A few questions on your coupling loop. I have built a few mag loops and researched most of what information I could find on them. Most of all that I have read uses a Faraday loop for coupling and it is mounted at the bottom, both of which were done for the maximum performance of the loop. I noticed that both you and Alex do not use a Faraday loop (just straight coax) and have the whole loop antenna inverted from the original designs which have the capacitor at the top and the coupling loop at the bottom. I understand the mechanical reasons for this inverted design, but is there a trade-off in performance?
Speaking of which, I think I saw in your video a vertical antenna in the background. Have you done a A/B test between it and your loop?
I built a loop (same diameter as yours) using 19mm (3/4 inch) copper tubing and had it outside up at about 6 meters for two years. During that time I also had a 15m dipole, a 90 foot Broad Band Folded Dipole, and a 44 foot doublet fed with 28 feet of 300 ohm twin lead to a Elecraft T1 remote tuner (not all up at the same time) at roughly the same height. Not too many times in the 2 years of A/B testing did I find the loop to be better than or equal to the other antennas on 20m - 10m. I should also say that before I started building the mag loops I did have a MFJ-1789 (Magnetic Loop) which I found performed pretty much the same as the ones I later built.
I also have a portable loop using 9913 coax and a Faraday coupling loop. While this loop does out perform small antennas such as my Miracle Whip, PAC-12, and HamSticks, this year for Field Day I also used a home made EFHW (End Fed Half Wave) with coupler on 20 meters and it noticeably out performed the loop. That being said, for a 1 meter tall antenna that only needs to be maybe 2 meters off the ground I would say that it's the best in that size and pretty hard to beat so maybe that is what makes it so popular.
So I guess my two questions would be: Have you compared the Faraday loop vs just a loop made from RG-58 (or heard any Pro/Con about the two), and have you compared your loop antenna A/B wise to any other antennas?
I loved your trees in your video by the way
73's
de George
WD0AKZ
Faraday Coupling Loop
Re: Faraday Coupling Loop
Hi George,
I've tried several types of coupling loops, including Faraday with variants and I've seen no difference between them.
Considering the simplicity, at the end I decided to stay with a simple loop which can be made from plain copper or coax.
I am not aware of any downfall of mounting the coupling loop on top.
I don't have any HF vertical antenna in that location, but comparing the ML with my 80-40-30-17-15-12-10m Carolina Windom antenna mounted on top of a 8 floors concrete building(normally connected to my WebSDR server farm), the S/N ratio is in the favor of the ML. On the other side the received signal level is lower by 1-2 S on the ML.
The MFJ ML does not offer a higher performance than a cheap home build ML. You pay mainly for the automation part.
Regarding the trees, I will update the movie next springtime
Thank you for your feedback and best regards,
73 Dan YO3GGX
I've tried several types of coupling loops, including Faraday with variants and I've seen no difference between them.
Considering the simplicity, at the end I decided to stay with a simple loop which can be made from plain copper or coax.
I am not aware of any downfall of mounting the coupling loop on top.
I don't have any HF vertical antenna in that location, but comparing the ML with my 80-40-30-17-15-12-10m Carolina Windom antenna mounted on top of a 8 floors concrete building(normally connected to my WebSDR server farm), the S/N ratio is in the favor of the ML. On the other side the received signal level is lower by 1-2 S on the ML.
The MFJ ML does not offer a higher performance than a cheap home build ML. You pay mainly for the automation part.
Regarding the trees, I will update the movie next springtime
Thank you for your feedback and best regards,
73 Dan YO3GGX
Re: Faraday Coupling Loop
Thanks for your reply Dan..
"I don't have any HF vertical antenna in that location, but comparing the ML with my 80-40-30-17-15-12-10m Carolina Windom antenna mounted on top of a 8 floors concrete building(normally connected to my WebSDR server farm), the S/N ratio is in the favor of the ML. On the other side the received signal level is lower by 1-2 S on the ML."
Yup, I was also seeing much better S/N but 1-2 S-Unit lower on the ML's. I have chatted to a number of folks that built/use ML's but very few of them ever have the ability to do a A/B comparison to anything else. I was thinking that maybe my loops were for some reason sub standard.
But as I said in my previous post, for it's size I don't think there is any other antenna out there that will beat the Magnetic Loop.
I'll be watching for trees next spring.
73's
de George
WD0AKZ
"I don't have any HF vertical antenna in that location, but comparing the ML with my 80-40-30-17-15-12-10m Carolina Windom antenna mounted on top of a 8 floors concrete building(normally connected to my WebSDR server farm), the S/N ratio is in the favor of the ML. On the other side the received signal level is lower by 1-2 S on the ML."
Yup, I was also seeing much better S/N but 1-2 S-Unit lower on the ML's. I have chatted to a number of folks that built/use ML's but very few of them ever have the ability to do a A/B comparison to anything else. I was thinking that maybe my loops were for some reason sub standard.
But as I said in my previous post, for it's size I don't think there is any other antenna out there that will beat the Magnetic Loop.
I'll be watching for trees next spring.
73's
de George
WD0AKZ