KV9U wrote: > He mentions that it is a suite of Windows sound card programs allowing > ARQ exchanges of messages, but one of the compelling features of fldigi > and flarq which make up the suite of programs, is that they work cross > platform. No other software of this type has this capability to work > with Windows XP, Vista, Mac, Linux and Free BSD. The impression seemed > to be that fldigi can work with Windows and Linux.
Yes, fldigi is a cross-platform program and works on both Windows and Linux, etc. > > A really important point was that Skip, KH6TY, found it possible to use > DominoEX modes with FM modulation and work farther than SSB phone. That > is a very significant new finding. Anyone else having luck with that? > What about other modes with FM? DominoEx has been found to be more successful than either PSK31 or MFSK16 (the two most popular high sensitivity modes), and for QSO's and contest exchanges, DominoEX 4 is still fast enough (but too slow for messaging) at 25 wpm, and works the best of all when you are far under limiting and with poor S/N. DominoEX is not as critical to tune and more resistant to multipath interference than PSK31, so I think it will be the mode of choice for FM DX, outperforming both PSK31 and MFSK16 when the S/N is very poor, as will always be the case for the weakest stations. > > Would it also be true that DominoEX (and other modes) would work even > farther with SSB digital vs FM digital? Yes, the advantage of SSB over FM we find to be around 3-4 dB or more. However, CW works as well as DominoEx 4, and going to CW is already customary in the weak signal community when SSB phone cannot make it. When propagation is poor, you will sometimes find stations calling CQ in CW on the phone calling frequency (144.2 MHz), and then QSY'ing to a clear frequency, just as phone operators also generally do. > > Even though horizontal polarization was emphasized, the fact is that > hams with FM only rigs do not have horizontal antennas and vertical to > vertical should work very well, even if there may be a slight edge to > horizontal. Has anyone else been able to do any comparisons between H to > H and V to V on FM? All the current SSB phone weak signal operators and VHF contesters use horizontal polarization. If those operators simply download fldigi and get an interface (the SignaLink USB works really well, even on FM-only transceivers with no VOX), they will have an incentive to work more grids and states during contests. For long distance FM DX, these operators, already equipped with high gain antennas (horizontally polarized) and amplifiers, looking for more grid multipliers and Q's during the VHF contests, probably represent the largest potential intererst group for working FM DX other than those with FM-only transceivers looking for new ways to enjoy the hobby. So, those who want to work them will need to get a horizontally polarized, fairly high gain antenna, and a small rotator. The gain of most current verticals that are not on a rotator probably tops out at around 6.2 dBi, which is not enough gain to work very far, except during strong openings. To work any reasonable amount of FM DX, a rotator and an antenna with at least 10 dBi of gain will be needed, and the VHF contesters generally have 14 dBi of antenna gain or more. It is not anticipated that very many of those interested in working toward VUCC on 2 meters, or even doing fairly well in VHF contests, will be satisfied with the range of their current verticals (even to someone else's current vertical), so if a higher gain antenna is needed, they might as well go to a rotator and horizontal polarization and be able to work the existing weak signal operators that we think will only need to add an interface in order to improve their contest scores by working both FM DX and SSB DX. Those who already have vertically polarized yagi's and still want to work repeaters can just rotate the yagi 45 degrees in roll and cover both polarizations with 3 dB less gain on each polarization. However, 3 dB is very significant in terms of range on 2 meters, so the operator may later decide to rotate the additional 45 degrees and pick up the additional 3 dB in gain. We are using 145.000 MHz as a calling frequency in our area, which has seemed to work out quite well. It is still within the SWR bandwidth of the high gain 2 meter SSB weak signal antennas and far enough away from repeater frequencies so as not to experience any desensitization. 145.000 is also within the ARRL Bandplan for 2 meters in the "Weak signal and FM simplex " area. 73, Skip KH6TY
