Re: [IRCA] Antenna test

[paul mcdonough <paul46692@xxxxxxxxx>]

Hi Craig,

 Interesting reading on the comparison of the two loops. Is there a web page with a description of your copper tube antenna? And is it practical to have the copper tube antenna at a home location (i.e. not in a truck but maybe a backyard etc). Thanks.

have fun,
Paul


--- On Fri, 10/10/08, Craig Healy <bubba@xxxxxxxxxxxxxxxxxxxx> wrote:

> From: Craig Healy <bubba@xxxxxxxxxxxxxxxxxxxx>
> Subject: Antenna test
> To: badx@xxxxxxxxxxxxxx, "Mailing list for the International Radio Club of America" <irca@xxxxxxxxxxxxxxxx>
> Date: Friday, October 10, 2008, 9:39 PM
> Recently I had the opportunity to use a commercially-made
> H-Field shielded
> loop antenna.  What I did was set it outside my truck and
> parallel to one of
> the copper tube loops I have in the back of my Chevy
> Blazer.  The antennas
> were both connected to an Alpha-Delta 4 position switch
> inside, and then to
> the Palstar R30CC.
> 
> Tuning through the AM band, I stopped at every signal of
> notable level.  I
> considered stations in Boston and NYC to be appropriate. 
> S-Meter readings
> were compared.  Since the antennas were identically
> oriented, the figure-8
> patterns were the same.
> 
> In every instance the copper tube loop had a higher signal
> level from bottom
> to top of the band.  In some cases stations inaudible on
> the commercial loop
> were listenable on the copper tube loop.  There were no
> stations heard on
> the commercial antenna better than the copper loop.  The
> commercial one was
> outside the truck while the copper loop was inside the bed
> with a fiberglass
> roof which was probably a slight advantage for the
> commercial one.
> 
> Considering that the overall parts cost of the copper loop
> was maybe fifty
> bucks tops, plus an hour's work, I think it's a
> much better deal.  The parts
> list is one 10' length of 3/4" copper plumbing
> tube, four 90 degree elbows,
> an Amidon FT-240-77 toroid, a few feet of #14 THHN stranded
> electrical wire,
> and an SO239 jack.  Not much to it and quite simple to
> build.
> 
> This particular loop is untuned broadband, just as is the
> commercial one.
> If a tuned loop were desired, it would be simple to put a
> 40 turn winding
> (plus or minus some turns) on the toroid core and add a
> variable capacitor.
> 
> I will be happy to say just what the commercial antenna is,
> though I'd
> rather not post it publicly.  Drop me a note if you are
> curious and I'll
> send a link to the sales web site for it.
> 
> I'd always wondered how well a moderately expensive
> commercial test antenna
> would do in a DX situation.  Now I know, and I won't be
> spending any money
> for one.  Another question answered, and I'm happy.
> 
> Craig Healy
> Providence, RI


      
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