Homebrew repeater

Discussion in 'The Okie Corral' started by lomfs24, Jun 13, 2005.

  1. lomfs24

    lomfs24

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    I was talking to an old ham the other day about simple cheap repeaters. Let me give you a little background first. I hunt in a remote area where we are very far from a repeater and about 120 miles from a decent hospital. We would be looking at a medivac flight if anything serious were to happen in there. I can hit a repeater that is linked with a large city with a mobile but I cannot hit it with an HT. I can do a crossband repeater with my mobile that kinda helps out a little. But what I was looking for was a simple repeater, run on batteries, that could be quickly and easily dropped off and set up in the early morning hours to cover handy's in a hunting area. Then picked up and night as we returned to our camp. We were using those expensive $30 FRS/GMRS radios from Wally World and they work about as good....well.....as a $30 radio should.

    So anyway, I was talking to an old ham and he said you can get a couple handheld radio's and link them together if you can serarate the COS, audio and PTT etc... You would set one at the top end of VHF and one at the bottom end of VHF and get away without having a duplexer. Granted, it wouldn't be the greatest but it would be a simple small area repeater that could be easily carried and set up.
    Now, to the question. Does anyone know how to do that? I am not looking for indepth instructions across this message board but rather a website that discusses this.

    Thank.
    W7DOA
    73
     
  2. Glock Bob

    Glock Bob Snack Attack!!!

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    The problem is that HTs aren't designed to RX and TX at the same time. Plus, most HTs max out at about 5 watts (some at 7), so you wouldn't gain any more wattage, just distance. I suppose if you had a ton of money you could rig up a portable repeater or just build a stationary one. You could set it up as a private code-access system and have those who want to access it pay a yearly fee. Then, all you'd have to do is unlock it when you're out and about in the woods and lock it down after you're through. There could be a monthly usage schedule where it could be emergency only on certain days at certain time blocks and open to every other member at all other times. It would be sort of like IRLP nodes that need a DTMF code entered in order to key up.
     

  3. lomfs24

    lomfs24

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    There are a couple problems with that.
    1) The ton of cash part. Seems to be more like an ounce or so rather than a ton.
    2) I don't need to increase watts. I need to increase range of HT's in a small area.
    3) It would be on state land and I am only there for about 3 or 4 weekends a year through hunting season.
    4) I would like it to be extremely mobile so that as we moved from ridge to ridge during the hunt the repeater could easily be moved with us.

    As far as HT's not being able to Tx and Rx at the same time. That's why you would have to be able to separate the COS, PTT, audio etc... so that as one started to receive the other one would be prompted to start Tx. Thereby making a reletively cheap extremely portable repeater
     
  4. Glock Bob

    Glock Bob Snack Attack!!!

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    But, if one was prompted to TX while the other keyed up, what would that accomplish? The TXing HT would have to RX at the same time in order to send out any kind of voice TX, otherwise it's just keying up and sending nothing. However, perhaps a manufacturer already makes such a beast. I know Kenwood makes the mobile that can act as a mini repeater, as I believe you already have one. However, that could run down the battery in your vehicle if you're not careful or get stuck out there for a while.

    You might want to look into a portable yagi antenna. Arrow Antenna makes them commercially, and you can even make your own. Lots of folks use them to get out to satellites with HTs, so it should be a help with hitting a repeater.
     
  5. lomfs24

    lomfs24

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    You are right Bob, I do have a crossband repeater. It is a Yaesu 8500. I have planned to set that up as a crossband repeater that would get out to a repeater about 55 or more miles away. The idea with the HT repeater was to create a larger cell, if you will, for out HT's between hunting partners not really to get out to a repeater.


    I don't know if I explained the HT repeater thing well enough. Basically, when on HT began recieving it would key up the other one to TX. The audio, rather than coming out on a speaker would be passed to the other HT that was keyed up to TX. That's why you would have to separate the COS, PTT and audio wires. There would, of course, be some moding required to do this. Then you would take the whole mess and put it in a project box that was water proof.

    Anyway, I was just looking for ideas.
     
  6. thenewguy

    thenewguy

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    Some of the nicer (read: more expensive) HTs have crossband repeat capability. My good 'ol ADI dual-band HT does, as do the modern Kenwood models. Since we all know the secret to an effective repeater is not power output but *location* (usually on top of hills and such) an HT-based repeater can work quite well. I've used mine a couple times with good results. :)

    You probably just don't want to leave a $400-500 Kenwood HT up in a tree somewhere, so you might look for a used ADI dual-bander on EBay that can work just as well.
    -Adam
     
  7. Glock Bob

    Glock Bob Snack Attack!!!

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    Ok, if modding is involved then it could work, I suppose, but it would make my head hurt thinking about it ;g . Now a crossband HT, I didn't even think about that. It seems my VX-5R might have that capability.

    So, in effect you're just wanting to boost a TX without actually boosting it (ie without pushing more watts). How very interesting. :cool:
     
  8. Glock Bob

    Glock Bob Snack Attack!!!

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    Are you or any of your friends Generals or above? If you all, or at least most of you, had HF privledges it would seem that you would be able to TX farther than VHF/UHF as HF is a longer wave length and requires less wattage to travel the same distance as higher MHz require.

    Also, 6m is open to Technicians, which is as close as we (us Techs) can get to HF. I know it's not the best or most popular band, but it would seem that would make it a good alternative to HF, assuming RF interference isn't too bad in the area you wish to operate within, as 6m suffers from it.
     
  9. lomfs24

    lomfs24

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    Unfortunately, NO. I am and everyone else there will be techs. 6M might work, we will have to play around a bit with that. I do have a Yeasu VX5R which has 6M capabilities. But I don't think anyone else has 6M abilities.
     
  10. thenewguy

    thenewguy

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    With a good location for the repeater, you don't need more power than an HT provides. It's all about location, location, location. :)
    -Adam
     
  11. Glock Bob

    Glock Bob Snack Attack!!!

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    There's always a catch if you look hard enough. I've found 6m to be quiet on one frequency and overcome with white noise just a few KHz up. Tone Squelch should clear up any unwanted transmittions of white noise, except of course those that happen simultaneously with someone TXing with your same Tone.
     
  12. lomfs24

    lomfs24

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    I don't think the VX-5R has crossband repeat ability. At least I have not found it on mine.
    Now you are getting the picture. For instance, let's say there was a ridge, one hunter is on one side and one is on the other side. Normal HT comms could not happen between the two. But with even a low power repeater in the middle at the top of the ridge it would be possible. That is just one scenario for it. A fast moving Search and Rescue party might also find the extra distance and extreme portability a plus.
     
  13. Glock Bob

    Glock Bob Snack Attack!!!

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    Yeasu makes a portable mobile rig, the model FT-817. However, it does not seem to have crossband repeat as far as I can tell. If it did it would probably be exactly what you were looking for.
     
  14. lomfs24

    lomfs24

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    That would be exactly what I was looking for if it had crossband repeat. The downside to crossband repeat is that then everyone has to buy, at least, a dual band rig. The other downside is the $600 price tag. I figure if I can find some plans for this, I can buy a couple older commercial VHF rigs that will go down into the ham bands for about $100 apiece, a couple bucks in solder and wire. And I'll take the other $400 in experience. If I did it that way as well, I could buy older VHF commercial rigs for use too. You can usually find them on eBay for around $100. True they don't have all the bells and whistles that a newer ham radio has but when I am hunting I only need one volume knob, one channel knob and one PTT button and a jack for a headset. That's all I want to deal with. Then I have cheap radios all the way around and I lose one or one get's damaged I am not out a $400-500 Kenwood.
     
  15. Glock Bob

    Glock Bob Snack Attack!!!

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    Ok, this is all starting to come together for me. I've made a diagram, below. It's crude, but I think it will sort of demonstrate what I think will work.



    [​IMG]

    HT1 and HT2 are set to two different frequencies that will not interfere with any repeaters in the area and are offset by a considerable amount, say the normal 600 KHz. When someone TXs on HT1 freq, the speaker wires, which would normally power the speaker, now are attached to HT2's PTT and microphone. The power through the wires trips the PTT button (can be accomplished via a relay or something) and the audio is sent to HT2's microphone, thus being TX'd on the second frequency. You could even run a small amplifier to boost HT2 up to 10 to 15 watts to help ensure better coverage.

    Does this make any sense at all? It does to me, but it's 11:30 at night and I've had a pretty long day.
     
  16. lomfs24

    lomfs24

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    OK, now we are getting somewhere. It does make sense, kinda. I think we are missing some caps somewhere. Some other things to think about that I didn't think about earlier is desensing (I don't know if that's how you spell it or not) one radio with another. I think if you used the whole band as a spread (tx at 144.000 plus a little rx on 148.000 minus a little and set a channel on the radios you will carry with an odd repeater split) you could actually get away with a single antenna, say, a J Pole of sorts hung in a tree. If you use two separate antenna's I think you would want to separate them by at least 6 feet but you could use a more conventional repeater split.

    I did find a PDF on rough schematics on how to do it with Bendix King VHF radios. Although they operate in commercial bands I think the idea could be used for ham radios as well. Just have to get schematics for what ever radios you wanted to use. I will include the pdf as an attachment to this message.
     
  17. greenlead

    greenlead

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    Are you talking about about repeating FRS or Amateur. I think the FCC has some regs limiting the range of FRS a bit.

    I do know that there are some premade repeater kits out there that consisit of the circuits necessary to make a quick erpeater out of HTs. I learned this when I was interested in doing one of these a while back via a few Google searches.

    How are you planning on taking care of the identificataion and licensing requirements for the repeater?
     
  18. lomfs24

    lomfs24

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    I don't believe there are restrictions on the distance of an FRS radio. However, there are restrictions on power limits and with the rinky dink antenna's that are put on those radios you just don't get anywhere.

    I am planning on repeating ham freq's. I will ID manually, and I will take care of licencing too. No need to worry there.

    Do you happen to know where some of these premade kits are? Or what they consisted of. I seems to me there is really nothing more than a couple wires and a cap or two. I suppose people would pay for that if it's in a neat premade package.
     
  19. EUPHER49

    EUPHER49

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    Paragraph 2 of the PDF doc is crucial:

    As with any repeater system not incorporating cavity duplexers, self-interference and receiver desensitization must be considered when using the system. Repeaters constructed using this document should be limited to two watts, use CTCSS (CG) receiver decoding, use separate battery packs on each radio, use input and output frequency separation of at least 1 megahertz and maintain an antenna separation of at least six feet. Radio mounted flexible antennas may be used allowing the entire system to be placed on the roof of a vehicle parked at a geographically high location.

    Cavity duplexers for 2m are VERY expensive!!!

    The transmit timeout feature is also required by FCC rules for remotely operated systems.
     
  20. Glock Bob

    Glock Bob Snack Attack!!!

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    Yeah, it may be a little tricky, mostly with the FCC. Technically you would be making a repeater of sorts, and would, therefore, need to register it as such and pay any fees. However, you are using HTs, which only require you to have an operator lisence. However, I would try it with some cheap HTs first, if only to see if it can be done. I doubt the FCC would really care so long as you keep the wattage down and the frequencies away from other repeaters to avoid interference.