Mid loaded inverted L for 160 - all bands with a tuner

[NT9K]

160 meter inverted L for smaller size lots.

Every winter, I plan to try to get on 160 meters and never get it done. This year I was determined to do it. I was considering a 1/4 wave inverted L, something like this design by WH2T:
http://www.bloomington.in.us/~wh2t/invertedl.html
A tip from Pete W5PEH about adding a loading coil made it possible for me to easily build and put up this antenna on my small size lot.

It is an inverted L, with 25 feet of vertical wire and 65 feet of horizontal wire. At the top of the vertical wire is a big coil. Take a 5 foot 1 1/2 inch pvc pipe, I used thin wall to keep the weight down. Mark 3 inches from each end. Now mark every half inch. Next get some double sided tape. I used 4 strips the entire length of the pipe. This will hold the turns in place. I then drilled a small hole on each end at the 3 inch marks.

I took a roll of 18 guage solid wire that I got from radio shack for 6 bucks and stuck one end through one of the small holes in the end. I pulled about 6 inches of wire out of the end of the tube. Next you wind the coil. When you get to the end, you run the wire down through the other small hole and out the end of the pipe.

Next get some spray paint. Pete used 2 cans, I only used 1 as it was all I had. After the paint dries, pick an end of the pipe to be the top and drill a hole for the hoist rope. That will be the top end. Now solder on 65 feet of wire to the top of the coil. Solder 25 feet of wire to the bottom of the coil.

Feed it with coax. Center pin to your 25 foot vertical wire and the shield directly to your ground rod. I just took a SO-239 and soldered my vertical wire to the center pin and a short braid to the shield. Clamped the shield to the ground rod. On the first test, it was usable with swr of 1.7:1 on 1.820. I shorted my vertical wire a couple feet and added some to the horizontal wire to get the sweet spot on 1.820. My swr is 1.5:1. My Kenwood auto tuner will tune all bands, but works exceptionally well on 40 meters!

Oh yea, I am feeding it with 100 feet of coax even though the feedpoint is 8 feet from my rig. Some have reported tuning problems with coax lengths less than 50 feet. Since building mine, I have added some more ground radials and tapped those radials into a couple separate sections of chain link fence. That really helped drop the noise level and now I can hear things that were lost in the static before.

This project is fun, easy and doesn't cost much to try. I hope you will give it a try and see for yourself how well it performs. Thanks to Pete W5PEH for helping me with it!

[W2BLC]

Many years ago I wrote some DOS software that shows how to shorten dipoles by inserting coils in the elements. It is very simple and the resulting antennas do work well.

You can find the software - FREE:
http://www.w2blc.us/antenna.exe

[ke1lg]

Hey Bill,

Sounds great! You don't have a pic/pics do you??

Steve in Maine
ke1lg

[W2BLC]

Sorry, no pictures - that was over 25 years ago. But, the theory doesn't change. Use as dipoles or inverted Vee. A tuner is suggested, as the smaller an antenna gets physically - the narrower the bandwidth.

[K5EST]

There is a group on Yahoo Groups,
topband-helical · Topband Homebrew Helical 160m
that has a small design for the 160 meter band. I
do think it is more of a compromise antenna than
Bill's article, but the little semi-helical does work.
http://uk.groups.yahoo.com/group/topband-helical/?yguid=302192994

73....Walter - K5EST - SKCC#940

[W2BLC]

The problem with all reduced size antennas is the reduced bandwidth limit.

The smaller the physical size of the antenna, the narrower the bandwidth. Although a tuner will "stretch" the bandwidth - the antenna is still inefficient and the farther the operating frequency is removed from the design frequency the worse the problem gets.

However, that said, the idea is to get on the air and a reduced size antenna is certainly much better than no antenna.

[N6WK]

Very interesting Bill,
I am going to build something like that for here on my small lot.

73,
Gordon

[NT9K]

Pete sent me a PDF of the inverted L and some photos. I have asked for permission from him to post them here. I will take some photos of mine later today. With 160 too noisy right now, one might hesitate to build this antenna until next Fall. Don't worry about that, build it now and enjoy it on the other bands. It really works well on the other bands and for me is much quieter than my inverted V on 40 meters. Try it!

[KB7GL]

Bill--

I'm curious why the L would be that much quieter? Since they're somewhat similar wires, I wouldn't have expected much difference unless one was running a closed loop. Perhaps it's due to the more omni-directional characteristics of the Vee?

[NT9K]

Hi Vic, I have the 40 meter inverted Vee and the 160 inverted L on a switch box and there is average 6 S units lower noise level on the inverted L. One isn't closer to my electrical mains than the other, so I can't explain it. Sometimes, I listen on the L and switch to my beam to transmit.

Here is a link to the PDF that Pete W5PEH made for this antenna:
http://www.skccgroup.com/nt9k/images/inverted_L_160.pdf

Here are a couple photos of Pete's coil. I'll post some of mine later.


See how the double sided tape holds the turns in place.

[Guest]

Bill:

Ever gonna show us those photos?

[NT9K]

Sorry, I'm not as dependable as I want to be or used to be. I looked for some more pictures, but I have lots of pictures. Anything in particular that you want to see?

I took my 160M inverted L down for the summer and just got it back up Saturday. I had to take down my 40M inverted vee and put the 160M in its place on the tower. I recently built a full wave delta loop for 40m and it blows the inverted vee away. I see more loops in my future.

I got lucky Saturday with the 160m L, I got it in the air, came in and put it on the analyzer and it was perfect the first time! SWR was flat 1:1 on 1.820. That doesn't happen very often.

[KC2MSC]

I looked for some more pictures, but I have lots of pictures. Anything in particular that you want to see?

Bill just getting back into the hobby after many years of inactivity and need some good antenna ideas...dealing with a small lot and would love to put something up for 160 and if it tunes up ok on the other bands...Bonus!

If its possible I would like to see how you have it strung up any pics or info greatly appreciated!

Tnx vy 73,

Jim[/quote]

[NT9K]

Hi Jim, here are a couple photos of it hanging off my tower. Notice my vertical section isn't quite vertical. Same for the horizontal wire, mine slopes pretty good with a nice sag in the wire. Also, these pictures are from last winter. I had taken it down and put it back up since. This time, I have it much closer to the tower. My hoist rope is about a foot from the center hole in the coil. I don't see any problems so far.



There is nothing fancy about the hoist rope, just tie it to a hole in the top of the coil. Give it a try, it works fine for me and let me get on 160m when I couldn't find any other way.

[KC2MSC now: WA2OQJ]

Excellent pics Bill and I appreciate you posting them. makes me feel good seeing it not perfectly vertical nor in the horizontal plane either...I am sure I am going to have to fudge the v and h elements also!

Thanks again for the post...look for me on 160!

73,

Jim

[W2BLC]

Looks like a great antenna idea for me when I downsize to the suburbs.

[k8jd]

It just occured to me that if you have a loading coil in middle of a longwire you want to use on ":all bands" with a tuner, wouldn't the coil choike off all RF on higher bands and only leave part of the long wire active excpt on the lower bands..... ??
Almost a trap to block RF there.
You would not have the "longwire gain" available on the high bands ???
A loading coil engineered to shorten a low band wire to simulate a quarter wave, to allow efficient coax feed is a good idea on a single band.
Additionally stubs or traps in the wire for higher bands would be the way to go/..

[W2BLC]

The coil makes up for the missing length. It is frequency sensitive and is used only on single banded antennas.

If you really want complications, the coil/RF choke can be applied - however, a properly designed trap is a more accepted approach.

[k8jd]

With 100 ft of (what kind of coax) you are getting attenuated reflected power from the coax loss, harder to tune? maybe just higher SWR readings with a lot less coax attenuation ? Closer to the true readings.