Owen Duffy wrote:

Owen Duffy wrote in
:

I just went and re-examined the article, and it is not series tuned as I
first thought, it is parallel tuned.

My calcs of your loop were all on the basis of series tuned loop, and are
not applicable to the parallel tuned circuit.

It is questionable whether the parallel tuned circuit is an efficient
coupling method for a low Z receiver.

Owen


I am able to get a noise peak tuning the capacitor and the preamps I use are
supposed to be a match from approx 25 ohms to about 125 ohms.

I believe this should work, but for some reason not like I thought it would.

Tony Giacometti wrote in
news:sO2dnUZbkeShCaLanZ2dnUVZ_v2pnZ2d@hawaiiantel. net:

I believe this should work, but for some reason not like I thought it
would.


Tony, I have described a simple untuned loop for field strength
measurement. The article is at
http://www.vk1od.net/SmallUntunedSquareLoop/index.htm . The sensitivity
of the loop is sufficient that external noise on 3.6MHz is much greater
than the receiver internal noise, ie S/N of signals on the band will be
about as good as they can be, a higher gain antenna will increase the S
meter reading, but not improve S/N ignoring the effects of noise blankers
and noise reduction. The predicted performance has been confirmed by
comparison to a calibrated EMC measurement loop.

The purpose of tuning a loop is preselection and / or better impedance
matching to improve gain (by reducing loss).

The purpose of shielding a loop is for better balance to achieve deeper
nulls, but shielding isn't the only way, nor the best way necessarily.
Roy mentioned that.

Try a simple untuned loop, the balun is REAL important (for deep nulls),
see how it works then see if you can get the improved version to work. It
is questionable whether the shielded loop construction is a real
improvement, it brings some loss elements (the s/c stub loss, the line
loss in the other half the loop) to the design, losses that be worse than
a balun.

Owen

Owen Duffy wrote:

Tony Giacometti wrote in
news:sO2dnUZbkeShCaLanZ2dnUVZ_v2pnZ2d@hawaiiantel. net:

I believe this should work, but for some reason not like I thought it
would.


Tony, I have described a simple untuned loop for field strength
measurement. The article is at
http://www.vk1od.net/SmallUntunedSquareLoop/index.htm . The sensitivity
of the loop is sufficient that external noise on 3.6MHz is much greater
than the receiver internal noise, ie S/N of signals on the band will be
about as good as they can be, a higher gain antenna will increase the S
meter reading, but not improve S/N ignoring the effects of noise blankers
and noise reduction. The predicted performance has been confirmed by
comparison to a calibrated EMC measurement loop.

The purpose of tuning a loop is preselection and / or better impedance
matching to improve gain (by reducing loss).

The purpose of shielding a loop is for better balance to achieve deeper
nulls, but shielding isn't the only way, nor the best way necessarily.
Roy mentioned that.

Try a simple untuned loop, the balun is REAL important (for deep nulls),
see how it works then see if you can get the improved version to work. It
is questionable whether the shielded loop construction is a real
improvement, it brings some loss elements (the s/c stub loss, the line
loss in the other half the loop) to the design, losses that be worse than
a balun.

Owen


Its late here, 11:37pm - I will look this over in the morning. Thank You

Just for your info, the loop ends when pointed east-west I get S meter
reading of 3.5
when pointed north-south I get S1 I believe this tell me the noise is
either east or west of the antenna location.
When I had the loop on the other side of the property I got an S5 noise
reading in the same direction.
I believe either one of 3 houses might be the culprit, maybe they will go
away for the holiday and I will be able to make a better determination as
to who the bad guy is.

Tony Giacometti wrote in
news:sO2dnUZbkeShCaLanZ2dnUVZ_v2pnZ2d@hawaiiantel. net:

Owen Duffy wrote:

Owen Duffy wrote in
:

....
It is questionable whether the parallel tuned circuit is an efficient
coupling method for a low Z receiver.

I am able to get a noise peak tuning the capacitor and the preamps I
use are supposed to be a match from approx 25 ohms to about 125 ohms.

Tony,

I have written a program to solve for transmission loss from the source
being the emf induced into the electrically small loop through to the 50
ohm receiver load on the output. The program models the transmission line
stub on one side of the loop gap, and the transmission line on the other
side to the tuning capacitor and 50 ohm load.

I need to do some more checking, but the program results support my
proposition that parallel "tuning" is not an efficient coupling.

The only way to ensure a near 50 ohm receiver for test purposes is to put
a 10dB 50ohm attenuator in front of it. If you are able to do such, does
the receiver noise peak with the loop tuning capacitor at minimum C?

Owen

Owen Duffy wrote:

Tony Giacometti wrote in
news:sO2dnUZbkeShCaLanZ2dnUVZ_v2pnZ2d@hawaiiantel. net:

Owen Duffy wrote:

Owen Duffy wrote in
:

...
It is questionable whether the parallel tuned circuit is an efficient
coupling method for a low Z receiver.

I am able to get a noise peak tuning the capacitor and the preamps I
use are supposed to be a match from approx 25 ohms to about 125 ohms.

Tony,

I have written a program to solve for transmission loss from the source
being the emf induced into the electrically small loop through to the 50
ohm receiver load on the output. The program models the transmission line
stub on one side of the loop gap, and the transmission line on the other
side to the tuning capacitor and 50 ohm load.

I need to do some more checking, but the program results support my
proposition that parallel "tuning" is not an efficient coupling.

The only way to ensure a near 50 ohm receiver for test purposes is to put
a 10dB 50ohm attenuator in front of it. If you are able to do such, does
the receiver noise peak with the loop tuning capacitor at minimum C?

Owen

I dont have access to an attenuator or anything that would work as one.
Right now the loop gets max noise with about 2/3 max capacitance.