SLOPER MOP Radio

[flintstone mop]

Hello all,
I was bouncing some thoughts around with Dave , W9AD about the magic that happens on 80M. He has a pair of Hy-Towers that are phased and he reports of interesting contacts with the mid west and West coast.
I had a flash thought reading some antenna books from ON4UN.

A sloper !!!!
I was reading in one of ON4UN's books about a half wave sloper. And I thought, I can do that! I have all of the materials. I THINK...The interaction with my inverted Vee would be minimal, coz the sloper would be perpindicular to the vee and the vee would be unterminated. I have heard that even though the sloper is a balanced antenna like a dipole that there still needs to be a ground radials on the ground side of the coax. Maybe I should read more from ON4UN.

What are your thoughts about this sloper?? The support structure is a wooden utility pole , so the sloper is not working against the support structure for a directional pattern. I just want to play, being that I have everything here to do it.

Would I be wasting my time. Would the Vee get the same results as Dave's verticals for 80M??

Thanks and we are enjoying the snow in Western Pa
Fred

[K1JJ]

I was reading in one of ON4UN's books about a half wave sloper. What are your thoughts about this sloper?? Would I be wasting my time. Would the Vee get the same results as Dave's verticals for 80M??
Thanks and we are enjoying the snow in Western Pa
Fred

Hi Fred,

I guess threre's not gonna be much comment here, so I'll take a shot...

For a period of maybe 6 years or so in the 80's, slopers were very popular in the 75M DX window. Putting up a 1/2 wave dipole with one end high and the other end low sloped in the desired direction sounded sexy and easy.

But, alas, it did not work as intended. If you model it, you will see the dipole still radiates better off the broadside [as it should] than it does in the sloping direction. Since computer modeling became popular, I've haven't heard but a few these days. It comes back to the same old thing... get your dipole up flat, straight and as high as possible for the best results possible.  Broadside.

The exception is when you put up multiple slopers in different directions on the same tower and use one as a driven and the others as either driven or parasitic reflectors. This seems to have some f-b, but to be honest, I've never been impressed from what I've heard when guys do comparisons against them with simple dipoles at the same height.


There is another configuration called the 1/4 sloper that uses a 1/4 wave wire sloped out and fed against the tower ground.  This seems to work best, [as far as "slopers" are concerned] but needs a good radial system. It exhibits charactoristics like a vertical antenna. Guys have had luck with this for DX. since you have a tower, can put out radials, and seem to want a lower angle of radiation for AM DX to complement your dipole, I would do some reading on it.  It's on the web and in ON4UN's Low Band DXing book.

But, probably your best bet is to bite the bullet and put out 60+ radials under your tower. Shunt feed it at the 50 ohm point up the tower [maybe 35' up?] and you have a FB vertical for 75M with top loading. Top loading cuz of your triband Yagi. It will be higher impedance feed cuz it will be close to 1/2 wave with the loading - a good thing for less ground losses.  Assuming the area is CLEAR of obstructions around it, you will see it outperform the dipole at 1500-2000 miles out and beyond, depending upon cornditions.  If ya get really crazy, hang out a rope into the distance in both directions and hang  vertical 'T's'  as driven elements around the tower . Driven array. There's much you can do wid that tower, OM.  Google it.


Good Luck and 73, OM.

T

[Jim, W5JO]

Hey Fred, don't you love it when Tom throws water on your fire?  I have an old friend that says, design it, calculate it, install it then make it work.  Antennas are the last black art left.  Now modeling software is trying to destroy that premise.

Truth is anything less than a 1/4 wave above ground is going to have a high angle therefore, close in contacts.  Could you do an inverted L for 160?

40 ft. vertical and ~125 horizontal with at least 4 1/4 wave radials underneath for 160.  Then add a couple of 1/4 for 80/40 and then just random length radials up to as many as you can?  You may need series capacitance or an L tuner at the base, but that is easy in an ABS plastic mailbox.

If so you can use that dandy tuner to match most any band provided your tuner  can take care of about 125 ohms reactive.  As I recall yours can.  I have been using 44 vertical with ~120 horizontal to work 160 with good reports from 120 miles to nearly 800.  Using a cheap MFJ differential T it will tune any band up to 30 meg.  You will have a vertical component and a reduced horizontal component, so it should let you work distant and some close in.

Just some thoughts.

Jim

[W2VW]

Tom Vu has the guts to tell people the stuff that they usually don't want to hear. Antenna become larger than life. Folks drool over designs with cool names like G5RV, Slopers and Vee beams. Some need to find out the hard way. They will spend time at the pissweak hotel. Same thing as telling your brother that his girlfriend is a stinkin' ho.

[K1JJ]

Fred: Yes, W9AD's verticals have a nice pattern. He has switched them for me out here on 75M.

Though, a well performing vertical array takes a tremendous amount of work and fine tuning for it to perform.  Many of the guys in the DX window spend hundreds of hours getting them to work top shelf. No free lunches.

Jim:  Yes, an inv L is a great antenna for 160M all around use. As for modeling, I sure wish I had use of antenna modeling  in the early 80's when I went thru 18,000' of #5 copper clad aluminum wire trying every antenna array you can imagine from the books. Had a 150' tower wid ropes and pulleys to support anything.  After wasting literally thousands of hours, I eventually settled upon antennas that I modeled years later - and could have easily seen the mistakes I made and would have avoided. Would have been a great shortcut. Things like trying to get a double extended Zepp wid reflectors to work too low to the ground compared to a simple Yagi. Or the interactions of various antennas that showed up on the antenna modeling. Or my own dismal attempt at slopers wondering what I did wrong until I modeled them years later to find out... Or not understanding that the "average height" of an antenna is what counts for low angle. [ Quad loops need to have their centers at the correct height, not the apex, etc - I learned the hard way, whereas modeling picks it right out] 

The computer pattern modeling really is dependable physics, BUT the real whirl terrain, obstructions, Earth soil, etc are the black art and can make one antenna perform well here and another perform poorly there.

Elmering is good. I just wish I had someone back then to tell me, "STOP ! - try this instead". ie, no matter how much I worked with a particular bad design, it was a loser. But then, few of us ever learn until we make the mistakes ourselves. Few are the guys who can learn from others' mistakes... 

Dave: Yes, I too have spent time singing the blues at the Pissweak Hotel. As you know, my first stay was with a Gotham vertical strapped to my back...

T

[Jim, W5JO]

You betcha Tom.  It is hard, unless you have almost unlimited time (which Fred has now, almost) and unlimited funds to play with one.  Many years I fooled with low dipoles and just dreamed of getting something more than 25 ft. high for 75.  Now that I have the time, I don't have the funds for a 75 ft. support. 

But, counting all my experiences on city lots and poor ground, I found that at least get the ends up as high as the middle.  If one counts on vertical, use radials, there is no modeling of your ground beneath your feet.  At least one can model radials.  Aslo use radials or have one damn good ground system for a long wire and put 150 watts or more into the line for reasonable results.

But, there are some principals that should always be used.  Minimum of 1/4 wave high for any supported wire antenna, radials under veticals and match that damn feedline to the antenna.  The thing that has made my job easier is the MFJ 259B.  At least one can actually see what is going on,  If you understand basic feed impedance, line impedance and system impedance, then the signal improves dramatically.  I just wish it gave sign of X.

I will bet that in a few months Mop radio will be blasting into Sulphur with a very good signal.  I am looking forward to talking to you Fred.

[K1JJ]

Ya know, Fred, looks like you really want to get up a worthwhile antenna array for 75M.
I've been thinking...

Take a look at this link below where we discuss a pair of driven, phased 75M, 1/2 wave dipoles. They need to be up a minimum of 55' or so. Gary/INR and Frank ran them and with super results. Axe G about his.  Even inv vees will work if need be. Use a rope boom from the tower to a tree, or just run the rope in both directions and hang the dipoles with rope/pulleys.

I remember back when I visited a ham store when I was 13. The buzzard W1 ham behind the counter has a little rubber stamp. He was a smart old guy. Every so often he would hear or read something from a customer and would stamp the stamp on it. It said, "bullshit".     I found out when I brought in an ad for a T-150 Knightkit I wanted to order. He stamped my ad and told me to save up my money for some Collins gear. [ He WAS right]

Anyway, Fred, I'm gonna stamp that stamp and tell ya to forget the sugar coated antennas for 75M and go with this pair of phased dipoles...     You will have a front to back for better hearing, forward gain of 4-5db, a lower angle than a single dipole cuz of the "boom", and a local cloud burner position. All wire and fed wid coax.  Think about it - you will be happy as a clam if you can find a way to put it up for 75M, OM.

Check it out:
http://amfone.net/ECSound/K1JJ21.htm


Jim:  Yes, it wud be nice if the MFJ-259B had the + - J.  Though the thing will tell ya if you move up in freq and X gets lower or higher....  I couldn't live w/o mine either.

T

[flintstone mop]

A lot of good thoughts here as usual. Thanks Tom for lighting the fire and the many responses.
I know I can get a wire up vertical on my utility pole with 67 feet. A little tuner on the ground and some radials and there we have a low angle radiator for 80M. The L for 160M will be on another support some other time. My Vee is doing FB for 160M. Haven't tried 80 or 40 yet on the Vee.
I don't have a steel tower at this new QTH. Just one expensive 68 foot wooden utility pole.
I'll keep reading this wonderful mail here.
Thanks
fred

[WA1GFZ]

Vee beams are quite cool antennas. I used one as a kid and dropped quite a signal in VK / ZL land on 20 meters way back when. G5RV is a gimmic antenna. Slopers never worked for me.

A spool of #8 bare from home depot makes great antenna stock. Comes in 500 foot spools and the extra can be used as ground wire. A short antenna requires good feed line not the plastic junk. I used #10 for the feed line spaced 4 inches with old Johnson spreaders. Resistive losses need to be as low as possible for a short antenna to work on 160. Plastic stuff may melt when you put the fire in the wire.  fc 

[flintstone mop]

YUP I could not live without my MFJ antenna god either. If I wudda had that in 1991 when I went wild with Ham radio and AM I cudda built that tuner Tom posted here and saved $700 dam dollars buying that dam bliss tuner.
Thanks
I'll post a pic here so that you cansee what I'm thinking about later today
G'day
Fred

[W2VW]

Vee beams are quite cool antennas. I used one as a kid and dropped quite a signal in VK / ZL land on 20 meters way back when. G5RV is a gimmic antenna. Slopers never worked for me.

You are 100% correct as usual Frank. I pictured the installation where someone doesn't have the room for a full sized dipole so they run both ends over to the same side of the fence. It's a sorry dipole that gets named a Vee beam.

[K1JJ]

Slopers never worked for me.

I picture slopers as  broken dipoles. They're common after ice storms. When one end falls down, they're now a sloper....

A fictious quote from the Big Man, WWW.The Kid from Brooklyn:

"Just imagine that some f**king  slopers start at 50' in a f**king tree and terminate at the f**king ground. What the hell kind of f**king antenna is that? 

T

[flintstone mop]

OK her are the pics I promised of the utility pole and what's in use here now.
The things you see going down vertical are dacron ropes for the feedpoint of the vee. You can see how the LL is pulled away from the entire installation. I want to run a 67 foot wire down to the bottom where the tuner/radials and a separate coax to the shack will be located.
Thanks for any further thoughts.
A pic says many things
Fred

[K1JJ]

Impressive installation, there, Fred!  Congrats.

As for the wire vertical plans...One thing to think about if you want to run a wire vertical down the pole:  Normally, a metal tower can be gamma matched and the tower excited with it grounded. The other antenna feedlines go down the inside of the tower and become at the same RF voltage points since they are grounded/terminated at the bottom. They really become part of the tower, like a Faraday cage.

But, in the case of this wooden pole, you have wires coming down for the rotator, for the feedline of the Yagi, the balanced feedline for the open wire dipole at 45 degrees angle, the horizontal dipole legs, etc. Many things for the separate, base fed vertical antenna wire to interact and couple with.  I have to think about this.  If you were to bond EVERYTHING together at the base, and gamma match it up higher, that might be no different than the effect of a simple separate fed vertical wire pattern-wise...

If you were to pull the vertical wire out away from the tower using a rope tramline, then these feedlines/wires would act as a reflector of some kind and slightly enhance the signal in one direction, but attenuate it in the other.  Kinda poor method.

Remember that verticals need a large perimeter of clear space to work properly. This scenario violates that rule.

BUT, in summary,  I think what you would have here would be that the vertical wire would simply "shock excite" the whole tower system. ie, all of your feedlines, Yagi, AND DIPOLE would radiate as part of the system.  They would all be at RF ground as they came to the ground and ran to the shack with the exception of that open wire feedline at 45 degrees.  A rather complex system with lots of horizontal polarization mixed in.  Much like a 1/4 wave vertical with a 120' horizontal T load on top and a 45 degree feedline L... wow.

Can you use a tree out back for a vertical wire in the clear - even if ya gotta make it a shortie 40'er with base/center loading? That wud give pure vertical polarization and have a cleaner pattern in the clear, OM.


T

OK her are the pics I promised of the utility pole and what's in use here now.
The things you see going down vertical are dacron ropes for the feedpoint of the vee. You can see how the LL is pulled away from the entire installation. I want to run a 67 foot wire down to the bottom where the tuner/radials and a separate coax to the shack will be located.
Thanks for any further thoughts.
A pic says many things
Fred

[flintstone mop]

YUP Tom
I didn't think of the coax for the Yagi and the control line for the rotator comming into play. That could bring RF into the shack, I guess. They are neatly stapled to the pole and run into a plastic box at the bottom for lightning protection then head underground to the shack. It's best to take the time on the forum than to find this out after a lot of work and then thers' a bad surprise when RF is applied.
I'll stay tuned.

Fred