Dallas Lankford Antenna
References and the “Must have” Beverage myth
VE1ZAC March 29, 2012
Those of you that follow my little antenna projects know that I am a great fan of the work performed by Dr. Dallas Lankford, a retired math professor and long time BCB DX aficionado. Dallas has spent an incredible amount of time experimenting with low frequency receive arrays and documenting his results. Dallas used to host his articles at the Kongsford DX site ( here : http://www.kongsfjord.no/ ) , but now uses Yahoo groups to publish all of his articles for antennas, his many expert R390A calibration and modification notes and other DX oriented musings. The Yahoo group can be seen here : http://groups.yahoo.com/group/thedallasfiles/?tab=s You need to join the group to have unfettered access to his articles and papers which he devotedly updates on a regular basis as he learns new things, finds previous errors, etc.
Dallas can keep track of visitors on the group through the Yahoo tools, but he does appreciate hearing from anybody who does experimenting with any of his ideas. I for one, use many of his ideas in my receive antenna experimenting, and I am deeply in his debt for sharing his findings on how well his remarkable arrays work. Even though his designs are aimed at BCB, they scale easily to top band, 80 and 40M and even VLF band. My experiments can verify that there are remarkable receive gains to be had by studying this body of array experimentation. In my opinion, this is cutting edge information for the ham and non ham DX experimenter.
Over the years I have built my own workshop versions of his CBTF Norton amplifiers and Emitter Follower FET version PPL amplifiers ( super chargers, as Dallas calls them) quite successfully. I am fortunate to be able to quickly design a board in EagleCad and cut it on a homebrew CNC converted Sherline mill. However, Dallas’s designs can be implemented other ways successfully using dead bug techniques and will work quite well. Lately I have started a 4 square receive array build with heavy Lankford influence and needed a bunch of PPL amps and Norton amps. I started the project before I found out that Jack Smith at Clifton Laboratories has these products available. Jack is a top notch designer and experimenter. He has produced excellent commercial versions of Dallas’s designs and made contributions to their improvements. Clifton Laboratories can be found here : http://www.cliftonlaboratories.com/
I ordered one of his Norton amplifiers and was dazzled with how well it is implemented. Frankly, I will probably not waste my time building these things myself in the future ! Jack now has the Lankford PPL supercharger available as well, (he calls it a ‘Hi Z Buffer’) and again, it looks incredibly well implemented. If you were holding off implementing some of Dallas’s antenna designs because of these amplifiers, I suggest you look at Jack’s offerings. Jack sells these as kits or assembled. Some of the kits have more SMD parts than others, but are do-able with home shop techniques. If you have been holding off learning how to do basic SMD soldering, this might be the encouragement you need to jump in. It’s not that hard. ( Note, there are an excellent series of “how to solder SMD parts” videos to be found at the Spark Fun Electronics website, found here : http://www.sparkfun.com/ This is also a good source for all things in the Arduino world ). I believe you can also get assembled Norton amplifiers from Kiwa Electronics as well. They can be found here : http://kiwa.com/
Note, if you are in the Halifax area and want to visit my shop or see a demo of how a geezer like me can handle surface mount soldering, feel free to ask.
A big thank you to Dallas Lankford, Jack Smith and the keen electronic ‘smurfs’ at Spark Fun Electronics..you folks all make the experimental part of the radio hobby come alive !
If you haven’t looked at Dallas’s antenna projects yet, but are interested in highly effective, low cost and low footprint receive arrays, I urge you to study his work. Dallas has demonstrated beyond any doubt that you can build arrays of Flag based antennas, bogs or verticals that will work as well as a field full of long beverage antennas, and oftentimes better. Another radio myth is shattered… you DO NOT need all that space for Beverage antennas to have outstanding and competitive receive antenna arrays.
If you live in an urban area and have a modicum of space, there are receive arrays you can build which will knock your radio socks off, I promise you. In fact, your biggest problem may be tracking down and killing sources of RFI from power lines, plasma TV low band invasions, unfiltered variable frequency motor drives and other nasty radio reception killers. I will be writing another article about my adventures with RFI suppression ( all successful accept for the plasma TV issue which has become very political). Watch this space !
Last year, with the usual inspiration I get from reading Dallas Lankford’s material, I experimented with a dual vertical array. This system has two 15 foot verticals , spaced 60 feet apart, with 10:1 transformers feeding speaker wire feedlines ( that’s right, I said speaker wire) that come into my shack. At the shack end I have a box with a Lankford designed adjustable phaser and two PPL amps, fed by two 1:10 transformers. The speaker wire feedlines are approx. 125 feet long and have dual common mode chokes at the shack end. The verticals are mounted on simple ground rod stakes, which penetrate the ground maybe 1.5 feet. There are NO radials, and my ground is notoriously bad.. mostly pyritic slate, with a scattering of soil on top. These are high impedance antennas at low band frequencies. The phaser box also has a Norton 11 dB amplifier on the output which can be switched in or out.
How does this thing work ? I have been flabbergasted at what this simple array can do. It is the lowest noise, most effective receive antenna I have ever used. I can compare results with:
A 4 direction K9AY loop
A 60 foot Misek style SWA array with adjustable phaser
A 30 foot GP vertical switch matched to 80,40 and 30M
A 135 foot wire windom/OCF dipole which can also be switch configured to a 160M Marconi vertical
A 200 foot reversible BOG
Here are some results:
Neighbours plasma TV noise on 80M.. S9 on windom and vertical, S2 with K9AY in opposite direction, can null it to nothing on SWA, S8 on BOG even in opposite direction. With the Lankford vertical array.. I can drop a 30 dB+ null on the plasma source. I can do this on 160M too.
LF AM stations from Eu.. 160 Khz to 200 KHz. Any evening I can hear 3 or 4 of these on the Lankford vertical array, sometimes even 6 or 7 of these stations, and often at S6 or 7 comfortable listening levels. I CAN NOT EVEN DETECT THEM ON ANY OTHER ANTENNA ! You want a demo of low noise receive methods ? This is it ! BTW, my receivers are an IC7700, K3 and mint condition R390A, although the R390A and K3 don’t go down to the LF band. This is with 2 small 15 foot whips, 60 feet apart, fed with speaker wire, on a small urban lot. Power lines all around, crap ground, lots and lots of negative antenna influences. The array is influenced by nearby antennas, something I cannot do much about. But it still works in a highly remarkable fashion.
160M, 80M and 40M ham signals.. very good reception with the Lankford verticals. In all cases, there is less noise and improved intelligibility on weak signals compared to any other antenna. On 160M, it compares favourably or better than the K9AY, although it is more convenient to use the K9AY because of the simple K9AY switching direction system. My Lankford array requires tweaking the phaser controls, plus the null from this 2 element array is bi directional and can only be moved through 180 degrees. The SWA has the capability of moving a 360 degree very deep null towards the noise source you don’t want. This can be effective, but takes quite a bit of fiddling to make it work.
For example, the SWA in late afternoon and early evening can null out Buffalo on 1520 KHz, and allow audible reception of Saudi Arabia on 1521 KHz. An astounding feat for a small yard antenna. I can do this any day of the year. But it is fiddly.
These results have stimulated me to move onto my next project, which is a 4 element vertical array, in a four square arrangement, using all Lankford inspired low noise methods with 15 foot elements and 55 foot spacing. The feedline switching arrangement will be the W8JI inspired time delay method (described in the 4th edition ON4UN Low Band DXing book). Feedlines will be shielded twisted pair. This compromise will fit on my lot and allow simple 4 direction switching similar to the K9AY. My next write up will expound on the construction and the results. It should be finished by May/June of this year. Two of the antenna elements will be 10 foot MFJ telescoping whip antennas on a 5 foot extender, and two will be 15 foot fishing poles with a wire inside them.
I have taken the bold step of removing the 200 foot BOG and the Misek 60 foot SWA to make room for this antenna array. The 4 square elements also have the benefit of being fairly low profile.. a valuable consideration in my neighbourhood.
I am also figuring out how to build a 50 foot boom on a ground mounted rotator to rotate the dual active mini flag array Dallas has described in his latest article. I won’t get to this for a while. My plan is to use Vactrols to adjust the nulls as Dallas feels is necessary, record tons of null info for band, time of day and azimuth and then use an Arduino to adjust them automatically from this data. Now that should be an incredible antenna array !
Stay tuned for the results of the 4 square active receive array next.