6 Metre Conundrum
 

I was wondering if anyone can explain to me how it is that the
following antenna puts out a reasonable signal on 6 metres (5-7 over
a 1600 km path from England to Spain. The rig is an ICOM IC 703 and
the tuned SWR is under 1.4:1 over the whole 6m band and 1:1 from
50.120 to 52 MHz.

The antenna is a loft mounted fan dipole cut and resonated for 40,
20, 17, 15 & 10 metres. You can see the design dimensions at
http://www.radiowymsey.org/FanDipole/FanDipole.gif , in practice the
dimensions were all trimmed by around 5 per cent. The final
resonances at the TX were measured as 14.3, 18.09, 21.188, 28.44 MHz
, the centre of the 40m loaded dipole I calculate to resonate at
around 30 MHz. There is a 1:1 balun with around 10 metres of coax
into a LPF and then the 703. No odd harmonics work out for 6 meters,
so I wonder what is doing the radiating?


Charlie.

--
M0WYM
www.radiowymsey.org

6 Metre Conundrum
 

wrote:


Easy, the 17m element is acting as an EDZ (1.25WL) doublet in 6m
and likely the other wires are by luck canceling the reactance at the
feed point. An EDZ is a nonresonant antenna but very effective if you
can manage the feedpoint resistance and reactance. It has some gain
over a dipole.

I use a wire antenna about 24ft long with a matching section detailed
in WWW.CEBIK.COM under feeding theEDZ and it's setup as a 6m
(50.16 center frequency) antenna with a 50ohm feed. Works very well
at a height of 25ft. It's also useful as a dipole at 17m due it its
length and feed. It's not as good as a three element beam but it's
broad beamwidth is useful for spotting.

Allison


Allison,

Thanks for your reply to what was my second post covering the same
issue, see "50MHz Antenna Conundrum" above. I guess that I allowed
the occasional senior moment :)


Charlie.


--
M0WYM
www.radiowymsey.org