What is the general consensus for where the 4 square should be resonant? If
you want to cover phone and cw, is it best to;
- set spacing and length of 70 ohm lines to 3.650. Then resonate verticals
at 3.8 and add a coil and relay to each one to bring it down to 3.5? This
way minimum power is dumped into the dummy load at 3.5 and 3.8. Does this
setup compromise too much on gain and F/B?
- or set spacing for favorite part of band, say 3.8, and set everything for
minimum power dumped in the dummy load for that freq. Then switch in a coil
at each vert with a relay to cover 3.5. Does this way make 3.5 suffer too
much?
- Or is there a better way than the above ideas?
- With sloping ground, is it more important that the feedpoints be in the
same plane rather than follow the contour of the land? I went to an elevated
feedpoint so that all the feedpoints are in the same plane. This works out
that one vertical's feedpoint is 7' above the ground while the other 3 are
14' above the ground. Or is the difference so small that I should just feed
all of them at the ground level?
Tnx
Tony
N2TK
-----Original Message-----
From: owner-towertalk@contesting.com
[mailto:owner-towertalk@contesting.com] On Behalf Of Iowaguy
Sent: Tuesday, August 31, 1999 12:57 PM
To: towertalk@contesting.com
Subject: Re: [TowerTalk] RE: 80 meter 4 square array notes from N0AH
My compliments to Paul on a very nicely written and informative article.
Great job Paul!
Two years ago I put an 80 mtr 4 square here using the K8UR configuration
("Lazy H", or "bent dipole") shown in ON4UN's book with the wires hung off
the 120' guy ring on my rotating tower. I did find that the mutual coupling
of the antennas in this configuration did NOT raise the resonant frequency
of the array (as compared to a single element)
as the classic vertical configuration does. I discussed this at some length
with Jim at Comtek (who was very helpful). He commented that he had heard
of similar observations from other "K8UR" configuration builders. So. . .
just a word of caution. . . don't always plan on the resonant frequency
rising by 100
Khz or so. It may or may not happen.
73 and good DX to all in the coming lowband season. . . Dave
W0FLS
-----Original Message-----
From: Dinsterdog@aol.com <Dinsterdog@aol.com>
To: towertalk@contesting.com <towertalk@contesting.com>; Dinsterdog@aol.com
<Dinsterdog@aol.com>
To: <towertalk@contesting.com>
Date: Monday, August 30, 1999 5:32 PM
Subject: [TowerTalk] RE: 80 meter 4 square array notes from N0AH
>
>Greetings All-
>
>I have recently constructed a 4 square for 80 meters.
>
>It has performed wonderfully so I thought I would share some notes about
it-
>First, a disclaimer- I'm not an engineer- my data is from what I remember
>reading from others and what I've experienced from putting one of these
>antennas together-
>
>If you want to put one together, here are some notes I hope you will find
>helpful-
>
>Ok, so whats a four square?? A four square earned its name by the way it
is
>put together. It consists of 4 verticals, placed 1/4 wave apart, in a
square
>pattern, that together, act as an array. You can aim your signal in 4
>directions, diagonally across the radiators, using a phasing system (I use
>Comtek's hybred coupler). The phasing system should provide power
>distributing and phasing to obtain a directional pattern.
>
>Two verticals can be used but you get much improved front to back, front to
>sides, and forward gain using four verticals.
>
>The antenna designed was formulated by Fred Collins, (W1FC) and Dana
Atchely
>(W1CF) in the 1980's. Steve Davis, K1PEK helped and the three designed a
way
>to phase the array so that it would work well- and be available for others
to
>use.
>
>Through various reports, the array provides a reported front to back gain
of
>around 20-25db. The forward gain claims I have read about range from 4-8
>db. A lot of factors go into these reports such as phasing methods,
materials
>used for radiators, full size verticals vs. shortened verticals, radials
>systems etc...So needless to say, it is not balck and white on exact gain
but
>needless to say, it has a punch-
>
>There are a lot of ways to construct the radiators. A lot of hams use wire
>hanging from long side arms off the top of towers. Others, like me, use
>aluminum radiators while others still use commercial verticals and/or
>insulated towers.
>
>Ok, so now some notes on how I put mine together-
>
>Based on a design in the Com Tek manual, I used 44 foot tall aluminum
>radiators with three 20 foot long top hats connected at the 39.5 foot
level.
>The first aluminum section had a diameter that started at 2 1/8 inches, and
>is tappered down 1/8 of an inch every 6 feet so that the last element has
>about a 1 1/4 diameter.
>
>I used black nylon cord to guy each vertical. They are guyed at 20 feet,
35
>feet, and at the 39.5 foot level using the tophats pulled out with nylon
>rope. Each antenna uses about 600 feet of nylon rope- I used 2,400 feet in
>all to guy the antennas.
>
>I used 60 1/4 wave radials per antenna using insulated 16AWG wire. About
>15,000 feet all together. My radials lay on top of the ground and are
pinned
>in place using landscape pins. I considered using raised radials to
conserve
>wire but other 4 square users suggested a minimum of 60 ground radials-
Lots
>of data on rasied radials but none of seem conclusive that a 1-4 wire raise
d
>radial system would be better than a 60 ground radials per vertical system
>used for an array-
>
>The radials that criss cross inside the square are spliced onto a bus line
>made up of 4AWG copper wire. This is said to prevent unwanted currents from
>developing as a result of criss crossing radials- It is a common practice
in
>commercial arrays- (Although several 4 square owners I spoke to just lay
the
>radials accross one another- and a few radial guru's told me that it was ok
>to just lay them out)
>
>The antenna array takes up about 1 acre of land, apprx 46,000 sq ft, and I
>use another 40,000 sq feet to keep everything at least a full wave length
>away from the tips of the array's radials- Thus a total of 76,000 sq feet
>were used to accomodate the system.
>
>To get the antenna to work properly, it is important to phase the system so
>that your signal goes where you want to and unwanted signals are rejected
by
>a strong F/B, and power put into the array is properly distributed with
>little wasted.
>
>There are a lot of ways to set up phasing on the antenna. ON4UN's 3rd
>edition on Low Band DX'ing addresses several ways. But to save time, and
to
>go with what had already been a proven product, I went with the Com Tek
>hybred coupler to control the phase relationships.
>
>The hybred coupler sits right in the center of the array, on a small post.
>It has 6 coax ports. One for the rig's input, 4 for each of the verticals,
>and one for the dummy load which dissapates unused power resulting from
>resonant issues. Because of the dummy load, the SWR of the antenna is
masked
>by the coupler- So how do you check the antenna's performance?
>
>You simply insert a watt meter between the dummy load and the dummy load
port
>and measure the power being dumped by the system. For example, if you run
>500 watts into the array, and the dummy load shoiws 50 watts being dumped
by
>the array, you have 10% of your power not making it out- Not bad-
>
>But most 4 squares owners, including me, try to get the minimum power dump
>not to exceed 3%. The antenna will work well with less than 10% of the
power
>being dumped. Once you start going up from there- your signal will still
>radiate well but you will notice a decrease in your front to back gain.
>
>To feed the verticals using the hybred coupler, you need to use 1/4 wave
75
>ohm feedlines. The feedline should have a velocity factor of at least 78%.
I
>used RG11 coax. A lot of coax is at 66% and if you cut your 1/4 wave feed
>lines taking this into account, you wont't have enough coax to get from the
>coupler to the antenna- 75 Ohm seems to work better than 50 ohm for
>feedlines- Some try 50 ohm but report better results using 75 ohm.
>
>I feed the system using a 400 foot piece of 9913.........
>
>Tuning and the Effects of Mutual Coupling
>
>When you make the first vertical, you need to test it as a solo antenna
with
>it's radial system attached. You want the antenna to be around 100KHz
below
>the desired resonant point because when the other three antennas are up,
the
>mutual coupling will raise each single vertical's resonant point by apprx
>100KHz......Thuis, the entire array will be most efficient around 100KHz
>abvove the original vertical's resonant point-
>
>For example, if you want the array to be most resonant at 3.775MHz, you
need
>to tune the first vertical constructed to be resonant around 3.675MHz.
>
>Now this is a touchy subject because mutual coupling does not always
produce
>a 100KHz jump. You might get only a 50KHz jump or have one as big as
200KHz-
>such as the case with mine- But 100KHz tends to be the average and the
>standard suggested by many 4 square operators-
>
>Of note, you must make a single vertical first, test it, tune it, then make
>each of the other three verticals exactly like the first one. This way,
each
>vertical should act in a like manner as the first, and you will have a well
>balanced array- Just think of seeing the first vertical in a mirror with
>four images- and that is what you want to produce-
>
>Some four square owners report as little as 50 KHz jumps due to mutual
>coupling on compromised 1/4 verticals such as shortened, top loaded,
>antennas. Full 1/4 antennas tend to have a bigger jump- but a lot of
factors
>will influence this jump such as the radial system, environmental factors,
>materials used for radiators etc...But if you go in expecting a 100KHz
>adjustment, it is a somewhat a safe bet that you be close-
>
>Ok, so what were some of my results- Well, first of all, my resonant point
>jumped almost 200KHz......so while the feedlines and spacing between the
>verticals are cut and measured for the phone DX window- I need to lenghten
>my verticals to bring them down a bit- Right now, my minimum power dump is
>5% at 3.900MHz and around 8-10% in the DX ssb window- it is a whomping 20%
>in the CW band but I can fix this by reducing the current array resonant
>point-
>
>>From a perfomance standpoint, K0RF, who holds a lot of 80 meter contest
>records, has looked the array over and feels it has as good of F/B and side
>to side rejection as his 3 element yagi- Measured front to back is as
great
>as 25dB on DX contacts and 20-25dB so far on a lot of stateside results.
>Front gain looks to be 6-8dBs based again, on testing the array with DX and
>stateside contacts and using a Butternut HF2V for comparisons-
>
>Since putting up the antenna just last week, I have worked HL5FUA, 7J4AAL,
>RA0CG, VK5NJ (QRP), VK2XN (dailey it seems with one QRP contact), EA8ZZ,
>CT4NH, and UA0FF...most of these contacts have been in heavy QRN as the
>season is still a bit early-
>
>The antenna does seem to hear better than the beverages in most situations-
>which is a good test per other 4 square owners- and even though it is a
>vertical array, it is really quiet compared to the Butternut HF2V
>
>As for tuning, I tested each of the individual verticals and found them all
>to bottom out around 3.900 MHz...so they are are acting like clones
although
>the bandwidth of the SWR bell curves vary by as much as 40KHz.............
>
>I need to add a slight bit of inductive loading or lengthen the top hat
wires
>to bring the antenna's most resonant point, as measured my the power dumped
>into the dummy load, down about 100KHz.......but over-all, I could just
leave
>it alone and I doubt the 3-4% gain in power I'll get will make much of a
>difference on the phone portion of the band-- it will however bring me
>closer to operating in the CW window a bit more effectively-
>
>You can make the antenna operate over the entire band usaing full size 1/4
>wave verticals per many reports- but you won't be as effective covering the
>entire band vs working inside a specific window- about a 250KHz bandwidth
>with a power dump of less than 10-15 percent seems most likely with my
array-
>- but larger bandwidths are reported using more effective materials-
>
>Materials used and budget:
>
>Aluminum from Texas Towers........................... $450 which included
>shipping
>400 feet of RG9913.......................................... 160
>220 feet of RG11............................................. 88
>Army surplus parachute nylon for guys 2,400 feet 160
>Wood supports and concrete............................. 50
>Hybred Coupler................................................ 350
>Misc supplies...solder, connectors, etc.............. 30
>Dummy Load................................................... 35
>Dummy load feedline 400 feet of the cheap stuff-) 100
>Radial wire 15,000 surplus 16AWG insluated..... 200
>
>total......................................................................
...
>....$1,623
>
>Not bad considering a 3 element yagi is around a gazillion $$$ and the four
>square is almost as good- not as good, but close thus far in many tests-
>
>Ok, so if you have any questions, please let me know- This was an involved
>project but a great learing experience. I had over 30 hams give me
feedback
>on putting this together- and while i didn't do everything they suggested,
I
>never could have finished this project with out their support- too many to
>thank but there are a lot of them- Locally, N2IC, K0KE, K0RF, W0YG, N4VI,
>W0AH to mention a few- and down south, W4AG, Stan, really made my day many
>times as he had almost the exact design for his array as I used in mine-
just
>a little variation in vertical height- he really provided a good model to
>build around-
>
>K4SQR, Jim, at Com Tek makes a great product and provided a lot of ideas-
it
>was nice to have a product actually work out of the box ...the hybred
coupler
>and Jim's design have worked great!
>
>IIf I get some energy, I'll be writing an artical for some magazine on it
in
>the near future- any feedback for this would be greatly appreciated- I'm
>still learning about this antenna array and lack a considerable amount of
>smarts before I claim to be an expert on them-- and I know I may have
missed
>a few important points- but from a ham's point of view- I hope this story
>helps others considering such a project-
>
>- 73 Paul N0AH Carpenter, WY
>
>--
>FAQ on WWW: http://www.contesting.com/towertalkfaq.html
>Submissions: towertalk@contesting.com
>Administrative requests: towertalk-REQUEST@contesting.com
>Problems: owner-towertalk@contesting.com
>Search: http://www.contesting.com/km9p/search.htm
>
>
--
FAQ on WWW: http://www.contesting.com/towertalkfaq.html
Submissions: towertalk@contesting.com
Administrative requests: towertalk-REQUEST@contesting.com
Problems: owner-towertalk@contesting.com
Search: http://www.contesting.com/km9p/search.htm
--
FAQ on WWW: http://www.contesting.com/towertalkfaq.html
Submissions: towertalk@contesting.com
Administrative requests: towertalk-REQUEST@contesting.com
Problems: owner-towertalk@contesting.com
Search: http://www.contesting.com/km9p/search.htm
|