"Mark Keith" wrote in message
m...
(RHF) wrote in message
. com...

- Fixed Capacitor(s) for single station tuning.


Speaking of fixed caps...Some of my 160m buddies and buddetts are
building loops for receive purposes. Some have wondered about
caps....I've never tried it, but for fixed single freq use, I don't
see why a length of coax couldn't be used. IE: lets say you had a loop
that needed about 75 pf to tune. RG-8 is appx 30-31?? or so pf a foot.
About a 3 ft piece *should* work. Or seems to me anyway...I prefer
variables, but this coax cap method might could work for someone that
needs a quicky cap, and has none at hand. MK

The oscillator section of a standard AMBCB variable would be right in that
range.. or, for cheap, quick and (not so) dirty, there are lots of 100pF
mica trimmers available..

In article ,
(Mark Keith) wrote:

Jim" wrote in message
...
You can build your own but it's actually not worth it.
--
Ron Hardin



I beg to differ about loops that you build are not worth it.
I designed and built many MW loops that are as good or better in some ways
that the Kiwa loop. The problems with homemade loops is poor construction.
This link has pictures of loops that I built.
http://www.frontiernet.net/~jadale/M...20Antennas.htm

Jim

I agree....My homemade loops are better for my uses than what you can
buy. I can design any feature I want, and generally they are bigger
and deliver more voltage than most storebought. I built two more loops
yesterday just farting around. "Both for longwave". Maintaining
balance is the secret to success. Also, I did an experiment on mine a
couple of days ago. I've been using a simple coupling loop on mine
lately, but do have a shielded coax coupling loop also. "IE: the coax
shield is cut in the middle at the top". One had mentioned an
advantage to using a shielded loop vs a non shielded. Well, I tried
both feeding my 12 turn 16 inch round loop. No difference whatsoever
in noise, or null depth. I had never noticed much difference with
single loops of each type either if you were careful to detail.
So far, I have not been able to see much of an advantage to a shielded
loop vs unshielded as long as you are careful with balance. They seem
to work about the same here.

The shield is electrostatic and would only help against local noise
(example - in the room computer) being the pickup loop.

If you had an un-tuned broadband amplified single turn shielded loop
compared to one that was not shielded then you would expect to see a
difference.

Loop antenna is a broad term.
Here are some features:
1. Small or large compared to the received wavelength.
2. Shielded or not.
3. Single or multi turn and shape type example - pancake or solinoid.
4. Tuned or un-tuned.
5. Several ways to couple them to the receiver.

Now you can mix and match the 5 above into many possibilities all with
different tradeoffs.

--
Telamon
Ventura, California

(I could
sure use a longwire connection to it, too.. AM reception inside our building
runs from terrible to hideous to non-existant..)

Out of curiousity Brenda Ann, what radio are you using for the BCB anf for SW?
My loop doesn't really do that good a job on that GE P-780, works well on all
the others, but not that one.

But (from experience) if you could hook you a longwire, you'd be pleased I'm
sure.

"donutbandit" wrote in message
...
"King Pineapple" wrote in
hlink.net:

http://www.selectatenna.com/

People should take time to read thoroughly before they post
..

Yes, you really should.

"Dxluver" wrote in message
...
(I could
sure use a longwire connection to it, too.. AM reception inside our
building
runs from terrible to hideous to non-existant..)

Out of curiousity Brenda Ann, what radio are you using for the BCB anf
for SW?
My loop doesn't really do that good a job on that GE P-780, works well
on all
the others, but not that one.

But (from experience) if you could hook you a longwire, you'd be pleased
I'm
sure.

I sometimes use the P-780, but mostly I'm using a Pioneer tuner that I feed
into our cable system for an FM signal on the tuner... but inside this
place, even the 780 doesn't do well, because of all the QRM.. doesn't matter
how good your receiver is, if it's not got a clean signal to start with, it
can't reproduce one.

I agree....My homemade loops are better for my uses than what you can
buy. I can design any feature I want, and generally they are bigger
and deliver more voltage than most storebought.

MK,
would you mind emailing me? I have a question.

but inside this
place, even the 780 doesn't do well, because of all the QRM..

Unbelievable, though I believe you. ;-) I've had that 780 in places and
offices and one home that was absolutely he** for RF but the ole' GE P-780
handled it as it always has.

*I think* the reason that rat sgack loop doesn't work with the GE P-780 is that
it is so well made that it doesn't need a loop, all my other receivers get
some kind of lift from my loop except that particular piece.

That was what I read and was told by an old timer when he saw the 780, he said
"wow, that battleship brings back memories, where in the world did you get
one of them." lol We must have say out there for three hours listening to that
radio and talking, he's in his 90's and just a super guy and he really thinks
highly of that radio.

BTW, thanks for being my 'dealer.' ;-) No....no...guys....no drugs involved.

Telamon wrote in message

The shield is electrostatic and would only help against local noise
(example - in the room computer) being the pickup loop.

Yes, And I could tell no real difference from it to a unshielded loop.
This assumes the unshielded loop is fairly well balanced though.

If you had an un-tuned broadband amplified single turn shielded loop
compared to one that was not shielded then you would expect to see a
difference.

I would think so. But so far I don't really see a drastic difference.

Loop antenna is a broad term.
Here are some features:
1. Small or large compared to the received wavelength.

A small loop is directional inline with the windings. A large loop,
broadside to the windings.

2. Shielded or not.

Again, this is debatable as to the effectiveness...I consider it an
option.

3. Single or multi turn and shape type example - pancake or solinoid.

A pancake coil is directional broadside to the loop. A solenoid,
inline with the loop. Or so I've read...So far, almost all of my small
loops are solenoid type. I have thought about planting a big pancake
coil on a door though...

4. Tuned or un-tuned.

All small passive loops should be tuned. At the least, using the self
resonant freq. With the cap, lower in freq...

5. Several ways to couple them to the receiver.

I use normal coupling loops, both shielded, and unshielded as a test.
I see no difference in results..I don't use preamps. Don't need em...

Now you can mix and match the 5 above into many possibilities all with
different tradeoffs.

Thats what I'm doing here, but with not always the results I want...
IE: I made a 45 turn LW loop that I hang up against my usual 16 turn
MW loop. I used the same cap for each loop, by using a switch. It
worked great on both "bands". Didn't mess up the MW loop. So then, I
decided to wind a LW loop on the same frame hoping for the same
results. The LW worked fine, but the MW was detuned. So I just now
ripped all the LW turns back off and will go back to the previous
method with a bit more separation between the windings. I'm rigging
mine up to cover from about 150hz to 2000 hz in two steps. "coils".
This lets me use the same cap for both, and I don't have to tack on
extra fixed caps for LW. But I still want to build some type of
unidirectional rotatable small loop. In messing with the LW loops, I
have discovered something about my radio I hadn't noticed.
"IC-706mk2g". Although it tunes down to 30 cycles, the radio goes
pretty dead below about 150 cycles. Not the greatest LW radio in the
world for real low freq's...:( It's ok from about 175 hz, up.. MK

The main reason I like to keep it on the group is if I lay a clam,
someone will usually correct me.

huh, OK.