Kenwood TKR-850 as a D-Star Repeater

In my opinion this type of thing needs more attention. After all do-it-yourself has long been a hefty part of this hobby. And there is no better way to learn than a hands-on project like this.

Reason number two would be economics, but I think that is obvious.

The third is spectral savings. D-Star is narrowband, but buying a new system just robs another frequency pair from the pool. It seems people rarely take repeaters off the air, even if nobody really uses them. And these days it seems there are more repeaters in a geographic area, than there is activity.

So it seems best in my mind to convert something already out there. This would make a great club project.

This is great example of continued innovation of D-STAR technologies by incorporating non-Icom products into D-STAR environment.

Date: Thu, 07 Oct 2010 05:32:17 -0000
To: dstar_digital@yahoogroups.com
From:
Subject: K8BIG Port B Using Kenwood TKR-850 Interfaced to ID-RP2C

The K8BIG Port B D-Star Repeater in Cincinnati, Ohio is successfully running using a Kenwood TKR-850 Interfaced to the Icom ID-RP2C in place of the Icom Band module (ID-RP4000V). The usable range of the repeater has been effectively doubled from around 25 miles radius to 50-55 Miles radius.

The K8BIG system is on the WCPO-TV Tower overlooking downtown Cincinnati, OH with the antenna at 700' AGL. There are 3 50,000 Watt FM Radio transmitters, 1 250,000 Watt VHF DTV Transmitter, and 2 3,000 Watt LPTV stations on the same tower along with various commercial VHF/UHF/220 transmitters so the RF environment is pretty harsh - add in the neighboring (2 Blocks) tower with a similar complement of transmitters and it is downright brutal for any radio equipment.

The Icom band module was being swamped by the high RF levels at and surrounding the site, causing very poor effective receive sensitivity even after the TX-RX BpBr Cans and an additional band-pass cavity. I had partially remedied this with one side of a reject-only mobile duplexer, but that introduced around 6 dB of insertion loss. Even with the 6 dB insertion loss the effective sensitivity was improved. The Kenwood repeater has a much tighter front end and much better selectivity with adjustable front-end helicals so the additional receive filter is not necessary and the 6 dB insertion loss was removed.

After the interface was built we were able to plug and play into the Icom ID-RP2C controller and gateway. With the exception of the increased range there is no operational difference in the repeater - everything works identically to the Icom band module. Commands work, data works, D-Rats works, etc.

I will be building more of the interfaces shortly which can be used to interface any 9600 baud-capable analog repeater directly to the ID-RP2C. Anyone interested please let me know.

Thanks.

Dan Woodie
KC8ZUM

You may want to look at;
Michael, VK5ZEA's Homebrew DV Node Adapter to ID-RP2C interface.

John, K7VE's Kenwood TKR-820 Node adapter retrofitting.

And/or my Motorola GM300 retrofitting and commentary.

As a technical side note, one thing to consider when converting analog repeaters is the receiver IF bandwidth. To date there has been little discussion on narrowing receivers bandwidth to match the narrower D-Star signal. Just be aware that converting a 1950's era repeater to D-Star that might have a 60 Khz I.F. would be vulnerable to adjacent channel interference. A good overview of the theory can be found in a reprinted article from Ham Radio Magazine 1985, by WD5IBS.

DV Access Point Dongle (DVAP)

Unlike the DV Dongle, the new product allows Amateur Radio operators to walk away from the computer and transmit/receive D-STAR voice and data using a two meter D-STAR radio..... The DVAP is basically a GMSK modem with a 10 milliwatt two meter transceiver built in.

This is more crap for hard core D-Star enthusiasts. As if paying $200 for a regular DV dongle wasn't insane enough, just so you could talk AMBE over the internet using your PC microphone and speakers... now you can pay that plus the price of a D-Star radio, just to talk on the precious D-Star network.

Why in tar-nation Robin, AA4RC wasted any time designing the DV Access Point Dongle is beyond me.

It seems more logical to promote the GMSK node adapter hooked to a real retrofitted analog radio. Converting analog repeaters to D-Star at a fraction of the cost seems like something I'd get behind. At least then more than one person can use it.

This is another toy... that to me was a huge waste of engineering time. I thought Robin was going to work on a complete open replacement for the $300 Icom D-Star gateway software, hence www.opendstar.org.

All that has resulted is an add-on called D-plus, basically written to augment the DV dongle that Robin sells.

The AMBE decoder should be at the repeater end. Then users who want to talk on D-Star over their PC's can stream their voice using an open codec (no dongle) to the repeater, at which point it can be converted to AMBE with a community dongle.

Who is steering the D-Star boat? Will the D-Star newsletter ever promote such ideas? Or is it a mere advertisement to aid Icom and Robin in their financial endeavors?

Homebrew D-Star Repeater?

In the past I've written about a passive D-Star capable repeater using a couple Maxtracs.

This of course is less than ideal as it's a carrier activated system, left open to intermod and such.

I have also written about Satoshi's GMSK node adapter. There was a tid-bit about this in the July 2009, QST, Eclectic Technology column by Steve Ford.

In the QST article it was talking about using Satoshi's board as D-Star Simplex Hot Spot. Mark, KB9KHM developed some windows software so one can use the node adapter as a simplex node to talk back to the gateway server of other D-Star repeaters.

Most of the bugs have been worked out, and the official non-stripped down Satoshi, GMSK node adaptor board can be used to make or convert an existing repeater for D-Star, with the capability to talk back to gateway servers for interlinking.

I suggest taking a look at David, G4ULF's blog.

His blog is a running log of development of a D-Star repeater that links to the worldwide dplus network running on homebrew components and standard UHF FM rigs.

Duplex use of the node adapter used to require two 18F2550 PIC chips running his code, instead of the one. Now KB9KHM's HotSpot software can emulate that. So you can get by with a mini-hotspot board, and just one PIC.

Satoshi's project has caught a lot of attention (and some flack), because you can construct the node adapter for about $75. An Icom D-Star system; one radio module, RPC controller and gateway runs about $3,000.

If you build or convert your existing repeater system, you can also keep backwards compatibility for repeating analog.

All you really need are direct (varactor or varacap) drive to transmit the GMSK data, and a discriminator output for receive. (As pointed out for the simplex hot spot use, most 9600 baud "data ready" radios will work.)

The retrofitted repeater system should be tuned for maximum 3 KHz deviation for best bit error ratio.

If the idea of running Mark, KB9KHM's windows based "hotspot" linking software for a permanent repeater installation doesn't thrill you, never fear, Dextra is here! (This is a very close basis of G4ULF's project)

Satoshi, 7M3TJZ/AD6GZ's D-Star Node and DV Adapter

Satoshi Yasuda, 7M3TJZ/AD6GZ, has two different constructions projects available. The one that is the main focus of this yahoo group - the node adapter - is basically a GMSK smart modem tailored to D-STAR.

The node adapter has two modes - simplex and repeater. In simplex mode, node adapter only serves to decode/encode the GMSK modulation used by D-STAR radios and turn it into a bit stream that can be fed into a computer. In repeater mode, the node adapter serves as a bit regenerative repeater. However, while in repeater mode, the node adapter does not have the capability to pass any data in/out of the computer. So, in repeater mode, the node adapter can not be linked to any D-STAR gateways/reflectors. This node adapter has no provisions to convert D-Star Digital Voice To Analog Voice. This hardware software combination operates in 100% digital mode.

He began by looking into the UT-118 works. It is entirely of his own design. Mr. Yasuda is/was a member of the D-Star standardization committee.

The main component is the CMX589A GMSK modem chip. The same chip used in many
of the Icom radios.

Probably the next most important chip is the 18F2550 PIC that runs his firmware.
This takes care of formatting/ recognizing the actual D-Star protocol, USB
communications etc.


More information can be found on Satoshi's web site.

Mark, KB9KHM uses his node adaptor in simplex mode with his D-STAR Hot Spot software that Mark wrote to provide a simplex RF point of presence to the D-STAR network. (He uses his D-Star HT with the adaptor hooked to an analog radio's packet port to pass D-Star digitally to a gateway server over the internet.)

In this video, Erik Finskas OH2LAK, of Finland shows his D-Star Hot Spot / node adaptor while holding a QSO:

And here is a slide-show overview of the GMSK Node Adapter:


In a later revision of Mark's hotspot software he added a routine that provides a way around the combination problem repeater mode and linking. Now you only need one pic, as the data received can be sent back out like a loopback, while still keeping a data stream to external D-Plus gateways.

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His AMBE DV adaptor on the other hand is a full blown adapter to turn an analog radio in to a D-STAR radio and does include provisions to encode/decode AMBE.

In this video Peter, DJ6ZR/AI4UE and Don, WD4CWE test D-Star on 6 meter and 10m with the Satoshi DV Adapter. With more info at http://dstarradioclub-international.com/default.aspx



Mark, G7LTT/NI2O also has had 10 and 6 Meter successful D-Star QSO's using Satoshi's AMBE DV adapters interfaced to two Yaesu FT-8900 quad band FM rigs.

Satoshi's AMBE DV adapter does decode and encode raw D-Star tailored GMSK unlike the the DV Dongle that Moe, AE4JY and Robin, AA4RC have in production.

Satoshi's does seem better suited for the D-Star to SIP translation project that is being investigated.