Hi Richard,

Thank you for your reply and your interest in my homepage. I will answer
your questions between the lines.

I will use the remarks that I get to improve the content of the article on
my site.

Hi OM,

I especially like your coverage of your antenna from I3VHF.

On your second page, unfortunately, you have some misconceptions about
loop antennas.

All antennas exhibit the same noise characteristics. If you erected
a conventional (electric) dipole in the same space, it would exhibit
the same characteristics.


I agree that they are electrically equivalents. However, my point is that
the magnetic loop has useful benefits over the dipole antenna for RX under
certain circumstances. I believe the magnetic loop construction will in many
cases deliver an acceptable signal at the receiver with less disturbances
such as atmospheric noise.

About external noise sources:

The loop is smaller (less surface) and therefore picks up less static noise.
The dipole covers a larger area in which there can be sources of noise.

The pickup loop that connects the coax to the loop antenna is isolated from
the antenna and it forms a shortcut for DC. The signal transfer is
inductive.

The magnetic loop tunes to the frequency and there is no external antenna
tuner needed.

About intenal receiver noise and mix-products:

The magnetic loop in itself is a band pass filter at the source of the
receiving signal. It eliminates strong signals outside the received
frequency. Therefore the receiver can receive the wanted signals with
maximum sensitivity. The band pass functionality of the loop protects the
radio from overloading. And as a result of that the radio will be quiet and
doesn't need to pick a weak signal from an overloaded band. The bandwidth of
the I3VHF is very small in the 40 m band. AM modulation is not possible as
the bandwidth of the loop is too small here for passing a standard AM
signal. The signal will be clipped and the transceiver react to that which
can be seen on the SWR meter. SWR starts to alternate on the rhythm of the
modulation. The bandwidth of the antenna gets larger in the higher bands. I
believe that in the 40 meter band the I3VHF only lets trough one frequency
in SSB. The receiver is almost mute tuning higher or lower.

As for receiving the readability is more important than signal strength. The
lower RX signal from the magnetic loop is often more readable than when
using a full size dipole at ideal height. I think that the advantages are
best in the Low bands, e.g. 80, 40, 30 meter.

For TX there are advantages of the magnetic loop over the full size dipole.
When one has shortage of space. The high small band pass filter that the
Magnetic Loop is, makes the radiated signal free of harmonics. Therefore
there is a smaller chance of rfi to be expected .

Maybe some of the points here are not based on solid scientific research.
But it is what I found doing experiments with the loops.

It is quite curious how you describe a front/back ratio for a dipole
(the loop is a magnetic dipole, and as such "should" show a
conventional dipole pattern).


The data is based on the specifications of the manufacturer of the I3VHF
loop antenna.

http://www.ciromazzoni.com/English/L...oop%20Baby.htm

In the manual, page 42, 43 there is a picture of the radiation pattern:

http://www.ciromazzoni.com/English/L...nna/Manual.pdf

It also surprised me as I expected a dipole pattern.

As for loop efficiency, you state:
"When a magnetic loop antenna is used for
3.5 MHz with a perimeter of 4 meter (13.3 foot) ,
it has an efficiency of approximately 3%."
Please show the math.

The 3 % efficiency is hypothetical based on the outcome of calculations
software that is available on the Internet.

For example the loop calculation software of G4FGQ.


73's
Richard Clark, KB7QHC

Best Regards,

Norbert , PA7NR