[TowerTalk] 40m 4el KLM - replacing linear loading with coils

Grant Saviers grants2 at pacbell.net
Tue Apr 28 19:20:58 EDT 2020


I bought a used EF180C (F12) LL loaded 86' rotary 80m dipole, tossed the 
LL wires, coils, and relays, modeled it with YagiMech (DXEng) and 
upgraded it mechanically for 90mph (was maybe 65mph).  The LL wires were 
replaced with two Phillystran guys to a longer crossbar.

Plugged the stock mechanical dimensions into EZNEC and found the 
resonating center inductances for 3.5 and 4.0. Then worked with Mike at 
Seco/Tornado drive to get a split coil variable Tornado, as it took 
about a 2:1 L range for full band coverage.    It's been in use about 7 
years at 102'.

A few years ago I talked to a CO ham who was going to build a Tornado 
based 80m 3L yagi, full band coverage.  Not sure it got built. 
JKantennas sells a 55ft 80m Tornado tuned dipole.  No sliding contacts 
or relays.

My MFJ screwdriver controller has 10 presets every 50KHz and it seems to 
repeat well against the home microswitch.  So if an inductance vs turns 
calibration was done, then a Tornado tuned yagi could cover all of 80m 
and do all the fancy stuff a steppir yagi can do with a similar controller.

Grant KZ1W.

On 4/28/2020 12:52, Mike & Becca Krzystyniak wrote:
> Greetings All,
> 
>      I was considering a similar approach, by taking the existing design and
> changing the linear loaded elements into center loaded dipoles. Start with
> coil placement at LL insulator and tune to that elements current natural
> resonant frequency.  Has anyone modeled it like this?
> 
> Mike K9MK
> 
> 
> 
> -----Original Message-----
> From: TowerTalk [mailto:towertalk-bounces at contesting.com] On Behalf Of
> john at kk9a.com
> Sent: Tuesday, April 28, 2020 1:35 PM
> To: towertalk at contesting.com
> Subject: Re: [TowerTalk] 40m 4el KLM - replacing linear loading with coils
> 
> Rather than try to duplicate a design that is decades old, I think it
> would make more sense to redesign the antenna using loading coils.
> VE6WZ has some loading coil information on:
> https://www.qsl.net/ve6wz/index.html
> 
> John KK9A
> 
> 
> 
> Richard (Rick) N6RK wrote:
> 
> 
> The problem is that you don't know the required inductance
> of the coils.  It would be difficult to determine this
> for anyone but M2.  At one time, W6ANR used to sell
> coils for 40 meter Yagis.  Perhaps he has the values
> and would be willing to give them to you.
> 
> The recent TT thread about determining the resonant frequency
> of Yagi elements would help you.  You could find the 4
> resonant frequencies of the 4 elements of the unmodified
> Yagi, and then use trial and error to tune the inductors
> to get the same element frequencies.  Seems like a lot
> of work.
> 
> Rick N6RK
> 
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