More info on the K9AY loop

By Al Merriman
hcdx list, July 10-11, 1999

Some answers to questions about K9AY Loops:

Single Loop. 
If you only wish to cover one or two directions a single loop will work just fine. 
When I did my initial testing with these antennas I temporarily hung a single loop from a tree in the front yard.   

Matching transformer. 
Per the original article and per my experiments a 9:1 transformer works best, at least for coverage of long and medium wave. 
Claims have been made by others that a 4:1 transformer will provide marginally better signals on short wave, but it has been my experience that the 9:1 works well there also. 
If you live in an isolated and extremely quiet area with no local close in noise sources such as televisions, computers, powerlines, your neighbors light dimmer, etc the transformer described in the original QST article will work well. 
If you're like most of us, and don't have that luxury, I would suggest a "magnetic" type transformer, where there is no direct connection between the antenna and feedline. This can make a real difference in minimizing local noise pests. 

Information on transformers of this type is available from the National Radio Club reprints.  Their reprint A69 "Noise & Interference Reducing Antennas" is available from: National Radio Club, Publications Center, P O Box 164, Mannsville, N Y 13661-0164, USA.  
Price for members in USA/Canada is $1.50; non-members USA/Canada $2.00, and all other countries $2.20 via airmail.

Patrick Martin: Do K9AY loops work as well as an EWE antenna? Are they as directional?

Al Merriman: Beyond reading two articles about these in QST and a bit of hearsay concerning their performance I have no experience with the EWE antennas.
In what I've written I've stated several times that F/B nulls approaching 40db are common with the K9AY's - does the EWE do this well?
One thing that I've heard several times about the EWE is that their performance is affected by slight changes in ground conductivity such as during rain, etc. If this is true - and I don't know that it is - this is one area where the two systems are radically different as the K9AY's require very little in the way of a ground and are not affected in the least by rain, etc - at least as far as I've been able to tell in a year of use.
To get max performance from the EWE I'm sure you would need a remotely tuned variable termination which should be fairly easy to implement using the twisted pair wire for the antennas like Steve Byan uses with his beverages.

Patrick Martin: Do you point the antenna in the direction you want to receive, or is the input pointed in the direction you want to receive?

Al Merriman: Main pickup by the K9AY's is from the feedline end towards the terminated end - just the opposite of a terminated beverage.

Patrick Martin: Do you have a length that works the best for MW?

Al Merriman: Per the original article antenna length should be "not much more than 1/4 wavelength at the highest frequency of interest".
This means that antennas up to 150 feet in length - and maybe just a bit more should give full LW/MW coverage including the X-band as a full wavelength at 1700 kHz is almost 600 feet.
My loops are 90 feet in length and with a 15db preamp give signal levels comparable to my slopers that are approximately 60 feet high at the high end and 150 long.

For those in Europe who are interested in these antennas, but do not want to build their own, Andy Ikin of Wellbrook Communications has these for sale. Andy can be reached at
aikin@globalnet.co.uk  

Wellbrook has a firm policy of no sales to North America.  I'm not sure what the current policy is to the rest of the world.  You can contact Andy for availibility and price and if you do so I would appreciate it if you would mention my name.