So you want to build a DSTAR repeater…

So you’ve played with DSTAR enough that you’ve decided you want to host your own repeater. Well congratulations! Welcome to one of the most challenging and satisfying activities in your ham radio “career”!

Here’s what you’ll need if you want to build a DSTAR repeater.

1. Antenna
2. Feedline
3. Lightening protection (suppressor, in addition to a proper ground system)
4. Duplexer (a flat-pack mobile unit will work if you’re in a low RF environment. If there are other transmitters around, you’ll want larger cavities – a band-pass/band-reject unit.)
5. A repeater site – as high as you can get, with easy access for maintenance
6. Internet access – including a public facing ip address so users can route directly to you from other repeaters
7. Power supply – 12V at whatever amps you’ll need
8. Miscellaneous cables…all good quality!

As a quick side note, all of the principles for analog repeaters applies to digital systems. Checkout www.repeater-builder.com for tons of good information.

Phew. Now that you’re done with the antenna system and internet access, you’ll need to make a decision. Are you going to go with the ICOM system, or a home-brew system?

For an ICOM system:
1. Radio module for the band you want to be on ($700 for UHF)
2. Controller module ($850)
3. Computer running Linux to run the gateway software (figure $300 for a solid system)

That’s $1850 in addition to items 1 through 8 above.

The other option is a home-brew system. I’ve built two of these already – one from Kenwood radios, and one from Motorola radios. Either of these requires access to programming gear/software, so you may have other costs you need to consider.

For a home-brew system built on Motorola radios:
1. 2 CDM 1550 UHF radios (one for TX, one for TX) – $300 from eBay
2. Raspberry Pi with SD Card to run the G4KLX gateway software ($50)
3. DVRPTR modem – http://dvrptr.net/ ($120)

For the CDM radios, you can’t run them at 100% power – these are mobile radios, and they are rated at 50% duty cycle or lower at full power. I’m using 30 watt radios at 10 watts. The transmitter doesn’t seem to mind this power setting, even when run for 2 hours continuously. Because of the acknowledgement packets that are sent after user transmissions, duty cycles easily get 100% during normal DSTAR use. Hold a net, or a long QSO, and you’ll find your transmitter melted if you try to run it at too high of a power setting.

You can add a power amplifier after the transmitter if you need more power. I’ve not found this to be necessary with the proper antenna and site. If I can hear the remote units, they can hear me. More power hasn’t been necessary.

I’ve also had success with a Kenwood TKR-820 repeater. But….programming these for me is harder. Alignment is a bunch of coils and takes some time. They have a built-in power supply. You really need to narrow-band the units, as that’s what the users’ radios are expecting. It will work wide-band, but it won’t work as well. The system needs to be narrow on both the repeater and user side.

Michael Brown, KG9DW, is a regular contributor to AmateurRadio.com and writes from Illinois, USA. Contact him at [email protected].

5 Responses to “So you want to build a DSTAR repeater…”

  • You forgot to include the 200 dollar price tag of the ICOM g2 software, if you were to put an icon setup in place. You also forgot to add the cost of employing a Linux professional for the compiling, install and setting up of the klx software.

  • Michael KG9DW:

    Few people ever need to compile the G4KLX software…there are builds available to download. I’ve done it once and it did take a bit to get it all compiled. And if you use a pi, there are sd card images available that will have you up and running in a few hours. The yahoo group for the pcrepeatercontroller software is great, I’d I’m also available to help hams learn.

    I’m not familiar with there being a cost for the G2 software but I’ll take your word for it.

  • Frank K4FMH:

    I keep getting my iPad and iPhone changing the word “lightning” to “lightening”. I see you get that too!

  • jeff n1kdo:

    Flat pack won’t work on VHF. A VHF duplexer for 600 KHz split is quite expensive, even used.

    The first thing I would recommend for anybody who wants to build a repeater is — think about this long and hard, and prepare to open your wallet wide.

    The next thing I would recommend is Advil. Or Scotch. Or both.

    Jeff

  • PJ2MAN:

    Nice info’s guys 73’s de PJ2MAN Sher

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