Low band RX antenna : Flag K6SE shortened

Hi all,

While going on workign on the filter + preamplifier, I wanted to post here the RX antenna I plan to build for 40/80m...
This is highly inspired from K6SE flag antenna, but I wanted to make it shorter to see how are impacted the over-all performances.

Original size is 2 meters high * 4 meters long, and provides the following results (with nominal 850 Ohm terminated resistor)






































I decided to shrink the antenna into a 2 * 2 meters footprint...
On 80m, gain decrzeased from -31 down to -36dBi, where on 40m, it decreasedd from -21 down to -26 dBi.
OK, that's only 5 dB difference (less than 1 S-meter point, which is acceptable for an antenna that is 2 times smaller.

Playing on the terminated resistor, here is what I get:



























The best trade-off is obtained at R = 720 Ohms, with whom I got 23.3 dB F/B on 80m and 22.3 dB F/B on 40m.
In terms of gain, I got respc -36.5 and -26.5 dBi on 80 / 40m.

In terms of radiation pattern, they are very similar to the "full size" one...
Here is what I got with the small footprint :








































I'll certainly have to play on the resistor value "on the filed" to optimize the F/B, but I believe this gives a good over-view of what can be acheived with such a small loop..

I will also to think of an ipedance transformer, since the impedance of the shortened flag is close to 750 Ohms (Which is a bit lower than the 900 Ohms of the original version)..

Ronan