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Was any attempt made to redress the imbalance?
David G3UNA
> On 17 July 2020 at 03:19 Fred Jensen mailto:k6...@foothill.net > wrote:
>
>
> They were around somewhat before the patent in several forms, and they
> were around in 1960, which is the last time I looked hence my
I took great care in the construction of my rotary dipole and feed
system to make it as balanced as possible. I made a clamp-on device from
a split ferrite bead that I can use to measure the relative currents in
the open line conductors, and they are very close.
There is one direction in
They were around somewhat before the patent in several forms, and they
were around in 1960, which is the last time I looked hence my estimate
of 60 years. Lots of other "balanced" antennas fed with open line were
also in use commercially during that rough period, they too exhibited
the same
.
73
Frank
W3
- Original Message -
From: "Fred Jensen"
To: elecraft@mailman.qth.net
Sent: Thursday, July 16, 2020 9:41:21 PM
Subject: Re: [Elecraft] KPA1500 in the IARU Contest Last weekend
Indeed! Probably the least unbalanced of "balanced" antenna system
7 MHz.
73, k3ICH (ex KN3ICH in1959)
-Original Message-
From: elecraft-boun...@mailman.qth.net On
Behalf Of Fred Jensen
Sent: Thursday, July 16, 2020 5:41 PM
To: elecraft@mailman.qth.net
Subject: Re: [Elecraft] KPA1500 in the IARU Contest Last weekend
Indeed! Probably the least
Indeed! Probably the least unbalanced of "balanced" antenna systems
that ever existed were the HF point-to-point rhombics and V-beams at the
RCA, Mackay, and Marconi shore stations in the first 60 or so years of
the 20th century. Despite very precise engineering to make them
balanced, the RF
On 7/16/2020 1:14 AM, Victor Rosenthal 4X6GP wrote:
If the antenna is well-balanced and fed via a true balanced antenna
tuner (preferably link-coupled) then there shouldn't be a problem with
common mode currents.
Few ham antennas are perfectly balanced -- they are often unbalanced by
their
There is some sort of popular folk theorem that open wire feed line doesn’t
carry common mode currents. It is obviously wrong. Both wires high, both wires
low, and that is common mode. Any RF that excites both dipole elements high
against ground will cause common mode currents on the feed line.
Jim
We're drifting off topic and you're pushing at an open door.
I accept that wire size has an influence, but in my experience on smaller cores
(UK limit is 400W) wound with RG316 I have observed the core getting hotter
than the wire.
BOK = Brick On Key. I think it was Alpha that used
Re open-wire fed antennas:
If the antenna is well-balanced and fed via a true balanced antenna
tuner (preferably link-coupled) then there shouldn't be a problem with
common mode currents.
Yes, you have to worry about nearby objects unbalancing the antenna,
which is less of a problem with a
On 7/15/2020 1:36 PM, CUTTER DAVID wrote:
It's all about size. Bigger core helps,
Dave,
No, it is NOT about size. It is about design of the entire antenna
system, including the antenna, the feedline, and other parts needed to
make the SYSTEM work. The principal characteristic of a common
Size is the most important parameter.
I've read your tutorials several times and they are an inspiration but it's
just like linear amplifiers: you can't say an amplifier designed for
intermittent service like ssb or cw is poorly designed because it doesn't pass
the BOK test. It's horses for
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On 7/15/2020 11:46 AM, CUTTER DAVID via Elecraft wrote:
Ferrite-cored chokes (balun) heat up and change apparent swr.
Not if they are properly designed and properly applied. And not all
antennas can be choked -- in general, only resonant antennas can be
effectively choked. Chokes applied to
Ferrite-cored chokes (balun) heat up and change apparent swr.
David G3UNA/G6CP
> On 15 July 2020 at 17:36 j...@kk9a.com wrote:
>
>
> That is quite an assumption. A 2el 40m beam with large efficient
> High-Q loading coils will have less bandwidth than for example one of
> the popular US
That is quite an assumption. A 2el 40m beam with large efficient
High-Q loading coils will have less bandwidth than for example one of
the popular US manufactured beams that use 68 turns of small wire in
each coil. The latter is more likely to have heating issues. I have
never noticed
Since it is so narrow I suspect it may be a trapped design or have loading
coils which at 1500w may be heating and detuning as a result.
73
jim ab3cv
On Wed, Jul 15, 2020 at 11:45 AM Ray Spreadbury via Elecraft <
elecraft@mailman.qth.net> wrote:
>
>
> A correspondent asked me why I needed to
Or water...
Are you sure your coaxial cable, balun and connectors are all dry?
From your description, the last thing I'd examine is the KPA1500
Good luck!
73
Frank
W3LPL
On Wed, Jul 15, 2020 at 11:19 AM Nr4c wrote:
> My first thought is “Heat”!
>
>
> Sent from my iPhone
>
Describe your antenna system.
Jim ab3cv
On Wed, Jul 15, 2020 at 11:19 AM Nr4c wrote:
> My first thought is “Heat”!
>
>
> Sent from my iPhone
> ...nr4c. bill
>
>
> > On Jul 15, 2020, at 4:43 AM, Ray Spreadbury via Elecraft <
> elecraft@mailman.qth.net> wrote:
> >
> > Hi
> >
> > I was a member
My first thought is “Heat”!
Sent from my iPhone
...nr4c. bill
> On Jul 15, 2020, at 4:43 AM, Ray Spreadbury via Elecraft
> wrote:
>
> Hi
>
> I was a member of the UK HQ team for this 24hour IARU event last weekend and
> was one of the two Ops on 40M SSB.
>
> We took it in turns to be
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