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[Articles Home]  [Add Article]  

Modified 135 Foot Doublet

James (N8NSN) on July 24, 2009
View comments about this article!

With a modest lot size and height limitations there have been several antennas of which have been tried at this home QTH. Having a two foot outrigger at the top of a 40 foot tower along with the pulley at its end has facilitated ease of changing antennas. An antenna that has always managed to end up back in this position is the 135 foot parallel fed doublet.

This doublet has been tried in the flat top orientation and a few different angles of inversion. The antenna is currently in an inverted vee configuration of thirty degrees. The top feed point of the doublet is at a modest height of 39 feet. The ends of it are at about 20 feet, give or take a small fraction.

About 6 years ago first experiments began on this antenna with a design from the 1970, ARRL Antenna Book (page 188 to begin). I used a home brew link tuner as described in the article. At one point a decision was made to get the parallel feed outside of the shack and installed a bal-un at the base of the tower. Here are the specifications from R.L. Cebik (W4RNL/SK) with the antenna at 60 feet. My results of course were different at the height of only 39 feet. Not so different that the performance was found to be unacceptable.

With the bal-un at the base of the tower the use of a home brew roller inductor was implemented it the simple "T" Match build. (note the by-pass switch at rear of tuner)

With the antenna at this point, I played with the 450 ohm feed line length to find a "sweet spot" for multiple band operations. This length will vary from station to station from soil conductivity, height above ground, and over all amounts of ground wires you may or may not have buried underneath the center of the antenna feed point. The arrangement here ended up with a parallel feed length of 43' and 4" of 450 ohm windowed ladder line. The SWR, though not critical with parallel feeders, ended up to be nearly 1.1:1 on 30 meters (entire band), 1.7:1 on the low end of 20 meters, 1.3:1 on 17 meters (entire band), and 1.5:1 in the ten meter band from 28.200 to 28.600. All of these figures are with the tuner in by-pass position. On the remaining bands very little cap is needed to bring the system to an acceptable level for the required 50 ohms of the rig.

With limited space to allow for antennas it was found that 160 meters was difficult to work. The home brew tuner did 'tune' the antenna in its center fed doublet configuration for 160. Several contacts were even made into South America, when the conditions were right. None the less, the efficiency of an antenna with only 67 and a half feet per side was obviously quite low. The soil conductivity here is very good and there are quite a ground wires under the tower from when the tower was once used as a shunt fed vertical. Considerations began to permeate reasoning with thoughts of feeding the antenna as a single wire, center fed "T" Without losing the capability to still use it as a center fed doublet, as well.

A little brain storming began with wanting to design a way to remove the bal-un completely from the circuit and short the two ends of the bottom feed point of the parallel feeders in one movement. A four pole double throw relay was the obvious answer. Coming up with a relay with contacts capable of a very high voltage capability was the next question. I remembered that I had a couple relays from a Cincinnati Ham Fest, several years ago, tucked away in a box. These are 120V AC relays. If you can only come up with the same type of relay; please exercise caution in your installation per moisture and water safety issues to be found in the outdoor environment.

The wiring for the relay needed to; remove the bal-un, short the parallel feed to a single wire to feed the center as (one) 135 foot wire at the top, and keep the ground potential for the unbalanced input of the circuit. Keeping this ground potential for the unbalanced input facilitated the entire parallel feed becoming a single wire feed, center fed, 135 foot cap hat "T" fed against the ground screen.

The results achieved here were better than first had been imagined. Engaging the relay has provided some thought of, but unexpected results. On 160 meters, all the way at the bottom end, with the tuner in by-pass mode an SWR of of 1.4:1 is achieved at 1.800 Mc and under a 2.1:1 clear up to 1.910. The antenna seems to work very well out to a 500 mile radius (at night of course). 160 is not the best band for summer time communications with the abundant static and other QRN conditions. I am looking forward to winter time testing! I have no doubt that this arrangement will perform better than the previous (no relay) set up.

On the 40 meter band I have found a very interesting attribute for the system. With the relay disengaged and the antenna fed as a center fed doublet the horizontal properties are prevalent. A little bit of the tuner is used here for a rig-acceptable SWR. When the relay is the engaged and the antenna fed in the single wire, center fed T; the vertical component exceeds the horizontal component. This has been determined by attenuating the receiver by 18 dB then watching the huge difference in S meter readings on European BC station signals between the two configurations of the antenna. This works as well with the local conditions and watching the variations of S-meter readings as the signals move through their vertical and horizontal components. Understood that the method of study in these readings may be seen by some as unscientific; none the less, the results may indeed be a valid observation. Working locals, doing A to B switching between their horizontal and vertical 40 meter antennas along with A to B switching here; has yielded similar results in S-meter readings on both my location and their location as we proceeded with the testing. There definitely seems to be a vertical component delivered in the single wire feed arrangement which is not found so much in the parallel feed arrangement.

In conclusion, it is good to be on top band in a more efficient way with this antenna system. The height above ground being only about 40 feet certainly limits the DX potential of the antenna. When the conditions are just right, ...who knows what can happen on 160 meters. Experimenting with antennas is a very enjoyable part of the hobby. Be adventurous and try different methods with various antenna systems in experimentation. For a multi band antenna; the 135 foot doublet is a great start. -- 73, Jim N8NSN

Member Comments:
This article has expired. No more comments may be added.
 
Modified 135 Foot Doublet  
by K8CIT on July 24, 2009 Mail this to a friend!
A very well written antenna article Jim. This is what I like to see on eHam. 73, and keep up the good work. Art K8CIT
 
RE: Modified 135 Foot Doublet  
by KY6R on July 24, 2009 Mail this to a friend!
Excellent article - great workmanship! Thanks.
 
Modified 135 Foot Doublet  
by WD9FUM on July 24, 2009 Mail this to a friend!
Thank you for a well written and informative article.
 
Modified 135 Foot Doublet  
by VA2SS on July 24, 2009 Mail this to a friend!
Nice article. Well done ! I also planned to experiment an antenna like this one. I lived in a city on a small area, so the challenge still exist !! :-)

73

J-F VA2SS
 
RE: Modified 135 Foot Doublet  
by HR2510 on July 24, 2009 Mail this to a friend!
Nice article Jim. This one gets printed out and I just might try to duplicate your antenna.
 
Modified 135 Foot Doublet  
by KA4TWK on July 24, 2009 Mail this to a friend!
James, Thanks for taking time to write this article. I enjoyed reading it and have been considering building a 135 foot doublet myself.

Question: Is there any particular reason you chose the length of 43 or so feet of 450 ladder line?

Thanks Again:
Bill ka4twk
 
RE: Modified 135 Foot Doublet  
by AI7RR on July 24, 2009 Mail this to a friend!
I love playing with antennas, especially yagi's.

I've been looking for something along the lines of the antenna in this article to overcome my limited space for making wire antennas.

A question I have though, is, how does one experiment with the length of ladder line without significant waste?

Thanks for the visuals. To me, that's very helpful understanding the construction technique's.

73,,Roger
 
Modified 135 Foot Doublet  
by W4HLN on July 24, 2009 Mail this to a friend!
I dont hardly have the room for the 135 foot Doublet but instead I used the LB. Cebik (W4RNL SK) 88 foot doublet from 60 meters to ten meters and its fantastic!

Worked two Hungarian Stations and an Italian station the other night on 40 meters running 100 watts in just a few minutes with no problems!

Doublets WORK! Great Article!


Ernie / W4HLN
 
Modified 135 Foot Doublet  
by WA1RNE on July 24, 2009 Mail this to a friend!
For 160 you need at least a few radials at the feedpoint to reduce ground losses.

Radials can be a pain to lay down, but you will see a significant performance improvement.



...WA1RNE
 
RE: Modified 135 Foot Doublet  
by N3OX on July 24, 2009 Mail this to a friend!
"For 160 you need at least a few radials at the feedpoint to reduce ground losses.

Radials can be a pain to lay down, but you will see a significant performance improvement. "

It's not played up in the article, but this system *does* have radials left over from the tower being used as a shunt fed vertical.

Probably be nice to have a few words on how many ground radials are in there for those who might want to try this.

Nice article tho....
 
RE: Modified 135 Foot Doublet  
by K5UJ on July 24, 2009 Mail this to a friend!
Nicely done piece but get rid of the window line and use ladder line; bring it in through plexiglass window pane to a Matchbox or some other link coupled bal. tuner, then forget 160; use an inverted L for that band and raise the ends of the inverted V so it's not an inverted V anymore. Then ur really in business.

88 foot dipole users on 80 m. read this:

http://www.w8ji.com/short_dipoles_and_problems.htm

Summary: Add 6 to 10 feet on each end. No room? Let the ends hang down. Use 600 ohm ladder line and a decent balanced tuner.

73

Rob K5UJ
 
Modified 135 Foot Doublet  
by WA3SKN on July 24, 2009 Mail this to a friend!
Congratulations on a well written, well documented article!
73s.

-Mike.
 
RE: Modified 135 Foot Doublet  
by N8NSN on July 24, 2009 Mail this to a friend!
by KA4TWK on July 24, 2009

James, Thanks for taking time to write this article. I enjoyed reading it and have been considering building a 135 foot doublet myself.

Question: Is there any particular reason you chose the length of 43 or so feet of 450 ladder line?

Thanks Again:
Bill ka4twk

--------

I love playing with antennas, especially yagi's.

I've been looking for something along the lines of the antenna in this article to overcome my limited space for making wire antennas.

A question I have though, is, how does one experiment with the length of ladder line without significant waste?

Thanks for the visuals. To me, that's very helpful understanding the construction technique's.

73,,Roger

-------------------------------------------------------

Hi Bill :-) and Hello Roger :-)

Being at a height of only 39 feet I started with 48 feet. The ARRL Antenna book from 1970 suggested 42 & 1/2 feet. I wasted about 4 feet of line... No biggie. I was looking for that sweet spot for my particular set up as mentioned in the article.

Look closely at the tower base where the feed line starts on the PVC, before it goes to the box... There is a set of small split bolts there to make playing with the length accessible and convenient. Also I could add a couple spark plugs there to facilitate a ground 'before it all enters the box'.

.......................................................

""" With the antenna at this point, I played with the 450 ohm feed line length to find a "sweet spot" for multiple band operations. This length will vary from station to station from soil conductivity, height above ground, and over all amounts of ground wires you may or may not have buried underneath the center of the antenna feed point. The arrangement here ended up with a parallel feed length of 43' and 4" of 450 ohm windowed ladder line. """

-------------------------------------------------------

by K5UJ on July 24, 2009

Nicely done piece but get rid of the window line and use ladder line; bring it in through plexiglass window pane to a Matchbox or some other link coupled bal. tuner, then forget 160; use an inverted L for that band and raise the ends of the inverted V so it's not an inverted V anymore. Then ur really in business.

-------------------------------------------------------

""" This doublet has been tried in the flat top orientation and a few different angles of inversion. The antenna is currently in an inverted vee configuration of thirty degrees. The top feed point of the doublet is at a modest height of 39 feet. The ends of it are at about 20 feet, give or take a small fraction. """

--------

"""About 6 years ago first experiments began on this antenna with a design from the 1970, ARRL Antenna Book (page 188 to begin). I used a home brew link tuner as described in the article. At one point a decision was made to get the parallel feed outside of the shack and installed a bal-un at the base of the tower."""

-------------------------------------------------------

by N3OX on July 24, 2009

"For 160 you need at least a few radials at the feedpoint to reduce ground losses.

Radials can be a pain to lay down, but you will see a significant performance improvement. "

It's not played up in the article, but this system *does* have radials left over from the tower being used as a shunt fed vertical.

Probably be nice to have a few words on how many ground radials are in there for those who might want to try this.

Nice article tho....

-------------------------------------------------------

I guess I could have made more mention of the radial field :-|.

There are only 30 radials of varying lengths from 30 to 60 feet. The station is grounded to the gills and bonded with the house electric drop and all other 'wired' devises, as well. Ground is VERY important on any band and in any location. Focusing on good ground would leave the scope of the original article. A lot of great articles have been written on grounding the station, the antenna system, and all sorts of other dos and donuts etc. etc. As well, I sit on top of an aquifer that is pretty close to the surface... Maybe this helps along with the very high soil conductivity here in the pit of the Miami Valley.

Thanks for taking the time to read this article tho...

:-) Jimmie N8NSN
 
RE: Modified 135 Foot Doublet  
by TERRY_PERRY_EX_W3VR on July 24, 2009 Mail this to a friend!
Very nice.

Thanks for all the time you put into the article.

I hope we get more articles like these!
 
RE: Modified 135 Foot Doublet  
by KI9A on July 24, 2009 Mail this to a friend!
Top notch article, Jim. So refeshing to see this type of stories on e-ham, rather than the sillyness that seems to have taken this site over.

Nice work, OM!

73- Chuck KI9A
 
Modified 135 Foot Doublet  
by K7TCE on July 24, 2009 Mail this to a friend!
Hi James,

My experience with this antenna has always been good. Hopefully you've inspired a lot of hams to try it. For what it's worth, I'm currently using the same antenna, but my 450 ohm wire was getting brittle so I replaced it with 300 ohm TV twinlead. It probably has a tad higher loss, but it looks better IMHO.

I'm confused about the gain figures you posted. I'm thinking 135' is the length of a dipole on 80 meters, and dBi is 2.1 dB greater than a dipole (dBd). So if we back out the 2.1 dB over isotropic from 5.4 dBi, where does the other 3.3 dB gain come from? Just asking, not trying to go negative, which is all to common here lately.

Thanks for posting.
 
RE: Modified 135 Foot Doublet  
by SSBER on July 24, 2009 Mail this to a friend!
Nice article, well written. Would this work well on 11 m?
 
RE: Modified 135 Foot Doublet  
by WB2WIK on July 24, 2009 Mail this to a friend!
Great article, and good work!

The only thing missing is the empirical comparison to other antennas installed at the same site, which is very valuable data.

But this sure looks like fun!
 
RE: Modified 135 Foot Doublet  
by N4LQ on July 24, 2009 Mail this to a friend!
Did you not mention the ratio of that balun?
 
Modified 135 Foot Doublet  
by K7LA on July 24, 2009 Mail this to a friend!
Thank you.
 
RE: Modified 135 Foot Doublet  
by TERRY_PERRY_EX_W3VR on July 24, 2009 Mail this to a friend!
"RE: Modified 135 Foot Doublet Reply
by WB2WIK on July 24, 2009 Mail this to a friend!
Great article, and good work!

The only thing missing is the empirical comparison to other antennas installed at the same site, which is very valuable data.

But this sure looks like fun!"

=======================================================

:: Why would a know it all like you need that? Perhaps he's politely giving folks the benefit of the doubt that they don't need that.

Jeezzzzz... it never fails.

W3VR
 
RE: Modified 135 Foot Doublet  
by N2EY on July 24, 2009 Mail this to a friend!
AI7RR asks:

"how does one experiment with the length of ladder line without significant waste?"

Simulation!

73 de Jim, N2EY
 
RE: Modified 135 Foot Doublet  
by N8NSN on July 24, 2009 Mail this to a friend!
by K7TCE on July 24, 2009

Hi James,

My experience with this antenna has always been good. Hopefully you've inspired a lot of hams to try it. For what it's worth, I'm currently using the same antenna, but my 450 ohm wire was getting brittle so I replaced it with 300 ohm TV twinlead. It probably has a tad higher loss, but it looks better IMHO.

I'm confused about the gain figures you posted. I'm thinking 135' is the length of a dipole on 80 meters, and dBi is 2.1 dB greater than a dipole (dBd). So if we back out the 2.1 dB over isotropic from 5.4 dBi, where does the other 3.3 dB gain come from? Just asking, not trying to go negative, which is all to common here lately.

Thanks for posting.

----------

by WB2WIK on July 24, 2009

Great article, and good work!

The only thing missing is the empirical comparison to other antennas installed at the same site, which is very valuable data.

But this sure looks like fun!


------------------------------------------------------------------------


The gain figures came directly from the W4RNL/SK :-( (Cebik) data. The inspiration for the antenna was the 1970 ARRL Antenna Book. The book does not give the critical data that is available in more up to date research materials. I am certain my gain figures on the lower HF bands are a bit less than the Cebic data due to the height above ground differences.

Other antennas I have tried in its place are the 'Double Bazooka' for various bands, the W6RCA pennant triangle for 40 meters (phenomenal antenna!), a 'Mystery Antenna' cut for supposedly all bands (uh... that one was a flop IMHO)... a multi band dipole (some call a fan) with 80, 40, 20, and of course 15 with the 40 section, a rectangular 40 meter loop/slot (another AWESOME antenna), and a few other variations of others. Each of the antennas I tried had advantages on their particular bands of design operations, of course. What I wanted was a single antenna to work multiple bands with a remote amount of efficiency and not degrade the aesthetics of my rented homes neighborhood. The neighbors think I am Frankenstein or something when I am out in the yard playing with my wires. LOL and I am sure you can imagine the negative comments to each other about every electrical problem in their homes being 'my fault'. "My toast got burned today and just yesterday that silly ham guy was dabbling in the copper again; I just KNOW he's up to something over there and my toaster has never worked right since he moved in 8 years ago..."

My lot is very narrow front to back and extremely wide side to side so, I don't have the capability to install a low band/all band parallel fed horizontal loop at any decent height. That would be my antenna of choice; a 560' horizontal loop at 80 or more feet high fed with 600 ohm parallel feeders. Some day...

The 135 foot doublet is a great place to begin for a multi band, single antenna. The relay and all that was an after thought for getting on 160 more efficiently, that is all it is. The relay switching is just a matter of convenience to not have to 'go outdoors' and switch things per desires. I can sit right here at the desk and do it on the fly from the switching mechanism. It's a really old school antenna and my design is nothing new or ground breaking, but it does indeed work for what my needs are with 160. Those needs? ...to have fun and learn along the way.

Thanks for the compliments on my meticulous work. When I was an electrician the panels I wired always looked clean and concise. Never a birds nest from my hands. ;-)

73,

Jim . .
 
By the way...  
by N8NSN on July 24, 2009 Mail this to a friend!
The home brew tuner I have been upgrading, since it began being built in Winter of 2005, is pretty much complete for now. I will likely have a better cabinet made for it eventually and spread things out a bit. One word of encouragement for prospective home brewers... Never get in a hurry... the best projects are ones that are added to a little bit at a time through experimentation.

The pictures in this article are hard to see in the limited bandwidth, here. If you'd like closer up pictures and to see the tuner as it stands today; visit my QRZ dot com page. I placed some information there about the antenna system and several higher resolution photos, as well. Go 2.0 on QRZ!.. good stuff.
 
RE: By the way...  
by N4BFD on July 24, 2009 Mail this to a friend!
Well regardless if the gain figure is off or not, as you can see by the plot the gain is going straight up, which is great of course for close in contacts.


=======================

by K7TCE on July 24, 2009

I'm confused about the gain figures you posted. I'm thinking 135' is the length of a dipole on 80 meters, and dBi is 2.1 dB greater than a dipole (dBd). So if we back out the 2.1 dB over isotropic from 5.4 dBi, where does the other 3.3 dB gain come from? Just asking, not trying to go negative, which is all to common here lately.

Thanks for posting.
 
RE: Modified 135 Foot Doublet  
by N2EY on July 25, 2009 Mail this to a friend!
K7TCE writes: "I'm confused about the gain figures you posted. I'm thinking 135' is the length of a dipole on 80 meters, and dBi is 2.1 dB greater than a dipole (dBd). So if we back out the 2.1 dB over isotropic from 5.4 dBi, where does the other 3.3 dB gain come from?"

Good question! Here's where it comes from:

dBi and dBd are theoretical numbers for antennas in free space. But the antenna described isn't above free space; it's above ground by a certain height. The ground acts as a reflector of sorts. It's not a perfect reflector because it absorbs some of the RF that hits it, but it's not a perfect absorber either.

The 3.3 dB comes from the reflected RF that doesn't go in other directions and isn't absorbed by the ground.

----

The following is not a perfect analogy, but can help in understanding antennas and ground effects.

One way to imagine antenna gain is to think of the antenna as a light bulb. A true isotropic antenna would be like a uniform glowing sphere that radiated light uniformly in all directions. A dipole would be like a flourescent tube that radiated very little light off the ends and most at right angles to the tube.

The ground can then be thought of as a reflecting surface. Perfect ground, such as salt water or a metal surface, is like a mirror that reflects almost all the light. Imperfect ground is like a painted surface; the amount of loss corresponds to painting of the surface. A pure white surface (low-loss ground) reflects almost all the light that hits hit; a gray surface (medium-loss ground) reflects some and absorbs some, a black surface (lossy ground) reflects almost none and absorbs almost all.

73 de Jim, N2EY
 
RE: Modified 135 Foot Doublet  
by K9FON on July 25, 2009 Mail this to a friend!
Great article!!! I used to use a 135' doublet and it worked great. Pretty much if i could hear someone i could work them. I still use a doublet, but it is now 270' long instead of 135' so i can get on 160.
 
RE: Modified 135 Foot Doublet  
by KA4KOE on July 25, 2009 Mail this to a friend!
Might try lengthening the ends for funzies to 5/8 wave on the lowest frequency for and extended double zepp. You may need to modify the feed line length. This will get you some gain on the lower bands.

Philip
 
Modified 135 Foot Doublet  
by WA1UFO on July 25, 2009 Mail this to a friend!
Great article Jim! For me, nothing is more fun that trying different antennas. Since I chase dx on cw with 100 watts only,I love to see new ideas for skywires. However, how does this antenna get such gain figures on 75 and 80? I am not trying to be a pain but would like to get some info on this. Tnx fer a good aerial article!
 
RE: Modified 135 Foot Doublet  
by N2EY on July 26, 2009 Mail this to a friend!
THANK YOU for a clear, simple, well written article that combines both theory and practical application.

But I have a concern about this antenna.

It seems from the description that the balun has a 4:1 ratio.

On some bands, the impedance at the end of the feedline is about 100 ohms or even less. Once it gets through the balun, this works out to 15 to 25 ohms. "T type" tuners aren't the most efficient at such low impedances, and a considerable amount of power *may* be wasted in the tuner because of it. Often this goes unnoticed because modes like CW and SSB are low-duty-cycle, and at the 100 watt level we're not talking about a lot of average power.

On other bands, the impedance at the end of the feedline is about a couple of thousand ohms or more. A balun designed for 50-200 ohms may not work very well at such high impedances. This won't necessarily show up as heat, though. If the balun doesn't do its job well, the result can be that the antenna is fed like a T against ground rather than as a dipole, or that it's fed as a combination of both. Often this goes unnoticed because the antenna does make QSOs and loads up. One common symptom of balun-isn't-transforming-well is "RF in the shack"

The antenna described may have none of these problems; they don't always happen. But sometimes they do, particularly when the layout and tuner-balun-feedline-dipole combinations are different.

One solution is to try different feedline/dipole length combinations, using calculations to get "friendlier" impedances at the end of the line.

Another is to use a true balanced tuner of known matching range.

All depends on the situation.

73 de Jim, N2EY
 
Modified 135 Foot Doublet  
by WA6MOW on July 26, 2009 Mail this to a friend!
This is what ham radio is all about. Thanks for taking the time to publish it on eHam. WA6MOW
 
RE: Modified 135 Foot Doublet  
by K1BXI on July 26, 2009 Mail this to a friend!
"Might try lengthening the ends for funzies to 5/8 wave on the lowest frequency for and extended double zepp. You may need to modify the feed line length. This will get you some gain on the lower bands."

True, but...........with any gain over a simple dipole comes directivity. Which means a loss in some other direction. Sometimes an advantage, other times not.

John
 
RE: Modified 135 Foot Doublet  
by KA4KOE on July 28, 2009 Mail this to a friend!
Notice the operative word..."funzies".
 
RE: Modified 135 Foot Doublet  
by KT8K on July 28, 2009 Mail this to a friend!
I didn't see anyone note that when the feedline is shorted and fed on 160m as a vertical with a big top hat it moves the high current node down into the vertical section. Since that directs most of the radiation low to the horizon, no wonder it does a good job for DX on 160m.

Very nice article. Thanks & best rx de kt8k - Tim
 
RE: Modified 135 Foot Doublet  
by N2EY on July 28, 2009 Mail this to a friend!
Re KT8K's remarks about using the antenna as a toploaded vertical on 160:

I bet it would work really well for DX that way on 80 as well, if the feedpoint Z is matchable without too much loss.

73 de Jim, N2EY
 
RE: Modified 135 Foot Doublet  
by NJSIDEBANDER on July 29, 2009 Mail this to a friend!
by SSBER on July 24, 2009
Nice article, well written. Would this work well on 11 m?
---------------------------

SSBER, no reason it shouldn't work on 11m. I use a similar antenna on the "freeband" portion of 11m when the HAM bands are dead, with good results.

---------------------------

James, Thanks for the well written article.

cw
 
patterns reply  
by N8NSN on July 29, 2009 Mail this to a friend!
by N4BFD on July 24, 2009
Well regardless if the gain figure is off or not, as you can see by the plot the gain is going straight up, which is great of course for close in contacts.

--------------------------------------------------------

Were you looking at the patterns just for 80 thru 30 fed as a doublet?

You'd be very surprised what the antenna does on 80 thru 30 in it's single wire feed set up. Let's not forget about the vertical components therein and the nice low T.O. angles supplied by such.

The T.O angle on 20 and up is extremely low fed as the doublet it originated as... GREAT DX antenna. If you can orient it just right for Europe off the broadside; you're in there to Australia and New Zealand as well...


If you want to see a better view of the plots... look them up with W4RNL Cebik or see them on my QRZ page.

Focusing on 'your perceived negatives' may stop you from having some wire fun."

:-D ~j N8NSN
 
RE: patterns reply  
by K9MHZ on August 1, 2009 Mail this to a friend!
Jim,

Nice work. You should submit it to see if it would get any ink in QST.

Cheers,

Brad
K9MHZ
 
Modified 135 Foot Doublet  
by KG6UTS on August 18, 2009 Mail this to a friend!
James,
I use a similar setup with a 135ft sloping dipole,63ft to 18ft. Feed is 450 ladderline, DX Engineering 1:1 balun, and 8ft of 213 to a Millen 92200 tuner. The Millen tuner doesn't cover 160 but I've collected parts for a homebrew that will. Switching is with ceramic Frankenstein knife switches since the balun etc are in easy reach. Our QTH is San Diego(DM12jr) about 2 blocks off the Pacific with good soil grounds. The antenna works fine on 75 for SoCal AM QSOs, probably cloud-warmer NVIS, and is great on 17/20/30. That 63/18 slope is basic for 75 but significant on 17/20. I'm not sure how the modeling would look on those bands, maybe a squashed spider, but there are definite lobes to NZ, JN, the NE, and Caribbean-South America. At the alt_QTH in the desert(DM13tf) we have an inverted L but will be adding one of these slopers this Fall. I have some 12VDC relays to try down there with homebrew bias Ts if the voltage drop on the coax isn't too great.
Thanks for the article!!
73
EdZ KG6UTS
 
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