Resonant Loop Design Info

[jFarley]

I have completed and posted a package of information which provides some information which could be used to build a high performance loop for HF.  I have uploaded that here:

http://www.mediafire.com/?1d8ov7bb72ja18x

This is an .RAR archive of schematics, images, and a readme in .RTF format.  You will need an .RAR de-archiver to open this, and there are plenty of free downloads available.  I use 7-ZIP.

This is not a step by step construction article.  At some point in the future, I hope to do that, most likely as a series of posts in the 30 Below Blog.  There I would like to blend the construction details with some of the underlying theory and have everything in one place.  For now, this will get some guys going.

I would like to ask the following:  please address any comments, questions, or error reports to me via PM or my public email.  I will get back to you ASAP which generally means later in the same day.  I would like to keep this thread clean without cluttering up the place, so I have locked it.  I have already created replies for FAQs and Errata which I will update based on any private feedback.

Many thanks, and happy building!

[jFarley]

FAQs

13Aug13

Q: What is the tuning range of the loop?

As described, the loop tunes from approximately 2400-7800 kHz.  Best performance is 60M and above.

Q: Can the tuning range be changed?

By adding turns turns or by increasing the size of the loop winding, the frequency range can be lowered, and vice versa.

Q: Can I get the schematics in .PNG or .GIF form?

They have been uploaded, and here is the link:  http://www.mediafire.com/?5hmfdoqj03f6z8v

Q: Can this loop be used at higher frequencies?

Yes, my recollections tell me that I have made loops for up to around 18 MHz, with poor performance.  But hindsight tells me that this was almost certainly due to the loops having poor loaded Q, and that it easy to fix.  Such a loop would use the same amp and power supply as the loop detailed in the Package; only the winding needs to be different.  I have run some numbers and have come up with the following as I would like to give one a try against 19 meter Euros:

The winding would be 2 circular turns of 1/4" soft copper refrigeration tubing, 14" in diameter, with a 3" gap between the turns.  An appropriately sized  frame could be built as described in the readme file in the Package, except that stubs for the wires would not be required.  The tubing could simply be cable tied to the Tee and Cross fittings through a couple of holes.

The winding should have an inductance of about 2.1 uH, and the loop will have a projected tuning range of 6800 to 24000 kHz.  Plus or minus.

Loaded Q at 15000 kHz should be around 735, giving a 3 dB BW of around 20 kHz.  The Effective Height of this loop should be around 46 meters, and the absolute output and sensitivity of this loop should be very good.  If the loop were made from 1/2" tubing, the loaded Q at 15000 kHz should be around 800, giving a 3 dB BW of around 18 kHz, and an  Effective Height of around 51 meters.

In either case, the FOMP (ability of this loop to nuke local QRN) would be around 0.11, which is a very good figure.  By comparison, at 15000 kHz the FOMP of a typical SML is about 0.24.

In the interests of accuracy and honesty, this question was a selfie...

[jFarley]

Errata

no doubt there will be

[Zane]

I will use my mod powers make a few unscientific comments.

While I don't have a lot of experience with a great variety of antennas, I encourage those interested in this one to give it a try. It will be well worth your time. Joe has done a really good job with this design. He'll quickly tell you that he's stood on the shoulders of others, but I think this is one fine antenna.

On strong signals, say S8 and above, I think that it's pretty equivalent to my Ewe. The Ewe gets its benefits from being a relatively quiet antenna, so I've been able to hear way more with it compared to the simple antennas I tried originally. However, when it comes to weak signals (like trying to hear Euro's from the Midwest), this loop will hear things that I'd never have a chance with otherwise. All this and it takes up very little real estate too.

Well done Joe!

Z

[jFarley]

13Aug13

FAQs have been edited.
Thank you, Z!

22Aug13
FAQs have been edited.