Portland Public Safety 700 MHz P25

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Otto

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So, I have been listening to the new system for a week or so since a large amount of users have migrated over. I am using a HP2 and I am finding that while listening along on the analog side with another scanner (BCT 15X or BC246T) I am finding that I am missing quite a bit of the transmissions. Operations using a yagi pointed at Council Crest improves things, but running mobile is horrific.

Question is, does anyone have any tips on improving my success rates on hearing transmissions? I've tried messing around with the P25 audio filters in the scanner, without too much success.
 

riccom

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Are you missing conversations or are they dropping ?
See if another tower may carry the conversation, or if you have a simulcast issue?

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bailly2

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put the antenna though a hole on the side of a empty paint can, near the bottom. best thing for LSM simulcast distortion
 

riccom

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He is using a yagi

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I also see the "missing transmission" behavior on my 996P2, 325P2, and TRX-1, all running different antennas. My control channel signal strength is full-scale.

I find it somewhat alarming/disturbing when I run all three at once and transmissions pop up on one radio, and not the other--and it's not because of a conflict with another simultaneous transmission. I get the impression that the "real" P25 transceivers have some sort of additional reception capability that provides reliable operation that the scanners don't.
 

Otto

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Are you missing conversations or are they dropping ?
See if another tower may carry the conversation, or if you have a simulcast issue?

Sent from my C6730 using Tapatalk


I am completely missing the conversation. This is a simulcast system with about five sites. I think I'll try aiming my antenna at another site to see if that changes anything. But honestly, most of my issues are while mobile. That really the main concern.
 

mm

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As I remember aren't most if not all scanners still using demodulator audio fed to a op-amp data slicer then this pseudo square wave data is then fed into the DSP decoder, IE they are not using IQ tap points.

As an example of using a real radio that uses IQ/cqpsk data, listening down here in South Salem on a recent model Motorola HT using the non-affiliated hidden talkgroup scan method the decode is excellent in a moving vehicle.
 
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mm

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I don't know if the following info is any help for users with scanners but I have my my Motorola ht programmed to allow me to select 3 sites, #1 east simulcast, #2 west simulcast and #3 goat mtn.

East and west simulcast have similar coverage for me with no missed traffic; however, on #3, goat mtn. I noticed that traffic is only active if a unit is affiliated on the goat mtn.site and I was missing a lot of traffic if locked to goat mtn.

I was actually missing traffic on my Commercial Motorola if locked on to goat mtn and this was resolved by selecting either east or west simulcast and ignoring goat mtn.

I would try entering in only east or west simulcast and redo your mobile tests.

I know my test are not the same as yours what with me using a Moto radio which brings up another thing.

I would love to put some of these Uniden and whistler scanners on my P25 trunking test set to see what the effective sensitivity is at a 4% BER and then add in some interfering signals to see how the scanner mfg's radios handle interference.

The only thing stopping me is the price of these scanners, my Motorola radios were almost frebbies pricewise and I'm too cheap to spring for anything above cheap price just to run some test on these scanners.
 

Otto

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Good info mm. I am currently only listening to the West Simulcast. I noticed the same thing you did about the Goat Mtn. Site. I get control channel there, but no activity.

But, I did find something interesting today while using the scanner mobile, is that everything was perfect while traveling down marine drive by the airport. That's when I remembered that one of the simulcast towers is located there. If I have time tomorrow evening, I'm going to swing my yagi towards that site ( which means I have to get up on the roof and unbolt it and turn it by hand) and see if anything improves for me on my end. My QTH is closer to the airport than Council Crest, so that could be a source of any simulcast distortion I might be experiencing.
 
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Thanks, mm--your comment about difference in receiver architecture makes sense. Makes me wonder if the existing scanner P25 solutions are viable without a fixed antenna and yagi unless one is very near one of the transmit sites.

As for sites, I get the west simulcast sites the strongest, with the east simulcast sites about half-scale, and Goat Mtn is too weak to even get a lock on.
 

mm

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Otto,

You could pick up a low price rotator from HRO or even a small rotator online and then rotate your antenna from inside.

Another problem I remember with many of my older Uniden Analog 800 MHZ type II / EDACS scanners was the poor and in some models the non-existant RF pre-selector which resulted in excessive IMD ahead of the receivers mixer.

In the early 2000's I had a bc330 analog trunker that I added in an off the shelf 800 MHZ bandpass filter from an even earlier project that made the difference between receiving a good quality signal.

This filter was made out of the RF PRE-SELECTOR from a GENERAL ELECTRIC 800 MHZ MP-D handheld that I picked up at a hamfest.

Even earlier in the late 1980's, 12 years before I had my bc330 trunker, when 2 agencies in the PHOENIX METRO area went to Smartnet trunking my trunking receiver at the time consisted of a non trunking bearcat bc220 scanner connected to a UHF TV tuner acting as a 43 to 48 MHZ downconverter.

The bc220 was scanning 5 voice channels that were downconverted between 43-48 MHZ and I found that cabling in a similar pretuned MP-D handheld 800 MHZ bandpass filter eliminated front end overload problems in the TV tuner when connected to the BC220 SCANNER.

Maybe these new scanners could use a good 760 to 870 MHZ bandpass filter added, something like one of the MINI-CIRCUITS inline SMA filters?
 

mm

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I just found a Mini-Circuits Band Pass Filter that looks good, it has a bit more insertion loss above 850 MHz but this should work for the 700 MHz range fine and even in the 850 to 870 range it is still useable,

if anyone wants to try and see if perhaps a BPF will improve their receiver performance here is the link.

http://www.minicircuits.com/pdfs/VBFZ-780+.pdf


I'm still leaning towards the method that Uniden and whistler use to pick off the data is what is causing the issue but still 40 dollars for a SMA connectorized filter is still within the good price range of dabbling around.
 

KC7VH

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Does anyone know when the transition from P25 Phase 1 to P25 Phase 2 will happen? I've been listening to the new digital system/talk groups with my 996XT and I'm wondering how long I will be able to do that. Thanks.
 

sparklehorse

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Does anyone know when the transition from P25 Phase 1 to P25 Phase 2 will happen? I've been listening to the new digital system/talk groups with my 996XT and I'm wondering how long I will be able to do that. Thanks.
Good question. There's been quite a few posts now referring to the new Portland P25 system as Phase II, but so far all I've seen on my scanners are Phase I transmissions. Is this Phase II information coming from an official source, or is it speculation?

Thanks.

.
 

ChrisP

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Good question. There's been quite a few posts now referring to the new Portland P25 system as Phase II, but so far all I've seen on my scanners are Phase I transmissions. Is this Phase II information coming from an official source, or is it speculation?

Thanks.

.
Not from an official source, but the system is Phase II capable and is advertising as such, but there are too many agencies that do not have Phase II radios at this time. The move to digital is in small steps. :)

- Chris
 
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sparklehorse

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But, I did find something interesting today while using the scanner mobile, is that everything was perfect while traveling down marine drive by the airport. That's when I remembered that one of the simulcast towers is located there. If I have time tomorrow evening, I'm going to swing my yagi towards that site ( which means I have to get up on the roof and unbolt it and turn it by hand) and see if anything improves for me on my end. My QTH is closer to the airport than Council Crest, so that could be a source of any simulcast distortion I might be experiencing.
Otto, did you get a chance to turn your yagi toward PDX? Curious if that improved your reception. I'm using a similar yagi at my QTH, also aimed at Council Crest. My decode here in SW is fairly decent with my Uniden 536, but I'm not too far from the tower. But like you I'm not having great luck monitoring the new system while mobile. I use my BCD436 for mobile use, with just an RS800 duck. Worked OK on the 800 system, but the P25 mobile reception is pretty bad. So I just ordered a Unication G5 pager from Scanner Master. Lots of good reports of those having superior reception on Phase I systems as compared to consumer grade scanners. Plus I like that it's fairly small and compact. I'll report back here once I've had time to evaluate its mobile P25 performance.

Gordon
.
 

Otto

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Otto, did you get a chance to turn your yagi toward PDX? Curious if that improved your reception. I'm using a similar yagi at my QTH, also aimed at Council Crest. My decode here in SW is fairly decent with my Uniden 536, but I'm not too far from the tower. But like you I'm not having great luck monitoring the new system while mobile. I use my BCD436 for mobile use, with just an RS800 duck. Worked OK on the 800 system, but the P25 mobile reception is pretty bad. So I just ordered a Unication G5 pager from Scanner Master. Lots of good reports of those having superior reception on Phase I systems as compared to consumer grade scanners. Plus I like that it's fairly small and compact. I'll report back here once I've had time to evaluate its mobile P25 performance.



Gordon

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I did turn the antenna towards PDX and my reception improved, but I am still missing some conversations when I listen with the analog on another radio. Not as many as when it was aimed at council Crest, but still not 100%. But I like to listen in the truck more than at home, so...

Mobile is still a horror show. Missed conversations, garbled messes, and just plain radio silence at times. I am using a Larsen 800 antenna on NMO mount, but I feel I need to investigate a new antenna. This set up worked fairly well on the Analog system (except for the front end getting smashed by cell phone towers on busy corridors) so I had hoped for similar results on 700... so far no luck.

I am considering the Unication Pager as well. I'll let you go first. Let us all know if that's a better solution than a scanner. (Unless I can figure out a /\/\ or kenwood P25 radio that would work better, but my skills in that department are less than stellar)
 

riccom

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The big m is good, but super tricky to get to follow, the unication, looks like a kick butt option.
I am surprised that the setup is as all over as it is.
On the nmo mount, are you using a pigtail or a stubby whip antenna?

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JB

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Portland Fire, Gresham Fire and Corbett Fire (District 14) were advised yesterday to use the AA, BB, CC talk groups on their radios from this point forward. This must be part of the transition to the new system.
 
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