Balun for loopstick antenna
 

Concerning the loopstick RX antenna identified as "VLF to Longwave:
Wideband Tuner" shown at:
http://www.stormwise.com/widetune.htm

I was told that the tap at 10% was to provide a match for a receiver
expecting a 50-ohm antenna.

Would I achieve the same result by using 405 turns, no tap, and a 9:1
current balun?

I am building a tuning cap box that covers from 25pF to 2uF in 25pF
increments. I am hoping to cover from 9kHz to 30mHz using the
variable capacitor box and 1,000 turns, with intermediate taps at 10,
33, 100, and 333 turns -- to be used as appropriate for each band.

Ken KC2JDY


Ken
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On Sat, 05 Feb 2005 09:14:37 -0500, Ken wrote:

Concerning the loopstick RX antenna identified as "VLF to Longwave:
Wideband Tuner" shown at:
http://www.stormwise.com/widetune.htm

I was told that the tap at 10% was to provide a match for a receiver
expecting a 50-ohm antenna.

Would I achieve the same result by using 405 turns, no tap, and a 9:1
current balun?

I am building a tuning cap box that covers from 25pF to 2uF in 25pF
increments. I am hoping to cover from 9kHz to 30mHz using the
variable capacitor box and 1,000 turns, with intermediate taps at 10,
33, 100, and 333 turns -- to be used as appropriate for each band.

Hi Ken,

I wasn't sure if your 30mHz was meant to be milliHertz or not, but
given the focus found at your link above, I presume you seek to listen
at the ELF and below.

When I looked at the truly meager coil offered at that site, I took up
my pen (metaphorically) to suggest you need something very, very, very
much bigger. 450 turns is truly pathetic. Some years ago, Scientific
American's column described a project that required 10000 to 20000
turns on a three foot ferrite rod.

However, none of this actually responds to your question about a 9:1
BalUn (and a current BalUn no less). This is waaaaaay out of the
common. (Read this will not be found off-the-shelf except at a
specialty store.) At these frequencies, standard transformer design
is suitable to design and construction details. Your stated need for
it to be a current BalUn would suggest your need for isolation.
Consider that those leads will need at least 3X and preferably 10X the
impedance observed in the coil you construct if that is what you are
trying to isolate. This means 50000 to 100000 turns of a wire pair
around a similarly long ferrite. Do you have the patience? ;-)

73's
Richard Clark, KB7QHC

On Sat, 05 Feb 2005 10:38:29 -0800, Richard Clark
wrote:

I wasn't sure if your 30mHz was meant to be milliHertz or not, but
given the focus found at your link above, I presume you seek to listen
at the ELF and below.

This is for manmade RF from 9 kiloHertz to 30 megaHertz. So, we are
talking VLF, LF and HF. A member of my ARC has temporarily wrapped
one of these ferrites with 50 turns of 22 ga. and is getting terrific
reception all over the shortwave bands.

Ken KC2JDY


Ken
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Not unusual really.
I wonder if he's actually resonant through the
whole HF spectrum though. Doesn't always actually
have to be resonant to "work". But tuned is much
better, naturally. I have to wonder why
they call it a tuner...?? It's an antenna as far
as I'm concerned.
Along the same lines as a ferrite antenna in a
radio, just bigger, or box loop, etc...
I did try making a MW antenna on a PVC form for MW.
Actually, it was a coil wound on PVC that was once
used for a short 160 dipole...
About 90 turns of 14 about a foot long. Tuned it
with a variable cap..It worked ok..
But a box loop is much better I think...You think one
of those little PVC wound loops is good?
Wait till you try a big box loop. But I don't normally
expect to cover the whole HF spectrum with a box loop.
I have one loop in the room here, that is a 44x44 inch
diamond, on a rotating stand. I use a multi gang
variable, that has a switch to allow using only a
single low value cap for the upper range of the loop.
I also have fixed caps I can tack in parallel to drop
down into LW. The loop has 7 turns, and is basically
designed for MW, using the average cap, but in all,
mine tunes from about 200kc to about 2150 kc in it's
present form. On LW, MW, or even 160m, it's quite a
bit better than the small PVC loop. It can be fed
indirectly using a built in ferrite loop as the
coupling loop, or can be fed with coax, etc...Mine are
all fed with coax to a coupling loop inside the main
loop, and I don't bother with baluns, etc.
They are not needed in most cases.
I don't normally use small loops for anything above say
2.5 mhz...A dipole, or even a random wire is usually
much better above that freq.
There are many designs for box loops, and Reg has
a good program for calculating the turns needed, etc.
I think it's rjeloop3.exe, if I remember right...
I have one fairly simple PVC design at:
http://web.wt.net/~nm5k/loop5.jpg
It's pretty easy to slap together. I never cared
much for the overly complex octagon designs much..
More work than is required...:/
BTW, the VLF natural noise stuff is kinda
interesting.. I might try to cook up something
for that...Never have listened down there.
MK

I said,
The loop has 7 turns, ....

Whoops...I was confusing with that loop on
the web page...
My loop has 5 turns, cuz it's bigger than the
35 inch a side version on that web page.. MK