Portable repeater, what to use?

Discussion in 'Mobile Radio Systems' started by KJ6HYC, Jan 20, 2011.

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  1. KJ6HYC

    KJ6HYC Ham Member QRZ Page

    For a portable 2M repeater, could you use 2 mobile type FM transceivers, tuned cavity, antenna(s), ID generator, radio interfaces, and a 12V power supply (batterys, solar cells, generator etc). Would the transceivers duty cycle or anything else be restrictive for this type of service? I understand there will be heat/weather proofing challanges. Has anyone had any experance with portable repeaters and/or this type of setup?

    KJ6HYC Wayne
  2. WB2WIK

    WB2WIK Platinum Subscriber Platinum Subscriber QRZ Page

    Even with a fantastic multi-cavity duplexer it's difficult to get any real receiving sensitivity out of such a setup because the TX noise will get into the RX due to lack of shielding and decoupling. The real limitation is the equipment itself, which isn't designed to work as a single-band repeater.

    Mobile rigs might survive a 50% duty cycle if they have very good heat sinks assisted by cooling fans, but it's unlikely any of the ham gear, unless it's sold as a repeater, will withstand anything like 100% D/C.

    Other than the receiver desensing issue, though, such systems work and are pretty common. For temporary operations such as handling radio traffic for a parade, having much reduced sensitivity might be just fine: Often you're only trying to cover a few miles, and don't need more than that. It's just enough to extend the range of hand-held radio users who normally couldn't hear each other.
  3. K7JEM

    K7JEM Ham Member QRZ Page

    You would be much better off making a portable repeater for the 440 band. The duplexers are much, much smaller and way cheaper.

    I built a 440 repeater into a small plastic toolbox, like you get from Walmart for $15. It contained the duplexer, a 7AH battery, and two data radios about the size of a cigarette pack. It only put out a watt or two, but for local use it worked like a champ. We put it on a nearby deserted mountaintop, with a solar panel, and it had fantastic range, more than 40 miles in most directions.


  4. WB2WIK

    WB2WIK Platinum Subscriber Platinum Subscriber QRZ Page

    Joe, that's amazing (or brilliant, pick one).:)

    There's a market for such an item. Ever think about selling them?
  5. K7JEM

    K7JEM Ham Member QRZ Page

    No, it's way too easy to build. I think anyone who really wanted to build one would come up with that idea.

    The parts cost about $500 new, less if used. Most people don't want to put that much money into one.

    Mine was made from radios that were unused for the original commercial application, so they were basically free. Same for the 6 cavity flatpack duplexer. The only real expense was the 7AH battery ($22) and the toolbox ($15). Even the antenna was basically free, an EDZ constructed of 2 brazing rods, a couple pieces of PVC, and a 10' piece of 1/2" EMT.

    It is simply amazing how well the whole thing worked, and how simple it was to put together.

  6. K9KJM

    K9KJM Ham Member QRZ Page

    I agree with both WIK and JEM, UHF IS much easier to build up a in band repeater, However depending on just what you want to do, A simple CROSS BAND repeater may be the much easier, Cheaper way out.

    A Yaesu FT8800R with a dual band antenna is all you need to set up a good cross band repeat system to greatly extend the range of say a small micro power hand held.............
  7. AK4GA

    AK4GA Ham Member QRZ Page

    No sir, it is not. You need to add equipment to properly identify.
  8. KJ6HYC

    KJ6HYC Ham Member QRZ Page

    Thanks for all the responces and the 70cm info, however it must be 2M, as it has to be compatable with the the rest of the local RACES system/radios/members.
  9. WB2WIK

    WB2WIK Platinum Subscriber Platinum Subscriber QRZ Page

    That's a pretty typical case. I've run into this also, working comms for parades and marathons and stuff. A X-band repeater would be really easy, but not enough people have X-band HTs. Every time a straw poll is taken, 2m wins because almost everybody has a 2m HT.
  10. K9KJM

    K9KJM Ham Member QRZ Page

    Quote: "No sir, it is not. You need to add equipment to properly identify. "

    WRONG! NO external equipment is required to make a legal cross band repeat set up! You can simply I.D. both your input and output link frequencies with any dual band hand held! Simple and easy.

    You only need to add extra equipment IF you want that I.D. to be fully automatic.
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