Re: Vertical Load Coil

by **admin** Thu Jan 10, 2019 11:07 pm

Ok Dinos,
At the moment I don't have the antenna with me, but I will have it back in about 4 weeks. It is being reviewed by a friend before he builds one for himself. The delivery time for the 5m telescopic whip is about 4 weeks, so he can't build his jut yet.

I do hope to make a temporary lash-up to get me QRV at the HF bands at the weekend, but for 14MHz I shall use:

- 3m telescope paintbrush handle, +
- 2m telescope IKEA curtain rod, +
- 75cm coat-hanger wire, +
- a "slack handful" of self-tapping screws

I will wind the coil for the lower frequency bands on two paint rollers glued together using 1mm enamelled wire, but I will need a lot more than 53 turns because the diameter is ½. I will see if I can get that photographed, too :-)

I get my plastic tubes from a local building merchant (or a ferriteria).

Best regards from Harry - SM0VPO

by SeAfasia Thu Jan 10, 2019 11:36 am

Admin wrote:Ok Dinos,

Wish you all the very best of luck with it.
If you want I can supple a couple of photos of my loading coil?
If the vertical ground-plane is 5m long then the coil will work exactly as I show in the pictures.

This is another project I have on the desktop, but I am also collecting pictures and material to make a 15 minute video about it.

BR Harry - SM0VPO

yes Harry,I do..
try to find some parts like the pvc tube to start it...
73s

by **admin** Thu Nov 29, 2018 10:27 pm

Ok Dinos,

Wish you all the very best of luck with it.
If you want I can supple a couple of photos of my loading coil?
If the vertical ground-plane is 5m long then the coil will work exactly as I show in the pictures.

This is another project I have on the desktop, but I am also collecting pictures and material to make a 15 minute video about it.

BR Harry - SM0VPO

by SeAfasia Wed Nov 21, 2018 5:40 pm

Admin wrote:Hi Dinos,
I also have a crude method, as a rule of thumb. I usually take 1/3 of the missing length and coil that up.

For example, a 1/4-wave vertical (ground-plane) is 5m high. Perfect at 14MHz.

For 3.5MHz it needs to be 20m long to be a 1/4-wave groundplane.
From 20m, subtract the 5m you already have =15m, and 33% of that is 5m. My coil is 30cm Dia. (100cm/turn).
53 turns = 5.3m of wire.

This can vary a lot with geometry, but this rule of thumb is well tested with a 30cm Diameter coil, with 1cm spaced turns.

With only inductance, I found that 25% of the un-loaded frequency (14MHz antenna tuned down to 3.5MHz) is also another limit. At 1.8MHz you will need some additional tuning elements to get a perfect VSWR without an ATU.

Of course, this works but is not very accurate. But it is another method that works for the HF bands :-)

Very best regards from Harry - SM0VPO

thanks a lot Harry..
try to build it...
Dinos..

by **admin** Mon Nov 19, 2018 10:25 pm

Hi Dinos,
I also have a crude method, as a rule of thumb. I usually take 1/3 of the missing length and coil that up.

For example, a 1/4-wave vertical (ground-plane) is 5m high. Perfect at 14MHz.

For 3.5MHz it needs to be 20m long to be a 1/4-wave groundplane.
From 20m, subtract the 5m you already have =15m, and 33% of that is 5m. My coil is 30cm Dia. (100cm/turn).
53 turns = 5.3m of wire.

This can vary a lot with geometry, but this rule of thumb is well tested with a 30cm Diameter coil, with 1cm spaced turns.

With only inductance, I found that 25% of the un-loaded frequency (14MHz antenna tuned down to 3.5MHz) is also another limit. At 1.8MHz you will need some additional tuning elements to get a perfect VSWR without an ATU.

Of course, this works but is not very accurate. But it is another method that works for the HF bands :-)

Very best regards from Harry - SM0VPO

by SeAfasia Fri Nov 16, 2018 3:54 pm

Ivan wrote:Hi,
Google offers a lot of pages. Try e.g.
https://m0ukd.com/calculators/loaded-quarter-wave-antenna-inductance-calculator/
or
http://www.seed-solutions.com/gregordy/Amateur%20Radio/Experimentation/HiQCoil.htm

73 Ivan OK1SIP

thnaks Ivan...
73 Dinos SV3IRG

by **Ivan** Fri Nov 16, 2018 3:39 pm

Hi,
Google offers a lot of pages. Try e.g.
https://m0ukd.com/calculators/loaded-quarter-wave-antenna-inductance-calculator/
or
http://www.seed-solutions.com/gregordy/Amateur%20Radio/Experimentation/HiQCoil.htm

73 Ivan OK1SIP

by SeAfasia Fri Nov 16, 2018 2:24 pm

Hi all,
is there any calculator for Load Coil?
Dinos..

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