VA3ROM's blog

I use Glenn's, KI6GD's, excellent "Magnetic Loop Calculator" (I have v1.4, 2009) to help in the design and experimentation with small loops. For 20m, here are the numbers (the program works with either Imperial or Metric units and various materials and shapes (copper, aluminum and shapes round, square and octagon) all which will affect the final product. Note: According to my ARRL Handbook, Belden RG-213 has a rated breakdown voltage of 3.7kV (RMS) and at the 50 watts operating power level the capacitor voltage is 3.3kV.

A few years ago, I wrote a couple of articles on modifying and using WA8LMF's 30m magnetic loop design. I've re-edited and put them on my website. If anyone is interested, you can download the ZIP file from here: http://tinyurl.com/cevk44m.

73,
Robert

This is the copper tubing magnetic loop that I'm testing outside. Since it has a stand, it's easier to set or move around and move stable in wind over the MFJ-933 tuner/wire loop. The 12.5mm (1/2") diameter copper tubing is wrapped in high-voltage rubber tape (60 kV) just in case someone were to touch the loop when it was transmitting! The copper look is 3.03m (10') and in inner, inductively coupled drive loop is 0.606m (2').

Well, finally got my Flex-1500, VAC and WSPR software working togetther (TX/RX/PTT and CAT). Had to setup the CAT as a Kenwood TS50 to get that to work.

Amazingly, my indoor magnetic loop antenna is doing a very good job for TX/RX with the 4m of #10 wire and MFJ-933. Will have to try the home made 12.5mm 3m copper tubing and coax capacitor tuning stub to see which one performs better. Since both are side by side, it's easy to switch between the two and make fairly comparative tests.