Hi John, Well, D-Star IS plain FM, you buy an FM transceiver and the add on board just utilises that for the GMSK data, like packet or any other data mode for that matter. Yes, I agree that the bandwidth is full scale all the time, but measure it on a scope and see that the GMSK data is the same from any source from something purchased and 'home brew'. The SN ratio in my operational tests from GB7AD/CD, near to WE are in my opinion much worse than WE in overall tests, where AD/CD are marginal signals, the drop outs are far far more obvious and noticeable, whereas WE/WB seem to work much further into the noise than what the Icom boxes by design actually achieve.
In the Bristol area of the UK, we are really lucky to have one mans work, seemingly do more than what Icom have put into place as a simple 'repeater' with connectivity, at the loss of a far better useable option from SZM's hard work, effort and understanding of how and why the signals deteriorate and loose data so frequently. If you could actually try the Icom and 'home brew' repeaters side by side, you would appreciate the difference and see what I feel to be something that would make D-Star (in the UK in most instances) something worth going for and better overall, even though everyone is using an Icom radio into the nodes in every case! I'm not knocking Icoms achievement in any way here, we do have some wonderful and really good 'nodes' over here, but the simple by comparison efforts by Andy, in my opinion, really do knock the spots off what is available to buy and use, 'out of the box'. If more would just 'try', modify some ex-LMR/PMR gear, (better SN, image rejection, etc etc) I dare say a lot more people would see the benefits from doing this, to compliment the already existing superb network we already have. OK, the Satoshi node adaptor did have its problems, SZM made a workaround for this, it is now stable and seems to keep everything 'alive' after the mod. The pictures on the WE site show the mod and hopefully anyone else experiencing hang-ups should follow the diagram for the 'mod' and implement it whenever they can. Keep up the good work everyone and happy experimenting! 73 De Neil, G7EBY. --- In [email protected], "john_ke5c" <k...@...> wrote: > > > As far as I can see or know, Andy's repeater doesn't buffer or 'hold' any > > data, it is purely passed directly and almost instantaneously into the TX > > from the RX, after the comparator circuit that helps smooth off the 0's and > > 1's. > > Andy then is almost certainly transmitting "plain" FM, not GMSK-FM. This > will work RF-wise moderatly well and is what NU5D did before he had an ICOM > stack. The bandwidth will be somewhat greater, and the S/N performance > worse, but the FEC will overcome some of this. Practically, I think the > communciation range is nearly the same and the main difference will be > bandwidth. NU5D should have done a side-by-side spectral comparison of his > "FM DStar repeater" and the ICOM stack, but I don't think he ever had both > going at the same time since he used the same duplexer and antennas. The > ICOM stack may also not have the best designed GMSK modulation possible, so > it may not be representative of GMSK performance per se. I think NU5D's main > problem was transmitter key-up delay - enough of the sync data had already > gone by that the receiving DStar radio had trouble locking up. > > 73 -- John >
