[IRCA] Broadside array testing gives me a GY DX record KGGS 1340 (long)

[neilkaz <neilkaz@xxxxxxxxxxxxx>]

My 10 pm CDT Perseus recording last night had a nice surprise for me with, "Brought to you by the Kansas.....Big Dog Sports AM 1340 KGGS..." ID and then into Fox sports (I think was same stn) poor but atop. KGGS in Garden City KS came on the air in Nov 2011 and is about 735 miles from here. 

Broadside means that the array elements are side by side and facing the same direction. My two Double KAZ (Double Delta) face due west and are separated by 260 ft. Each antenna is 120 ft long with the two apexes 23 ft high and the bottom wires 2 ft above ground. Here's a Bill Whitacre drawing of the basic idea for a single one.
http://realmonitor.com/BH/DKAZ_2_sizes.pdf

Why space two cardioid loop type antennas side by side? Two reasons: 1) to make the array beamwidth more narrow. 2) To get better side nulls from the array. If you place two antennas side by side a half wavelength (at the incoming wave angle) apart, in theory the resultant array pattern has perfect side nulls. Of course, this also creates a nice narrow main beam. As you go farther apart than 1/2 wavelength, the main beam will become even more narrow but at the expense of side lobes which can become large.

Of course, 260 ft is too close for major side null improvements except for the upper BCB, but it is all the room I have here in Barrington. Top banders take note that this would be a nearly ideal spacing for 1900 KHz. A good compromise for the entire BCB would be about 400 ft spacing. (Wider would still be better for the low end, but even at 400 ft, the X-band will be suffering somewhat from some side lobes for ground wave and low angle skip.)

OK so lets see how performance is improved vs using a single element and noting that with this close spacing the real improvement is for the high end. Daytimes 1690 WVON to my south is definately reduced with the array and similarily WKSH 1640 to my north is reduced. At night the effect is less, since there's some high angle skip from these two and at that high angle of incidence, 260 is close so I have nothing close to 180 deg phase difference between the two antennas. But for 1680 WRJO at night which is low angle skip, I get a nice improvement in side nulls, often leaving Iowa TIS's almost alone. 

On 1340, the freq of interest for my new catch, the calculated array pattern shows a beamwidth of a bit less than 70 degrees for the array (15 deg above the horizon) vs about 100 deg for a single element. This should result in significant improvements. Daytimes, both Joliet to my south and Milwaukee to my north are reduced enough to allow KROS to be mostly dominant. This is in constrast to a single one where KROS is still in there but not dominant and also better than I've ever had with any BOGs which I think have beamwidths in the 75 to 80 deg range. When ever I can narrow the beamwidth of my antenna systems, I get better DX. Sometimes it seems like all the same stations come in, but many of these stations are almost never reported by nearby DXers and once in a while something really nice sneaks in.

The resistor terminations are good enough on each antenna to pretty much kill any back end regional or GY signals leaving me with a nice narrow beam towards the west. Similar effects are noted all over the upper half of the band with many regionals and GYs from IA,MN(mostly southern) KS,NE, SD, and some ND and MO. Colorado regionals also come in as does CO on 1510,1530, and 1580 on night powers. There's simply less side QRM when I use the array vs a single antenna, and even lower down in the band I can tell there's at least slight difference. I've yet to break the GY wall and get into CO/WY/NM or MT but hopefully someday, although May certainly isn't the best time for long distance DX to the west from here.

A DXer not interested in just a specific frequency could use a phasing unit to put a deep null off one side or the other and steer the beam a bit. The beam is wide enough that steering won't help much, but phasing a 40dB+ null could really clobber a pest from the side.

In summary and before I continue to describe a somewhat smaller array with more simple elements, I strongly feel that my testing this month has proven the concept of arraying two antennas in a broadside manner.

One could also array normal single loop type antennas, like the SuperLoop,Flag, Delta Flag (KAZ) or whatever as they are simple to build and broadbanded and not so critical of slight tolerances or signals coupling in from nearby wires and fences etc. 

A simple broadside array of two Delta Flags could be built on a good sized suburban lot and perhaps cheaply using a tree for each support. A typical Delta Flag has a 138 deg beamwidth and 5.5 dB front to side ratio. This means that while stations from the back side are nicely reduced, stations from the side can still be major pests.
Here in the RF jungle that is the midwest, it is difficult to get GYers with much clarity when the BW is the wide since too many are coming in at once.

Here's some calculated measurements for a simple broadside array of two DF's spaced 225 ft that could fit into some good sized lots. You'll see how performance improves across the BCB as frequency increases. 

600 KHz BW 121 deg F/S 6.5 dB ... 900 KHz BW 108 deg F/S 7.5 dB ... 1200 KHz BW 93 deg F/S 9 dB ... 1500 KHz BW 80 deg F/S 11 dB. This simple array would allow one to make an assault upon the GY DX records list and to get all sorts of rare upper band stations. Of course at about 400 ft spacing, beamwidths would be considerably more narrow and a superb antenna system would result. If you have less side by side room even at close at 150 ft could help out the upper band somewhat vs a single antenna.

For much of the winter season, I tested an end fire array (in line) array of two Double KAZ elements aimed 285 deg which I could just shoe hammer into my field. Results were superb with often improved F/B and null aperture and beamwidths just under 80 degrees from my calculations and observations which seem to be about the same BW as BOGs. However, my DX was clearly better with the array than I'd ever had with the Phased BOGs. Some of this is because F/B is much more broadbanded so I can record much of the band, but some is also because patterns were cleaner with fewer extranious lobes. As an example, over nearly 20 years and with many antennas favoring the WNW direction I'd spent hours in good cx on 1590 trying for KLFE from Seattle without success, but on the endfire array they were reasonably common! Similarily, I never expected to get KCLK 1430 from WA late at night a few times. I took down my endfire array to make room to aim due west for the broadside array testing but!
  expect it may reappear for fall SSS. 

Dallas Lankford has done some superb work with endfire arrays of Delta Flags and is to be thanked for developing this concept and expanding upon it with his superb QDFA. I didn't try to build a QDFA since I don't have room for 4 endfire elements here in Barrington and since I don't feel that I have the ability to build the circuitry and hardware required, but for those who have ample room and can build circuits better than I can, the QDFA would be tremendous. 

I simply make do with the hardware and space I have available and strive to improve my DX, and hope that others can expand upon my experiences and improve their's.

I'll close in again stressing that improved directivity will improve anyone's DX, especially domestic DX on crowded channels.

73 KAZ Barrington IL







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