Topband: Compromise vertical loading questions

[Charlie Cunningham]

Hi, Bjorn

Well I would expect that moving the loading coil higher would be more
beneficial than improving the top loading spokes, as it would move the high
current portion of the antenna higher aboveground (the radial) and there
would, hopefully, be less loss In the loading coil by having it in a lower
current region of the antenna. Improving the top loading spokes might be
helpful also, but I think less than moving the loading inductance higher.
Of course, since the loading inductance will be in a lower current region of
the antenna, it may require a bit more inductance to resonate the antenna.
Good luck! Have fun!

73,
Charlie, K4OTV

-----Original Message-----
From: Topband [mailto:topband-bounces at contesting.com] On Behalf Of Björn
SM0MDG
Sent: Wednesday, January 29, 2014 2:48 AM
To: topband at contesting.com List
Subject: Topband: Compromise vertical loading questions

Here are some question for anyone with more tech skills than me;

My compromise vertical at 8Q7BM is made of thin wire attached to a DX-Wire
15 meter glass fibre pole. The vertical wire goes all the way up, but as the
pole’s top sections are very thin/weak the three top loading spokes (each 12
meter long) are attached at about 13 meter.  The antenna has a 1/4 elevate
radial towards the water at 2-3 meter height. The whole structure is within
1/4 wave of the water line.

The antenna is self resonant at 2.2 MHz and I use a coil wound on a water
bottle to bring it down to 1.8. The coil appears to be about 8-10 uH
according to online calculators.

My questions are;

How much I can improve by moving the coil up. What improvement should I
expect if center loading at about 7 meter? How about moving the coil all the
way up to the top loading spokes? Is it worth the effort? (the pole won’t
support much up there).

My top loading spokes are sloping more than the recommended angle. According
to the ON4UN Low Band book I got the impression that the difference should
be minimal when close to salt water. I have tried to slope them less, but
easily get in trouble with the weak pole in the wind. And there are pats to
the beach every where so options are few.

Which one of the two above actions would be the most beneficial? Move the
loading coil higher up or rearrange the top loading spokes for a better
angle?


73 de Björn,
SM0MDG
8Q7BM
SE0X









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