The rotatable Flag at HC1PF
Just reduced the dimensions of the original carried from Italy
The original W7IUV rotatable flag, that has been used in Italy for many years (see here) could not fit where I wanted to install, on a 2 inch
20 foot high steel tube, far enough from the TX antenna. So I decided to reduce the dimensions and the weight.
As I said several times, pennants and flags “want to work” and their dimensions are not critical at all, provided we keep, more or less, the same relation between the sides.
The lobe and the F/B is still the same but, of course, the smaller capture area produces a reduction in gain or, better to say, increases the negative gain by 5 dB, as shown in this Eznec plot:
Going from -30 to -35 dB is not a problem for a good preamplifier. (I am using the J-310 source follower cascaded with the BF981 variable, both by KD9SV).
These are the reduced dimensions:
Horizontal wire: 6.63 m
Vertical wires: 3.21 m.
Load resistor: 900 ohm
Xfmr: 2/8 turns on binocular BN73-202
That’s me installing the flag.
My reference South point is the Cotopaxi
5.897 m. high, at
50 km. distance.
This is the screen shot on the SDR-IQ showing the signal of the 1.843 oscillator at one wavelength distance with the flag pointed towards it.
And this is the same with the flag pointed on the opposite direction: the 1.843 oscillator signal is down in the noise, thus with at least 20 dB of Front to Back.
This is the rotatable flag completed, high enough above the electric fence: five turns of wire, each 183 m. long – like been inside a 5 turn coil at 10 kV pulsing voltage !