Owen Duffy wrote:

Tony,

The key to improving the loop is to
-increase the induced voltage; and / or to
-improve its efficiency.

I agree, but how is the question


Increasing the induced voltage means increasing the size of the loop.
With a small loop, doubling the size of the side will win nearly 6dB of
induced voltage, but it also increases the inductance of the loop which
might degrade impedance matching and defeat most of the increased induced
voltage.

Improving the efficiency means addressing conductor / transmission line
losses and better impedance matching. Most of the 50 some dB of loss is
attributable to impedance matching.

I expressed surprise at the shunt tuning capacitor in an earlier posting.
I know it is a popular circuit, and it features in the ARRL Antenna
Handbook,

and alot of other places also.


but that doesn't make it a good circuit. Try the variable
capacitor in series with the coax inner conductor, you should improve the
gain by around 20dB.

this one I will try, does this not make the loop a closed loop?


Then try a shunt capacitor on the receiver side of the variable
capacitor, start with 1000pF, you should see further improvement in gain
but with a narrower bandwidth.

Don't have anything like this on hand, this is a variable capacitor I would
assume.


This is not a new circuit, you will find it in books, certainly at least
where the tuning / matching network is right at the loop gap. The
relocation of the capacitors by a length of transmission line does change
things a little, and it is more complicated to solve, but behaviour is
soemwhat similar.

Should you try this, your findings would be interesting.

I might be able to get to this in a day or two and I will let you know what
happened.


The mathematically based approach might not be popular, and I am no
mathemetician, but the approach does reveal why the antenna is
inadequate, and suggests what can be done to improve it.

Owen


I was thinking that maybe I didn't have enough capture area with the loop I
currently use.
My next step was to figure out how to increase the size of the loop so it
captures more signal. Since I havn't looked for any info on a loop like
this I was going to ask you if you had anything on a larger loop but one
which isn't too large and can be rotated either by hand or a rotator.

I think you answered my question(s) at the top of this post.
Doubling the size would still make it small enough to rotate by hand or with
a small tv rotator, matching though might be the other issue as you
mentioned.