed (in-county) without wasting RF power beyond the jurisdiction. That also explains why other jurisdictions farther away aren't being being picked up here.

So now that you've got me thinking about directional antennas, what I may try is re-purposing my outside TV antenna, which may work pretty well even though the band is a little higher than the DTV bands... I'm kicking myself for not thinking of this first ! Thanks!

 

[tvengr]

Paul, the former Uniden rep, suggested turning off digital AGC if you have poor reception. The AGC action can increase garbled audio problems. You can adjust the P25 threshold for minimum decoding errors. The best setting may vary for different systems.

 

[NYRHKY94]

You've got a good idea, maus92, about using a directional antenna. My location has terrain issues and I'm pretty sure the signals I'm getting are reflections - line of sight is poor in that direction.

Thanks to bchappuie for suggesting the online manual (link above). It details how to set for manual threshold for P25 systems and with that you can not only see the error rate in real time, but can easily adjust the threshold to see the results.

I hadn't thought about how with a networked system you could give reliable coverage where needed (in-county) without wasting RF power beyond the jurisdiction. That also explains why other jurisdictions farther away aren't being being picked up here.

So now that you've got me thinking about directional antennas, what I may try is re-purposing my outside TV antenna, which may work pretty well even though the band is a little higher than the DTV bands... I'm kicking myself for not thinking of this first ! Thanks!

I’m using a 13db Yagi with my BCD536HP. It’s mounted in the attic pointed at a tower for a P25 system that is 35 miles away. Getting 2-3 bars and audio is nice & clear. My wide band antenna couldn’t pull the system in.

 

[iMONITOR]

Thank you everyone, and especially the advice about Services - some EMS stuff wasn't defaulted in my Profile.

Woo Hoo! I'm getting some traffic now, and learned something I should have known - a preamp is not your friend. Even the better ones have a higher noise floor than the 536 has, so you are just ADDING noise in the digital realm. Here, I have about a 35 foot run of cable. I had been using RG-58 since I had it handy but replaced that with a double shielded, better cable and saved a Db or two. Running straight from the discone antenna, I'm getting readable traffic - not 100% but enough to let me know I'm on the right track.

I have a couple of questions though...

Digital AGC - good or bad for marginal signals?

Digital Threshold - I'm assuming it's for sensitivity adjustment, and the default is 8. Is a 9 more sensitive? Or is a 7 (or lower) more sensitive?

Again, truly appreciate the help !

RG-58 is no good for a scanner, especially at 700-800, way too much loss. You say you replaced it with double shielded what? A discone is not ideal for 700-800MHz.

Don't use AGC, try putting the digital threshold back to stock setting.

 

[skideric]

You've got a good idea, maus92, about using a directional antenna. My location has terrain issues and I'm pretty sure the signals I'm getting are reflections - line of sight is poor in that direction.

Thanks to bchappuie for suggesting the online manual (link above). It details how to set for manual threshold for P25 systems and with that you can not only see the error rate in real time, but can easily adjust the threshold to see the results.

I hadn't thought about how with a networked system you could give reliable coverage where needed (in-county) without wasting RF power beyond the jurisdiction. That also explains why other jurisdictions farther away aren't being being picked up here.

So now that you've got me thinking about directional antennas, what I may try is re-purposing my outside TV antenna, which may work pretty well even though the band is a little higher than the DTV bands... I'm kicking myself for not thinking of this first ! Thanks!

Yup,i use a Homemade,but kicking TV Antenna for lots of Scannning,with a 8 Port Extreme Port multiplier,works GREAT! Also use an Old Orig RS Discone Ant,with same type 8 Port Extreme,love those too!

EDIT: Just wanted to add that i am just below Dothan,Al & i pick up traffic in Jackson Co.,Washington Co.,(FL) Conv,DMR.Also Dale Co.,Coffee Co.,Henry Co.,& Of Course Houston Co. (P25 Sim).Get some Ga Traffic as well..

 

[Ubbe]

- a preamp is not your friend. Even the better ones have a higher noise floor than the 536 has, so you are just ADDING noise in the digital realm.

That's not true. Most amps, even the $10 for sat dish, have a better noise figure than most scanners and will improve reception. What is important to know are that no scanner can handle the full 10-20dB gain of an amplifier. You have to reduce the signal level before it reaches any scanner or the high level will instead give a worse sensitivity and a scanner might even go into overload. A good working total gain from the point of the antenna to the scanners antenna port might be 0dB to +6dB.

The more filters you can install and the less numbers of high power transmitters nearby will let you use the higher gain setting. I have tried cheap $10 sat dish amplifiers and expensive $500 low noise amplifiers at both a very weak signal location and at a place where the roof antennas where surrounded by numerous transmitters giving high signal levels, and both amplifier types always improved reception more or less when installed directly at the scanner coax.

/Ubbe