me.
I do like your paper and have it. I also wish that you continue to
get more hams to actually build more things.
73,
Barry
K3NDM
-- Original Message --
From: "Jim Brown"
To: elecraft@mailman.qth.net
Sent: 1/14/2019 2:21:30 PM
Subject: Re: [Elecraft] Slightly Unbala
I agree. And I maintain that the problem is exactly the same with the
common solution of a single-ended tuner feeding a balanced line through
a balun. If there is a big mismatch the choke will get hot.
73,
Victor, 4X6GP
Rehovot, Israel
Formerly K2VCO
CWops no. 5
http://www.qsl.net/k2vco/
On 14
On 1/14/2019 9:02 AM, Barry wrote:
The simple answer is that the common mode chokes available to hams are
of the unbalanced type.
Huh? We're hams -- we're not limited to products we can buy! And we can
build far better than we can buy. In 2010, I published the design for a
common mode choke t
nd here with
> balanced line can be problematic. So, I usually recommend the approach
> above for overall simplicity and assurance of maintaining feed balance.
>
> 73,
> Barry
> K3NDM
>
> -- Original Message --
> From: "Vic Rosenthal"
> To: "Al Lorona&
. So, I usually recommend the approach
above for overall simplicity and assurance of maintaining feed balance.
73,
Barry
K3NDM
-- Original Message --
From: "Vic Rosenthal"
To: "Al Lorona"
Cc: elecraft@mailman.qth.net
Sent: 1/14/2019 1:12:37 AM
Subject: Re: [Elecraft
I’ve measured common mode current when feeding a balanced line with a good DX
Engineering 1:1 balun and an unbalanced tuner, versus a real balanced
link-coupled tuner (Johnson Matchbox). To my surprise, the currents are closer
to equal with the unbalanced tuner and the balun! But the Matchbox se
he exception is to use very
> expensive coax. :-)
>
> 73,
> Barry
> K3NDM
>
> -- Original Message --
> From: "Don Wilhelm"
> To: elecraft@mailman.qth.net
> Sent: 1/13/2019 6:59:18 PM
> Subject: Re: [Elecraft] Slightly Unbalanced dipole?
>
>
Why would a common mode choke at the antenna feedpoint present more problems
than the common practice of feeding a balanced line through a single-ended
tuner and balun?
I’ve done a lot of experimenting with the latter and have learned that a) the
best configuration is with a 1:1 balun, and b) th
A nonscientific and fortuitous observation . . . with a result that came as no
surprise:
A week ago I carefully set up a Buddipole configured as a middling compromise
between a vertical dipole and a vertical with one above ground counterpoise
wire radial in a lazy L. Some fiddling got it right
-- Original Message --
From: "Don Wilhelm"
To: elecraft@mailman.qth.net
Sent: 1/13/2019 6:59:18 PM
Subject: Re: [Elecraft] Slightly Unbalanced dipole?
Al,
If not placed at the antenna feedpoint (up at the antenna), then the feedline
may radiate due to common mode cu
Over a decade ago I did some un scientific experiments to investigate this
subject. I set up a test transmitter a few hundred feet away from my rotary 40
meter dipole. I took some field strength measurements with the dipole, then
lengthened one half of the dipole perhaps 6 inches and shortened
Al:
Al et al;
I do agree. And in fact my 250 ft center fed antenna with 75 ft of
window feedline terminates at the operating position into a Balun
Designs 1171T. Then a coax jumper of about 2 ft long, which is actually
a model 8232 from The Wireman, Common Mode Choke between the balun and
For HF, I doubt that many (if any) dipoles are fully balanced. On higher
frequencies (VHF), the antenna can be far enough away from other objects
and the ground that it could be considered unaffected by the
environment. But a 40m dipole at 40 feet is less than a half wave from
the ground and o
You guys keep talking about coax-fed antennas. Yes, although it may be easy to
wind coax around a toroid and put it up at the antenna midpoint, that's not so
easy with open-wire line. This discussion was very coax-centric and I wanted to
open your minds that not everybody feeds their antenna wit
center and you can find
75 ohms. Of course you will have to address the 75 ohm, but the match will be
1:1.
Mel, K6KBE
From: Ray Albers
To: Elecraft@mailman.qth.net
Sent: Sunday, January 13, 2019 1:58 PM
Subject: Re: [Elecraft] Slightly Unbalanced dipole?
A friend once told me, "A
Al,
If not placed at the antenna feedpoint (up at the antenna), then the
feedline may radiate due to common mode current.
For feedlines using parallel conductors, the problem is not as bad if
the feedline exits at right angles from the radiator for at least a half
wavelength. In that case, th
It is reasonable to put a choke at the antenna with open wire line. Open wire
isn’t magic, it can carry common mode currents, too. Both wires high, both
wires low, and that is common mode.
wunder
K6WRU
Walter Underwood
CM87wj
http://observer.wunderwood.org/ (my blog)
> On Jan 13, 2019, at 3:42
By the way, whenever Jim says, "...a very good common mode choke at the
feedpoint of an antenna...," he means an antenna fed with coax. For the rest of
us, of course, that choke would (should) go at the output of the antenna tuner,
whether in the shack or close by.
Al W6LX
_
On 1/13/2019 12:23 PM, Don Wilhelm wrote:
The OCF antennas are infamous for conducting RF into the shack.
And for being very noisy on receive.
73, Jim K9YC
__
Elecraft mailing list
Home: http://mailman.qth.net/mailman/listinfo/elecra
Your friend is a wise man. That is, indeed, reality. There's a
discussion about this in one of my tutorials.
http://k9yc.com/CoaxChokesPPT.pdf
The PRIMARY reason for putting a very good common mode choke at the
feedpoint of an antenna is to prevent the feedline from radiating into
your neigh
That's why I use the statement "xxx ft center fed wire with balanced feed". I
do have the ability to measure the current in each side of the feedline. As
long as it is within 5%, about the limits of accuracy of measurements, I'm
happy.
Bob, K4TAX
Sent from my iPhone
> On Jan 13, 2019, at
A friend once told me, "Almost none of us has a balanced dipole."
What he meant is, few of us are lucky enough to be able to put a dipole
high up and completely in the clear - most of us have to put it up where we
can, and one side will be closer to houses, trees, gutters, chain link
fences. t
To answer the question "Could a couple of inches or so difference in the
length of the legs of a dipole ever work in your favor?"..depends on
the frequency. For lower frequencies likely NO, for higher frequencies
maybe YES. Thus 2" for a 160M dipole would be 0.066% while 2" for a 10M
dipo
Ron,
With a slight difference, I cannot see that it would either benefit or
degrade. The current distribution on the radiator might be a little
off-center, but it will still work.
But it is one reason for using a very good current choke on the feedline
- to keep RF off the outer braid of the
I was asked a question by a newcomer to HF today. After thinking about it,
I realized it had never really occurred to me. So I’ll pass it on to the group
and see what the antenna gurus think.
Is there ever a time where a slight imbalance in a dipole could be
beneficial? My first incli
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