In a message dated Fri Jul 3, 2009 10:16 am ((PDT)), "john_ke5c" [email protected] john_ke5cwrites:
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. Hi John, I think you are helping to perpetuate a myth that non Icom D-Star repeaters are "dirty" in terms of bandwidth. When compared to a professional PMR/LMR repeater modified for use in D-Star service the Icom D-Star repeater does not appear to come up to the same standard when measured with a spectrum analyzer. With tests recently comparing the two types of radio, the Icom D-Star repeater used twice the modulation bandwidth compared to a current PMR/LMR radio using GMSK modulation! Guess will depend on the type of repeater TX modulation system used how successful the end result is in D-Star GMSK service. In the UK, Andy G4SZM has had success with the Philips/Simoco PMR/LMR repeaters + Satoshi's GMSK DV node adapter board for GB3WE and GB7WB, where a few others have had the same with Tait T800 repeaters. I have GB7LF at Lancaster in NW England in stand alone repeater mode at present as does John, G8VIQ with GB7BM at Birmingham in the centre of England using the Tait repeater and GB7MH/GB7NE will not be too far from entering service with similar equipment. The advantage of using the Icom D-Star equipment apart from it coming ready built in a box is the network that goes with it, though gradually the difference is being eroded by network access using other methods. The big disadvantage however, is the effect on your wallet/check book and as such can place it out of reach of some groups. When this occurs radio amateurs/hams have never been slow to improvise and many get great enjoyment out of doing this. There seems to be confusion about GMSK and FM. FM is the type of modulation, GMSK is the information being modulated by this method same as would be with analog audio, data, etc, you name it. Regards, Bob, G3VVT keeper/owner GB7LF [Non-text portions of this message have been removed]
