US 2990 240415 - Trying out my home-brew Magnetic Loop Antenna!
ฝัง
- เผยแพร่เมื่อ 1 พ.ค. 2024
- POTA activation at Blanco State Park
Radio: Elecraft KX2
Antenna: Homebrew Magnetic Loop Antenna
Key: Elecraft KXPD2 Precision Keyer Paddle
This wasn't the first time I'd used my freshly built magnetic loop, but it was the first time I had taken it to a park. I'd done some playing around with it in my home and on my back porch. The design is relatively simple: an aluminum strapping inner loop and SO-239 supported by a PVC pipe; an electrical junction box from Amazon; An air-variable capacitor I had picked up at the Belton Ham Fest last year (since replaced with a 365+365pF Dual Gang air variable - this provides wider range) and a reduction drive to make fine tuning easier; and some LMR-400 coax I bought from ABR. I feed it with a choked 10-foot length of RG-58, also from ABR. Great coax! I've only made one internal loop, but two external ones (second not shown in the video). With the single loop, I can tune 40-12 meters, and if I add the second loop, I can tune 80-20 meters, all with acceptable performance! I need to do some more modification to see if I can get it to tune up on 10 meters, since it won't quite tune that high in its current configuration. I'm not sure yet if the modifications will be to the internal transmit loop or the out radiating loop, or both.
To use a mag loop is simple, although because of high amperage at the transmit loop and the high voltage at the capacitor, I recommend exercising caution! RF burns hurt! First, disable the internal tuner on your radio, if you have one. Second, adjust the variable capacitor until you have an increase in band noise (heard but not shown at the beginning of the video). Third, fine-tune with very small movements to get the best SWR you can. I achieved step three using the "Tune" function on my KX2, which is configured to output one watt while it displays the SWR on the screen. Alternatively, one can use an antenna analyzer or something like a NanoVNA to confirm your SWR before transmitting with your radio. The KX2 is designed to handle this situation; I'd use an analyzer with any other radio I own.
I've got to say - I was pleasantly surprised with how the activation went! Once I was spotted, it wasn't long before I succeeded in getting my first ten contacts (not all QSOs are shown in the video), then went on to get several more over the course of a couple of hours. Lots of fun! My only complaint is that this antenna doesn't lend itself to easy hunting - it's better for a set-and-forget (read: twiddle periodically) scenario.
One tip - bring a compass with you, so you can determine the directionality of your loop (nulls on the broad sides) relative to your location. While I was able to get spotted fairly well all over, I did notice a vast difference in the quality of the signal based on the direction of the antenna.
All in all, this was a fun and educational project, which was much more involved than building and tuning a simple wire antenna - it required more trial and error than some other antenna projects I've tried. I used the ARRL Handbook and Antenna books for reference, as well as an online article called "The Optimum Magnetic Loop" from w6nbc.com, as well as several other research pages.
73 de AI5LC
Congratulations on your antenna constructions!! Bravo!! It was nice to hear your contacts. Have a great day! vy 73 de David AE4LH
Thanks and 73!
When are subtitles available? Will they be in English and Morse?
Hello! I haven’t done subtitles since there is no speaking. I’ve thought about doing Morse subtitles, but part of my learning experience was to listen to Morse code without any subtitles, which I found very helpful.
@@HamRadioTX ....it was a joke but ok ;p
Oh, lol! Now I get it! :)