|
Kurt Loken
¿ªÔÆÌåÓýHello Jerry, There is more to this capacitor than meets the eye...but at its basics it is indeed controlled separation ?as a tuning mechanism...but dialectic choice is very important. ?Your formica dialectic wouldn¡¯t work too well, I¡¯m afraid. ?I once tried to make a loop something like this using a playing card as a dialectic and it didn¡¯t work out too well. ? I learned about dialectic loss tangent after than experience. One way you can tell that you have big losses in a mag loop is that you will have trouble getting a coupling loop to give you decent SWR without it being much larger than the typical 1/5 circumstance of the main loop...or you will need to make it a squished down oval close to the main loop. ? This antenna I show does have some loss, more than a several hundred dollar vacuum variable would give, but it is not too bad for my needs or most people¡¯s needs I suspect. ?This antenna has a bandwidth of less than 40 kHz at 20 meters. ?Teflon is your friend. There is no soldering allowed in my design. ? ?The dirty secret of copper tubes is that everything inside the skin depth is a waste of money. ?My strip of copper here has more surface area than what is typically used by folks making it out of tubes...and it is easy to collapse. The cap I show is actually breaking my long term rule for this loop. ?In my loop no metal other than the main loop and coupler is allowed above the feed point, but I am using metal push to fit connectors for my Teflon tuning drive in this prototype. ?I will 3D print these in the next prototype.? The map I show of my WSPR receipts were from inside my house with the loop sitting on my kitchen table. ?But yeah...I¡¯m sure others could do better.? Kurt On Dec 21, 2019, at 3:12 PM, Jerry Gaffke via Groups.Io <jgaffke@...> wrote:
|
