Oh dear. Of course I know that stuff. BTW, except for very lossy RX antennas
the only thing I know of that gives a "flat" SWR is a dummy load.
The OP said, "My antenna, for 40 mtr's, is a 67' wire up about 25'." Why should
he make a 40-meter dipole so complicated?
Wes N7WS
On 1/16/2019 9:
You have several choices.
1. Add voltage or current balun at tuner output. Voltage 4:1 is simpler.
2. Connect the ladder line directly but loop the coax by the tuner a few
times around a large toroid. This is equivalent to adding a balun. Do not
ground the tuner.
The first option guarantees ba
On 1/16/19 12:11 AM, Wes Stewart wrote:
Why don't you cut the dipole in the center, add an insulator and feed
it with coax? Put a CM choke at the feedpoint if you insist and lose
the ladderline and tuner. _Prune the wire length for resonance. _
You do realize that "pruning" for resonance wi
I have three suggestions:
1) If you are feeding the antenna at the precise end of the wire, move
the feedpoint out a few feet. That's because you need "the other half of
the antenna." Because of the high impedance at this point, only a few
feet are needed.
2) Don't connect one side of the la
Why don't you cut the dipole in the center, add an insulator and feed it with
coax? Put a CM choke at the feedpoint if you insist and lose the ladderline and
tuner. Prune the wire length for resonance.
Wes N7WS
On 1/15/2019 7:15 PM, John Pierce wrote:
I haven't read all the comments on this
I haven't read all the comments on this thread and thus may requesting
redundant info. My antenna, for 40 mtr's, is a 67' wire up about 25'. I
have 30' of 450 ohm ladder line connected to the end of the antenna and
bringing the antenna into my basement. So I guess you could say that I have
a non
On 1/14/2019 6:32 PM, Wes Stewart wrote:
You do realize that if the common-mode current on the line is due to
asymmetry between the antenna and the line, then choking at the
feed-point reduces the CM current at that point, but just like your
example said, a quarter wave *down* the line you have
You do realize that if the common-mode current on the line is due to asymmetry
between the antenna and the line, then choking at the feed-point reduces the CM
current at that point, but just like your example said, a quarter wave *down*
the line you have a CM peak. If asymmetry isn't an issue t
It is one hell of a nice read Jim, THANK YOU for publishing it.
73s and thanks,
Dave (NK7Z)
https://www.nk7z.net
Award Manager, 30MDG Grid Contest
ARRL Technical Specialist
ARRL Volunteer Examiner
ARRL OOC for Oregon
On 1/13/19 9:24 PM, Jim Brown wrote:
I'm not going to go beyond this on the re
On 1/13/19 11:24 PM, Jim Brown wrote:
>> The instrument used to measure this is quite simple.
> I'd be very interested in how you're measuring the current at the
> antenna feedpoint. :) That is NOT so simple.
The common mode current can be measured 1/2 wavelength from the
feedpoint. Here is an
On 1/13/2019 6:46 PM, Al Lorona wrote:
the feedline is a wire dangling from the antenna
that isn't connected to anything on the other end.
That "dangling wire" is actually *two* wires, and the field of one cancels the
field of the other for no net radiation or reception -- at least that is the
>>> the feedline is a wire dangling from the antenna
>>> that isn't connected to anything on the other end.
That "dangling wire" is actually *two* wires, and the field of one cancels the
field of the other for no net radiation or reception -- at least that is the
condition we're trying to achie
On 1/13/2019 3:42 PM, Al Lorona wrote:
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.
What I actually mean is an antenna matched to its feedline at the
operating frequency(ies).
For the rest of us, of cour
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