RadioBanter - View Single Post

May 3rd 12, 04:40 PM posted to rec.radio.amateur.antenna

On 3 May,
wrote:

wrote:
On 3 May,
wrote:

I was refering to the case where there is nothing to adjust the match
and getting something under 3:1 at the end of the feed line.

It was well within 1.5:1 within (part of) 10 and 12m bands.

After spending several hours with EZNEC trying to get that combination
under 5:1 with no success, I find that hard to believe unless something in
the system is really lossy (like the feedline) and masking the SWR or the
length of the feedline just happens to be at a length to help the match.

Well I modelled it and matched it fine on the two bands The ends of the
feeder are about 4" apart and effectively the inner ends of the longer dipole
are an 8" length of 600 ohm line, so that length comes off the 12m dipole
elements. I couldn't get it to match with it as a genuine fan (inner ends
paralelled) with any small spacing at the ends of the dipoles, so I made them
about 8" apart.

Then they matched up nicely. The feeder is short, and low loss, as seen by
the out of band (mis)match.

The trick is to make the dipoles far enough seperated so as to be seen by the
feeder as seperate elements. This lost me much time.

--
BD
Change lycos to yahoo to reply