Air capacitor vs plastic capacitor


Max Italy
 

Hi, i used for my 40x40cm air loop a cheap plastic capacitor ($1 on Aliexpress) and it works great. I have always seen using air capacitors, except in some low cost commercial loops like the Tecsun AN100/200 so i wondered what kind of improvement it could give to my antenna and i purchased one, it 's actually a 2x365pF but i used only one section for testing.
I did a comparative test, both capacitors had a RCA jack to quicky change from one to another.
Result: although i heard talking about Q factor of capacitors i did not find any difference in the reception. There may be differences at higher frequencies, who knows, but not on MW. I may try to make more tests with more critical conditions like a strong signal on an adiacent channel.

I wonder if someone has done the same test with high Q FSL. Tests is what i look for because theory not always gives the real dimension of the problems.
If they work the same way of an air capacitor it is a big save of money, not just to make one FSL antenna but for all the experiments where you do not want to buy more or pass the same capacitor from one antenna to another.

Also it would allow to put two of them in parallel with the second one of low capacitance like 15pF for fine tuning (most of them have the FM section with low capacitance).

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