Your Ladder Line Fed Dipole

[chrissim]

I mentioned in a post a while back regarding my beam getting destroyed by a severe storm. Since August I've reverted back to dipoles. I live in an HOA with a new president who isn't tolerating any bending of the rules. Between that and the matter of my wife and I considering moving within a year, I decided not to re-erect the beam.

Currently, I have a delta loop for 80/40, a fan dipole for 17, 20, and 10, and a single dipole for 15 meters. I'd like to eliminate two runs of coax and use a ladder line fed dipole. I've experimented some with home made ladder line and was not satisfied. Therefore, I am considering ordering a Dx Engineering ladder line dipole. Their package is likely cheaper than purchasing all the parts separately and building one.

I have an old MFJ 962C transmatch with a built in 4:1 balun. Current thinking is one would forego the 4:1 and use a very short run of low loss high quality coax to a 1:1 isolation/choke near the station entrance which then would connect to the tuner.

Here's my conundrum: If I do it right, I would need the DXE ladder line dipole, an array solutions ladder line static suppressor and a 1:1 choke made specifically for wide range impedance ladder line. This puts me in the ballpark of $250.00 or so. Alternatively, I could simply purchase the DXE ladder line dipole, calculate the correct length of ladder line and run it directly to the transmatch to the 4:1 balun built in – a much cheaper solution.

IMPORTANT: My station is on the second story of our home, so no practical ground exist. I have read that it is necessary to have a good ground on the transmatch when running ladder line; this concerns me.

After a ridiculously long explanation, I'd like hear from some of you who are using ladder line and how you route it, what type of balun/choke you use, and if you use any type of static drain. Am I being overly cautious and concerned?

Thanks for the patience.

 

[WA0CBW]

I use an inverted flying "V" dipole (each leg is 41-feet long) with the center mounted on a 3-foot standoff from my 30 foot tower. I use standard "window" ladder line a little more than 30 feet long to the basement window coax entrance port. Just before entering the port I transition the ladder line to two pieces of parallel RG62 coax. The center of each coax connects to each leg of the ladder line. I use two "bltz" bug type surge arrestors to join the parallel coax to the ladder line. A bananna plug is on each leg of the ladder line and plugs directly into the SO-239 of each blitz bug. The shields of both pieces of coax are connected together. The other end of the parallel pieces of coax are connected to an MFJ balanced line amp meter. From there they connect to an MFJ differntial ballanced line tuner. This setup lets me tune 80 thru 10 meters. Using parallel coax lines as balanced lines has been described in several QST articles.
BB

 

[prcguy]

A 135ft ladder line fed dipole has served countless hams very well for many decades. Its best to run the ladder line right to a balanced tuner as in WA0CBWs case but I've had ok success running a very short length of low loss coax through the wall to a 1:1 baun then the ladder line. I had a Johnson balanced tuner for awhile but my house is covered with metal lath and stucco and I never committed to a big hole in the wall for the ladder line to make use of it.

I've been using baluns from CWS Bytemark, who seem to be an OEM supplier to other mfrs. Here is their 1:1 balun rated 5kW continuous, 10kW peak (under matched conditions) for $50: http://www.cwsbytemark.com/images/BAL- 50 Rev C-Web.pdf

You could also upgrade to a lower loss, wider spaced ladder line like this: Ladder Line 600 Ohm 18 AWG 50 ft to 500 Ft | eBay You would be surprised how much different the antenna will tune and operate with 600 ohm line vs 300-450 ohm window line. A friend runs a 50ft total length dipole fed with 600 ohm line (impossibly small for 80m) and it easily tunes with a Johnson Matchbox and puts out a respectable signal on 80m, where it would not tune on 80m using window line.

My current antenna is a hybrid with a critical length of ladder line to a 1:1 balun then coax to the tuner. About 20ft of ladder line runs across the roof and I made standoffs for the ladder line by screwing about 18" of PVC pipe to cinder blocks for a ballast, then cutting a slot in the end of the PVC, sticking the ladder line in the slot and putting a cap on to keep the ladder line secure. I spaced a few of these across the roof to hold the ladder line off the roof on the way to the balun.

The Array Solutions static suppressor looks good and I would be leery of running ladder line to a pair of 50 ohm rated lightning arrestors due to the high impedance of the line where normal operating voltages on transmit could fire a gas tube. Grounding would be required for the Array Solutions supressor and possibly to meet NEC requirements, but not for any performance issues. The dipole and feedline would be balanced all the way to a balun or tuner, so ground is not part of the antenna system, except for dipole height above ground and the resulting upward patterns.
prcguy

 

[chrissim]

Thank you both for the information. I did consider running the ladder line to the Array Solutions suppressor, terminating it at the ground rod below, and bringing another run of ladder line 21 feet up to my second story station. From there it would be inserted via a 1:1 choke/balun which would meet the coax, about 3 feet of it.

I just hate to blow the cash. If I do it as it is recommended by current trends, I could spend another $250.00 and get a hexbeam - of course I'd have to figure out a way make the thing inconspicuous from the HOA police.

I'm hesitant to run the ladder line without a transitional balun and no coax due to the many items of conductance at my station. Suppose I'll take the weekend to consider options.

Thanks again.

 

[kj3n]

I have read that it is necessary to have a good ground on the transmatch when running ladder line; this concerns me.

To use the British vernacular: Bollocks!

A dipole fed with ladder line (or coax, for that matter) is a balanced antenna. Why would you need additional grounding at the tuner?

I run a 134 foot long doublet with about 75-80 feet of 450-ohm ladder line to a 4:1 balun, and then about 10-15 feet of RG-213 coax to a Palstar AT-1500DT. Loads perfectly fine 80-10.

 

[chrissim]

To use the British vernacular: Bollocks!

A dipole fed with ladder line (or coax, for that matter) is a balanced antenna. Why would you need additional grounding at the tuner?.

If I am ever offering my "two cents" I normally quote a source and often provide details from that source and where to find it (normally referencing a well known antenna book or author). I could not find any details in any of my trusted resources as to why one would need to ground the transmatch specifically. It was an ambiguity, one of those precious gems of internet information that I ran across that lead me to ask.

I know prcguy's information can be trusted and I know you have success with your antennas. You've both answered my question and offered finality. I am curious though, KJ3N, do you use any static drain or discharge type of gizmo? I've always used polyphasers or alpha delta products for slow voltage buildup and the like on my coax. I wonder if I should do the same with ladder line...

Thanks again.

 

[kj3n]

I am curious though, KJ3N, do you use any static drain or discharge type of gizmo? I've always used polyphasers or alpha delta products for slow voltage buildup and the like on my coax. I wonder if I should do the same with ladder line...

In my case, no, I don't use anything on the ladder line itself. Given that I use a 4:1 balun on my ladder line fed antennas, the antenna appears as a DC short. There's not any real chance of static charge buildup in the first place. Remember that a balun is essentially an AC transformer. If you measure both sides of an AC transformer with an ohm meter, what do you see?

I also have an RCS-10 outside (where all the antennas meet) that has arc plug protection, and an Alpha-Delta manual coax switch inside with an arc plug. Not a lot of chances I'll see any static buildup anytime soon. Now, if I get a lightning strike, then all bets are off. Lightning does what it damned well pleases.

 

[chrissim]

Okay, seems like I have a good start on ladder line fed dipoles. Thanks WA0CBW, PRC, and KJ3N. There are certain practical questions the books don't answer. Certain intangibles that I have difficulty visualizing. You guys took care of that. Of the three forums I read, I only participate in this one. Reason being anyone, regardless of the level of question, is not made to feel like a bone head. Priceless.

 

[cmdrwill]

chrissim, thank you, I am sure The Forums members appreciate your thanks.

 

[chrissim]

I thought I would post an update. I constructed 600 Ohm open wire feedline and put the entire dipole together a couple of days ago. I raised it to about 65 feet and brought the feedline directly to an MFJ feedthrough panel (it has balanced line connections). From there, I used about 8 inches of 14 AWG from each leg on the feedthrough panel to the tuner's 1:1 built in balun.

It tunes great 40 through 12, but presents some difficulty on 10 meters. I will likely have to shorten or lengthen the transmission line a bit.

Regardless of the 10 meter challenge, in the two nights I've had it up, I was able to work South Cook, Eastern Kiribati, and Ghana. There is some RF getting back to the station as my PC speakers can attest, but I'll deal with that later.

This was intended to be an experiment and I wasn't completely sold on the idea. However, I've since took down all of my wire antennas with the exception of the 80/40 delta loop. I'm pleased with the single transmission line solution. No longer do I have coax handing from the sky. It also weighs significantly less than a quality 1:1 balun and RG213.

The next step will be to place an Array Solutions ladder line surge suppressor in line. I initially thought I would add a DX Engineering or Balun Designs 1:1 to the mix and bring about 3 feet of coax into the house, but since my tuner has one built in, I don't think I'll go that route - although I imagine I would benefit from less RF by doing so.

Thanks for the suggestions and assistance.

 

[prcguy]

You might check the diagram for your tuner and built in balun to see if its output is truly balanced or if one side of the balanced line output is at chassis ground. In that case it would not be balanced and could introduce common mode RF onto everything connected to the tuner. I've seen tuners and baluns in tuners wired both ways. 1:1 baluns also cover a wide range from having a great deal of input/output isolation to not so good and that can vary over the 160 to 10m range depending on brand.
prcguy

I thought I would post an update. I constructed 600 Ohm open wire feedline and put the entire dipole together a couple of days ago. I raised it to about 65 feet and brought the feedline directly to an MFJ feedthrough panel (it has balanced line connections). From there, I used about 8 inches of 14 AWG from each leg on the feedthrough panel to the tuner's 1:1 built in balun.

It tunes great 40 through 12, but presents some difficulty on 10 meters. I will likely have to shorten or lengthen the transmission line a bit.

Regardless of the 10 meter challenge, in the two nights I've had it up, I was able to work South Cook, Eastern Kiribati, and Ghana. There is some RF getting back to the station as my PC speakers can attest, but I'll deal with that later.

This was intended to be an experiment and I wasn't completely sold on the idea. However, I've since took down all of my wire antennas with the exception of the 80/40 delta loop. I'm pleased with the single transmission line solution. No longer do I have coax handing from the sky. It also weighs significantly less than a quality 1:1 balun and RG213.

The next step will be to place an Array Solutions ladder line surge suppressor in line. I initially thought I would add a DX Engineering or Balun Designs 1:1 to the mix and bring about 3 feet of coax into the house, but since my tuner has one built in, I don't think I'll go that route - although I imagine I would benefit from less RF by doing so.

Thanks for the suggestions and assistance.

 

[chrissim]

You might check the diagram for your tuner and built in balun to see if its output is truly balanced or if one side of the balanced line output is at chassis ground.

Thank you for the hint. I looked at the schematic and it appears to be chassis ground. I might consider adding 1/4 wavelength counterpoises for the bands presenting the RFI.

I'm stubborn, and since the beam came down and the new dictatorship of the HOA will not allow the erection of another, every penny I put into a "new" antenna system is a penny I could spend on a new beam. I suppose I'm being child like and throwing a tantrum, but after careful consideration I have decided to cut my nose off to spite my face! In fact, and I apologize for elaborating, but spending a mere $20.00 on an antenna system that is inferior to what I had pisses me off to no end. I don't wish violence upon the HOA committe, but I am kicking myself in the arse for moving here.

Apologies for going all berserker and whatnot.

 

[SouthOrRadio]

In 2006, I built a 250' dipole fed with 450 ohm ladder line.

It terminates into a Palstar AT-Autos balanced output.

It tunes from 160 meters to 6 meters.

The tuner is grounded to a common equipment grounding point in the shack.

I tried using a DX Engineering 4:1 balun, using a short length of coax from the
tuner, but the built in balun in the tuner did a better job and was easier to tune.

 

[chrissim]

The tuner is grounded to a common equipment grounding point in the shack..

You mention a common equipment ground point. Does that then lead to a ground outside your shack? My station is in a spare bedroom on the second story of our house - about 21 feet up. No practical ground is possible. From W8JI:

"With a second story (or worse) station, ground rod or rods (or even buried radials) have very limited effectiveness except on very low frequencies. Still, we should probably have or attempt to have an RF ground when using an antenna feed system with high common mode current, or when using any antenna located close to the operating area."

I've spoken to the guys at DX Engineering about my predicament and asked for suggestions. It seems nothing will supplement having a true earth ground, and I sense this is my problem in terms of RF. I tried implementing a 1:1 current balun yesterday as well as 1/4 wavelength counterpoises at my station and neither had any impact. The RF through the speakers connected to the PC isn't so bad at 100 watts, but when I run power it's very obvious.

 

[SouthOrRadio]

chrissim:

I have a 4' piece of 3/4 inch copper tubing with 5' lengths of #10 bare copper wire soldiered all along the length of the tubing as a command ground point.

Each #10 wire goes to the ground connection of the tuner, amplifier, transceiver or antenna switch.

A short #8 wire goes from the tubing to the ground rod right outside the shack.

I have heard of people using an artificial ground,but I have no experience with one

MFJ Enterprises Inc.

You might try to use a short length of coax, to a balun mounted outside, to eliminate the RF in your shack.

Here are the reviews for the artificial ground.

http://www.eham.net/reviews/detail/2118

Another source about grounding,

http://www.radioworks.com/nbgnd.html

 

[prcguy]

Your PC speakers are probably picking up RF radiated from your antenna and in that case no amount of grounding on your antenna will have any affect, you would have to deal with the problem right at the speakers. That might include wrapping the speaker power leads and audio or USB cables with an appropriate amount of turns through a ferrite torrid or getting inside the amplifier and adding bypass caps to the power supply, audio input, etc.

Many years ago I had lots of problems with RF getting into phones, my doorbell, shutting down my DSL router, etc. The antenna was a remote auto tuner a the top of a tower feeding a horizontal wire and the tower with associated grounding was the counterpoise.

I modeled the entire antenna, tower and ground system with EZNEC and found the tower and some of the long ground runs were radiating as much as the antenna wire. I junked the auto tuner idea and went to a mostly balanced antenna, first a G5RV dipole with a common mode choke between the balanced line and coax then a ZS6BKW with the same choke. All my RFI problems went away and I get better reports on all bands except 160m because the ZS6BKW is too small for that band.

I did get some RFI into an occasional stereo under test in the garage and but only with a specific model and that was picking up RF right into the speaker cables.
prcguy

You mention a common equipment ground point. Does that then lead to a ground outside your shack? My station is in a spare bedroom on the second story of our house - about 21 feet up. No practical ground is possible. From W8JI:

"With a second story (or worse) station, ground rod or rods (or even buried radials) have very limited effectiveness except on very low frequencies. Still, we should probably have or attempt to have an RF ground when using an antenna feed system with high common mode current, or when using any antenna located close to the operating area."

I've spoken to the guys at DX Engineering about my predicament and asked for suggestions. It seems nothing will supplement having a true earth ground, and I sense this is my problem in terms of RF. I tried implementing a 1:1 current balun yesterday as well as 1/4 wavelength counterpoises at my station and neither had any impact. The RF through the speakers connected to the PC isn't so bad at 100 watts, but when I run power it's very obvious.

 

[chrissim]

prcguy: as always, thank you for the information. I've read numerous articles about grounding and I think I tend to fixate on it because in my predicament, I am unable to do it by the book. I am familiar with the concept you discussed and I have tinkered with wrapping wires through ferrite snap ons.

I've had RF issues with the beam as well and it's normally centered around 17 through 10 meters. My uncle has a 50 foot tower and yagi. His system was professionally installed yet when he runs power, his touch lamp cycles on and off. I have the same issue. In fact, and I found this amusing, my wife was watching the tele one envening in which the sound runs through a home theater system. She could hear me calling CQ (muffled but intelligible) through the subwoofer.

I don't know that curing this RF problem is critical to DX success, but it's an annoyance none the less.

Thanks again.

 

[prcguy]

TVs can come and go but the DX must go on! Most of the small snap on choke cores need a lot of turns to be effective at HF. Here is a chart that compares various ferrite materials and number of turns for different frequency ranges. This was intended for comparing feedline chokes but the same applies to speaker and other audio cables. Common-mode chokes
prcguy

prcguy: as always, thank you for the information. I've read numerous articles about grounding and I think I tend to fixate on it because in my predicament, I am unable to do it by the book. I am familiar with the concept you discussed and I have tinkered with wrapping wires through ferrite snap ons.

I've had RF issues with the beam as well and it's normally centered around 17 through 10 meters. My uncle has a 50 foot tower and yagi. His system was professionally installed yet when he runs power, his touch lamp cycles on and off. I have the same issue. In fact, and I found this amusing, my wife was watching the tele one envening in which the sound runs through a home theater system. She could hear me calling CQ (muffled but intelligible) through the subwoofer.

I don't know that curing this RF problem is critical to DX success, but it's an annoyance none the less.

Thanks again.