Posted by
Don Sanders on
Dec 07, 2018; 4:39pm
URL: http://elecraft.85.s1.nabble.com/Flumoxed-tp7646765p7646912.html
As Don has said, a good dipole as high as possible, even in an attic, fed
with balanced line will out perform most other compromise multiband
antennas.
While being retired in Ecuador I had the advantage to try several antennas.
The best over all was a fan dipole for 40, 30, 20,and 17 fed with RG6 up 80
feet AGL mounted on 30 foot bamboo poles at the top of a hill. Next was an
88 foot inverted L fed with 300 ohm line, then two RG6 coaxes, then
homemade open line. The horizontal sloped from the 33 foot peak to a 20
foot pvc mast. I noted no real difference with either feed line.
I also mounted the 88 footer with 66 feet in a slight vee from 33 feet peak
to 20 foot supports for the ends and 11 feet vertical at each end. This
also worked well all bands about as well as the inv L. I easily worked
Europe Asia, South Africa, eastern and asiatic Russia with QRP or 80 watts.
This was a test to see if an 80 meter ant could be installed in a limited
space as many homes in Ecuador have lots that are small.
While any antenna is better than no antenna, effort should be made to have
the best antenna possible. Wire antennas are simple, economical and easy
for most hams to iinstall.
Dr. Don W4BWS
EX-HC4/W4BWS
On Thu, Dec 6, 2018 at 9:58 AM Don Wilhelm <
[hidden email]> wrote:
> That statement is true - however ---
> The problem is not radiation from the conductor, but how to get the RF
> current into the conductor and not in other unintended places.
>
> For those who want to build their own antennas, I suggest starting with
> a resonant dipole fed in the center. That provides a good match for 50
> ohm coax, and a good current mode choke (balun) at the feedpoint keeps
> RF from flowing back onto the outer shield of the coax which can create
> a lot of RF in the Shack.
>
> Off Center Fed, and End Fed antennas can be made to work with more care.
> The feedpoint impedance does not match coax, and special care must be
> used to keep the RF on the radiator rather than coming back into the shack.
> I realize that OCF and End-Fed non-resonant antennas are popular because
> they can be used on multiple bands, but there are problems feeding them
> while keeping the RF on the radiator and not in unintended places such
> as the shack.
>
> For those who want multiband operation, I still suggest a center fed
> radiator fed with open wire or ladder-line to a good current mode choke
> balun at transition point to coax is a better choice than OCF or end-fed
> antennas - keep the coax short and use a tuner that can match the
> resulting impedance.
> Make the length of the dipole approximately the length of a half-wave at
> the lowest operating frequency desired. It will be more "tame" for RF
> in the Shack than many OCF or End-fed antennas.
>
> 73,
> Don W3FPR
>
>
> On 12/6/2018 8:56 AM, ANDY DURBIN wrote:
> > "RF current into a conductor will radiate, even if it's at eye level."
> >
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