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P25 repeaters

Discussion in 'General Technical Questions and Answers' started by KN4EHX, Oct 26, 2019.

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  1. KN4EHX

    KN4EHX Ham Member QRZ Page

    Hey everyone,

    Thanks for stopping! I’m on a quest to buy or build a p25 repeater. Besides Motorola Quantar repeaters what are my options? I’d like something that can be programmed with a modern PC because I personally don’t have any DOS computers, but it is possible through my friends.

    The Quantar repeaters are usually very expensive and being my first repeater I’d like to keep cost down if I can. It must be UHF since all VHF pairs are taken in my area.

    Before anyone roast me over frugality I’d like to add I’m a graduate student and I work full time so investing in a top of the repeater will be a work in progress. With that said I’d like to get something up and running in the meantime. Maybe this will become my backup in the future. So play nice!

    Besides Motorola Quantar what are my options? I’m aware many other manufacturers made P25 equipment so they can’t be the only ones out there. EF Johnson, Icom, Kenwood, Tait? I can’t seem to find much information on what to look for or model numbers.

    I have flirted with the ideal of using a MMDVM with two analog radios, but I lack experience in that realm. The added benefit would be the ability to use other modes in addition to P25 so if anyone is well versed in that subject I’m all ears.

    I’d like to think there is a way to use two Astro Spectra radios to create a repeater, but that is likely wishful thinking. The reason for wanting to do that is the power output on the high power models is around 100 watts. A couple other Motorola models as well like the MCS 2000.

    For those who are curious I am in a good spot for establishing a repeater. I live on a farm with high mountains, excellent views, and access to electricity in several locations. Luckily I do have good mechanical ability and building skills. This will be a big endeavor, I’m up to it, and I have some knowledgeable friends to help.

    I just need you guys to give me some good information on what to get as far as the repeater goes. The digital stuff is all new to my ham mentors besides one who worked for Motorola in the 90’s as a tech.


    I’m very thankful for your time, suggestions, and support.


    Also to add I’m too far away for the closest P25 repeater, but perhaps we can link together for a better coverage in this area.
  2. K7JEM

    K7JEM Ham Member QRZ Page

    Is there a reason you are wanting P25, as opposed to DMR or DStar, etc? There are not a lot of ham repeaters on P25, AFAIK, and the equipment can be pricey.
    N3AB likes this.
  3. KN4EHX

    KN4EHX Ham Member QRZ Page

    We have pretty good DMR and Yaesu Fusion coverage. Could be better on the DMR front, but there is definitely a lack of P25 around here.

    P25 radios are usually built rock solid and are plentiful - not Baofeng plentiful, but you won’t have to search for long to find one that tickles your fancy.

    Do I need it? No.
    Do I want it? Yes.

    I’m just trying to offer a different flavor of digital mode. Exactly why they made more calibers than .22 Long Rifle and 45-70 government.

    The Kentucky long rifle of radio would be good ole CW. Think plain vanilla, but some people like chocolate or strawberry. Thus they sold more than one type of ice cream in a box.

    Yes, I inevitably will probably have to shell out Lazzeroni or Godiva prices for a p25 repeater. Thus is life I suppose.

    On the flip side it is possible to have a Neapolitan flavored repeater that is capable of more than one digital mode with the addition of a MMDVM. Exactly why I asked my question on QRZ.

    I’ve searched but can’t find the answers I’m seeking. There is a few videos on YouTube of MMDVM repeaters using P25, DMR, and Fusion all within seconds of each other. Yes, a real repeater not just an openspot.

    Unfortunately I don’t know how to make a MMDVM hotspot and I also don’t know what the options are in regards of P25 repeaters. I should probably lean towards making a repeater with an MMDVM, but I’m not too picky.

    I’d like to have decent power output if I can. I would think 50 watts or more would be preferable, but in general with UHF line of sight with good antennas is probably the most important part of the equation and using a good coax with minimal loss.

    Just trying to do my homework like a good ham.

    Thank you for the reply. Stay tuned perhaps someone has a good answer. I think the MMDVM technology could expand more potential for hams and it probably doesn’t have to be very expensive.

  4. K0SPN

    K0SPN Ham Member QRZ Page

    Have you built a repeater before? Are you aware of the real equipment and expenses involved?

    Just in case you haven't (and for those thinking about it), realise that you'll need the TX/RX, a duplexer (not those little diplexers from Comet, et al), for UHF you'll definitely want hardline, and depending on distance, probably something larger than 1/2", maybe additional filter(s) after the duplexer depending on site RF, some kind of rack or shelving to put the hardware in. Double shielded coax for all interconnections.
    You talk of using mobiles, yet want something in the 50W range, but mobiles are not designed for 50W continuous duty service, so you'll want to set the power to say 5W on the mobile and then have an amp to get your desired power level. Sure, repeaters aren't really used continuously, but you get a couple people having a ragchew for 30-45 minutes and that's at least 90% continuous duty; even with big fans, that's asking a lot of a mobile.
    Depending on site, you may need a circulator (handy regardless of site), and with that goes a low pass filter for the TX side.
    Oh, and a controller of some variety, and various interconnection cables, maybe a preamp for receive.
    And then there's the site. Is it high enough ? What's the cost? Do you know insured tower climbers?
    Don't forget the antenna; those cheap fiberglass base antennas won't normally stand up to this type of service

    Sure, you can cobble something together that may work for a while, but if the coverage isn't there or it's down frequently, no one will use it.
    And then once it's actually running, there's always the possibility of someone being and asshole and interfere with people, have you a plan to deal with that?

    I think a lot of people really underestimate what building and running a repeater entails.
    Not meant as discouragement, just to think about what's truly involved.
    W6KCS and K7JEM like this.
  5. KN4EHX

    KN4EHX Ham Member QRZ Page


    Most of my life’s endeavors aren’t small and require many years of hard work and dedication. No one established a repeater or built Ben and Jerry’s Ice Cream by sitting around and not doing anything. No one went through medical school or engineering school without hard work and dedication.

    I’m well aware of the implications of such a task. I am a property owner so site won’t be an issue. As far as a contingency plan for marauders who wish to cause harmful interference I don’t have a plan, but I imagine there is plenty of information about that on QRZ and the wealth of information among the local repeater owners.

    Insured climber(s). I don’t have to go too far.

    Duplexers: not so hard to come by. I have a close friend who is a good source in that regard.

    Coax: I did mention using good coax! Brand suggestions? Times perhaps? They have some good deals on hardline at the past couple ham fest I’ve been to.

    Antennas: I’m certainly not one to skimp on antennas.

    Money will come for me soon enough. Although I don’t make six figures at the moment I won’t have to wait for very long.

    I gather I should just wait for someone else to put up a P25 repeater. I’m discouraged now. I seem to catch more flak than answers.
  6. KV6O

    KV6O Ham Member QRZ Page

    I just unloaded several pallets of Quantrars... all 800Mhz though. Little use on the ham bands. I don't think I want to see another Quantar.
  7. WB9QPM

    WB9QPM Ham Member QRZ Page

    Don't be discouraged. I like the Quantar and have modified many for amateur use. Highly programmable, once you learn how to "adjust" the wireline tables. Over 100 watts out, depending on the band, continuous (meaning till the cows come home). Easy to add an external controller, so you can run P25 or analog on the same machine.

    The software runs on windows, any version newer than 98SE. The programming cable is a simple 9 pin serial cable., which can be used thru a USB to serial adapter.

    You might want to check for a 2 meter pair in your area. In my area more repeaters are going silent than are being put in service. Two pair have become available in the last month.

    Keep your chin up and don't let the detractors bother you.

  8. N7WR

    N7WR Subscriber QRZ Page

    Because of the public safety infatuation with P 25 almost every major repeater manufacturer make s P 25 repeaters. In addition to Motorola there are Harris, Kenwood, RCA, Tait, etc etc
  9. KN4EHX

    KN4EHX Ham Member QRZ Page

    It seems as if the Quantar is the quickest P25 repeater to find, but it is pricy. Although you do get what you pay for and it is surely a good investment.

    I agree there is plenty of silent 2 meter analog pairs around here and I’d certainly like to have one, but our coordinator through SERA directly states on the East Tennessee page there is no known open 2 meter pairs available. It has been suggested to “buy” a frequency pair from someone who isn’t using theirs if possible.

    As I’m reading more into the MMDVM option there has been a few people who have used the Motorola MSR 2000 to make a multi mode digital unit and would probably work continuously as well.

    If anything else a Quantar would likely be a very good investment.

    I’m fortunate to be located where I am. From my house with 50 watts simplex on VHF or UHF I can reliably make contacts with mobile stations running 50 watts. If I had a tower of some sort I would like be able to further expand the coverage range. Technically I already cover 3 counties with just 2 meter calling with enough elevation it could be 4.

    Credit goes to N2LEN. I’ve never talked to him and hopefully he doesn’t mind me sharing his video. This is super cool and I think this a great ideal in respect of being able to use many digital modes.

    I appreciate the support from you guys. It is a big endeavor, but many others have gone before me to build repeaters. Given enough time and dedication I believe great things can be accomplished. Perhaps it will be a work in progress and I’ll improve where I can, when I can, and however I can.

    In an ideal world I’d have nothing but the finest equipment setup by the most expert engineers in the industry, but this is ham radio which means I’m doing this on my own volition and property so I won’t be causing anyone other than myself problems. I want to be optimistic of course.

    Still open to ideals.

    Thanks again,
  10. KA2IRQ

    KA2IRQ Ham Member QRZ Page

    There's always one post by someone trying to impress everyone with the expertise that is needed and the high cost involved. Don't be discouraged... do your due diligence and be realistic about things, speak to others locally about what is truly needed in your area, but move forward on your terms. Innovate. Keep asking questions. Learn first, implement later. Change course as needed.

    It would be nice if all the expertise here on actually answered the questions posed.

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