Folks, I think you are focusing only on transmitting loss and have overlooked the impact that loss has on noise figure. If your HT has a low NF (doubtful) adding 3-dB loss in Rx will raise the NF 3-dB higher. The actual loss of sensitivity could be more than that.
Filter's size determines efficiency and insertion loss. The tiny diplexer in the Arrow is a compromise between performance and size. I have a Comet 416B and even it has some loss about 47w out for 50w in. But that is not anywhere near 3-dB. I use mine to connect my dual-band vertical to my FT-847 which has separate connectors for 2m and 70cm. I used this antenna to contact the ISS a few years ago (worked well because the ISS never rises above 11-deg. elevation, here). But I do not use if for SSB or other weak-signal use. Ed - KL7UW At 02:26 AM 9/26/2009, Jeff Yanko wrote: >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" <n...@mwt.net> >To: "Gary "Joe" Mayfield" <gary_mayfi...@hotmail.com> >Cc: "'AMSAT-BB'" <amsat-bb@amsat.org> >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 amsat...@amsat.org. 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 amsat...@amsat.org. 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 amsat...@amsat.org. 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 amsat...@amsat.org. 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 amsat...@amsat.org. 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 73, Ed - KL7UW, WD2XSH/45 ====================================== BP40IQ 500 KHz - 10-GHz www.kl7uw.com 500-KHz/CW, 144-MHz EME, 1296-MHz EME DUBUS Magazine USA Rep dubus...@hotmail.com ====================================== _______________________________________________ Sent via amsat...@amsat.org. 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
