Mike,

My point was not who likes or dislikes small loop antennas but for any antenna can be calculated or estimated the gain figure or its antenna factor.

During my dialog with well respected Martin he was doubtful about the antenna efficiency and antenna mismatch factors to be included in calculation of antenna. So by submitting various articles I showed that is not a concept being

Introduced by me but comes from antenna theory that is widely accepted by engineering community.

You personally like Chavdar’s parameters used in his work and published in his articles, well he frequently jumps from one subject to other. He introduced common base amplifier with low input impedance for small loop antennas but he did not explained why it was his better choice. Intuitively I feel the same, however, when I review Martin’s plots in his article about Broadband Amplifiers using small loop antennas as well as ?published Duffy’s articles about similar subjects- their choice would be 50 ohm input impedance receivers or even with higher impedances, probably expect frequencies below 1-2 MHz.

Regards,

Raphael

On Oct 31, 2022, at 12:37 AM, vbifyz <3ym3ym@...> wrote:

?Rafael,

The article is about a shielded tuned loop with a split capacitor matching to 50 Ohm.
30dB loss on 7MHz compared to a full size dipole is not bad at all for a receive only antenna. Maybe a problem for a quietest of locations - see my comment below on that.
Transmit is a different story, but I am not aware of people using shielded loops and split capacitor matching for TX.

I don't think parameters like loop efficiency and loop mismatch loss are suited to compare small loop RX antennas.
Personally, I like parameters Chavdar LZ1AQ uses in his work on small active loops: the antenna factor (the ratio of the preamp output to the field strength, 1/m units) and the noise floor expressed in field strength units (uV/m). Very intuitive.

Then there is the main reason we use loop antennas for RX - a deep null allowing to minimize some interference (local or DX). In the city and suburbs it improves the signal-to-interference ratio, and allows hearing signals which can not be heard with wire antennas. In quiet rural locations there is no such reason, and there is usually more room available, so small loops are not the optimal solution. If you don't like the poor antenna factor and low efficiency of a small loop, just use a full size wire.

If you are in a quiet but space constrained area, then a short active vertical may be a better solution, because of its higher antenna factor (compared to both wires and loops)? and lower uV/m noise floor (compared to an active loop).

73, Mike AF7KR