[Mobile-Portable] Question about HF mobile - film at 11:00

[Chuck Mabbott]

Paul,

Before I put the coupler into play I spent a couple of
evenings with the analyzer fiddling.  I have the K400
trunk lip mount.  Clamped it down and put in a
ham-stick for 10 meters and got a decent SWR.

Moved up to the 20 meter and got a decent SWR.

Moved up to the 40 and could not get it below 2+ and
80m was worse.  So checked for tightness and found a
couple of loose things and still would not come down.

So I fastened a ground strap from base of antenna to
trunk lid and it helped a little but not enough.  So I
hooked the ground strap from base of antenna to the
frame itself.  Scrapped a little paint to get a good
connection.

Then I got decent SWR are 10, 20, 40, and a little
flaky on 80 around 1.4 to one.  So I played around the
connections some more and ended up with 1.2 on 80 and
everything else decent.

So then I hooked in the coupler and found it would
tune from 10 to 80 but 80 was not real stable.  But
the coupler would lock in.

Went back to the book and after looking it over I
moved the ground from base of antenna to the ground
lug on coupler.  I removed the ground from coax from
the base of antenna to coupler.  Used only the center
feed line.

Every thing settled right down.  But you have to go
through it on regular intervals and tighten stuff.
But that is my tale and seems to be OK.

Interesting reading....

http://www.sgcworld.com/mobilegroundtechnote.html

What is your setup?

--
73  Chuck AA8VS


--- Paul Goble <goblefam at swbell.net> wrote:

> Chuck:
> 
> I found your treatise to be very interesting!  I
> just changed HF antenna mounts and am using the same
> ground connection as before, but now the only bands
> my screwdriver will tune are 80m, 20m and 17m.  Used
> to be able to tune 'em all!  What surprises me is
> that the 1.5:1 SWR bandwidth on 80m is several 10's
> of KHz more than previously.
> 
> So this is generally caused by insufficient ground? 
> That is my assumption, but I sure could us a "sanity
> check" - HIHI!
> 
> TIA,
> 
> Paul ND2X/5
> http://www.nd2x.net/pix/new.jpg
> 
> 
> Chuck Mabbott <aa8vs at yahoo.com> wrote: Mobile set
> ups can get odd, to say the least.
> 
> How is the antenna grounded?  Mag mount or fastened
> to
> the bumper?  
> 
> If mag mount on trunk lid the and the ground is not
> sufficient 15, 17 & 20 will tune fairly decent but
> you
> usually can't get 40 40 below 2. something.  
> Run a ground strap 3/4 - 1 inch wide or better from
> trunk lid to frame of car.  As I recall the ground
> connections have an impedence around 8 ohms so the
> connection is critical.
> 
> <SNIP>
> ----
> Your Moderator: Dick Flanagan K7VC,
> mobile-portable-owner at mailman.qth.net
> 



      ____________________________________________________________________________________
Luggage? GPS? Comic books? 
Check out fitting gifts for grads at Yahoo! Search
http://search.yahoo.com/search?fr=oni_on_mail&p=graduation+gifts&cs=bz