Sunday, July 19, 2009

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)

Sunday, July 12, 2009

British Columbia Wireless Amateur Radio Network.

The BCWARN infrastructure includes and supports:

-Electronic Mail via WinLink (over 2.4ghz microwave, AX.25 packet radio and Pactor3)
-D-Star Digital voice and data
-VoiceOverIP using Asterisk private branch exchange (PBX) open source telephony switching technology
-File sharing
-Remote printing and facsimile
-Video conferencing & instant messaging

Thursday, July 2, 2009

Bandplans - 900 MHz and above

Nearest I can determine, the last time ARRL bandplans were reviewed was nearly 20 years ago for 50 MHz and above.

There is some ARRL Microwave Band Planning in it's initial stages that I welcome as it's long overdue in my opinion. So I do look forward to reading other peoples thoughts on how to tackle the problem of promoting ultra wide band data modes and somehow keeping some harmony with any existing activity on these bands.
Chairman and Liaison Appointments: Microwave Band Planning Committee: Tom Clark, K3IO, Chairman.

I noticed that Will Payne, N4YWK is a part of some sort of active ARRL Microwave Band Planning. He has a help wanted thread on the LinkedIn ARRL Ham Radio Operators group. He appears to be surveying conventional repeater use. (He is seeking help fill in two "lost decades", the 1960's and the mid-70's to mid-80's, contact Will if anyone you know who may have old repeater listings.)

The historic growth of repeater populations on the lower bands might serve as a bellwether for future growth on the microwave bands. Historic growth graphs would also be informative for the ham community at large.

Also in the The ARRL Letter, Vol 27, No 29 (July 25, 2008), there is this interesting snippet:

* ARRL Board of Directors Plans the League's Future at Second 2008 Board Meeting

Regulatory Matters:
The Board voted to establish an ad hoc study committee to review Part 97 of the rules governing the Amateur Radio Service to ascertain what rule change(s) would be beneficial to promote wideband digital modes, while at the same time minimizing potential interference to narrowband modes.

And more recently:

It Seems to Us: Coexistence - Radio spectrum management is a difficult business. The most useful part of the spectrum has been fully allocated for decades, yet new uses continue to be developed. Where can they go? It's a question that requires ever more imaginative answers.

Nov, 2011

With those observations pointed out. Basically I feel investigating and possibly revising the bandplans is long over due.

I feel that 900 MHz and above are the future of ham radio. On SHF frequencies outside the ham realm, wide band modes are exploding. Such hardware can be adapted to the amateur service. Doing so (as the former HSMM WG showed) is probably the easiest way to populate these bands. Our SHF allocations have the band space to accommodate such modes so this is a natural fit.

Therefore I feel wide band (OFDM) modes should be promoted as first class modes of operation on these bands. Presently they are see by many hams as secondary to "conventional modes" like FM and analog ATV. The present voluntary band plans for 900 and above seem to detour ham from experimenting with these "futuristic" modes, as they are unsure how they fit into to the existing plan if at all. The other detriment of antique band plans is when (potential) manufactures look at is for reference on what would be a marketable ham line or product.

Bandplans for 900 MHz and above, unlike for below 900 MHz, need to have a futuristic theme in mind, to provide a path to the future. This futuristic thinking is also because one must realize it will take years to substantial SHF utilization to occur anyway.

One of the purposes of a frequency coordinator is to recommend standard operating procedures. The frequency coordinator's main job is to make sure your repeater will not interfere with nearby repeaters already established.

They have the duty to not only produce bandplans that satisfy the needs of repeater owners within its area but also to protect the interests of coordinated systems in adjacent areas, weak signal modes, digital communications, AM and FM simplex, and satellite uplinks and downlinks. They define the bandplan for both coordinated and non-coordinated activities within its territory.

In the event your coordination body's band plan is behind the times; Aside from the FCC's frequency limits spelled out in Part 97, everything else is technically a voluntary band plan.

From what I have observed, the frequency coordinator's job (at state, regional
and nation levels) isn't an on-the-air practice so it seems they are totally off
the hook when it comes to holding up their duties.

Until things are formally updated, just observe Good amateur practice . Make your best effort to check for other band use. And if you determine the conventional band use doesn't offset your experimentation, then I tend to think what you are doing on our underutilized SHF bands IS in the best interest of the amateur radio service.

(You can see this has been on the ARRL’s to-do-list for at least a year or better. But we are talking about the ARRL here.)