80 meter Sloper array

[ke7trp]

One thing that I have thought about for 3 years now is to use four 80 meter SLOPER wires off the top of the tower. Then I would have a remote switch box mounted up there to phase them. 

I am told about a simple design that inserted a COIL (6 percent long to lengthen the three back facing antennas while you are transmitting on one, creating a directional pattern.

 I have a remote coax switch that uses a Type 86 switch (read HUGE high power switch).  It is water proof and made to mount on the tower. It uses rotor cable to switch and has a nice little desk top box. I would like to use this to control the slopers. 

I am looking for plans and discussion on such a system.  I cannot find much in my hand books, antenna books and on the net.  I wonder why such a system is not more poplular. 

I did have a qso with a ham that had four slopers off his 100 ft tower and ran all four coax leads down.  He then controlled them at the base with relays.  He said it was awesome and very directional.

What do you guys think? Ever use such a system?

[K3YA]

A good friend W4CTG (SK) ran such an array on 80M chasing DX for many years.  Worked great!  He used a hybrid coupler phasing box, similar to those marketed by Comtek and others, to achieve proper phasing.  ON4UN's book describes it thoroughly.  I would absolutely recommend using a all driven array like he did rather then a parasitic system.

Only issue is that the angle of radiation may be too low especially with the 1/2 wavelength long elements.  Joe also had up a horizontal dipole that generally worked much better out to 500 miles or so.   For even medium distance DX guys with a 2 or 3 element horizontal array would beat out Joe's antenna, and all the vertical arrays for that matter.  It was only on the really long hall stuff that a vertically polarized antenna like you describe shines.

[ke7trp]

I need to order that book today.   I was thinking of 1/4 wave slopers on 80.  I have been told many times that they work decent off a tower but have not even seen a plot. 

Thank you for the post and the story about the guy that had the array!

C

[KM1H]

The DX fights on 75 were usually won by a 2-3 el yagi at 1/2 wave high and with a decent location and equal feed power for both long path and after the band went long to EU and AS.

In DX contests my inv V at 180' was always in the top SO 2-3 80M band scores, often #1 and we took top North America or USA all band many times with 1200W. With a decent low angle lobe the ground gain was impressive, something a vertical doesnt get

Some 4 squares in a salt marsh were competitive but rarely on the morning short path which often preferred a higher angle. I fondly remember blowing thru a huge pileup to Vietnam in one call on SSB 15 minutes after sunrise.

This is from the Northeast and Mid Atlantic states, dunno about others. Im in NH about 30 miles from the ocean from the NE to a bit past SE and its downhill all the way.

Carl

[Bill, KD0HG]

Carl, good post.
The thing is, you can get a good 3 to 6 db "ground reflection" gain from a horizontal antenna that you don't with a vertical.

Also, if your local ground conductivity is poor out to a few wavelengths, a horizontal pol antenna will clean the clock of any vertical.

Bill

[K1JJ]

Slopers were VERY popular on the 75M DX window in the mid to late 80's. They worked "OK" and showed about 10db f-b in most cases. Some ran 1/4 wave slopers fed against the tower and others had vertical dipoles with reflectors and other arrangements.  But I think for the most part many of the guys became disappointed with them and later switched to other antennas, like the 4-square verticals, Yagis, phased dipoles and the like.  

There was a time when it seemed everyone was running a sloper, but these days they are rare. It's probably why there is not a lot of info on them.  As already said, a certain component of a sloping element is vertically polarized and needs some kind of ground screen or good Earth to work against.

TCI always recommended a large ground screen for their vertical dipole arrays. Most of us have poor ground conductivity so are out of luck.

Some guys also used their tower's guy wires as the slopers. They would cut the guy wires to the required length and switch them in and out using relays. There are also clever ways to do this with real dipoles using phased switch boxes that are commercially available now.

K3YA's suggestion to run the ComTek box and all-driven-array is probably the best way to go with slopers.

That said, if I had a single tower and wanted to get the best f-b and forward gain on 75M - and also maintain all horizontal polarization to grab that full 6db of ground reflection, I would go with a pair of driven, phased 75M dipoles.  Let's say the tower is 60' tall. I would hang an aluminum 40' (or longer) boom at the top using overhead wire trussing so there is no torque on the tower. Then using ropes and pulleys on each end of the boom pull up two 75M inverted vees with their legs pulled out as far as possible.

A pair of phased dipoles switched East/ West is a killer antenna. No better way to get a directional, with 20db f-b, horiz polarized, 4-5db forward gain signal on 75M at only 60' high. It's almost a free lunch...

Ask Tina/W1IA, Brandon/K5IIA, Gary/INR and a host of others who have run them.

T

[Steve - K4HX]

Lowers the take-off angle too, so the gain at the lower angles is more like 6 dB.

[K3YA]

What Tom said.

For a low 2 element horizontal you pretty much need to use two driven elements.  There isn't enough coupling for a parasitic array to work well.  However, if you have a little more room for a close spaced 3 element wire yagi, they seem to work even at low heights.  Use small center loading coils and relays to switch the director and reflector.

[Steve - K4HX]

Quarter-wave slopers are more often than not just malformed, disguised inverted-Ls.

[ke7trp]

Wow. Thanks for all the information. 

I dont have room for two dipoles.  I wish I did.  While my lot size is large for the area, Its small for a ham radio op. 

I only have one 55ft tower with a 4 el Mosely beam on it.  The tower cant support much and with our 60mph+ monsoon winds, I really dont want to load it down much more.

I do not have room for half wave slopers here.  I can do the 1/4 wave slopers and I agree its not going to work very well for my main use which is Cont US AM roundtable. I worry the angle will be low.

Thanks for the history on the sloper.  I hear old timers talk about them alot when I brought up the subject but wondered why they are not used much anymore.  Story after story of big local signal and talking into Europe with ease.  Maybe the bands where better then. A single wire off the tower like that seems like a great solution for 80 meters for most people but you just do not see it in practice much anymore.

c

[The Slab Bacon]

Just FWIW, when Deano (WA1KNX) was living out in Tucsan, he used to put quite a strapping signal into the east coast with his phased verticals.

[KM1H]

A sloping dipole is still horizontal polarization with the lobes broadside. Many became dissapointed when pointing them incorrectly and were often claiming reception that evening was skewed path! Having W2PV as a source helped many of the NE gang! It wasnt until years later when AO and later ELNEC showed the masses the true pattern.

[K1JJ]

A sloping dipole is still horizontal polarization with the lobes broadside. Many became dissapointed when pointing them incorrectly and were often claiming reception that evening was skewed path!

Yes, this is a good point.

If a dipole were hung truly vertically with the feedline at horizontal right angles, then it would be vertically polarized and omni-directional.

But if sloped somewhere in the middle between horiz and vertical, then it will tend to radiate more off the broadsides - just like it normally does.  This is a fooler.

Probably the best way to run a system is with four slopers off the tower in different directions with a directly fed phased switchbox. Then we simply pick the best signal.  But this should be modeled extensively first to determine the optimum slope, the optimum phasing angles and the optimum height above ground. It's probably not a simple matter to get it all correct for a big f-b ratio and main lobe going in the directions we expect...

T

[Steve - K4HX]

K8UR bent the bottom leg of the dipole back in towards the tower, so the high angle horizontal stuff is cancelled and the system works more like a true vertical.

[KM1H]

It's probably not a simple matter to get it all correct for a big f-b ratio and main lobe going in the directions we expect...

Ive always used Beverages since the late 70's so never worried about F/B and its pretty hard to hurt gain.

K8UR bent the bottom leg of the dipole back in towards the tower, so the high angle horizontal stuff is cancelled and the system works more like a true vertical.

Never followed up on his design as I had the phased cage verticals that were very competitive back then. Sort of remember some comments when modelling came along that there was some problem with them ??

[Steve - K4HX]

Never followed up on his design as I had the phased cage verticals that were very competitive back then. Sort of remember some comments when modelling came along that there was some problem with them ??

The system is more narrowband than similar vertical arrays. The dipoles are not completely balanced since one leg is much closer to the ground. A competing system using catenaries to hold four quarter wave vertical wires (or shorter with T top loading wires) works just as well and probably has less high angle component. K3LR using such an arrangement to create a 3 element vertical array switchable in four directions. Only the tower is fed. The other elements are passive, set up as a reflector or director by switching in/out a loading coil. The four catenary elements can also be floated to provide an omni option.

[K1JJ]

I built a semi-similar "competing" system on 160M a few years back.

The 110' tower was grounded and shunt fed driven.    There was a director in front and a ref in back of the tower 1/4 wave away.  These were near full-size parasitic elements with a T-top - and a small coil at each base for tuning against ground. There were about 15,000' of radials in the ground.

I put a beacon in the woods behind the array and tuned the two base coils for max f-b, and then in front to get a reasonable compromise for forward gain.

It worked like gangbusters into Eu on 160M CW, its intended purpose.

Had the pleasure of knowing Dennis/K8UR  pretty well in the 80's and we hung out sometimes. He was the founder of ComTek as well as quite the astute RF engineer in other endeavors.

T