Mike Coslo wrote:
Do the single core designs really not work? I had a single core
homebrew that seemed to work, but I'm a tad confused after hearing that
they don't.

The single core designs are usually voltage baluns and
what we hams want are balanced currents. I don't see
why you couldn't just add a husky 1:1 W2DU style choke
on the 50 ohm side of your 4:1 voltage balun to inhibit
common mode current. The extra toroid in the afore mentioned
QEX article is a 1:1 choke attached to a 4:1 voltage balun.
--
73, Cecil http://www.qsl.net/w5dxp

Cecil Moore wrote:
Mike Coslo wrote:

Do the single core designs really not work? I had a single core
homebrew that seemed to work, but I'm a tad confused after hearing
that they don't.


The single core designs are usually voltage baluns and
what we hams want are balanced currents. I don't see
why you couldn't just add a husky 1:1 W2DU style choke
on the 50 ohm side of your 4:1 voltage balun to inhibit
common mode current. The extra toroid in the afore mentioned
QEX article is a 1:1 choke attached to a 4:1 voltage balun.


I think you are right, Cecil. I'm digesting the pdf now. Probably take
a few reads tho' it's been a long, long day....

- 73 de Mike KB3EIA -

On Wed, 03 May 2006 13:22:45 GMT, Cecil Moore
wrote:

The single core designs are usually voltage baluns and
what we hams want are balanced currents. I don't see
why you couldn't just add a husky 1:1 W2DU style choke
on the 50 ohm side of your 4:1 voltage balun to inhibit
common mode current. The extra toroid in the afore mentioned
QEX article is a 1:1 choke attached to a 4:1 voltage balun.

Did you read the article Cecil? He place the current balun/choke on
the opposite side. Looked like an interesting approach.

Danny

In my many years I have come to a conclusion that one
useless man is a shame, two is a law firm, and three
or more is a congress. - John Adams

email: k6mheatarrldotnet
http://www.k6mhe.com/

Dan Richardson wrote:
Did you read the article Cecil? He place the current balun/choke on
the opposite side. Looked like an interesting approach.

Yes, I'm wondering if things would change if the positions
were reversed? How does that choke perform when it sees
2000 + j1000 ohms?
--
73, Cecil http://www.qsl.net/w5dxp

When it sees 2000 + j1000 ohms there's hardly any current to choke
anyway.

"Reg Edwards" wrote:
When it sees 2000 + j1000 ohms there's hardly any current to choke
anyway.

Yes, but how much current is there 3/8WL back from that point?
--
73, Cecil, W5DXP

"Cecil Moore" wrote in message
om...

"Reg Edwards" wrote:
When it sees 2000 + j1000 ohms there's hardly any current to choke
anyway.

Yes, but how much current is there 3/8WL back from that point?
--
73, Cecil, W5DXP

Isn't that where you should be placing the choke? Give it some work
to do! Don't blame the choke for doing nothing. Blame yourself!
----
Reg.

"Reg Edwards" wrote:

W5DXP wrote:
Yes, but how much current is there 3/8WL back from that point?

Isn't that where you should be placing the choke?

Kinda hard to do if the feedline is ladder-line. Maybe a more
logical thing to do is to increase the length of the ladder-line until
a current maximum point is available at the coax/ladder-line
junction.
--
73, Cecil, W5DXP

Please all, remember,

The common-mode currents the choke is suppressing are not necessarily
related to the antenna impedance (the load) or the transmit/receive
currents flowing in the antenna, though there can and will be some
coupling between the two on an antenna (if you measure antenna Z
with/without a choke they will usually differ).

To place the choke in the best spot, you need to measure the common
mode current on the feedline and not the load impedance. If you have
common mode currents induced by an unbalanced situation in the antenna
itself, right at the antenna is probably best. Other places might be
good if you are coupling electrical noise to your feedline.
W1HIS's article was most interesting in this respect.

I would assume that because the feedline current is common-mode (the
same in both conductors), it will usually travel at the velocity factor
of a wire in air rather than the feedline velocity factor, though I do
not know this.

73,
Glenn AC7ZN