Well, not quite I think. I think it´s one LC network
for CW part of band and one for SSB part.
W7EL network doesn´t have enough bandwith to cover
3500-3900 kHz, you need to use two LC networks or
just use one and retune it.
Still no explanation what the "new Lahlum" metod is.
Seems to be a modification to Lewallen but what is
Lahlum? Is it a person or what is it???
Looks like you can use two phasing setups, 0 -90 -180
like Lewallen and also 0 -124 -224, maybe the later
deal is the "new Lahlum"
I would have tought that WA3FET was the father of the
second phasing setup, think K3LR was involved in it
too.
Time will tell I guess!
73 Jim SM2EKM
--------------------------------------------------------
Jim Lux wrote:
At 05:28 PM 11/18/2004 +0100, Jan Erik Holm wrote:
Just checked the WX0B website and his 4 SQ box.
As far as I remembered it used to use the Lewallen
current forcing method however now he is talking
about "the new Lahlum" method. Anyone know what
that is? Sure looks like current forcing to me.
Or do I have to wait until 2005 to read it in ON4UN´s
book.
73 Jim SM2EKM
Looking at the photo, I'd imagine it's a set of multiple LC networks,
rather than a single network as used in the W7EL. This lets you do a bit
better job synthesizing the phases, and potentially could remove the
requirement for 1/4 wavelength lines, which creates a bit of a
installation problem. For instance,you could use 1/2 wavelength cables.
Unfortunately, the manual is a dead link(404), so I can't comment further.
This is a good compromise solution when you want to have your switching
centralized, and with a reasonably symmetric array. You do have
potential loss from circulating currents in the feedlines. The reactive
component to cancel the feedpoint reactive component is back at the box,
so the reactive power is carried in the feedline. In an ideal system,
you'd have the reactance at the antenna, so that the feedline is at 50
ohms, and all the box needs to do is generate the right phases. Of
course, the matching network at the antenna would then need to have
multiple values, since the feedpoint impedance changes with the array
steering direction. And, it would be quite "challenging" to tune up
(broadcast antenna engineers earn their pennies doing this).
It would also make the total system cost higher.
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