The AM Forum

OK,  
If all goes well I should have my ticket in the near future and I need to start thinking about transmit again and not just receive...

A search for "DIPOLE" here in technical lead to a heap of info and opinions.
To spare the gang I did a lot of reading and I have an open mind. I'll describe what my QTH has to offer space wise, what equipment & material I have on hand and what my goals are freq. & power wise at the moment. I just don't think the G5RV is the way to go based on what I've read here and what i've been told.

I Have:
*A well constructed 102', G5RV in the air w/ 32' of 450ohm ladder feed that I will convert / cannibalize, add to, as needed.

*A virgin, Johnson 275w matchbox ( no PL259 provisions )

*An MFJ super tuner deluxe w/ open line option that has seen better days.

*An FT101E in decent shape w/ tube finals 

*A shack located at the center of a the present dipole & about 50ft directly below it.  

* Two healthy trees that now support the G5RV at about 50' high. The future flat top will have to be 90' or less in length to clear the canopy of leaves in summer.


* A 6 pack of suds when the climbing is done.


SO,
I would like a reasonably resonant dipole that gets along well with the Johnson tuna and Yaesu, on 80m thru 20m with 450ohm "cheap brown stuff" into the shack/tuner.
I don't want to take a bath in RF if I can help it and a true heavy guage, open ladder feed will be in the future as $ allows.

I guess the real question is what length will get me in the ball park as far as resonance / SWR and what multiple of 450 feed should I cut so I don't hit a node.
I need at least 65 ft or so to keep the feed vertical, then curve it to the out side wall and a heavy knife switch.
 

Pictures save a lot of time and are more interesting. I'll post some when I get a chance later in the week.
                                                                           Thanks,

                                                                                     Dylan

you'll need a am filter for the EE - already got one? if not I will give you my spare - it's a must have. buddly gave it to me so just passing it on if you need it

OK Derb.
I'll have to lift the lid. I'm pretty sure I have one in there but it's been 20 years and I'm 150mi away from my rig at the moment. The SK who owned it before me was a SSB person.                Thanks again, DJ                 

FT101s can sound full BC quality.  If not more.  Timtrons mods on one of those rigs was putting out 40 to 18K audio.  I was shocked.  I have heard several on the air with studio mics along side of guys running BC rigs. The FT101 had higher FI audio. The trouble is that if you dont limit the bandwidth, you will come on 20 KC wide and piss everyone off.  An FT 101 should have a carrier of about 20 to 30 watts max.

A good FT101 is a fine AM rig though. You need the am filter.  You wil want some kind of amplifier so start looking if you dont have one.  GOod AM starts to happen on the low bands about 200 watts of carrier in my opinon.

As for the antennas.  If you are going to run a dipole you have a few options:

1.  A resonant coax fed dipole for one band.
2. A 450 or 600 ohm fed antenna into a balanced tuner like the Johnson matchbox.  This will let you run 10 to 80 with one antenna and have little loss.  This is called a Zep by most people.

The G5RV works. Dont knock it.  Lots of guys run it.  If thats what you have, Run it. The key is to get on the air and start talking. 

Most of these antennas is going to be good for 500 to 800 miles on most days. When the band is in, anywhere...

I started out with a matchbox, a zep(van gorden all bander) and a ranger at 55 watts.  It worked very well and I had the option of using different bands.

My advice is to get online, Order 100 ft of the heavy 450 ohm ladder line. Run it to the matchbox, Put up as much wire as you can from 20 ft or higher horizontal.  You can get on 80, 40 and even 20 with that simple setup.

I am exploring the world of verticals now as I want to start talking farther out.

Clark

Try this................been using it for years with no complaints. Workz good if you're a little stuck for space. With the right tuna, it'll get ya 160-10. It dont strap on 160, but it does work. It straps pretty good on 80, and 40. Especially if you got a little horsepower to push it. Although I have used it with piss-weakers and still been heard without any problems.

If you have 1 or 2 more "healthy trees", you may want to try a large loop. 

For 80 meters you will need about 280 feet of wire arranged in any shape other than a straight linel

Mine is close to a triangle, 40 feet up and I have had very good luck with it

The Matchbox will adjust the impedance for you quite well.

Since you didn't list 160 meters I'd replace the G5RV with a 1/2 wave on 80, middle band 3750Khz (468/3.75=124.8 ft), call it 125 feet center fed with balanced line. That'll tune you up on 40 and 20 FB OM!

But I'm just a buddly!!

Good stuff, thanks.
I was hesitant to even ask the dipole question with so much info out there and on here. It's funny that you guys brought up the folded dipole and loop. Both of those shook out of the mix as I read.
So there is no length of 450ohm feed line to avoid or seek ?

I found the folded dipole a good compromise tree wise and it would be interesting to fabricate. I collect old ant. insulators and I like to put them to work.

The "Zep" all bander puts me back out at 100+ ft and into the trees. I have a primary wire that bisects my QTH by "right of way" and it really screws things up. I could have 200+ft run at 60' with out the F'ing KV utility stuff here. I'm going to have to pay out of pocket to get it run up the driveway. It's keeping me from building a garage where I want it also. I'll have it moved one way or another.

I will use the G5RV for now but the leaves have grown in and I'm pretty sure they are touching the far ends of the wire. I'm going to try and cook them off there with H.V. from a Brutal neon sign transformer I have here. ( tree fire anyone?  :o )

Now I'm curious about what shape the audio section is in my Yaesu. If I remember correctly it was "gone thru" by a reputable ham in the 80's. I do remember a CW filter. I was frustrated with my code copy skills. It's still some thing I would like to overcome. I really want to work solar QRP CW up in the park here.

A loop for 160m has been in the back of my head for a while. I'll bring that up after I do some more homework. I have some ideas for pex or the sched. 40 PVC as a loop material with the conductor in the center. I'll save that for a seperate post.

Truth be told, fabrication is what really keeps my interest. I can't drive by a some  "High Tension" towers up here with out thinking how nice it would be to convert them to RF service. I've been obsessed with towers and antennas since I was 9 or 10 yrs old.


Thanks again, this weekend should be interesting!
                                                                       DJ in NY

DJ,

Forget the G5RV....gimmick ant.  You have a tuner, so make good use of it.

For the best pattern, take-off angle and efficiency, put up a simple, flat dipole fed with quality openwire. Make the openwire (and dipole) from #12 or bigger wire with good spacers made of Delron? Teflon or similar material. It's easy to make and you don't need a lot of feedline from your description. The dipole wire is just as important as the openwire for losses - use #12 or larger. The shorter the antenna below 1/2 wavelength long, the bigger the wire needs to be.

Important:  Put the dipole up as high, FLAT and straight as possible.

BEST CHOICE: With 80M as your lowest band, if pressed for space and high supports, make it 90' long, open wire fed and you will be better able to fit it into a flat, high space and also have a great pattern on 40 and 20M.  Make it 130' long and the 20M pattern breaks into a 4-way cloverleaf.

But, a high, flat dipole that is 125' long for 80M and 40M is ideal.  Be sure the dipole is broadside to your favorite directions on 40M cuz the pattern is sharp with 2.5db gain.

It is more important to get the dipole high, flat and straight rather than long. For 80M I'd rather have up a 90' long dipole fed with openwire that is erected textbook high and straight rather than a 125' or 260' that zigzags and gets lost in the trees near the ground.   A flat dipole is always better than an inverted vee. You want to shoot for a minimum 90' for 80M or 180' for 160M dipole length  - or consider a Slab Bacon arrangement.

Another approach is to use simple, separate coax-fed dipoles for each band. Or a fan dipole coax fed for several bands, though with your 90' limitation, this will not work for 80M.

If you follow these simple guidelines, you will save yourself months of experimenting and being PW on the bands.

T

Well,
High, Flat and Straight I can do.... and 90' gets me out of the foliage.
So by default, It looks like open ladder to 90' with the J. Matchbox for now.  

If the neighbors thought I was kooky before, wait till they see the circus monkey ladder to the high wire act in the trees.    ;D

Once I kick Central Hudson G&E out of my back yard I'll have space for dedicated, tuned ants. and all kinds of short wave shenanigans.

In case you guys think I'm messin' round, a trim job on a 50' Maple in the path of my dipole project turned into a 2 day, knock down, drag out tree felling.
Did it by my self, with a 30yr old chainsaw and 120" of marine nylon rope. (Sat & Sun )
I have a half cord of firewood drying for next year for my efforts also  ;)

                                          Thanks guys,
                                                   I'll have pics as i go.
                                                                  DJ

Whoops.....double posted  :P

DJ said:
"High, Flat and Straight I can do.... and 90' gets me out of the foliage.
So by default, It looks like open ladder to 90' with the J. Matchbox for now. "

Good decision!   On 40M it will be up about 3/8 wavelength  with 2db gain - this will be your best antenna for both DX and moderate work of the three bands.  On 80M it will be a good local antenna that will be par with anything else.

Since it's in the clear, it will have a great pattern, less interaction with surrounding ground objects -and have low losses with the openwire feedline.

You will be very pleased with that set up. Just be sure to use quality feedline spacers, quality end insulators and #12 or #10 wire throughout.

If you have trouble getting a match on the Matchbox for all bands, try a slightly different feedline length or add some more range to the input link of the tuner. Be sure to mount the Matchbox at the point where the openwire enters the shack. (On the wall, etc.}  Run the feedline away from the dipole at a strict right angle for at least 60' if possible. A drop straight down to the ground (7' above ground) and a right angle to the shack wud be perfect.

An antenna like you propose is a work of art and is about the least neighbor-offensive... but still VERY effective.

Let us know how it works out.

T

DJ, please take K1JJ's comments seriously and forget the G5RV--it works, but nothing to be gained from using it over a simple dipole of at least 90'. Follow his other suggestions and you'll come out very pleased with the results.

Walt,W2DU

Just to show I have nothing against using open wire and antenna tuners,  ;D  here's a 1988 shot of four of five "K1JJ Super Tuners"  I used in the shack.  They were pretuned to various directional wire arrays that all used complex openwire phasing - for instant switching.

The openwire you see is #5, copper covered aluminum. It came from an 18,000' scrap spool that was hardline inner conductor. I went thru all 18,000' in 2 years of experimenting. I had a single 150' tower at the time. Using an early 386 computer and MiniNec as a modeling guide, I tried every wire antenna array known to man... ::)  The biggest was a 36 element Sterba curtain array (with reflectors) for 20M. It was about 180' wide and 90' high.

These days I use all hardline and coax to feed 50 ohm or lower antennas using low impedance matching. No more openwire.  I find hardline/coax easier to run underground and more environmentally stable. No other reasons, really.

T

OK,
Woof, 18,000 ft, I feel lazy now...
( Geeze, is thata solid state amp for the portable fone too? juss kiddin. )

I really need to get things together here workshop wise. I have MUCHO raw materials and tools but it's all been on hold for a garage/shop that I haven't built yet.
BEAR may stop by my QTH this weekend, he will verify all this  ;)

Any info on type and source for #10 or #12  ant./feed wire?
( that resists stretching once drawn, solid or strand )



* I'm the neighbor that people come to for tools, material, help lifting things, plow outs, toaster and tractor repairs, dog advice, reloading, welding, beer and firewood to name a few.
I provide entertainment in the form of impulsive hobby projects. They can kiss my cubical quad if there's an issue   ;) but there won't be.
RFI wise, every one has cable or Sat.

                                               Tanks for the pics/ info guys        
                                                                                     D.

The Backhoe is my best pal here.

DJ,

Sounds like you will eventually have a big station there, no doubt.

For wire, pick up a 500' reel of HomeDepot black PVC insulated, stranded #10.  Use that for both the flattop, openwire and future projects. It will be heavy, so also pick up some 3/16" "aircraft" steel cable to run thru the tree crotch/limbs or whatever you use for support. Friction will break most ropes - you need steel cable.  Use pulleys with strong rope to hoist up the dipole itself.  Support it in the middle, otherwise you will need to keep it slack or find a way to cushion the wind induced pulling.

T

Ahmagonna eye ball DJ's QTH in poyson this weekend... we'll see what we'll see.

I may have him capacity coupled to the entire HV power line before I am done! (only kidding)

we'll see what there is to see... no telling right now. I've scoped his QTH via the satellite imagery available, but that doesn't
tell the story.

I'll report back to the mother ship.

                       _-_-bear

My dipole is 119' high at the apex and droops down to 100' at each end.  The apex angle is about 135°.  I consider it more of a horizontal dipole than an inverted vee.  I could use the same rigging and erect a true flat top horizontal dipole at 90'. That would give less of a null at near vertical angles and better results at closer-in distances. I have often wondered if it would make any significant difference at greater distances.

But then, using the tower as a vertical for 160, that would change it from a 119' vertical tee to a 90' vertical tee.  I figure the tower  length above the dipole is pretty much wasted as far as the vertical radiator is concerned.

When I first designed and built it years go, I hadn't predicted that the dipole would have that much effect on the performance of the vertical, but the close proximity of the tower to the feed line going up through the middle of it causes the dipole to have a profound effect.  The legs of the dipole could just as well be bonded directly to the tower.

I was very careful to balance the lengths of the legs of the dipole and the angle of slope on each leg.  There is practically zero coupling between the dipole and the vertical tower. The tower is insulated at the base, so with it floating free from ground, it is a half wave on 80m, so it should be resonant.  I can run a full kw to the dipole, and not a trace of rf shows up at the base with vertical feed wire disconnected.  I can adjust the 80m tuner feeding the dipole to exactly 1:1 SWR and ground and unground the tower and it makes only the tiniest microscopic flicker of the meter pointer in the reflected power position.

The dipole works well on 160 as a 1/4-wave dipole, even though the tuner setting is very critical and I can QSY maybe +/- 5 kc/s without having to readjust the tuner. I used it on 160 before I installed the ground system, and worked all over N. America.  I didn't bother to try feeding the vertical tower without any radials.

Given that experience, in your situation I would put up a 90' long dipole and feed it with open wire feeders tuned with the Matchbox and you should be in business.  I would aim for 80' to 90' of open wire feeder if possible.  That would keep the dipole leg + feedline length at 125'-135', and the reactive component of the load as seen by the tuner at a minimum on all bands. I have never had good results trying to feed an open wire resonant line near the midway point between maximum voltage and maximum current.

It's almost easier (and more fun) to list antennas to avoid.  I'll take a stab based on my experience and working others with bad signals and what I've been told over the years and observing what professionals do (broadcasters usually):

For simple vertical and wire antennas anything manufactured is suspect.  This is because usually they use marginal materials that may not hold up to AM or legal limit AM.  What are the problem points?  Traps, stubs, baluns, or mechanically cheap flimsy material to name a few.  Possible exception, the Hygain HyTower but look at what one costs new.  Then ask yourself if you will use a ground mounted vertical on the high bands where a high dipole, quad or beam are much more feasible.  Now you start thinking you can do better for less, making a vertical for 80 and 40.

Anything that covers all bands with low vswr at feedpoint all across every band.

Anything physically small:  B&W folded dipole, anything made by GAP, any 43 foot vertical, Isotrons, EH Antenna.
Any modern manufactured transmatches (tuners) made for hams.  Ditto for coax switches.

Carolina Windom
Off center fed dipoles
G5RV
Anything with Miracle, Mystery, or Junior in its name.
Anything that uses a balun or unun at or in the antenna or in the feedline to it.
Loaded antennas with the exception of capacitance hats.
Inverted Vee if the ends are under 30 or 40 feet off the ground.
Most "stealth" antennas:  They often are made with super skinny wire, or are in attics, or are concealed too close to the ground.

There are simply physical laws that can't be circumvented.  The basic key to success is found in getting what you want but playing by nature's laws instead of trying to get around them.  The most clever of these something for nothing antennas work well enough to lull users into a feeling of complacency.  "It's good enough," or, "I work everyone I want to."  (But they don't hear me very well.)  They also have an appeal because some of them are easy.   Genuinely good antennas are usually not quite as easy to construct but are worth it after the work is done.  Some things above may work electrically but fall apart mechanically.  Others may start out working (depending on how you define working) but wind up being unreliable after being outside for a year.

I've probably forgotten some but maybe you all can add to the list.  Some may object to some of these I've included.  If you put up a 1/2 wave center fed flat dipole at 50 feet or more, feed it with ladder line and a link coupled tuner and your carolina windom blows it away and handles a 30 minute 350 w. carrier I will gladly eat crow and thank you for the information.


rob

I have never quite understood the advantage of a "windom".  ???

How does one properly feed a 1/2 wave antenner that is not symetrical to the feedline?? It would not be balanced or feed properlu if it was 1/2 wave. At least in my humble opinion. It looks like a nightmare to tame as far as radiating feedline and rf in the shack issues go.

Now, if you made one leg 1/4 wave and the other leg 3/4 wave it should (at least in theory) work out to somewhere in the 50 ohm range feeding it bacially at a current point. And possibly offa some gain? I dont think that configuration would be considered a "windom" ??

As far as the famous (or imfamous) G5RV abomination, IIRC it was originally designed to be a 80-10 "all band" antenna that gave a 50 ohm match WITHOUT a tuner. First of all If you need a tuna with yours, you've defeated any advantage of it. Secondly, to work properly it needs to ba installed EXACTLY per textbook as the parallel line feeder part is a radiating element on one of the bands. I have never seen anyone put one up properly. And 3rd and most important I HAVE NEVER HEARD ANYONE THAT IS USING ONE HAVE A REAL SIGNAL they are all piss weakers.

The bottom line is: Put up as much wire as you can, find a good way to feed it, and put out a signal.

But, I guess some are happy to brag about their "carolina windom" and "beatin up on the biscuit burner"  ;D  ;D

                                                          The Slab Bacon

All I can say is search " Dipole " on e-bay for some solid entertainment.  ;)

There are some reputable / knowledgeable fellas hocking there wares on e-bay but also a lot of snake oil... eg: "miracle slinky and super slinky" antennas with a warning about RF exposure, so they are not just talking DX listening.

Don, That's got to be a sight at 119ft.  I guess with the guys and tower it's a testament that the two arrays don't couple. Did you secure a source of ladder line insulators and have you built the feed? ( I'm going to search the posts, I remember a long thread about ladr. insul. sources not long ago. )

With out getting too far out there, I have friends who sculpt / blow glass in New England.
I've been thinking it would be interesting to have them cast a series of retro looking ladder line insulators in glass. I've watched them cast all kinds of objects ( including dead mice and toy cars ) just goofing around.
Something about a clear glass ladder set sounds real nifty.
 
Here's an interesting Question: Would glass w/ a high lead content screw up the dielectric effect w/ RF ?
                                DJ

Glass is kinda brittle, and heavy for ladder line use.

If glass is used for insulators it is often "Pyrex" or tempered glass to make it less prone to breakage...
typically glass is used for end insulators on big ants, but again, it breaks.

the lead in glass does not effect its insulative qualities afaik.

                   _-_-bear

Maybe some  hams are actually limited by legal restrictions, but that mentality has spread to the point that many (I hear conversations over the air about it all the time) are afraid to put up a visible, high profile, effective antenna even when there are no anti-antenna laws or HOA rules on the books to keep them from it.

If hams continue to sneak around on their own property with their tails tucked firmly between their legs to put up "stealth" antennas that are not legally necessary, the situation is only going to get worse and new legal restrictions will come down.

It's almost getting to the point that fear of antennas has become institutionalised, and stealthy antennas are expected and assumed. The situation is worse to-day than it was back in the bad old days of harmonic TVI and fringe areas.

Well if I put my money where my mouth is I'll have a nice, visible set up Don.
There's just something hypnotic about wire antennas and towers. ( as if I have to say that here)
If I've been away from the house for any time the first thing I look for is the height of the coax to 450ohm junction. If it's at about 12 feet things are probably in one piece.

I'm a good neighbor.
I keep my lights on motion detectors or timers,
( light pollution is a pet peev of mine )
I keep my collection of materials neat and out of sight.
My dog only does her business in my woods & is quiet.
I just need to get over worring what people think of my hamminess.
A cutie pie that lives back up the dirt road behind me thought I figured out how to steal cable when I was rassling w/ RG8U on the roof. I laughed and explained what I was up to. She just tilted her head and smiled.  
When the leaves are up I can't really see any neighbors. I can wizz of the front porch if I like....( I guess anyone can, I just don't risk a summons  ;)  )

                                                            DJ

 

How about the maypole?  Lots of guys in AZ use them.  BIG signals. Simple to make and put up. 

Also.. Alot of AMers I know recently switched to the Cobra ultra lite.   This is shortened dipole that has three wires.  Some actualy gained signal here.  Everyone loves them

C

What the hell is that ? ? ? ? ? ? ? ? ?  ???  ???  ???

http://www.k1jek.com/

Its a Open wire line fed antenna with multiple horizontal wires so its shorter.   10 to 18 is only 73 ft long.  160 up is 140 ft.  Lots of guys switched to this to gain a band on the low end and not have to string up all that wire.  They really work well. 

C

It Looks interesting.....
I'm going to keep my A.D.D. from kicking in and stick with the 90 ft. diaper pole/ ladder.
I'm curious how that models pattern wise though.
                                                 Thanks,
                                                              DJ

I'd venture a guess that a 73' 'crapp brown stuff' folded dipole would work well also....... and be a lot cheeper than $130 Ultra lite (shipping included).

FWIW, the cobra needs a tuna, and they suggest a balune  ($30)

.... ..and rat shack sells 3 conductor tv rotator control cable..   Ya could probably us that stuff, and that crappy brown stuff with 3 insultors fer ~$50.  and have the bragging rights to a  genuine home brew dipole antenner....


klc

When using a shortened dipole fed with openwire on several bands, probability dictates that you will have low impedance points in many spots along the line and on the flat top. Stick with #10 wire throughout and not worry about these losses.

In additional, using a balun for a dipole on all bands is guesswork. It will match on some freqs and be off on others. No balun needed. Use your link coupled Matchbox and see a 1:1 match with low losses (#10 wire) everywhere. Cheap, simple and most effective, caw mawn.

DJ, your proposed #10 wire, 90' long, flat and high dipole fed with openwire/tuner will run rings around any "snakes" out there.. ;)  (I mean Cobra snakes)


T

yes, the snake antenna....

Another one of those projects from the old ARRL books, made commercially now.

Each leg is ONE piece of wire, folded back on itself twice... (looks like 3 wires in the pictures)



But alas... it only is rated for 1kw... so it isn't of any interest to most AMers....

 ;)

It is kind of amazing how people will fall victim to folklore and legend when it comes to antenners!!  Where's ol P.T.Barnum when you need him??
                      
                                        'Nuff said.......................................

I like the look and sound of this product, It's not as nostalgic as the ol' ceramic but it's light, rea$onable and neat. I searched for reference to it on on the board but found none. Any opinions before I mail off my Greenbacks?

* Warning:
The narrator in the demo video for says "uuhhh" over 90 times ! Really!

http://www.73cnc.com/73cnc/laddersnap.html

                                                                         DJ

The "snake" antenna is basically a Beverage-on-the-ground receiving antenna, using a piece of coax. It has been debated whether it is any better than a plain piece of insulated wire stretched across the ground, but some folks swear by them.

It has nothing to do with transmitting or power levels.

Actually I was referring to the "Cobra" snake... ;)

DJ - Stay away from the cheap clip-on plasdick spacers. A few ice storms and wind and...  Plus at higher freqs, who knows how well they will perform.

You sound like a guy who works with and builds strapping stuff there.  Look on the web and find a local plastics house and stop by. They often have scrap strips of Delron? Teflon,and even Plexiglas that can be used. Just cut to length, drill holes in the ends and slide them onto the open wire - tie them using #14 solid insulated copper wire from Home Depot. Use #10 stranded for the actual openwire and flat top.

Stretch the two openwire lengths out between a pair of trees about 4' high once the spacers are on. Then pull the two wires tight. Then move the spacers  to their positions (about 2.5'-3' apart max) and tie them on with the #14. I've knocked out 200' of openwire in an hour... quick and easy once you know how.

You need #10 wire for the "hot spots" that will show up on the feedline and flat top when tuning a shortened antenna - or when using it on the various higher bands.

To do it right, don't take short cuts like the masses. A db here, a db there - after a while they add up. The average ham takes the fast and easy way out and pays the price by being PW... ;D  The OT's on this BB will set you straight since they've been there before and have already tried all the Gotham verticals of the whirl.

T

I have had better results with solid conductor wire than stranded.  The latter always eventually broke with me from metal fatigue from swaying in the wind, one strand at a time, until the whole thing failed.

I have gobs of #8 copperweld on hand and that's about all I use for antenna projects now.  Yes, it's a PITA to handle, but once up I know it's going to stay up. My open wire line is made of #10 copperweld, of which I had an abundance when I put my present antenna up in the early 80's.

The ham who gave me the big spool of the #8 copperweld had three 100' towers guyed with the stuff.

why Don is a AM badass:

just above the top set of guys you can see his 75 dipole feedpoint.

any more work on th dawg house?

Well, I admit I run about 90' of the hammy hambone OWL, the stuff with no. 16 stranded but have never had a problem.  I'm interested in the resistance loss between no. 16 and no. 10 though.  The dipoles are both no. 12.   It just seemed like anything thicker than no. 12 would be so darn heavy.  I think I have not had any breaking on the line because the no. 16 stranded is that stuff with about 22 strands per side, I support it so much it doesn't move around a lot, and at the feedpoint, the I solder the hell out of the connections.  The dipole wire bare spirals at the center insulator have the OWL wire spiraled between them then I saturate the whole thing with gobs of silver solder and a 150 watt iron so the no. 16 wicks up the solder partly down its length and the whole transfer point is kind of stiff.  I've heard guys complain that their feedline breaks off at the feedpoint after a while.  I've never had that happen.

That's the problem with stranded wire.  The strands tend to break right at the junction between where the solder blob is bonded and the rest of the wire.  I think the problem is that the solder holds the wire too rigidly, and even slight movement of the wire in the wind flexes the wire right at the junction and eventually causes metal fatigue.

I connect the downlead to my beverage using split copper bolts, those things designed just for the purpose of making heavy duty electrical splices.  When I partially disassemble the beverage in the spring, I notice that the copper that was under pressure in the bolt clamp is still shiny and bright even after a winter in the elements, so oxidation shouldn't be a problem, and I would think the mechanical clamping action of the split bolt allows a little more wiggle room that would solder.

For my dipole, I use the same run of wire for the OWL as for the antenna itself.  I just looped it through the insulator and twisted several turns, so there is no splice between feedline and antenna wire.  The only problem with that is that I am SOL if the insulator ever breaks and I need to replace it.

The key is to never leave a soldered joint exposed to ANY type of pull or stress.  Tie the wire off with strain relief insulators or a mechanical hold of some kind. The soldered joint should float freely, be taped and sealed to the weather.

I have used #10 Home Depot stranded for about 25 years. I have 2el 75M quads at 190'. They have never broken. The key is to support any wire antenna in the middle.  Even solid wire will stretch if unsupported and wind/trees have their way.

INSULATED stranded is the key. It will stay shiny and strong for years under the PVC.

The problem with copperweld (besides hard to work with) is I once used it and the end ceramic insulators rubbed through the thin copper plating. The steel core rusted and it broke after two years. Make sure the wire does not rub the ceramic in the wind. I taped it off to limit motion and that solved the problem, but stayed with insulated stranded after that..  I feel single strand copper is more prone to fatigue and break compared to multi strand. Don, maybe we shud try a test with two samples and see which breaks first from repeated bending by hand... ;D


Beware of that "Flex" wire. The tiny strands will rot.  A big, single strand will last for decades.
And try to resolder Flex strands once they have turned brown in the wx. No way to clean it that I've found.

T

The secret to using copperweld (first use quality stuff with a substantial sheath of copper, not that cheap-ass copper plated steel wire often sold as "copperweld"), is to carefully pre-form the wire to match the contour of the insulator and make sure it is tightly clamped round the insulator, then there will be no significant motion. Also use glazed ceramic.  Unglazed ceramic insulators have about the same abrasive characteristic as an emery wheel or sharpening stone. My #10 copperweld has been up for 29 years, and so far, no problem.

Ke7trp  Blows Coach whistle and thows white flag!!!!!!!!!!!!!!!!!!



The Cobra works Damn well into a balanced tuner. BIG signals from those antennas. Most run a HB or a Matchbox.  There are guys running BC rigs into them with no trouble.  Some HB there own cobras. 

Remember. Its not about having the ultimate antenna. we all know you can get something better performing. Its about having a multi band antenna that fits on a standard city lot and does not atract alot of attention.  10 to 80 with a big signal on 73 ft antenna, Is a good thing for ALOT of hams out there that do not have the room! Alot of these guys could not have been on 75 with us until they found this option!

C

All good things here, thanks.
 
I'll at least begin the 90' flat top & ladder tommorow.
I think I'll go with the continous run of #10 as Don mentioned.
Minimal vulnerable joints. 
I like the copper split nut idea, I have them in stock.

                                         DJ

Clark,

I admit I have never heard of a Cobra until now so obviously I have never tried one, therefore it can be argued I am not qualified to address this.  But, (always a but hi hi) a few general antenna maxims and principles:

1.  If you jam enough power into anything you'll get out. 
2.  Have these Cobra users done any A/B testing with a known good design?
3.  There are some observeables that give me pause:  1 KW spec'd maximum power:  It is actually as important or more important for a QRP op to have an antenna system that can at least handle the legal limit.  QRP and power restricted antennas are often power limited because they use lower limit components, and these in turn can be extra lossy.   Ironically this should be of greater concern to the 50 or 100 w. guy who should want every watt to make it to the antenna if  possible.

4.  Personally, I don't like the window line used (the term ladder line is a misnomer in this case) however that can always be tossed out and be replaced with good ladder line. 

5.  I especially don't like the use of a balun in the feedline.  A balun might be okay if its transformation function is perfectly matched to its primary and secondary components, say 50 j0 to 600 j0 but if that can be achieved, it will be on only one frequency.  Outside of that, (which is almost always) baluns start to fail IOW they at least start to heat up and get lossy.   What is needed is a "variable balun" namely a link coupled tuner. 

Get rid of the window line and balun by using ladder line and a link coupled tuner and what's left is that center fed dipole folded over on itself.    I am not sure what the electromagnetic principle is behind that idea but with that left, why not put up a regular 130 foot dipole and let the ends hang down so it is 90 feet long.   One answer is that it won't cover 160.  True, but any horizontal antenna on 160, unless it is pretty high up will work poorly anyway.  "Pretty high up" means at least 100 feet.  Now we're into the multiband antenna trap:  Hams really can't decently cover all bands with one antenna, and when I see a claim that one antenna does that, it raises another suspicion with me about performance.   I don't know what this thing does on the high bands but I'd love to see someone model it on say, 15 meters. 

I just want to make one last general point before I shut up, only because I have forgotten to mention this in other topics:  Antenna manufacturers have to some degree, gotten away with making and selling bad antennas, because slopbucket can compensate for a lot of deficiencies.   Slopbucket has low duty cycle.  It has a narrow passband.  It spreads its energy across a narrower bandwidth (usually).  This doesn't have anything to do with your friends who are all AMers, but the general ham population of casual SSB ragchewers can put up crap antennas and think they work okay, but such an antenna on AM might burn up or turn an AM guy running a Valiant into a pissweaker.  The demands of AM are why there is so much fanaticism on the subject of antennas that really work.  But anyway, like I said before, I have not tried that Cobra antenna and maybe I should.

rob

On pages 6-19, 20 and 21 of The 18th edition of the ARRrrhL Antenna Book there is  a section on 'linear loaded short wire antennas'.   The antenna with the 3 leg-folded-back onto itself occupies about 1/3 less space than a resonant antenna......


klc

Question:
I'll eventually have room for a 130' flat top here.
I would like to leave the 20' difference at each end to hang down, for now, as I've seen done by others.
When I have the room and move the Ant., I would have the 130' with no splices in the full run, including the ladder feed.  Pros, cons, noise, weird resonance?
I made good progress this weekend.

The YAZOO 101 needs some attention. It's got a soft, 30 to 40Hz +-,  hum that comes in w/ zero vol. and fades as the vol. is increased. No other function effects it. I'm thinking cap but It does vary. A good cleaning and check for critters may help.   ;)  
      I'll work it  out.            Thanks,     DJ

You might be able to find some helpful information here (http://www.yazoobrew.com/home.php).


That should work.  I have heard them called "inverted U"s.  You might get some directional effect from the vertical ends. Just make sure no-one walks into them while you are transmitting.  An rf burn to the eye might be hazardous to the vision.

Or you could just fold back the extra wire over the horizontal legs of the dipole.  Copper split bolts would work for holding the folded wire in place (don't use anything galvanised), and don't solder.

DJ,

By lengthing it to 130' (when it is eventually pulled straight out to a dipole) from 90', you will be raising the radiation resistance on 75M, which is a good thang.  90' on 75M was on the low side, but still OK.

The downside is 20M - you said you wanted to use this band too. Instead of a sharp figure 8 with gain, you will now have a 4-cloverleaf that has sharp nulls broadside. I wud suggest a second antenna to cover 10-20M, like a center fed openwire dipole that is 22' total flat top. That will give a nice dipole figure-8 on 10-20M.

Using that 130' dipole on 10M, etc will produce a useless octopus horizonal pattern. No control - pot luck.



T

Once again, thanks. I do my reading before posting to spare an endless thread but some times you just have to ask for a distilled answer. i think I'll cut it for the full length with the 90deg drops. If I get any strange / unwanted effects I'll zip tie it up tight against it self as Don said.  ( I found UV resistant zip ties FWIW. )
Even w/ the drop the HV / RF end will be about 25' in the air safety wise.

I can create a seperate 20m/10m friendly antenna from the G5RV pieces parts.

I'll report back on the FT101 hum.
                                                            All good stuff  :)

Have a good Memorial Day.

 

"I can create a seperate 20m/10m friendly antenna from the G5RV pieces parts."

DJ - Because of skin effect, 10-20M is even MORE critical than the lower bands for needing heavier conductors/ losses. Use the #10 wire for the entire 10-20M ant too.

T

thanks Tom
I guess the G5RV will end up a receiver only antenna or a portable QRP jammiedoo....  

I have to admit, when I grabbed the 500' roll of 10# ( with a grunt ) I had second thoughts. I looked at 14# & 12# but stuck to me guns. Once you pull the insulation back it really isn't that bad. I'll support it well in the center & it will be fine.

If my idea works out for securing the ladder spacers it will be one for the books ( or the trash...)

I have plenty of wire, insulators and spacers left for a heavy 10m / 20m diaperpole. That will be next. I can make up a wound coax/PVC balun to get me from open wire to RG8U and around to my shack.
 Lossy: maybe. Excuse to use ladder line: Yes  ::)

P.S.
 Duty Cycle:
The AM vs. SSB duty cycle was pointed out and made a believer out of me as far as beefy components for AM service. I never thought about it before.

                                      
                               Is it Friday yet? I have stuff to build...
                                                                 DJ

Hah, I just opened the Yazoo link. Based in Nashville TN by pure coincidence  ;)
That's a well constructed web page.
Text book perfect weather here, I need to get away from the damn keyboard!!
                                                          73    DJ.  
                          

"I have plenty of wire, insulators and spacers left for a heavy 10m / 20m diaperpole. That will be next. I can make up a wound coax/PVC balun to get me from open wire to RG8U and around to my shack."


???    It's very important to go into a link coupled tuner for the openwire to coax transition, esp on 10-20M.  You will get a 1:1 on any freq with minimal loss.  Using a balun is guesswork and will be way off on most freqs.

Do a search here for "K1JJ Tuner" and build two tuners -  one for 10-20M and one for 40/75.  Buy two 500pf vac variables on eBay, get some copper tubing and you can make two easily.

Tuner schematic:
http://amfone.net/Amforum/index.php?topic=18054.0

T

Yep, I see now.
I thought the wound baluns were broader than that. Now that I look at it, I guess it's the nature of the beast, as it's a fixed value. The K1JJ tuna is within my ability fabrication wise. I'll look at some of the working examples out there.
 
Lightning protection is also on my reading list. I need to condense the crap load of information out there and tailor something reasonable here. As it is now, I disconnect every thing, toss it out the window and clamp it to ground away from
the house. A few weeks ago I awoke to the sound of rain & thunder at 2am. I scrambled and was shunting and grounding leads in boxers shorts and slippers, in heavy rain, waiting to get lit up. Catskill electrical storms are fierce and sudden. I have a nice old, large, Con-Edison knife switch that I will put to work soon.

I appreciate the patience. I like working with this stuff, it takes me out of my comfort zone knowledge wise. Waaaaaay out some times.  :-\

                                      Is it Friday yet? I have stuff to build.
                                                              DJ


 

   
 

The coax wound on the PVC in the photo looks like a coax choke.  If they are wound with the right coax; right no. turns and diameter for a given range of bands, they are find for choking off common mode RF (RF on the outside of the shield) but I don't know about using one for Z transformation and even if that's possible I would go the link coupled tuner route.  Coax chokes are superior to bead 1:1 ununs as common mode chokes because they don't heat up and saturate. 

Actually disconnecting everything and throwing it all outside is pretty good lightning protection.  that's basically what I do.  You just have to get in the habit of having everything off and disconnected and all the antenna feeds pulled away outside all the time in storm season except when you are at home, awake and able to react quickly.  I do this at night and when I'm away from home.  The only time I relax and leave everything hooked up is in the dead of winter.  When it's -20 I figure the chance of a thunderstorm is pretty low. 

I don't want to discourage you or anyone from going all out with all lines bonded together at the AC service entrance; everything bonded so it rises to the same potential during a hit and all that, with a buried perimeter ground strap all around the house, cad welded to rods every 15 feet or so.  I'd like to do all that but I'm not a broadcaster who has to have a station on the air all the time no matter what, in a site that is designed from the ground up for radio transmission.  I'd love to plow the property and lay down gravel and dig trenches and turn the place into a real radio station but I'd probably have a torch procession to my front door if I did all that.   So I just unplug everything and pull the feedlines away from the house outside and let it go at that. 

One thing about lightning I never hear the experts dwell on (they're all full of cadwelding and bonding everything, and gas discharge units blah blah) is that no matter what you do, 50 amps at 100KV is going to go where it wants and professional transmitter sites with all the protection you can think of, often have gear get zorched in a thunderstorm.   But they have the do rei mi to just go out and buy a new rig, processing box or whatever they have that got fried.   As a ham, I do not, and since I don't have to be on the air all the time, I stick with the disconnect insurance plan.

If yer gona throw it all outside don't forget to unplug an disconnect the grounds too. :)

73

Jack.

 A bit of knowledge led me astray.
( again, I need to read more and Bullsh*t less. )
I'll use the J-matchbox in the meeny time and build a link coupled tuner down the road. I like the remote, step motor driven version that pops up in a search.

Yeah, it ALL goes out the window, including the ground cable and gets clamped to a 8' ground rod. I unplug all line level stuff in the shack and get the cables away from the duplex outlet.
My place is/was a cob job from the last owners, electricaly and plumbing wise. I'm going to bring dedicated BX fed quads up into my work area, right off the panel.
My plumbing is copper free. It's all PEX. Some hate it some love it. I used PEX because it's a temp situation here and PEX will survive freezing. My house needs to be Bulldozed and i can't see plumbing it out in copper.
On the subject, I wonder what PEX vs. copper plumbing does when lightning comes to visit. The shadow knows.

SO...
I plan on loading up and actually modulating this weekend. ( Do ya' hear me Bear? )
Lord have mercy....

Mmmm... well good luk!

I gave '2YOI my suggestions in a private email.

it boiled down to this: get on with the simplest thing you can.

I'll be listening this weekend... try in the AM or after ~5 in the afternoon when conditions are best...
Talk to whomever you can! :D

                    _-_-bear

While feeding the mosquitoes, gnats and black flies my blood, I figured I'd put the 130' dipole together.

I measured out two runs of the 10# wire for each half of the dipole and the drop, secured to a tree with a few feet extra for breathing room. I then secured the other end to a piece of pipe and drew a foot or so more out of the wire to pre-stretch it and create pin straight runs to work with.


I chose to thru-drill the PVC separators, not just slot them. I made a jig up and took my time.
It was an unexpected PITA! Despite a solid drill press, good drill bits, a "V" block, "C" clamp and patience, getting consistent, parallel, spacing was tough but I got it.

What I learned was:

Use the "Gold" PVC 1/2" pipe from Home Creep Show. It does stand up to UV and is very tough stuff. I tried to shatter it, it just compresses.


Find the off-set from the ends to give you the distance between conductors.
Chuck a fine point Sharpie marker in the drill press. Make a simple jig with a stop and mark the circumference. Rotate the piece with the press locked and the tip just touching the work. You should be able to slide the pieces in and out and not crush the marker tip.

Lay the piece in a piece of angle and mark a line the length of the tube to create 2 cross points for drilling. Use as fine a marker as will work. This improves accuracy.

Lock the bit as far up into the chuck as possible to minimize flex.

Don't flip the work to drill the 2nd hole. Any skew will go in the opposite direction and double the error if you flip the piece to drill the second hole. Slide the piece over in the V block.

It sounds obvious but the bit will want to walk off the radius. Allow the bit to bite a bit before applying more pressure.

Use a counter bore, a larger size bit or chamfering bit to clean up the sharp edged holes. This payed off in a big way as i went to slide the 30 or so separators along the 65' of 10# wire. They would have been biting into the PVC skin the whole way.

Slide the tubes along one at a time. Sliding 2 will bind up and grab the jacket & tear it. One in each hand at a ft. or so apart sped things up.

Use bug spray.

The pay off is a very clean, solid, uniform look to the ladder feed.

I'm using UV resistant zip ties inside the tube to trap the wire, 1 per side. Then I squeeze a dab of heavy duty PVC glue on each side from a 50cc vinyl irrigation syringe. ( drug store item ), This fuses the PVC wire jacket and pipe. Little or no space is left for critters to move but water can escape.

The potential center support is beefy, no?  ;)
I'd like to turn a ribbed center support my self out of polycarbonate stock. The Pyrex is heavy, fragile and part of a set I don't want to screw up.
 I hope it lasts a while.    
              
                                     D.

Frank,

I'm space-challenged on a midget city lot and that design looks real interesting. Two questions. One, your drawing shows a vertical length of feedline before it heads off horizontal. Is there a specified length of the vertical run (like a G5RV) or was that just for convenience in drawing? Two, how robust a tuner is required if the antenna is fed with a DX-100?

Thanks,
ldb
K5WLF

The insulating material mentioned earlier is called Delrin. I am trying to get my 268 foot center-fed dipole up soon(fed with crap brown OWL).

the length of the feed line is not critical, However you might have to adjust it some to keep from having a current node right at the tuna. IIRC, mine is somewhere around arond 50' or so. It's been a while since I even looked at the sketch. I am using 14ga crappy brown stuff for feedline. (I was too lazy to make my own)

One of the larger mofojunk type tunas should be OK-FINE with a DX a hundred class transmitter. Just dont use one of those little dinky ones. If you plan to run legal-limit (or more)  ;D class power, you should get serious and build a beefy tuna. I have used mine with a Valiant and one of the bigger mofojunk tunas without any problems. The 4X1 rig, however is another story, that brought about the end of that tuna and the need to build a serious one!
  ;D  ;D

Thanks, Frank. That's what I needed to know. I've got one of the Mighty Fine Junk 941E's (300 watt) sitting on the shelf. I probably should get a bigger one, or just build a K1JJ tuna in preparation for the day when I finally get some high power excitement happening. I'm currently running a coil-loaded 97' LOA dipole on 160 and it seems to radiate pretty well, but the bandwidth is dismal. Think I may just have to get busy build a new antenna.

Thanks again,
ldb

Just keep in mind that you are dealing with the short antenna / high feedline current scenario. Anything you can do to minimize I/R losses will work in your favor.

Good luck and have fun! !  You won't regret it!

Yo, guys...

The OP, made the post a year ago or more now... since then he got his ladder line up, had a FB signal, also got his license, and since then moved to a new QTH in the same area, and has not been heard from on the air for some time...

                  _-_-bear