How do i build a simple UHF repeater?

Discussion in 'General Technical Questions and Answers' started by VK20, Mar 8, 2009.

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  1. VK20

    VK20 QRZ Member

    Gday fellas.Great site.Im from Sydney Australia.Ive been on the local repeaters for several years now down under.Lately our repeaters have gone to crap.Its very hard to have a decent conversation because of either repeater owners or users giving us quite a hard time.Can be fun sometimes giving it back.But thats not radio.Id like to build one.
    I know its possible to build a repeater from 2 handheld radios wired up together.The question is.How is it done? Could someone please assist me with some info or put me on the right track to building a simple uhf repeater made from either handhelds or mobile radios. Thanks.
  2. N8EKT

    N8EKT Ham Member QRZ Page

    Last edited: Mar 8, 2009
  3. K8JD

    K8JD Ham Member QRZ Page

    Your biggest concern is getting a high tower or building to set up equipment and antennas, that is tamper proof with limited access to authorized people to work on troubles and upgrades.
    Two handheld radios will not get much range, Mobiles with some power and good front end selectivity from strong signals out of band is a better idea. The Duplexer is a requirement so you only need one antena and feedline./ This can get rather expensive for a commercial unit and VERY difficult to homebrew even with access to precision machine shop gear.
    Good luck :D
  4. W9GB

    W9GB Ham Member QRZ Page

    This sounds like a content issue, and not a technical issue (poor coverage, unreliable operation, etc.)

    Far too many amateur radio operators think the installation and operation of a repeaters is "just a purchase of equipment" -- It is NOT.

    The Repeater Builders web site address many technical areas unknown or assumed by the casual user. Good resource to start your research.
    Intermod, cavities are 2 great topics to start with -- IF you are not techncial then you will have to $$ someone to set it up properly (to be usable)


    Can you hear me now?
    That is why mobile phones exist -- realible communications by anyone to anyone -- anywhere in the world.
    Twitter is the next generation -- in short text/data!
    Last edited: Mar 8, 2009
  5. VK2TIL

    VK2TIL Ham Member QRZ Page

  6. VK2AKG

    VK2AKG Ham Member QRZ Page

    I believe you are describing the UHF CB repeaters in Sydney. These are truly the cesspools of the radio spectrum whose sole redeeming feature is that they give the antisocial somewhere to play (this makes the simplex UHF CB channels useful for others).

    Ignoring such people or staying off capital city UHF CB repeaters is a much better option.

    Alas on Sydney's UHF CB repeaters it is. See channel 7 prime time TV news items:
    - Sydney CB Radio Wars
    - Young Sydney Mum Attacked By CB Radio Thugs

    I believe that all of the legal UHF CB repeater channels are already allocated in Sydney. Whilst something like that which you propose can be done, it will neither be effective nor legally permitted.

    If you decide to ignore the law and do something different which is effective then the people you are trying to escape will merely follow you to your new repeater.

    That said, if you truly have a _genuine_ interest in radio then you have some options

    (a) move to the 27MHz HF CB band where you can meet some kindred spirits, this requires no license, very little expenditure and can be a good place to start (NB whilst they are generally nicer people the number of people on HF CB is a LOT less than on UHF CB - don't expect to get an answer every time you call)

    (b) purchase a receiver and take up short wave listening as a hobby. Have a look at "Amateur Radio" magazine's monthly column "Spotlight on SWLing" by Robin Harwood VK7RH which will give you a glimpse of this hobby (sold by newsagents). Be aware that, to be useful, the receiver MUST be able to receive SSB.

    (c) study and obtain an amateur foundation license (theory, regulations and a practical test) then move to ham radio. This license standard is within most people's abilities but be warned it does require WORK (yes, I know, a four letter word of Anglo Saxon origin).

    If you decide to go with option (c) you will be happy to know that childish or illegal antics are not long tolerated on the ham bands. Amateurs can and do assist the authorities to enforce the regulations within their spectrum.

    73 Frank vk2akg
    (who has no problems with _amateur_ repeaters in Sydney)

    edit: overseas readers who may assume the original poster is an amateur with a 2x1 call should note that:

    - VK20 is _NOT_ a callsign issued by our regulatory authority

    - VK2O is a scientific licence issued to the Hunter Institute of Technology 150km / 100 miles North of Sydney (NOT Sydney, NOT amateur)
    Last edited: Mar 9, 2009
  7. VK2TIL

    VK2TIL Ham Member QRZ Page

    AKG; the links were an education for me.

    I lead a sheltered life in the country!!

    I used to hear some terrible things on the truckie's channel when passing through Sydney; the (non-truckie) idiots made it almost unuseable.

    If I traverse Sydney on a journey these days I switch the CB off until I'm through.
  8. VK2AKG

    VK2AKG Ham Member QRZ Page

    The vast majority of UHF CB users in Sydney are normal decent people who are speaking to their co-workers or friends over short distances. They are not interested in speaking to people outside of their group. Most use low power hand radios on simplex channels, have no concept of repeaters and have enabled CTCSS in the belief that it is an extra "private channel" - they can become confused when someone outside their group talks on "their" channel.

    On the other hand, with few exceptions, the Sydney UHF CB repeater cesspools and the occasional bozos teasing the truckies on ch 40 are best avoided.

    I use 300 mW simplex UHF CB on work sites with no problems however, when driving through Sydney, I think you will find the following repeaters more to your liking:

    438.550 & 438.700 (they are linked)

    146.800 & 147.250

    73 Frank
  9. KW7RF

    KW7RF Ham Member QRZ Page


    Click on the link above
  10. K9KJM

    K9KJM Ham Member QRZ Page

    Do follow the links provided by GB. That is great information.

    Building and maintaining an in band repeater is not for the faint of heart or wallet.

    As already pointed out, The tower site is a main concern that is needed before any equipment.

    It is possible to "build" a repeater with a pair of radios and something like either a homebrew or a Hamtronics COR, but not really worth the effort any more now that good used commercial repeaters are on the market for a very low cost.

    A good old used Motorola Micor UHF repeater can usually be purchased for less than the shipping will cost! And they just keep going and going and going!

    Remember, An in band repeater is 100% duty cycle. Even mobil radios will start to get warm in a hurry and need an external cooling fan. Little hand held radios, While they might "work" will go up in smoke in short order.

    Also consider "cross band" repeat operation. With something like just a Yaesu FT 8800 and a dual band antenna and you are in business with no hassles.
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