The AM Forum

..hi from tim...i was thinking, and all input is great...does an inverted L have any directional properties?...i know the polarization is vertical, but what if 2 were set-up, the same vertical length, plus the same horizontal length, but one running to the east, the other north, etc.   any thoughts?..

..tim..

.sk..

Supposedly (i.e. from what I have read) they have a very small amount of gain in the direction opposite from the one taken by the horiz. part of the L.  The amount of gain probably depends on what % of the total length is horizontal.  I'm writing about Ls that are fed at ground level with a decent ground system.  I'd expect the most noticeable effect of this if any is noticeable at all, would be with a L that is 50% horizontal.

OHHHH how I wish I could think of a way to modify my present 70 foot utility pole to change the dipole over to an "L". I would have to ditch the entire open ladder/dipole and tuner and create ANOTHER radial field......30 minimum radials 120 feet long?? I would not like to take something that works down and design an experimental system during the upcoming Winter.
An L, like any of our low band ants starts to do something if you can get the vertical at least 65 feet. The horiz part at least that high.
The L has both vertical components and horizontal....A very good local and DX antenna.
Having a phased array can be done. But I never heard of using an L in an array like that. The horizontal wire would mess things up, I think.

Hi Tim,

I've modeled these before and just called up the files.

The L's will act like any pair of phased verticals. Gain will be down and the patterns are a bit distorted from real verticals but not enuf for amateur concerns.

The real chore is; input impedence is going to be real low on each element. In the 10 - 15 ohm region. Steve's (K4HX) procedure for setting up his 40M loops is probably the best way to approach this.

Set up one L and get it working good. Then take it down and setup the other and tune/match it. Then setup the entire system, decide on your phasing ( I like @135 degrees. It give a real nice f/b), and fine tune.

Remember, the system will be directional in the direction of the element with the LAGGING current phase.

Tim,

The pattern will depend much on how the two L's are fed and in what phase.   Or one could be driven while the other tuned with an inductor against ground to make a parasitic beam.  (ref or dir)

If it were me, I'd pick my two favorite directions, space them about 1/4 wave apart, and feed them 90-140 degrees out of phase - and use a relay system to change directions. (Adjust coax feed phasing lengths for best f-b) This will produce a unidirectional pattern that contains some horizontal and vertical polarization. You want SOME higher angle on 75M as well as 40M for closer stateside work.  Living up in Canada may make picking your population density directions more difficult, however.  In the states, many of us can go ~NE/SW or E/W  and cover Eur at the same time.

As Buddly said - if you are doing this for 40M, Steve's loops are a killer idea. I've seeen them work into Eur many times..

T

One thing I forgot to mention, Tim, is the modeling I did was for 1/4 wave wire lengths. 50 ft vertical and 75 ft horizontal. As Tom mentioned, they were parallel to each other broadside to the desired directions.

..interesting stuff...but i dont think i made myself clear. i was wondering if an inverted "L" has directional properties?...just one, running horizontal in whichever direction....

..tim..

..sk..

Yes! ;D
Slightly.

Ok ok....

Think of a verticals omni pattern. You'll loose 1.5 - 2 db in the direction of the horizontal wire.

Hi,

If I was looking for directionality in a wire antenna I would sit down and Build a W8JK Phased array.
for what ever band of interest.

http://www.hard-core-dx.com/nordicdx/antenna/wire/w8jk.html

It does werk Well. :)

73
Jack
KA3ZLR

So the greatest signal strength developed would be "broadside" to the horizontal portion?

No.... directly away from it!

Fred. Why not add the L and keep the OWL antenna also?   I have both here.  I have a Huge coil mounted at eye level and can tap the L where I want it. I have it tapped for 160 now. The T3 runs full bore into it and there is no heat and flat SWR.   I have minimal ground radials but I do have 8 Rods in Copper Sulfate around the base.  Works FB.

 

C

Clark Thank you
I will think about that...but I'm afraid there will some coupling of the vertical wire carrying RF from the TX into the ladderline. Playing with antennas in the 160M and 80M bands need 100's of feet separation to keep them from interacting with each other. I have burned up front end components from coupling RF to another terminated antenna. Even un-terminated affects the tuning and pattern of the active antenna.
I got to have a plan.....and commit to it.

Build a Loop.. ::)

73
Jack
KA3ZLR

I used an inverted L for many years at the former QTH. Wire ran vertically about 60' from ceramic feedthrough in window of ham shack, then horizontal to the north another 65'. Ground plane was a 5' steel cyclone fence around the yard.
It worked great from a city lot, other than the issues with running an AM KW into it with neighbors phones, cable TV, you name it.

But I worked KH6CC on 160 CW with it, and all over the USA on 75.

The antenna performed decently from 160 to 40 meters. It sucked on 20 meters and higher.

In short, I highly recommend the inverted L where space is a concern. You could look at my former 60' x 65' one as an inverted vee, fed on one end, instead of the center. The point of max current and radiation on 80 was at the top.

It absolutely outperformed a short 80 meter dipole (65 feet long, made of copper strap) on the same supports.

Always remember: An infinitely small isotropic antenna is only 2 db down from a full sized dipole- AS LONG as you get the losses down in the ground system and its wire conductors.

A corner fed L works well.

I saw this mentioned a couple months ago..........I can do this!!!! I was dreading the ground radials.........There was an engineer "CEBIK" who experimented with weird antennas and has a web site...   http://www.cebik.com/  and I could never find info on a "corner fed L" .............
A small Question for modelers.....Mine would be a "T"..... Vertical wire 65 feet. And the wire at the top would be in two directions (like a dipole). The ladder line connects to the vertical wire and the "T" wire part. Am I complicating things  (again???) My thinking is more wire better or just stick to the drawing????
I am thinking again that 160M might be happier with the additional wire.

I have a sign-in to Cebik's site....is there a link to the corner fed L? I would like to look more into 160M
MY FOCUS is 160M

Fred

Try these two for starters: 
 
http://www.antennex.com/preview/Folder01/lant/lant.htm
http://www.antennex.com/preview/archive3/ltv.htm

BTW, I've done a 160 meter corner fed L using what height I could get from my oak trees.  I was able to extend the horizontal fully but had to fold back part of the vertical portion.  It still works well and with less ground loss due to the vertical current portion being high above ground.  All kinds of combinations, permutations and derivations can be contrived with a little imagination and making the most with what you have to work with.
Darrell  KF4DX

Here's another 'L'ink of interest.


http://www.cebik.com/content/fdim/fdim10.pdf


klc

I'll try that link on the computer that I have a sign-on .very secure site and they do not like their stuff shared..................


Any way Darrell Do you remember this one???? I finally found it from a while ago......160-40M corner fed "L"
 NOW the question issss.......this antenna in use?? Does it work??
Fred

Yes Fred, that antenna works very well.  Make the vertical portion as high (long) as you can.  You can get some other ideas on folding the vertical portion from these sites.
You shouldn't need a login or password to access these sites. http://www.antennex.com/preview/Folder01/lant/lant.htm
http://www.antennex.com/preview/archive3/ltv.htm

Darrell KF4DX

Horizontal and lower than 150 100 feet?
Only if your goal is to be piss weak on 160.

Very good link. The corner or center fed "L" should have equal lengths of wire for the vertical and horizontal part of the antenna. I do not think the corner fed 160-40M would work UNLESS the vertical portion was folded on itself to contain the footage of wire needed for 160M..........125 feet horizontal and the vertical folds 125 feet of wire, however high you can get, on itself. So a 65 foot high tree/tower/pole would be mandatory.

Sorry Tim,
We went off in a possible hi-jack about L's. The best antenna for 160M on a small lot or just for the sake of using the advantage of some vert signal and horiz radiation.

But due to the horizontal wire into play, I do not think you can get directional or phase L's. Nothing becomes directional on 160M and maybe even 80M until you get that sucka a half wave length high??? (horiz wire?)
Phasing plain ole verticals even 1/8 wave tall would work. But not a compromised "L"

The minimum vert length of 65 feet and the rest horizontal is just the beginning of an effective antenna for 160M........Bill , KD0HG, said efficiency might approach 30% on a minimum sized "L". Radials BIG thing here......40 at least as long and as straight as you can get!!! No snaking around to lay the footage down. STRAIGHT
I have a 65 foot pole about 75 feet from the house and I cannot make myself build an "L" using that pole. We're back to the old problem of * How effective is the radial system *** TX RF too close to the house and RFI issues**** The neighbors ......
I DO have a BALANCED dipole on that pole fed with ladder line and no issues with RFI at QRO AM. 40M starts some RFI issues.
I do not have the money for any kind of a tower. A 65 foot mast from DX engineering is a monster to put up. And would not support an extra wire for an "L".
I was in a mental tizzy when we first moved here to Western Pa. and I failed to do a lot of things right to get my station in a better position....so I have to live with my decisions. 1 acre of property that was overgrowth and $3000 needed to clear it away so I could start to do something......
Enuf of my babbling sorry guys.
Peace
Fred

Hi,

That's your opinion, my goal then was to talk local within 300 mile Radius, mine produced the
results I plotted. The Little group I was in had no Problems with my signal SSB Phone, and also
it was decent 0n 80 and 40. oh well.

73
Jack
KA3ZLR

And another thing a Vertical loop on 40 is very efficient and directional.

Fred,
   If there is any interaction between my L and the Inverted V over the top, Its minimal.  I ran the V like this for a couple months before adding the L. In my eyes, all I gained was another antenna.  I have a contactor that Grounds the L out in the shack. I do not see any difference in direction with the switch grounded or open.  Good luck!

C

Jack,  sorry for being a smartass.  When I give antenna advice I assume the recipient wants the best antenna for getting out around 1000 miles within his limits of space and money based on my experience.   Loops can work well, if you have the money to get them real high up on 160 and the supports can get expensive.  If you get to do what you want to do with yours that's FB and you should go with it.

Rob

Hi Rob not a Problem O.M. I wasn't questioning your suggestions no not at all, I'm Leary of
Questions on Directiveness of single wire antennas,.. and the story's are inclusive yea ya
gotta getem up High.. :)

Directiveness on Reception I used at one time a Directed Vertical Loop for reception werked
great man but horizontal single wires...eh...I'm not gona say no but only if the transmitted sig
is aimed directly at the wires broadside. yes there is a certain amount of gain compared to
straight on. how large well put it up and find out, there are no Exacts in antenna building till
it's in the Air O.M. we both know that. I quit sweaten Theory a long time ago.LOL

I still like the JK Phased array I like the Bazooka on the upper bands 40 - up and I like loops
I've built them all at one time or another right now all I have up is a Bazooka for 20 meter PSK
it's up 20 Ft. and I werked a guy on Galapagos Island with 1 watt on a bazooka. :)

I'm waiting on the leaves to fall for the big wires to go up. :)

73 O.M.
Jack
KA3ZLR

Hey Jack
Now Receive directiveness WILL come from animals like Ewes, Flag antenna, K9AY loops, and LOOOONG beverages terminate(?) or unterminate(?)
Transmitting it is height above ground for a vertical 1/8 wavelength or more (with 65 feet vert height as a beginning) and horizontal is wire length and definitely height above ground, with 1/2 wave as a starting point. There are phased arrays for 160M, but it'll cost ya.
Anything else is a compromise and the antenna WILL work but not what you were expecting. 80M starts to be easy street and 40 and up is a piece of cake. But then you can skip over areas that you want to cover.

I'm for that Fred, it's that time of year again :)

Here's a Homebrew Vertical for 160 published in June QST 2009 I like verticals  :)
I haven't built this one yet...you and I both know big gains are not to be found in
single wire antennas you get what ya put into them and most are just throwed up.


With all due respect. :)

73
Jack
KA3ZLR

http://www.hamuniverse.com/k6mm160metervertical.html

Here's a Good tutorial here and a 160 Wire that does werk I had one up wind tore it down. :)

http://www.amwindow.org/tech/htm/160smallants.htm

Go by what is said here in this Article you can't go wrong.

And another thing about loops you can put an open in them an they change their
Attributes like a 80 meter horizontal loop put an open in it at the feed point keeping
all sides equal in a complete circle an now you have a 160 meter vertical I've done it,
it werks.. :)Very well.



73
Jack
KA3ZLR

Gotham Vertical - See Pics

On the Vertical, there seems to be a bit of reactance between the phased array.

klc

heheheheh also causing a vertical reaction, testing the hydraulics out.
Nice pics!!!!