Hi Joe and all, I doubt if the Arrow diplexer has 20dB of loss. If it did, we'd never receive a signal! :)
I believe somebody here on the -bb will be performing a test on the Arrow diplexer using a vector/network analyzer. It will be interesting to say the least. There were preliminary reports saying the device had a loss anywhere from 2.65 to 2.80dB. That's close enough to 3dB which is technically half power loss. Add the loss of a short piece of coax and it will certainly be pushed over the 3dB line. If I recall correctly, cross polarity is also a 3dB loss. I have noticed that when I rotate the antenna I might get a stronger downlink but I never lose it when I rotate it back. Before, when I would do that it would drop once I rotated in either direction from the peak signal. Basically what is going on is the lossy device is removed and replaced with a more efficient one, that extra net gain you just boosted now shows how the system on the antenna side of the diplexer is truly performing. I don't have an antenna analysis program to perform a test, but what does a 7 element 440 yagi pattern look like and what is its overall gain? What we need to do is break down the antenna configuration into 3 segments, see what their losses and gains are then combine them for the overall figure. The 3 segment would be the antenna, the diplexer and the coax. Each one will be tested individually to give an accurate number for each. 73, Jeff WB3JFS ----- Original Message ----- From: "Joe" <[email protected]> To: "Gary "Joe" Mayfield" <[email protected]> Cc: "'AMSAT-BB'" <[email protected]> Sent: Friday, September 25, 2009 6:42 PM Subject: [amsat-bb] Re: Arrow antenna reconfiguration results - UPDATE > as in the texts below, there is something else going on here. > > That Diplexor can not be all that bad. two reasons. > > How many db down is the front to side of that antenna? > > and I can not imaging someone would sell a diplexor that has greater > than 20 db of losses. > > because of the statement that how criticalpolarity was with the > original, and now the antenna has to be nearly 90 degrees cross > polarized to make it drop out uhh > > that close to 30 db, > > at least 20,, > > something else is going on here > > Gary "Joe" Mayfield wrote: > >>> >>>Another issue I came across was how wide the beamwidth is of the Arrow >>>Antenna between the Arrow diplexer and the new diplexer. I was wondering >>> >>> >>if >> >> >>>this was going to happen and it did. The reason that this happened was >>> >>> >>with >> >> >>>the old diplexer, the signal attenuated so much that you had to be >>>pointed >>>right smack dab on the bird, a few degrees off and you lost the signal. >>>Now, with the new diplexer, you can point the beam in the general >>> >>> >>direction >> >> >>>and still copy the bird. In most cases I had to turn the beam 90 degrees >>>before I completely lost the downlink! Twisting the antenna to make >>>polarization changes makes absolutely no difference now. This also >>>attributes to the fact that now I'm copying the entire pass without >>> >>> >>dropouts >> >> >>>or fades. Makes sense. What I've regained over the lossy diplexer makes >>> >>> >>up >> >> >>>for any polarization differences, etc. for a better copiable signal. >>> >>>Next weekend I will have to try more passes and get a feel of how much >>> >>> >>this >> >> >>>system has changed. >>> >>> >>>73, >>> >>>Jeff WB3JFS >>>Las Vegas, NV >>>DM26 >>> >>> >>> >>> >>> >>> >>>_______________________________________________ >>>Sent via [email protected]. Opinions expressed are those of the author. >>>Not an AMSAT-NA member? Join now to support the amateur satellite >>>program! >>>Subscription settings: http://amsat.org/mailman/listinfo/amsat-bb >>> >>> >>> >> >>_______________________________________________ >>Sent via [email protected]. Opinions expressed are those of the author. >>Not an AMSAT-NA member? Join now to support the amateur satellite program! >>Subscription settings: http://amsat.org/mailman/listinfo/amsat-bb >> >> >>_______________________________________________ >>Sent via [email protected]. Opinions expressed are those of the author. >>Not an AMSAT-NA member? Join now to support the amateur satellite program! >>Subscription settings: http://amsat.org/mailman/listinfo/amsat-bb >> >> >> >>------------------------------------------------------------------------ >> >> >>No virus found in this incoming message. >>Checked by AVG - www.avg.com >>Version: 8.5.416 / Virus Database: 270.13.113/2395 - Release Date: >>09/25/09 17:52:00 >> >> >> > _______________________________________________ > Sent via [email protected]. Opinions expressed are those of the author. > Not an AMSAT-NA member? Join now to support the amateur satellite program! > Subscription settings: http://amsat.org/mailman/listinfo/amsat-bb > _______________________________________________ Sent via [email protected]. Opinions expressed are those of the author. Not an AMSAT-NA member? Join now to support the amateur satellite program! Subscription settings: http://amsat.org/mailman/listinfo/amsat-bb
