<?color><?param0100,0100,0100>Dear LF Group,<br><br>G3YSX wrote:<br>><?/color>Also if you think back to the RSGB convention, there was one >paper that suggested that we are massively overestimating the >efficiency of our antennas. If that work holds up, then we will have >to drop power to conform to the licence ERP condition......<br><br>I think this is the wrong way round - if we are overestimating efficiency, that means we are getting less ERP than we think we are, and would have to increase power to reach the 1W ERP limit. ERP is essentially defined in terms of the field strength at some distance that is produced by an antenna, and available field strength measurements tend to show that using the radiation resistance/antenna current formulae do indeed overestimate the ERP by about 0 - 10dB. Prof. Mike Underhill's work suggests small antennas may be more efficient than we think, but the experimental evidence does not support this, at least in the co ntext of typical amateur LF installations.<br>________________________________________________<br><br>I am glad I am not one of the judges for the LF transatlantic awards. Clearly some communications have taken place, using what are now quite well established and widely used techniques. Whether this constitutes a QSO is just down to interpretation of the rules, and everybody seems to have a different idea of what the rules should be. I think what we have seen since last September are incremental steps in transatlantic communications, but there will never be a single moment when everyone agrees the Atlantic was bridged. Marconi went home happy after hearing the letter 'S' a few times; it took a few more years before he was able to send messages both ways routinely.<br><br>It is clear the QSOs that have been achieved are very marginal, and there is plenty of scope for improvement. Part of this is just logistics; for example, the strongest transatlantic QRSS signal is undoubtedly VE1ZZ's, but Jack does not appear to have equipment to receive this mode. The lack of a generally available 136kHz segment in North America and other parts of the world restricts the possible activity. The length of time required for a QSO, and the times at which propagation is optimum are obstacles in themselves. However, there are also many technical improvements that can be made; QRSS has worked very well, mostly because it is simple to implement and tolerant of many imperfections of the signal and it's channel, but the last few weeks have shown we are approaching the practical limits of this mode's capability. Although 1W ERP is only a minuscule signal when compared with other amateur bands, it is still difficult to achieve at LF most of the time. Most techniques and equipment have just been transplanted from HF, where different considerations apply. We are still a long way from drawing a line under LF communications, transatlantic or other wise.<br><br>As far as this reflector goes, I think it would be a mistake to have separate reflectors for LF operating and technical subjects. A reflector that was just about who had worked who would be very dull indeed. A reflector about technical ideas needs some operating background as a sanity check on some of the whackier ideas that people put about -it's no use if it doesn't work. It's a bit like RadCom - many readers enjoy the technical and constructional articles although they may have no intention of building anything. If you took these out, I doubt the readership would increase, or anyone would really benefit. A better idea might be to keep this reflector as it is, and have a separate RSGB "slanging match" reflector where people could post insults of one sort or another. Better still, an absorber rather than a reflector - instead of bombarding everyone's e-mails with junk, it could all be written to a CD-ROM, which could then be discarded by RSGB staff at regular intervals :-)<br><br>Cheers, Jim Moritz<br>73 de M0BMU<br><br><br>
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