Owen Duffy wrote:

Tony Giacometti wrote in
:

Owen Duffy wrote:
...
I will be offline for a few days, I look forward to hearing of the
outcome.

Owen


I tried both configurations, both raised the noise level which I am
thinking must be related to the gain you said I would get, I didn't

I take it that 'raise the noise level' actually means you got more noise
out of the receiver / higher S meter reading on band noise.


yes!



need the preamp at all. I didn't get the nulls like I get from the
original loop - that was a mild surprise - there was only a 2-3 S unit

Neither the preamp, nor the tuning changes you made should change the
directivity (ie the pattern, the depth of the nulls) of the antenna.


I didn't use the preamp for these tests, but the noise level did change and
yes, the nulls were not that deep.

As I wrote this was a mild surprise and I did recheck all connections and
redid the test with the same result.



difference between noise peak and noise null, The original loop
normally has S1-2 99% of the time when nulled. The current loop has a
difference between noise peak and noise null of 7-9 S units. Now don't

I have already told you those measurements don't mean anything to me.

misunderstand me, but I like the low noise level. What concerns me
with the other 2 configurations is the gain makes the noise increase
so much that I am not so sure I would be able to hear the weaker ones.

If you want to improve the depth of the nulls, you have to concentrate on
the balance of the antenna, the symmetry of the loop, its feedline, its
environment etc. I think Roy might have said that earlier.

yes he did, and I am not sure why the depth of the nulls changed.


I think this project as simple as I thought it would be ...... just
isn't. What I would like to accomplish with this loop idea is to have
the low noise and the ability to null out the noise from my neighbors
houses. But at the same time have enough gain to be able to hear the
weak signals. Now I don't have preference for using the preamp or not.
Whatever works is what I want to go with.

It is fairly simple, you might have needed to learn a bit, but you
probably also had to unlearn some stuff.

true, I had to unlearn some things that most likely floated around for
years.



Maybe changing the type of loop to a different style of loop would be
the way to achive what I would like to obtain.

You have already been told there is no such thing as a low noise antenna.
The loop has the advantage of being able to null out signals from two
opposite directions, which can help if the interference is predominantly
from one (or both) of those directions. You can improve the depth of
those nulls, but pattern or directivity is unrelated to the power
transfer problem.

did I misunderstand you, I thought the noise was nullable but at 75 meters
the signals were mostly omnidirectional? Or is this one of the unlearned
things?



Obviously, there is a miriad of designs and configurations. Since I
need the loop only for 75 meters and have a limited amount of real
estate this cuts the pile down to a lesser amount.

What to do...................well, maybe I should start over - why not
try a different type/style of loop. A larger loop might be better for
gain but how big before its not able to null out noise cause I can't
rotate it due to its size?
Does the loop have to be coax? can it be some other type of wire?


Remember that symmetry is key to the depth of the null. If it is harder
to build a larger loop with equally good symmetry (including to the
environment), you have more gain, but poorer nulls... and your main
reason for selecting the loop is for rejection of interference using the
nulls. You need adequate gain, and the best balance rather than the other
way round.

Your input is much appreciated.

Thanks

73
Owen


Ok, I want to build a larger loop to get more gain, if possible deep nulls
for reducing local noise, I would like to try wire instead of coax. I want
to mount it on a PVC pipe frame. Can you give me any ideas as to what shape
and size? Whats a solenoid loop?