4-Square Site

M4D

Since the demise of my full size 80m 4-square when I moved QTH in mid 2010 I had missed my fantastic 80m antenna and my pair of phased verticals for 40m.  At my new urban location I had tried to persevere with one single, elevated vertical on 40m and even base loaded it for 80m for a while.  However, eventually the local urban QRM/QRN got the better of me and I gave up completely on the low bands in favour of 10m and 15m ..... my 4-ele 10m yagi will just turn without overhanging my neighbours properties!  Perhaps that will give an idea of how small my plot is now.

In mid 2013 my wife and I purchased a small camper van and it wasn't long before I started to think that it could make a very nice mobile shack!  I found a nice "ham friendly" caravan site in North Norfolk that is actually owned by a ham....several e-mails later and he told me that he would be happy to turn over part of his site to me for portable operations.  I decided that I would give the location a try in the 2013 CQ WW SSB contest with a pair of phased, elevated verticals for 40m in the single operator, low power assisted category.  Although the final results have not been published as yet (January 2014) early indications are showing #4 in the world, #3 in EU and #1 G station.  This got me started thinking about improving my performance still further for future contests.  I started to think about the possibility of running three verticals in an 'L' configuration and switching to use either pair to give 4 directions and I also considered having the three verticals in a triangular configuration and switching the pairs to give 6 directions.  However, I learned of the SJ2W 4-square pcb's from Steve (M0BPQ) and decided that a home-brew 4-square would be my solution of choice.

In early December I purchased the hybrid phasing system pcb from the SJ2W web site.  Delivery service was very good and the board is excellent quality.  All the required parts were purchased either locally in the UK or on e-bay to complete the construction.  Later, when it's all finished and fully tested I will publish a full BoM for this project but for the time being below are some photos of the board etc. during different stages of the construction.

 

1.     2.      3.     4.     5.    

6.     7.      8. M4D     9. M4D     10. M4D    
11. M4D      12. M4D     13. M4D     14. M4D     15. M4D     16. M4D     17. M4D     18. M4D     19. M4D

1.  The board as delivered from SJ2W
2.  Parts are gathered
3.  Tools are gathered......I don't do subtle!!!!
4.  Antenna, feed and dummy load connections
5.  Relays installed
6.  Completed board with 50 ohm resistors across antenna connections for testing
7.  Completed board with MkI switch box .....MkII will come a little later
8.  Board mounted in IP65 rated box....well, until I drilled some holes in it it was IP65 rated!
9.  Finished phasing system.
10. .....there are even instructions on the box!!
11.  Control box MkII .... internals, it's not rocket science!!
12.  Control box MkII, external.
13.  Control box MkII.revA ....complete with meter to monitor power into the dump load.
14.  Homebrew dump load and RF detector to monitor power into it.
15.  The complete system.....not much more to do now before it's ready for on air testing.
16. & 17.  The phasing system on the scope - looking pretty good I think.  According to my calculations I have 0°, -102° and -185° ......after my initial measurements I discovered that I had a faulty probe on the scope.  I have verified these results as repeatable.
18.  Custom background for the dump load power meter after calibration.
19.  75Ω, 82% VF coax with feed lines connected ready to cut to electrical ¼λ lengths.
Click on each of the above pictures to see a larger version....

Here is a circuit diagram for the phasing and relay box.....

M4D

M4D
This is the diagram for the RF detector and power meter for measuring power into the dump load.

M4D
Here is the diagram for the relay switching and direction LED's.

Initial testing was completed before mounting the board in it's box and phasing angles are -192° / -97° / 0°.  Phase angles were measured using a Tektronix TDS-1002 oscilloscope.  I already have 75Ω foam dielectric coax (velocity factor 82%) for the antenna feed lines so I just need to cut the correct electrical ¼λ lengths and make them up.  There is documentation available (for example ON4UN's Low-Band DXing) that quotes optimised phasing for a 4-square as current magnitude 0.872 and -218° (front), current magnitude 0.9 and -111° and 1.0 and 0° rear.  So, perhaps my measurements are closer to an optimised 4-square??  Time will tell.

Photo 15 above shows the whole kit including some low power dummy loads for final testing and measurement of the phase angles.  I used my MFJ-259B as the signal source so these low power resistors are fine for this purpose.  The low power dummy loads are simply a couple of 100Ω resistor in parallel across a coax pigtail.  I always hate to throw away PL259's but when it comes down to it I find they are a pain to de-solder and re-use so, over time, I built up a collection of coax ends with PL259's attached that I still just cannot throw away.  This is an ideal use for them.  I still have a couple more kicking around somewhere!

During testing of the dummy load and calibration of the power meter in the switch box the thick film 100w, 100Ω resistors didn't even get warm after quite a few 30-40 seconds bursts of key down CW at powers from 5w in 5w increments up to 100w.  I figure that the die cast enclosure that they are bolted to will be heat sink enough for them.  After all, if I see more than a few watts power at the dummy load meter there's going to be something wrong somewhere.....right?  On my previous 80m 4-square using a Comtek phasing system I used to see about 10w or so for 1kw input.

Photo 19 above shows a couple of reels of 75Ω, 82% VF coax with PL259 connectors on each end ready for cutting to electrical ¼λ lengths.  Again I will use my MFJ-259B for measuring these.  It's easy-peasy.....below is extracted directly from the MFJ-259B user manual

7.0 TESTING AND TUNING STUBS AND TRANSMISSION LINES
7.1 Testing Stubs
Resonant frequency of any impedance stub or transmission line can be measured. Select the first (or opening)
measurement mode in the MAIN menu.
Connect the stub under test to the "ANTENNA" connector of the MFJ-259B.
Note: The line must be open circuited at the far end for odd multiples of 1/4 wave stubs (i.e. 1/4, 3/4,
1-1/4, etc.) and short circuited for all half-wave stub multiples (like 1/2, 1, 1-1/2, etc.).:
If a balanced line is used, operate the MFJ-259B only from internal batteries. Keep the MFJ-259B a few feet
away from other conductors or earth, and do not attach any wires (other than the feedline) to the unit. Use the
ANTENNA connector’s shield for one lead and its center pin for the other. Two wire balanced lines must be
suspended in a fairly straight line a few feet away from metallic objects or ground.
Coaxial lines can lay in a pile or coil on the floor. Internal or external power can be used, and the MFJ-259B can
be placed on or near large metallic objects with no ill effects. Coaxial lines connect normally, with the shield
grounded.
When tuning critical stubs, gradually trim the stub to frequency. Adjust the feedline or stub using the following
method:.
1.) Determine the desired frequency and theoretical length of the feedline or stub.
2.) Cut the stub 20 percent longer than calculated, and short the far end of a half-wave (or multiple of a halfwave)
stub or feedline. Leave the far end open for feedlines or stubs that are 1/4 wavelength or odd multiples
of 1/4 wl long.
3.) Measure frequency of lowest resistance and reactance, or lowest impedance. For fine tuning look only at the
“X=?” display. Adjust for X=0, or as close as X=0 as possible. The frequency should be about 20% below
the desired frequency if everything worked as planned during the length calculation.
4.) Divide the measured lowest “X” frequency by the desired frequency.
5.) Multiply the result by the length of the feedline or stub to find the required length.
6.) Cut the stub to the length calculated in step 5, and confirm lowest “X” is on he desired frequency.

I used the above method for cutting my phasing lines in conjuction with VA7ST's Christman Phasing Calculator (see the links page on this site) for a pair of phased verticals on 40m.  When measured on my scope I achieved phasing of -88°....not bad at all for such a simple system.  Many of us own, or know someone that does, a MFJ antenna analyser.

My 4-square radiating elements will be wire verticals supported by 12m Spiderbeam poles with the feed points at approx 2m above ground with 2 elevated radials per vertical.  In fact two of them will be from the phased pair that I used to good effect in the 2013 CQ WW SSB contest.

On air testing will take place the weekend of the RUDX contest 15th/16th March 2014 in readiness for the CQ WW WPX contest a couple of weeks later.  Please listen out for G4ATA/P or 2E1FVS/P before and after the RUDX contest and M4D during the contest.  Callsigns used for the WPX contest weekend will be G4ATA/P and M4D

5th March 2014 - Not much to add at this moment apart from the fact that the ¼λ feedlines have now been cut and a 30m length of RG213 for the main feed is ready.  Last job is to make ready a length of control cable and test the direction switching is all OK.  The first on-air testing will take place on the evening of 14th March.

At last the time for testing arrived.  Everything erected, connected and worked first time without any problem.  The vertical elements are 4mm insulated stranded copper supported on 12m Spiderbeam telescopic fibreglass poles.  The radials are 1.5mm stranded insulated copper.  The feed points are approximately 2.5m above ground and two radials at the same height per vertical.  Photo 1 beneath shows the first three verticals up with no radials attached and photo 2 shows the complete, connected 4-square.  Photo 3 shows the 4-square at grey line taken at 05:30 UTC 16th March 2014.

Testing was carried out before, during and after the Russian DX contest 15th/16th March 2014.  Many DX contacts were made into the USA, Canada and Japan with very encouraging signal reports many of 59++, 59 +10dB, 59 +20dB.  At the same time many front to back comparisons were made and reports were between 3 and 5 "S" units difference comparable to between 18 and 30dB which matches the difference I was experiencing on receive.  Power into the dump load was approximately 2-2.5 watts for 700 watts input at 7.070 MHz rising to about 10 watts at 7.199 MHz.  For the WPX contest I may trim the verticals a little to bring the frequency up nearer the centre of the SSB portion of the band.

Photo 1  M4D  Photo 2  M4D   Photo 3  M4D

3rd April 2014
So, the CQ WW WPX SSB came and went!  I was back at this location with my 4-square and inverted "V" for the contest.  I think that conditions on 40m were not so good but, in spite of that, I still managed 855 QSOs with 540 WPX prefixes.  Before erecting the verticals I trimmed 5cm from each.  Now, at 7.130 MHz the power into the dump load is negligible for 400w output.  It rises to approximately 4w at 7.199 and around 8w at 7.055 MHz.

Photographs below.....
1.  Four verticals laid out ready to erect.
2.  This provides location for the base of the two "free standing" but guyed verticals ..... the other two verticals are fastened to the fencing seen in photo 1.
3.  The finished setup.
4.  This is all that is needed to fasten a 12m Spiderbeam pole to a fence post....this will withstand wind strong enough to make the top of the Spiderbeam nearly horizontal!!
5.  This is the guying arrangement for the two verticals that use the base shown in photo 2.
6.  Feed and radial attachment....If this was to be a permanent installation it would be slightly different.....and waterproof!
7.  The operating position in my camper van showing 12v power supply for the switching of the phasing system (OK, I know a 30A power supply is a bit overkill!!), Dentron MLA 2500B, Tokyo Hi-Power HC2000 ATU (used for antenna switching and power measurement not matching!), laptop for logging and FT2000 and phasing control unit.
8.  The complete 40m 4-square antenna system incuding 30m of RG213 for the main feed.
9.  My CQ WW WPX contest summary shown by SD.  I have used SD for years in contests.  It's so easy to use and reliable I wouldn't use anything else.

Photo 1  M4D  Photo 2  M4D  Photo 3  M4D

Photo 4  M4D  Photo 5  M4D  Photo 6  M4D

Photo 7  M4D  Photo 8  M4D  Photo 9  SD

So, that is the complete story of the build and testing of my 40m 4-square!  I am very happy with the performance and reports that I have received over the two long weekend of use and testing.  It performs just as well, if not better than I expected.  Power into the dump load was never more than 10 watts for over 700 watts output, front to back reports were consistently between 20dB and 30dB for DX contacts (the inverted "V" shown in the pics was only used for "local" inter G and near EU contacts), the ability to switch directions and having such a profound effect never ceases to amaze me and many of the stations I speak to.  Of course you need some space to have an antenna like this but it's within the reach of many.....the verticals are only 10m apart, and I'm sure you can be "creative" with the direction  and spacing of radials without too much detriment to the performance.....and the radials are at such a height that you can easily walk underneath them.  Also, don't forget, there are only two radials per vertical on this system.  Perhaps you could tell your XYL that you are putting up new washing lines for her!!!!  It's just such a shame that I don't have room for this antenna at my very tiny, urban QTH.  I would love to say that I have worked every single station that I have been able to hear with this antenna...that is true with just one exception which is BD6IQD!  I was one of many EU stations calling him in WPX...he was a booming 59++ but I did not hear him work a single station.  I guess, like a fisherman, there is always "one that got away"!!  It's just such a shame that I may have to wait until CQ WW 2014 in October for the next outing of this antenna.....it's so much fun.

If you have reached the bottom of this page thank you for taking the time to read.  I hope that you have enjoyed, perhaps smiled and perhaps learned a little.  I know that I learned a lot during the construction of this antenna system.
Thanks to SJ2W.....a fabulous PCB.
Thanks to ON4UN for his excellent book - Low-Band DXing (although so much of it is still WAY above my head!!).
Thanks to my XYL for putting up with my "Lego and wires" etc in the kitchen...and my absence during the weekends of RUDC and WPX 2014!

Orders now being taken....e-mail me!!!!

73 es gud DX de John G4ATA (aka M4D & G8DYT)

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