[Antennas] VSWR on Log Periodic.

Wed, 24 Apr 2002 22:36:28 -0400 (EDT)

 Hi Frank:

   You should be aware that SWR is an indication as to how well your rig/coax is matched to the antenna from an impendence standpoint and not much more.  You can use an antenna tuner to acheive a good match, but this doesn't necessarily relate to the effectiveness of the antenna.  

   While it is true that a high SWR means less power radiating from the antenna, low SWR doesn't necessarly mean the opposite. Nor does it comment on the effectiveness of the antenna.  For example, a 80-10 meter G5RV usually has a higher SWR than a dipole cut for 20 meters, but the G5RV has gain on that band.  So the G5RV may actually have higher SWR while outperforming the dipole which has a lower SWR.  

   Remember, a dummy load will provide a 1:1 SWR, but we all know it is not a good antenna.  

Ron W7MRR

--- On Wed 04/24, A10382  wrote:
> 
> Measuring at the transmitter gives a good indication of how 'friendly'
> the
> transmission system (everything after the rig) is to the transmitter or
> amp.
> 
> Measuring at the antenna (power AND vswr) is the real indication of how
> friendly everything else is to the antenna.
> 
> How about a remote control meter at the antenna feed.  Of course this
> remotely operated device would have to have almost no effects itself on
> the
> system when not 'reading'.  Then you can measure at BOTH ends.
> 
> This would seem ideal.  Is this thinking 'in band' or 'out of it' ?
> 
> 73
> Frank
> 
> >
> ----- Original Message -----
> From: "George, W5YR" 
> To: 
> Cc: "Dave Shrader" ;
> "antennas"
> 
> Sent: Wednesday, April 24, 2002 8:37 PM
> Subject: Re: [Antennas] VSWR on Log Periodic.
> 
> 
> > Measurements made in the shack are readily interpretable and
> convertible
> to
> > readings at the antenna. And probably much more accurately than they
> could
> > be made at the antenna since the presence of the operator and
> > instrumentation tends to alter the operating environment.
> >
> > A couple of short- and open-circuit line measurements and either a
> real
> > Smith Chart or its computer complement and all shack readings can
> then be
> > translated to the antenna feedpoint.
> >
> > 73/72/oo, George W5YR - the Yellow Rose of Texas
> > Fairview, TX 30 mi NE of Dallas in Collin county EM13qe
> > Amateur Radio W5YR, in the 56th year and it just keeps getting
> better!
> > QRP-L 1373 NETXQRP 6 SOC 262 COG 8 FPQRP 404 TEN-X 11771 I-LINK
> 11735
> > Icom IC-756PRO #02121  Kachina 505 DSP  #91900556  Icom IC-765
> #02437
> >
> >
> > Don Havlicek wrote:
> > >
> > > In my opinion, the ONLY meaningful SWR measurements are AT THE
> ANTENNA..
> > > NOT at the shack!
> > > Don - N8DE
> > - - -
> >
> > Your moderator for this list is:
> > Larry Wilson KE1HZ [email protected]
> > _______________________________________________
> > Antennas mailing list
> > [email protected]
> > http://mailman.qth.net/mailman/listinfo/antennas
> >
> 
> - - - 
> 
> Your moderator for this list is:
> Larry Wilson KE1HZ [email protected]
> _______________________________________________
> Antennas mailing list
> [email protected]
> http://mailman.qth.net/mailman/listinfo/antennas
> 

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