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Thread: P25 Ham repeater question

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    Default P25 Ham repeater question

    Our group would like to put up a P25 VHF ham repeater and since a Quantar is out of our reach because of price and Range 1 availability
    We were wondering if putting 2 PM1500's or XTL5000's together using a ham repeater controller would work. Or is there another option
    Thanks Jim K4AJM


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    you could do it that way. the only issue is the fact that the audio is encoded and decoded a extra time this introduces distortions etc.

    the ideal inexpensive way would be to directly modulate a fm transmitter with a cleaned up capture from a disciminator. I built one of these to show it could be done.

    Hardware
    2 maxtracs
    1 digital audio delay loop (500ms) (used a old echo chamber circuit)
    1 567 tone decoder set to 1800hz (to detect digital waveform)


    configuration

    connected the input of the delay line to rx high speed data filter output U601-1 rx board.
    connected pin 3 of 567 (tone in) to detctor (pin 3 P5 rx board)
    output of delay line to pin 5 J5 accessory jack (tx radio)
    output of 567 (buffered through NPN transistor to pin 3 j5 accessory jack (tx radio)

    thats it not exactly type aproved but works

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    Quote Originally Posted by phido View Post
    Our group would like to put up a P25 VHF ham repeater and since a Quantar is out of our reach because of price and Range 1 availability
    We were wondering if putting 2 PM1500's or XTL5000's together using a ham repeater controller would work. Or is there another option
    Thanks Jim K4AJM
    A Quantar is about the only proper way to do it. Mobile radios don't have the duty cycle to handle the long bantering of most hams.

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    Are you implying that hams ramble on about things even if they are not relevent to the matter being discussed just so that they can have the most airtime on a repeater and so that they can hear their own voice even if they have nothing to say about anything at all especially if the repeater is heavilly used and ahs a 30 second timer to prevent users from timin


    LOL

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    As I've always said, if you can't speak your piece in 60 secs YOU TALK TOO MUCH!


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    Quote Originally Posted by Pezking View Post
    A Quantar is about the only proper way to do it. Mobile radios don't have the duty cycle to handle the long bantering of most hams.
    I agree, that would be my 1st choice but when was the last time you saw a Range 1 Quantar for sale at a fair price or any price for that matter. As for the
    duty cycle how about running a 110w PM1500 at 25w? External amp- pa ?
    Do you think the quality would be bad or just not up to Quantar standards? We have been looking for alternatives but so far nothing we can afford.
    BTW we do have a couple of PM1500 we might be able to use.
    Jim K4AJM

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    You will be disappointed with the audio of back to back radios, for my experience see: http://batboard.batlabs.com/viewtopic.php?f=10&t=80768

    Range 2 VHF modules normally tune down to the top of the 2M band OK (but back off the PA power) and right now on the 'bay there is a set of VHF modules available which just needs to be chucked into one of the bargain Quantro chassis on the same auction site. It will need a tune (always needed with the Quantar after freq changes) and a duplexer but easily done for less than two grand.

    For not much more there are R1 and R2 stations up for auction there and here in the For Sale forum.
    Last edited by Astro Spectra; Dec 31, 2012 at 10:28 AM.

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    Astro Specta is 110% correct. I have played with several VHF R2 exciters/receivers in the 2M ham band. They play just fine. Sometimes SINAD on the RX can be a little off if you go down into the 144 range on some receivers. If you are concerned about not being able to run 100W get a 25W station (25W VHF P.A. is broad banded and covers R1 & R2) and use it to drive an external high power amplifier. There was a gent in TX selling some of these cheap to the ham community. I bought one. They are much cheaper than those on the popular auction site. Mine even had an Astro Modem on the wireline card. Those things are getting hard to find. I live in western NC and if you need any help just let me know. I maintain Quantars daily...

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    You forgot to add a let me reset the timer in the middle of the ramble. LOL
    Common sense is Uncommon.
    You can't fix stupid, but eventually it takes care of itself.

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    Or the repeater CWID on EVERY transmission. And annoying courtesy tones.

    My Quantar is set up so CWID is TX'd without the PL. I have a 3-second transmitter hangtime (to avoid cycling on weak signals) but have the wildcard set with a rule not to TX the PL when there's no RX PL being received. In other words the hangtime doesn't have a PL. Nice and quiet, and anyone who uses a hamster radio will not have issues with their junk rig not decoding the PL reverse burst.

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    I agree, my repeater only has CWID when there is activity. No PL on the ID or hang time.
    No time, temperature or weather report either.
    Common sense is Uncommon.
    You can't fix stupid, but eventually it takes care of itself.

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    One you get your low power setup running you could try what I did for a UHF repeater that was not P25.
    I gutted a Micor except for the power supply and 100w PA.
    I then took my low power output and ran it though an adjustable rf sampler into a dummy load.
    I then used the sampled rf to drive the PA.
    I used a pair of SM50 for the rx and tx radios. The tx radio was programmed down to 5w.
    Most of all have fun with it.
    Bob
    Last edited by BobbyBoucher; Jan 01, 2013 at 09:08 PM.
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    Thanks to all for the advise, we have seen the light. I have been looking for a range 1 Quantar for a while with no luck but then one popped up
    on Pbay and I took the plunge. We will see if I made the right move. I hope you guys will help this Quantar nubee on this new adventure.
    Thanks Jim

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    Quote Originally Posted by iam4thapack View Post
    Astro Specta is 110% correct. I have played with several VHF R2 exciters/receivers in the 2M ham band. They play just fine. Sometimes SINAD on the RX can be a little off if you go down into the 144 range on some receivers. If you are concerned about not being able to run 100W get a 25W station (25W VHF P.A. is broad banded and covers R1 & R2) and use it to drive an external high power amplifier. There was a gent in TX selling some of these cheap to the ham community. I bought one. They are much cheaper than those on the popular auction site. Mine even had an Astro Modem on the wireline card. Those things are getting hard to find. I live in western NC and if you need any help just let me know. I maintain Quantars daily...
    Thanks for the advice, are you also a ham ? I live in Southeast Tennessee just 2 miles from the NC line. Since this is my first adventure into Quantars I am sure that I am going to
    need a lot of advice. The Quantar I purchased is a range 1, gold chassis but it does have the Onan PS

    Thanks Jim K4AJM

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    Having talked you into it we'll be obliged I'm sure you will be pleased with the end result. Feel free to post any questions.

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    Quote Originally Posted by Astro Spectra View Post
    Having talked you into it we'll be obliged I'm sure you will be pleased with the end result. Feel free to post any questions.
    You got a deal.... Tnx Jim

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    Hi Jim, please go to this post: https://www.p25.ca/threads/161-Quantar-Manuals and read the Quantar tuning vhf PDF psoted by newtomotorola. The deviation and mod balance adjustments are critical to the P25 transmission performance.

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    We are thinking of just buying a range2 and converting the Modules to range 1 with the jumpers on the boards so the controller thinks it has range 1's in it. Believe there may be some slight mods to get the TX and RX to lock though, but not not sure. Also can the Range 2 Hi Pwr PA's Circulator (Isolator) be tuned, once changed to range 1 as I believe that the isolator to be the only device holding it back from going full Range1 full power unless pwr transistor are different. If someone has already done this can you give us some info or start a new thread with detailed info on these Range 2 Quantar mods.
    Radio Referenced...Those who think they know it all are very annoying to those of use who do.

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    Quote Originally Posted by Astro Spectra View Post
    Hi Jim, please go to this post: https://www.p25.ca/threads/161-Quantar-Manuals and read the Quantar tuning vhf PDF psoted by newtomotorola. The deviation and mod balance adjustments are critical to the P25 transmission performance.
    WOW that info is priceless Abig thanks 1 and all, this is a great group
    Jim

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    @moetorola

    You do not need to go to the trouble of the board ID change for a R2 to R1 in VHF or UHF. In fact I would specifically recommend against it to help the future tech who has to service the resulting Franquantar, unless you actually implement all the band related SMT component changes and trim the VCO hybrids to full range 1 specs.

    The existing R2 VCOs will tune to below 146 MHz (tune line is typically 1.4 V, YMMV). You can easily check the tuning range of your specific receiver and transmitter modules by going to the metering page in the service menu and looking at the VCO tune volts, anything above 1 V is OK, around 1.5 V or more is better (fractionally less phase noise).

    Simply program the Quantar with your out of band frequencies just as people do with their Astro and Astro25 radios. But remember that either way you WILL have to align the Quantar, particularly as Ive mentioned before the deviation and mod balance adjustments critical to P25 modulation. This needs a service monitor, Aeroflex tester, or a scope and HP8901B mod analyzer combo (my personal favorite).

    You really need a network analyzer to tune the pre-selector out of band as mechanical hardware mods may be required, thats too hard for most people. Instead I recommend removing the pre-selector and replacing it with a Mini-UHF joiner and using a single external full size bandpass cavity filter, even if you are using a duplexer for single antenna working. Most duplexers used on 2M are asymmetric band pass band reject configurations designed for the narrow 600 kHz ham split. These have poor out of band rejection and the Quantar needs extra protection at busy sites, particularly if you remove the pre-selector.

    You do not need to tune the PA circulator. Its hard to do anyway as the thing has a cover without access holes. Motorola uses a 150 to 174 MHz part in the TLD3110 25W VHF PA that is supposed to cover all of R1 and R2 so they obviously are not worried too much about performance between 136 and 150 MHz. When tuning a circulator its not insertion loss that changes but the return loss. If you are worried about IMD add an external circulator or IMD panel. If you happen to be connecting via a transmit combiner then it has will have an isolator (circulator with a load) in it anyway.

    Note that the high power PA contains a number of low pass filters to limit harmonic output. When you use a R2 PA on R1 your harmonic output will increase slightly but more importantly the harmonic LPF filter sections will have slightly worse impedance matching. This is why I recommend setting the power on the R2 PA to 75 W when operating on 2M. I manage both commercial and amateur Quantars and Ive never had a PA failure with out of band operation.

    And finally a happy Quantar is an aligned Quantar.

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    For tuning the receiver module, you'll need the cable probe. I just ordered one last week. The part number (new) is 3082059X01, and the list price is $15.49 CAD (Should be nearly the same to you USA guys).

    This probe fits into holes on the front of the RX module and allows for peaking/nulling of the filters.

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    The pre-selector is a bit hard to tune too far out of band and frankly it is such a compromise design anyway, particularly on VHF. This is why I recommend ditching it and using a stand-alone cavity.
    The 3082059X01 is well priced for Moto. Another option is a bit of semi-rigid coax with a connector on one end, you poke the unterminated end in the holes...

    Talking of such, nice new AV there Mars.

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    Great! Thanks for the info Astro Spectra. Our frequency is 145.35TX 144.750RX. We had D-Star,,, and well hated it, the audio was very poor. Once I showed them the quality of P25 vs. D-Star it wasn't to hard to convince them. And trying to get a few of us techy type to use P25. We have a VHF TRBO programed analog only repeater but will be exchanging it for a UHF TRBO possibly to connect to the DMARC Group. Most of my experience was with 800 MSF500's and then about a year with Quantar's but could tinker with them like I wanted too being in use and all. Then all of that equipment was scraped for GTR8000's. The Quantar's that were trunked were recommissioned as 8Call90 and 8tac91 repeaters so still cannot play with em,,,LOL We are currently looking for a VHF quantar so keep me in mind.
    Thanks Again Astro
    Last edited by moetorola; Jan 04, 2013 at 11:00 PM.
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    I was scanning Pbay and ran across this item
    Motorola Quantar Power Supply TLN3259A FRU 625 W AC

    is there anyway to know if this PS will work with the Quantar I just purchased, since I haven't received it yet the only details I have are
    VHF Range 1 ( low split) Quantar Repeater, 110 watt, Gold Chassis, SCM has 20.xx firmware, Wireline Board,in good clean shape and Gauranteed
    I know its a long shot but from the picture of the Quantar I purchased I know it has the older Onan (exploding PS) and I an considering
    bidding on this unit as a backup. What do you think
    Jim

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    Save your money until your existing supply dies (if ever). A ham repeater is not like a public safety system, you don't need to hold a complete spares. The part number for the non-Onan, 625W Motorola made supply is CPN1047 or CPN1048.

    If you want to spend more, save up and buy a complete machine. Smart eBay sellers part stuff out and sell bit by bit because that way they make more than selling the whole caboodle. A complete machine can be used ad a test system or put into service as a secondary machine on the understanding that may need to be robbed out to keep the primary machine working.
    Last edited by Astro Spectra; Jan 05, 2013 at 07:23 PM.