Trevor Day wrote:

Excuse me for 'jumping in' here, it was difficult trying to locate a bit
of the thread that referred to the current title (CFA) I would like to
ask you learned chaps a question about the 'EH' antenna which I
appreciate is not the same as the CFA but its near enough for me:-)

I have built a couple of these and used them on 40m. Performance hasn't
been brilliant but they have worked and I was reasonably satisfied with
the contacts achieved considering the fact I used a barefoot K2 at
around 10 watts o/p and the antenna was sat on the shack bench connected
to the K2 by a 1 metre BNC to BNC cable laid across the bench. (I only
mention this last to try and forestall the inevitable comment that the
feeder does all the work)

All of this was done out of interest just to see if the antenna worked
at all, as my gut reaction was, and still is, sceptical regarding the
claims of its method of operation. I am not a mathematician, so the
various lengthy discussions regarding Maxwell's equations et al pass me
by; I am more interested in the practical aspects of this rather than
the theory. My question refers to the SWR bandwidth achieved using this
system. For an electrically very short antenna of this type I expected
something extremely sharp at resonance, perhaps in the order of 5 or 10
KHz between the 2:1 SWR points. In practice, the 2:1 SWR points are
some 100 KHz or so apart. When fed with 100 watts from an IC706, the
antenna itself does not get warm and neither does the short feeder so it
doesn't appear to be acting as a dummy load. Can someone satisfy my
curiosity and tell me (drawing comparisons with springs and dampers if
need be:-) how this is achieved.

Thanks,
Trev G3ZYY


Sigh.

A couple of questions:

1. Have you tried using something like a loop or other non-magical
antenna of similar physical size for comparison? Or putting a 20 dB pad
between your rig and a decent antenna? Most people are amazed at how
much they can do with 100 mW.
2. I assume you're using a "phasing network" or some similar device to
achieve whatever it is the antenna is supposed to accomplish. The wide
bandwidth is a sure sign of loss, and the majority of it is just about
surely in the "phasing network" and/or whatever matching network you're
using. Have you checked to see if either of them is getting warm after a
few minutes of key-down (with breaks to ID of course)?

But don't be surprised it they don't. If you're running 100 watts of CW,
your average power output is probably no more than 20 watts while
transmitting. If you're running SSB, it's considerably less than that
unless you're using serious compression. Try running your rig normally
(keying or talking) to a good-sized dummy load and see how long it takes
for it to get noticeably warm. Then imagine it to be the size of your
matching/"phasing" network and think about what you'd expect to happen
if it were absorbing *all* your transmitter's power. It is, after all,
absorbing most of it.

Roy Lewallen, W7EL