The two half waves in phase gain their improved performance by being
spacially separate. The more you load it to shorten the two dipoles,
and the closer you arrange them, the less they provide any benefit. It
would have no benefit at all as a short portable antenna.
By the way, any vertical antenna is not insensitive to ground. A
vertical dipole merely doesn't need anything extra for a return current
path, but it will still have all of the normal ground loss for the
radiated field that is a function of the ground conductivity.
Dave AB7E
On 9/29/2022 12:30 PM, Fred Jensen wrote:
The Franklin is two vertical, co-linear half-waves fed in-phase.
Google will offer way more than you want to read. Obviously a large
structural challenge for a full-size one at MF. The one I built as a
test was heavily loaded and worked about like EZNEC-4 predicted. I
think it's insensitivity to "ground" may be one reason it works well,
but that's just a guess.
73,
Fred ["Skip"] K6DGW
Sparks NV DM09dn
Washoe County
Dan Presley wrote on 9/29/2022 12:20 PM:
Fred-can you share details on this antenna? Not familiar with it.
Thanks.
Dan Presley 503-701-3871
danpresley@me. com
[email protected]
On Sep 29, 2022, at 12:08, Fred Jensen<[email protected]> wrote:
I've long wondered why hams haven't done more with Franklin
verticals? KFBK [1530 kHz in Sacramento] uses one located in the
southern end of the Sacramento Valley, and it's known as a Flame
Thrower. I think KNBC [680 kHz?] in SF had one back in the 50's
sometime too. They're big at MF, but much more tractable at HF, and
they are amenable to loading techniques. I built one [fairly heavily
loaded] out of Buddipole parts I had, and its performance,
particularly when I was still activating summits, was surprising.
Like a small loop, the Franklin pretty much ignores ground ...
although KFBK's probably likes being located in rice fields filled
with water. 😉
73,
Fred ["Skip"] K6DGW
Sparks NV DM09dn
Washoe County
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