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[aprssig] Re: How Much Antenna for PCSAT?

gerheim at cox.net gerheim at cox.net
Wed Aug 15 13:44:25 UTC 2007


I forgot - it keeps the SMA connector clean and free of debris!  


---- gerheim at cox.net wrote: 
> Thanks.  I'm going to google the maldol antenna asap.  BTW, the OEM antenna also will +not+ poke out your eye.  (Its only other endearing feature!)  
> 
> 
> ---- "Stephen H. Smith" <wa8lmf2 at aol.com> wrote: 
> > gerheim at cox.net wrote:
> > > I've been trying to hit PCSAT with a D7.  Apparently, the rubber duckie isn't enough wire.  Will a telescoping whip do any better?  
> > >
> > > KB9GVR has been having some success.  
> > >
> > > My goal is to send it an APRS packet from a moving motorcycle, so big antennas are out of the question.  I almost managed it back in January.  
> > >
> > >
> > >   
> > 
> > 
> > If you are referring to the OEM duckie that came with the TH-D7, it is 
> > little more than a badly-shielded dummy load.  You need something that 
> > is electrically a half-wave design that doesn't depend on a ground plane 
> > as a 1/4-wave whip (even full-sized) does.  The problem is that the D7 
> > is simply too small physically to be a significant ground plane (i.e. 
> > counterpoise) to most whips.
> > 
> > I have used a dual-band Maldol replacement whip for the TH-D7 (can't 
> > remember the model number) with great success. This whip is made of 
> > thin, flexible piano wire (non-telescoping) about 20" long . The base 
> > and matching transformer is terminated in an SMA connector for direct 
> > connection to the D7 without the clumsy SMA-to-BNC adapters many people 
> > use.  The base of the fitting is flared out so that it contacts an area 
> > on the top panel of the D7 that is about 2 and a half times the radius 
> > of the SMA socket alone which drastically reduces stress and twisting on 
> > the lightweight SMA socket on the radio.     This whip radiates about 
> > 10-15 dB more RF than the OEM duck (actually measured on an IFR-1500's 
> > spectrum analyzer). 
> > 
> > If you are trying to use this for satellite modes, you need to hold the 
> > radio horizontal and at right-angles to the satellite track so that the 
> > dipole-type radiation pattern (max is at right-angles to the whip)  will 
> > extend from one horizon to overhead and then down to the other horizon.
> > 
> > 
> > 
> > 
> > --
> > 
> > Stephen H. Smith    wa8lmf (at) aol.com
> > EchoLink Node:      14400    [Think bottom of the 2M band]
> > Home Page:          http://wa8lmf.com  --OR--   http://wa8lmf.net
> > 
> > NEW!   World Digipeater Map
> >   http://wa8lmf.net/APRSmaps
> > 
> > JavAPRS Filter Port 14580 Guide
> >   http://wa8lmf.net/aprs/JAVaprsFilters.htm
> > 
> > "APRS 101"  Explanation of APRS Path Selection & Digipeating
> >   http://wa8lmf.net/DigiPaths
> > 
> > Updated "Rev H" APRS            http://wa8lmf.net/aprs
> > Symbols Set for UI-View,
> > UIpoint and APRSplus:
> > 
> > 
> > 
> > _______________________________________________
> > aprssig mailing list
> > aprssig at lists.tapr.org
> > https://lists.tapr.org/cgi-bin/mailman/listinfo/aprssig
> 
> --
> -Al Gerheim
> 
> HP-49G+ Software Page:
> http://members.cox.net/above
> 
> 
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--
-Al Gerheim

HP-49G+ Software Page:
http://members.cox.net/above





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