The K9AY receiving loop antenna

Not to take anything away from Gary Breed, K9AY, who makes and sells these things under the corporate name AYTechnologies, I decided to make my own K9AY antenna system and controller.  Basically, after looking at the currently available commercial version, I figured I could make a better unit for less money and be happy.

The basis for the K9AY antenna is that it has a steerable null.  The gain around the antenna is close to unity, except for the terminated side of the loop, which has a deep null.  This can be switched around using a combination of relays that change the loops and termination.  This comes in very handy for MW and SW listening, when co-channel stations can create annoying interference and hetrodynes.  I have had good success pulling many stations out of the muck, especially in the AM band using this antenna.

This antenna requires a good ground to work against.  For optimum installations, I would recommend placing two radials under each side of the loops.  This will keep the ground conductivity below the antenna fairly constant, thus the value of Rterm will remain consistent for each band.

My other idea is to add a preamp right at the antenna to overcome transmission line loss and the loss from a 4 port passive receiver coupler.  Something around 10 dB, low noise (obviously), low parts count and rugged.  I decided that a Norton preamp was a good design, with only one active device, a common 2N5109 BJT.  Most of the time, this preamp is switched off and out of the circuit.  There have been several occasions, however, where an extra 10 dB made the difference between no copy and good copy.

This is the schematic of the relay board and preamp combined:

K9AY antenna controller with preamp
K9AY antenna controller with preamp

The parts list is as follows:

Symbol Part Symbol Part
C1 – C5 Ceramic 0.1 uf capacitor R1 2 Kohm ¼ watt
FB-1 Ferrite bead, Amidon FB-43-101 R2 8.2 Kohm ¼ watt
K1 – K3 Omron G6K-2F-Y small signal relay R3 100 ohm ¼ watt
L1 22 uH ¼ watt R4 51 ohm ¼ watt
L2 100 uH ¼ watt T-1 9:1 balun
Q1 2N5109 w/heat sink T-2 Norton feedback trans

The 2N5109 transistor is a CATV unit and it has a 50 input and output, that reduces the number of impedance transformers required. The value of Rterm is determined by which band one wants to operate on.  I used Omron G6K series low signal relays.  Again, because this is a receive only antenna, those relays will work well.

Terminal board connections, TB1:

Terminal Use
1 SW loop
2 SE loop
3 NW loop
4 NE loop

Wire loops go between Terminals 1-4 and 2-3.

Control terminal board connections, TB2:

Terminal Use
1 Preamp power
2 Rterm
3 Rterm ground
4 Ground
5 Relay 2
6 Relay 3

To create a low noise preamp, I decided to use surface mount devices and to try and make all the traces as close to 50 ohm impedance as possible.  I created this SMT printed circuit board:

SMT K9AY board, not to scale
SMT K9AY board, not to scale

From this, I ordered 6 boards from PCB express:

K9AY PCB
K9AY PCB

This is the board with all passive components installed:

K9AY loop antenna control board partial
K9AY loop antenna control board partial

This is the board completed:

K9AY antenna control board completed
K9AY antenna control board completed

My current K9AY is an amalgamation of parts removed from various equipment.  The relays are large, 12 VDC units which do not have the best contacts.  It works well enough, but I’d love to get one of these units into the control box at the base of the antenna.  Unfortunately, my antenna field is still in about 18 inches of snow, so it will have to wait until some of the snow melts off.

I would position this antenna as far away from transmit antennas as possible to avoid overloading the preamp and or causing problems with the switching relays.  For the average amateur set up, 75 to 100 feet separation should be more than enough.

ABC turns to HF during tropical Cyclone

Super Tropical Cyclone Yasi, a category 5 storm, came ashore this morning between Cairns (pronounced Cans) and Townsville, Queensland around midnight Thursday (9 am Wednesday, NY time).

Tropical Cyclone Yasi, February 2, 2011
Tropical Cyclone Yasi, February 2, 2011

Radio Australia carried Australian Broadcasting Company (ABC) Queensland coverage of the storm, which was extraordinary.  Spot coverage, emergency information, sheltering information, updates and calls from listeners in the midst of the storm.  Some of it is pretty intense.  One fellow, John, out in the country all by himself in the height of the storm sounded somewhat forlorn, I hope he makes it.

Due to the size of the storm, wide spread power outages are expected and may last for weeks or months.  As a part of this, there are numerous outages and potential outages in their AM and FM broadcasting chain.  To that end, ABC has two shortwave frequencies available for their Queensland service; daytime (8 am to 8:30 pm local time, 2100 – 0830 GMT) on 9710 KHz and night time (8:30pm to 8 am local, 0830 – 2100 GMT)  is 6080 KHz.

Once again, HF (shortwave) radio gets the job done when local stations, cell towers, and internet connections to dead.  Sometimes it is the low tech answer.

Last Radio Playing

Sounds like some dire prediction, but no, actually it is a good radio show heard on Shortwave, WWCR-2 to be precise.  The show, at least during the weeks that I heard it, consisted of blues and other music that you likely won’t hear anywhere else.  Allan Gray, the host, also often interviews musicians and other persons of note.  I stumbled on this show a few weeks ago while listening to 12,160 KHz on Saturday afternoon. WWCR is touted as “World Wide Christian Radio” and there are many religious shows to be sure.  They also air several secular programs like World of Radio, Golden Age of Radio, DX partyline and Ask WWCR and Info Wars and others.

Allan Gray

From reading their schedule, Last Radio Playing can be heard on WWCR-2 Tuesdays at 5pm est (5,070 KHz) , Saturdays and Sundays at 3 pm est (12,160 KHz) and on WWCR-3 at 8 pm (4,840 KHz).  WWRC is located in Nashville, TN.  They have four Continental 418 HF transmitters with a carrier power of 100 KW each.  WWCR-2 uses an azimuth of 85 degrees true and WWCR-3 uses an azimuth of 40 degrees true, both into Rhombic antennas with 14 dBi gain.

Today the show consisted of Christmas Music, which on the AM wide band receiver, sounded pretty good.  Anyway, if you are so inclined, tune in and take a listen.