-----Original Message-----
From: [email protected]
[mailto:[email protected]] On Behalf Of Graham
Sent: Friday, February 15, 2013 12:48 PM
To: [email protected]
Subject: Re: LF: Re: how to increase the Q of my loading coil?
I would go along with that
I would think the higher the Q the higher the losses in
such a coil , the bigger the circulating values .. I look
at 500 as the next band
down from 160 , differing set of rules than coming up
from 136
..Top coil , takes the voltage out of the shack / tuner
house , while increasing the vertical amps , and yes, rain +
Q = problems !
Ground is more important than the wire in the air or the
tuner losses ....... all the old (now very old) marine
installations only had 30
or 40 feet of vertical wire from the radio room roof
to the top
wire , but a few 1000's tons of iron and salt water to tune
against
GL-73-G..
--------------------------------------------------
From: "Alan Melia" <[email protected]>
Sent: Friday, February 15, 2013 1:28 AM
To: <[email protected]>
Subject: LF: Re: how to increase the Q of my loading coil?
Why? I think you might need to look at the priorities first.
Experience says you will not notice the difference unless you have
tackled the problem of ground and environmental losses first (as
Stefan has done) The improvement obtained by improving the Q of the
loading coil may probably only increase the efficiency by a
minute amount.
You say you have a Q of 200 now.... this indicates a bandwidth of
about 2kHz meaning you will probably need to retune across
the band. A
Q of 400 to 500 should be possible but unless the reduction in RF
resistance is a substantial fraction of the Rloss it is
wasted effort.
It also means that your tuning will be very weather
dependent. I feel
that unles you have situation of Rloss <15ohms you will
barely notice
the difference......except a "flighty" system, difficult to keep
peaked, and possibly a number of fried PA devices when it goes wrong.
Litz will improve the Q slightly, coil form factor needs to be right
as well, and Litz is a devil to work with (note "proper" Litz has
strand numbers are twisted in powers of 3, anything else is just
bundled and will not achieve the theoretical advantage) If you miss
one strand out of the soldered connection of the Litz you
will lose a lot of the advantage.
Top loading may well turn out to be more effective, but it
all depends
on your partcular location, and you need to make measurements of the
antenna systtem, and possibly the field it generates, not guess
(though that is very seductive :-)) but in my experience is usually
wrong! )
You are right in that the best way is to make incremental
improvements
to the antenna, but be very critical, weighing the cost in
effort and
cash for the improvement .......what works for others may
not work for you.
Best of Luck
Alan
G3NYK
----- Original Message -----
From: "Dimitrios Tsifakis" <[email protected]>
To: <[email protected]>
Sent: Friday, February 15, 2013 12:31 AM
Subject: LF: how to increase the Q of my loading coil?
Hello group,
I would like to increase the Q of my loading coil for 475 kHz. . It
consists currently of a 20-litre plastic bucket with standard house
240V electrical wire (with PVC jacket). I measured the Q
and found it
to be about 220 (XL is about 2 kohm). I do have some Litz
wire I can
use. I also have a piece of large diameter (25 cm) storm
water pipe,
which I think is made of PVC. Would you recommend using a
PVC former
or should I look for a more exotic material
(glass/porcelain)? Would
you think the inter-turn capacitance is very detrimental and some
exotic winding technique would yield better results?
I understand that ground losses are bigger in my case than the
inductor losses, but I would like to address the inductor first.
73, Dimitris VK1SV
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