LW/MW Loop : Self Resonance Measurements

20181209 :
I added an improvised electrostatic shield on the multiturn loop. Simply some kitchen aluminium foil wrapped around the loop (yes, with the proper gap) and connected to the coax shield with a test cord with alligator clips.

This is a simple test, and shows a considerable improvement of noise performance for the loop, both on the LW, and also on the MW band.
NDBs (navigation beacons) started showing up in the 250 - 500kHz band, some noise disappeared from long wave broadcast stations, and the noise level on MW is considerably lower, even with the antenna still indoors. I expect the noise level to reduce further when the loop is placed outdoors, 10 - 20m from all noisy houses.

A new MW evening propagation test is planned for tonight.

A mechanically improved shield will be made. I have some copper tape, sold as snail repellant, that will be wound around the loop and connected to the coax shield.

The loop design is now beginning to take shape, and when a cheap LNA capable on low frequencies arrives in some weeks. I will test this and, if necessary, build it into the connection box of the loop, along with a bias-tee arrangement.

20181210 :
The MiniVNA Pro2 arrived this morning, and some measurements of the loop were made. Initially I could not get the Bluetooth system to work, so I used the USB port, and got it working.
With 10 turns the self resonant frequency of the loop turned out to be around 900kHz, somewhat consistent with the performance I have seen.
The test with 20 turns lowered the self resonance to about 300kHz, I estimate that to be due to a combination of the 4-fold inductance and a considerably increased stray capacitance between windings. This is also consistent with the performance I experienced when initially testing with 10 and 20 turns.

The electrostatic shield made very little difference to the self resonance, so it will be re-instated in the final version of the loop.

Next experiment : Reduce the number of turns of the loop to 5 or 6, and see how much the self resonance increases.