Hi George, I appreciate your help a lot and the next week is surely early enough.
73s de Ulrich, DF6JB Am 26.08.2011 um 14:15 schrieb George Dubovsky: > I have the schematic of the active antenna, but I will not be able to get to > it until Monday. > > 73, > > geo - n4ua > > On Fri, Aug 26, 2011 at 6:00 AM, Ulrich Bangert > <df...@ulrich-bangert.de>wrote: > >> Gentlemen, >> >> my friend Frank and I both miss the matching actice antenna for our >> Standford Research FS700 Loran frequency standards. We also do not have a >> schematic of it. Nevertheless we have tried to re-engineer the circut from >> the part's list and the circuit description in the FS700 manual. Our result >> is shown in the accompanying schematic.pdf. >> >> The generator in the left in conjunction with the 10 k resistor represents >> the expected high footpoint impedance of the very short (3 m) antenna. The >> VDD in the right in conjunction with the 100 ohms resistor represents what >> it believed to be inside the FS700. >> >> Not shown here is a 100 k resistor that may be included between the filter >> output and the 7 k resistor to form a 30 dB divider together with it. Also >> not shown is a 390 micro henry inductance which's impact is not to be found >> in the circuit descripion. Also not shown is a small neon bulb for >> overvoltage protection. >> >> The ac analysis shows that the overall filter function is well around 100 >> kHz. But it seems as if the fet (a 2N5991 in the original) would not have >> enough gain to counteract the overall damping included in the front end let >> alone to deliver some additional gain for the receiver's front end. >> >> We both feed the receiver currently with dipoles for 80 m ham radio and a >> resistor that makes the receiver think the active antenna is connected. The >> receiver has a possible total of 130 dB gain and my receiver says it uses >> 94 >> dB gain while Franks receiver says it uses 102 dB gain. The noise margin is >> also a bit better on my location. However, if one looks at the manual f.e. >> at page 17 one could get the impression as if a receiver gain of 75 dB may >> be considered much more normal as our values. Instead of improving the >> reception everything gets even worse if the active antenna is connected. I >> should also note that my qth is only 200 km away from SYLT (our German >> Loran >> station) while Frank is even 70 km nearer to it. >> >> Questions: >> >> 1) Anyone an idea what we are possibly doing wrong? >> >> 2) Anyone an idea for the 390 micro henry inductor? >> >> 3) Anyone own the original schematic? >> >> TIA for your help >> >> Ulrich Bangert >> www.ulrich-bangert.de >> Ortholzer Weg 1 >> 27243 Gross Ippener >> >> _______________________________________________ >> time-nuts mailing list -- time-nuts@febo.com >> To unsubscribe, go to >> https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts >> and follow the instructions there. >> > _______________________________________________ > time-nuts mailing list -- time-nuts@febo.com > To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > and follow the instructions there. Ulrich Bangert Ortholzer Weg1 27243 Gross Ippener Deutschland Tel +49 (0)4224 95071 Fax +49 (0)4224 95072 Mob +49 (0)172 8006546 www.ulrich-bangert.de _______________________________________________ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.