Dear Petr, at the input of my VLF-LF converter I have just a simple low pass filter with a cut-off frequency of about 80 kHz. This is sufficient even for a low-power mixer IC like an NE602 or similar
Hello all, Thanks all for your comments, it helps. I can't recall that anybody would ever mention the possibility to change serial connection of the coils of a variometer to the parallel one. If the
Hello Petr, 50-550kHz seems a "big shot". If you want to tune (bring to resonance) the antenna using a variometer it would need a ratio of (550/50)^2 = 121. The variometer I use on 500kHz has a range
Hello Ha-Jo Thanks for your suggestion. My transmatch woud be used mainly for RX, however, I still believe that a tuned antenna is better than detuned one. At least it is a good preselection for RX.
You can use a simple vertical LOOP made from one piece of HEAVY, well insulated wire and one vacuum variable capacitor... Advantages: No need of many wires dug into the ground to lose power No hoisti
Petr, you can use a Pi filter, but I am afraid that the values might become rather inconvenient: A short (relative to the wavelength) wire antenna will act as a R-C series circuit where C is the ante
And, by the way, the "sphere in sphere" variometer has a big drawback: Its Q is quite OK at maximum inductivity but very poor at its minumum. Explanation is simple. Just assuming the resistance of th
Hi all, I want to make a small transmatch (RX, TX up to 10 Watts, or so) to tune LW 41 m (or smaller T-ant) in the range 50 ... 550 kHz. I am not too good in theory... but I believe that the most eff
Dear Petr, I guess the easiest solution would be to seperate receiving and transmitting. For receive it is not necessary at all to tune the antenna. I am using my LF T-antenna for receive from 10 kHz
