Testing the Hi-Voltage Capacitor on the Magnetic Loop Antenna

I did some preliminary testing of the Hi-voltage capacitor I completed last week and found some interesting things.Rather than commit the 40m loop design I decided to try and adapt the existing loop antenna I have previously described. To make this work in a configuration similar to what I have in mind with the 40m loop, I installed the capacitor at the top and used a toroid instead of the shielded coax loop for the coupling at the bottom of the loop. To do this is needed to replace the vertical PVC supports to accommodate the configuration. The reducer I used for the 1/2″ pipe on the 40m loop was replaced with a 3/4″ version. This configuration worked well. The capacitor is in the range of being able to tune this loop on 20m. Previous experiments indicated a good match with 5 turns on the FT140-43 toroid. It turned out that 6 turns would give me a perfect match 1:1 SWR at resonance. Here is the SWR plot on 20m.

2016-10-04_9-34-06

The  bandwidth at the 2:1 points measured at 45kHz. This compares favorably to the original capacitor which was indicating a bandwidth of around 68kHz. This indicates that the Ohmic losses are indeed lower and therefore efficiency should be higher as well.

I did not have enough time this weekend to run all the measurements I had planned but I did operate the antenna indoors at 45W with the FT-817ND and amplifier.The Califonia QSO party was underway and I made numerous contacts in California without difficulty with this loop. The capacitor handled the power without any issues at all!

 

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2 responses to “Testing the Hi-Voltage Capacitor on the Magnetic Loop Antenna

  1. usingnestineurope December 10, 2016 at 1:08 pm

    very interesting write up,
    out of curiosity, which state were you transmitting from please for those contacts with California?

    Like

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