Recommendation for 860MHz UniTrunker rx?

[GroundLoop]

I'd like to dedicate a radio to UniTrunker decoding of the local TRS.

What is a good-quality 860MHz receiver with a known mod for a discriminator tap?

It doesn't have to be a scanner, of course, since it will park on one freq forever. Looking for something with a really good front-end since we have a lot of pager interference and other nonsense.

I'm using a Realistic PRO-34 now, but it's getting a lot more noise than the Uniden scanner I'm controlling.

Ideally something last-gen, not too expensive. Can be portable or desktop.

Any ideas?

 

[Jay911]

If you have the ability to program it, you might try an 800MHz Motorola Maxtrac radio. IIRC it must be the one with the 16-pin accessory connector - there is baseband audio off one of the pins.

Personally I like the PSR-500 with its USB based CCDump feature for monitoring, since no tap is required. That may be out of your price range or not in your philosophy. If it's not going to move, a PSR-600 might be useful for the same reasons. IIRC, both of these radios have a tap published (in the PSR-500 prerelease thread maybe?).

You get pager interference in the 860s? That's odd. If you can find a BC780XLT or BCD796XLT, you might try that too. I have tapped my 796 so I know it has a tap point.

 

[GroundLoop]

Thanks Jay911. These are good leads.

The Motorola Maxtrac idea is very interesting, since it seems like it would have the best (most selective) receiver.. but boy did that lead into a hornets nest of reprogramming Motorola radios for listen-only. Maybe a single-channel conventional receiver program would be easier to discuss.

I originally bought a Uniden BC346XT to be the control-channel receiver, similar to your PSR-500 idea, but it turns out that Uniden passes too many corrupt bits to UniTrunker, which can't tell the difference. The actual receiver gets less noise than the Realistic, but still isn't so hot. So I get a lot of bogus site info, corrupted data, and a big mess of garbage sites in the morning. Word is the PSR-500 does a better job of flagging bit errors, and UniTrunker's analog decoder does the best job. Maybe a GRE radio is still the way to go.

I'm actually not sure it's pager interference, and probably jumped the gun in saying so. It's just some burst of noise or signal loss that makes it drop out on the Realistic, and it varies day to day. I want to build a good 850MHz receiver with a quality antenna or yagi for one TRS.

How do you like the BCD976XLT for discriminator output? Is the receiver pretty good?

I haven't given up on Maxtrac, but re-use seems to be a sensitive subject.so I'll have to find a trusted and connected friend to discuss it.

Thanks again!

 

[Jay911]

I have done the Maxtrac one before. You don't have to program the radio up for receive-only on a trunk system - just program the frequencies in to the radio conventionally. As a matter of fact it won't work if you program it up as a trunk system, because you won't be hearing the control channel either on the baseband audio pin or otherwise. The only issue is if you have a trunk system that rotates its control channel - then you have to get involved in setting up a scan list and making sure the radio is in scan, doesn't have priority enabled (which interrupts the audio), will start up in scan if the power is lost, etc.

Yes, apparently the Uniden has a buggy trunk protocol in its actual programming. Kind of disappointing, especially for those of us trying to use the CC Dump features. You could try a tap on that radio so you are getting the raw audio which UT would then handle on its own. I am pretty sure people have figured out taps for most modern radios - try one of the sites like mods.dk (which I think lets you look at one or two tap schematic/procedures a day/week before requiring donations) or even here on the RR Wiki - Discriminator output - The RadioReference Wiki - for more info.

I have to be honest, I used the 796 tap once right after I did it, confirming that it worked, and then the project that I was going to use it for dried up, so I haven't used the tap again since. So I can't tell you what its performance is like.

The reason I was surprised about pagers in the 850/860 range is because my experience is that pagers are in the hi-VHF or 900MHz ranges. I wouldn't expect them to be in the middle of the trunking band. What you might be getting is Nextel - I haven't myself had the problem, but I know the iDEN frequencies in my neck of the woods are smack dab in the 862-865 range.

 

[scottbailey]

+1 on the MaxTrac. You might also look at the Spectra. Since they (regular Spectra - not Astro Spectra, though they would work too) won't do narrowband and can't be rebanded they're hitting the market at literally whatever someone will pay for one since they have pretty limited commercial use. I've seen them go for as little as $10, and often less than a MaxTrac even though they are higher end than a Maxtrac. IIRC you can get discriminator audio on pin 11 of the back connector - which I believe is a standard DB15 or DB15 HD connector. See Interfacing External Equipment To Your Spectra Radio

Also with the MaxTracs you'll need to make sure you get a model that has the ability to do conventional channels since most don't. I don't think this is an issue with the Spectras.

Maxtracs that will do conventional (which is what you would need for this purpose will have a model number starting with (x can be an number): Dx5MGA or Dx5MJA. Most that I've seen are MQA or MWA which are trunking radios. From what I've seen, SOME will do 1 or 2 conventional channels too - but you'd have to be very specific with matching the model number. See MaxTrac VHF/UHF/800 MHz Model Information

 

[zz0468]

The Motorola Maxtrac idea is very interesting, since it seems like it would have the best (most selective) receiver.. but boy did that lead into a hornets nest of reprogramming Motorola radios for listen-only. Maybe a single-channel conventional receiver program would be easier to discuss.

That's not an issue for your application. In conventional operation, you just type in "blank" instead of the TX frequency. This is true with the Spectra's, also.

 

[Radioman96p71]

I personally use 4 Maxtracs that I reflashed from trunking to conventional mode, set them up with all the available EDACS LCNs and let it go. I even have the 5-pin model (which are about 10-15 bucks on ebay). A quick jumper and a cut trace and you have baseband audio to the accessory connector. Properly aligned, they are some fantastic receivers, and do the job of idling on the control channel well!

 

[scottbailey]

I personally use 4 Maxtracs that I reflashed from trunking to conventional mode

By reflashed do you mean 'bought a firmware upgrade chip/kit'? Otherwise - have a link to instructions/info? IIRC you had to buy a new firmware chip which at was at least 2-5x the $10 price of the radio. Or are you referring to a straight EEPROM copy/reprogram operation?

 

[GroundLoop]

I too am very curious.

It's a very strange subject, Maxtrac reprogramming.. I've been reading up the dozens of web pages that describe the Motorola part numbering, programming process, and so on, but then the software is NLA (end of life) and unavailable.

I sense that people *have* it, but are not sharing because Mot has instilled the fear lawsuits like no other. It's creepy. Then you need an old PC XT or somesuch from the 80's to run at the right speed with a real 16550A com port. That's the only part I DO have.

I've seen some conflicting information on whether the Trunking radios can be converted to Conventional use.. some say no way, some say the Trunking radios have 1 to 8 conventional channels available (talk around), and some say you can "just reprogram them". I can't tell if this means swapping parts (EPROM?) or reprogramming with Mot tools, or reprogramming with even more rarefied Mot "lab" tools.

 

[Radioman96p71]

I used a EEPROM flasher and rewrote my trunking chips to be conventional. I had 8 of these radios, a couple i sold, a couple i put back to trunking to use as single-channel monitors on a local Moto Type2 system.

The software is extremely glitchy for the trunking side, the LABRSS to do the actual conversion will run on most Pentium (thats just Pentium, not P2/3/4 etc) under 1 GHz machines. The flashing of the chips is done in Windows using the software that came with the board.

The process is pretty straight forward, open the radio and copy down the stickers with the retune info on them. Pull the EEPROM chip and check the version number on it. Put the chip in the burner and made about 10 backups, then put the chip in a UV 'oven' for about 30 mins and erase it. Put the chip back in the burner, open the Conventional .bin file you acquired, write it and the verify. Reinstall the chip in the radio, fire it up and hook it to LABRSS, go thru the steps to clear the board and then re-initialize it as a conventional model, realign it and you are golden.

All-in all the whole process takes about an hour to do each radio if you have the proper tools. Luckily, the trunking 800MHz 5-pin radios are worthless on eBay so you can get a lot of them for about $5 a piece from the right places.

I don't really give a hoot about Moto threats, I feel these have been End-Of-Life long enuf and Moto has gotten all the money they will ever get out of them! With that said, you probably know how to get what you need now

Hope that helps

 

[scottbailey]

I've seen some conflicting information on whether the Trunking radios can be converted to Conventional use.. some say no way, some say the Trunking radios have 1 to 8 conventional channels available (talk around), and some say you can "just reprogram them". I can't tell if this means swapping parts (EPROM?) or reprogramming with Mot tools, or reprogramming with even more rarefied Mot "lab" tools.

It's pretty simple actually - either a specific model allows conventional channels or not - some do some don't. There's a list of known model numbers and if/how many conventionals they have at MaxTrac VHF/UHF/800 MHz Model Information

Look in the 'Chn' column - if it has a single number then that's how many conventional channels it will do. If it has x/y/z then the z part is the # of conventionals. If you get one with at least one conventional, then you can just "reprogram them" using the regular programming software along with a RIB ($25 or so on eBay) and a cable (IIRC you can use a regular network cable with the MaxTracs and at least some of the aftermarket RIBs).

Or, as detailed above, you can take a trunking only model and copy the firmware off of a another model and make it do what you want. If you're not familiar enough with Motorolas to know where to find said NLA programming software, then the firmware swapping method probably isn't for you unless you want to build a wall using $5 MaxTracs instead of bricks.

 

[GroundLoop]

Thanks Adam & scottbailey!
That makes a lot of sense. I'm going to find one of the models that takes conventional channels. It's been a long time since I UV-baked EPROMs. I"m going to start with the shortest path possible -- programming new Conventional channels.

One thing I've seen is the reference to the number of "talk-around channels". Are these 'bonus' Conventional channels in an otherwise Trunking radio?

Most of the eBay surplus seems to be all-Trunking models.. D35MWA5GC6AK, for example.
The page here:
RadiosAndAntennas < Main < TWiki
Makes it sounds like 8 channels could be re-purposed for ATCS, which is just a conventional channel. They might be assuming EPROM cloning.. it doesn't say.

Thanks again.. coming in cold, stuff takes a bit of decoding.

 

[scottbailey]

One thing I've seen is the reference to the number of "talk-around channels". Are these 'bonus' Conventional channels in an otherwise Trunking radio?

Talk-around channels are still conventional and mean the same thing in the context of what you're trying to do.

The actual difference is that not all models are capable of talk-around. Remember that the 800 band is 806-870, with repeater outputs in 851-870 and the inputs - where the mobiles TRANSMIT is 45MHz lower at 806-825. Talk-around involves the mobiles transmitting on a frequency that is in the 851-870 range - where they normally just receive. Many (most) MaxTracs don't have transmit capability for 851-870, and if they do, then they have 'talk-around channels' - meaning that the conventional channels can be programmed for talk-around. In your case, you won't be transmitting, so you don't care.

Most of the eBay surplus seems to be all-Trunking models.. D35MWA5GC6AK, for example.

Yep. I remember a wise man once saying:

Also with the MaxTracs you'll need to make sure you get a model that has the ability to do conventional channels since most don't.

Maxtracs that will do conventional (which is what you would need for this purpose will have a model number starting with (x can be an number): Dx5MGA or Dx5MJA. Most that I've seen are MQA or MWA which are trunking radios.

The page here:
RadiosAndAntennas < Main < TWiki
Makes it sounds like 8 channels could be re-purposed for ATCS, which is just a conventional channel. They might be assuming EPROM cloning.. it doesn't say.

I don't know much about ATCS, but if you read further down on that same page, it provides a better summary. I believe any model with at least one conventional channel will work, subject to the modifications required below:

ATCS (MCP/BCP)

The 900 mhz radios are programmed to the actual desired BCP frequency. In order for most of these radios to work properly they must contain at least one trunked [Note by scottbailey: I think they mean conventional not trunked] channel (only with trunked firmware, this restriction is not applicable for conventional firmware equipped radios), which is then followed by the ATCS channels.

The 800 mhz radios need a bit more work. The fixed tuned front end filters must be removed and/or replaced with new adjustable or fixed front end filters. The VCO needs to be modified as described in the Batlabs site, and special programming must be done using specially modified RSS software. This work must be performed by someone who is familiar with the work that needs to be done. Most likely either another hobbyist or ask the group.

If you want to listen to the ATCS MCP (896/897Mhz) and the ATCS BCP (935/936Mhz) sides of the data,

simultaneously, you must, acquire 2 radios, one 800 mhz and one 900 mhz.

MaxTracs have a long history of being repurposed for amateurs (900MHz), ATCS, Trunking, and other 800/900 data protocols. There is a small goldmine of information on making them do things they don't out of the box. Read up on Maxtrac and Radius Mobiles, the BatLabs forums (join because not all forums are visible unless you're logged in), and Motorola MaxTrac / Radius / GM300 Index Page.

BTW I just read for the first time that some of the MaxTrac series (i.e. M214/M216) are capable of channel steering via the accessory connector (i.e. ground pin x to pin y to go to channel z)...hear that UniTrunker? Maybe someone will come up with a cheap serial interface for computer-controlled tuning. You could actually get the "Motorola Sound" without all the complications and controversy of actually running trunking on a Motorola. Oh and did I mention it's like $10 per receiver

 

[GroundLoop]

Thanks again scottbailey. Seems like the ATCS guys are up for more rework than I am.


Your point about channel steering via UniTrunker sounds very interesting, and not too far off from what it does already.

Really, I would love to have a fully software-defined pc-based TRS scanner. Dual-receivers (one control, one voice), with an awesome UI that shows the whole state of the airwaves, and directs a relatively dumb (but excellent RF) narrowband receiver to tune on command. No SDR needed, just a pair of suitably hacked MaxTracs. UniTrunker is 90% there.

 

[GroundLoop]

I just wanted to close this thread with THANKS!

I went from knowing nothing at all about MaxTracs two weeks ago, to using one right now.
I have a fine surplus unit feeding discriminator to UniTrunker, with record Health scores.

I picked up a D35MWA unit for cheap, which was programmed for Trunking.
From the excellent info here and on repeaterbuilder, I dropped all the trunking Modes and added eight Conventional channels. It's receiving just fine off the discriminator pin on the 16-pin header.

And most importantly, it does pull in signal better than my PRO-34, which was the whole point of this crazy trip through DOS 5.0 boot floppies, my ancient Pentium laptop, Hong Kong RIB suppliers, COM ports, and a whole lot of web pages.

Cheers!

 

[Forts]

I personally use 4 Maxtracs that I reflashed from trunking to conventional mode, set them up with all the available EDACS LCNs and let it go. I even have the 5-pin model (which are about 10-15 bucks on ebay). A quick jumper and a cut trace and you have baseband audio to the accessory connector. Properly aligned, they are some fantastic receivers, and do the job of idling on the control channel well!

Do you have any details on this process? I have a few of the 5 pin models that I would love to tap to use as feeds for UniTrunker, but I've had zero success on finding the proper tap points.

Thanks!

 

[GroundLoop]

I have a 5-pin MaxTrac and got discriminator audio from the same place the on-board comparator does -- right off the jumper (JU601).

Connect to the center pin and you too have your choice of before or after 300Hz high-pass.

Ground comes from Pin 11 on the J6 header.

 

[Forts]

Thanks! I've got UniTrunker working great on a local EDACS system using that tap point. Now to get my tap working with P25....

 

[exkalibur]

Jay911, if you program a Maxtrac for a trunking system, you'll still get control channel audio out Pin 11.

In a "commercial" application, this is exactly what someone I know does. He's got a 900MHz Maxtrac programmed on a bogus talkgroup on a 900MHz system and out comes the control channel. The radio automatically goes to the new control channel if/when it switches.

A local shop in town had a custom program written "Single Talkgroup Activity Tracker" or something similar that allowed a customer to see the activity on their talkgroup only. This ran on the base station's GTX. Only down side is when the dispatcher transmitted, you lost your display, but not a huge deal.

 

[GroundLoop]

exkalibur, doesn't this result in the MaxTrac attempting to affiliate/transmit?