Another Antenna/Balun Question

[K1JJ]

Vely, vely well thought out, Steve.

The points you mention concerning house absorbtion and less hops are more reasons to do everything possible to get to the magic number of 60' above ground on 75M. We all have our backyard limitations and do what we can.

It must be kept in perspective that this  ~ 3db improvement is a lot. Hams kill themselves to put up 3el Yagis that give only a 4-5 db improvement over a dipole.  Antenna db is hard-earned... probably one of the most difficult things to pull off since there are so many variables and things that can go wrong.

The end result is to listen to the many stations on the air. Over time you can tell the stations that are doing things right and the ones who are not by their average signal strength consistency.  The one station that comes to mind is Ed, WA3PUN who had a dipole at 60' for years. He was always the Channelmaster here for the 350 mile trip.

A db here, a db there - they start to add up after awhile... :-)

I think most newcomers instinctively know they need to get the dipole up as high as possible, but usually don't know the real reasons why or the specific parameters to shoot for. Your info gives all the right reasons to plan for the best possible erection from the start. (Viva)

I think many simply throw up a G5RV in the trees and then slowly make improvements from there over time. This thread gives a specific plan to do it right the first time.  How many times in new hobbies I wish I started out right, but had to learn as I went along.

Another point to remember is if we are hard-pressed to reach 1/4 wavelemgth above ground, it is better to use a simple 1/2 wave dipole rather than two half-waves-in-phase, extended double Zepp, etc. The shorter antenna will have less ground coupling and a lower angle of radiation, thus less loss in comparison and better angle. Also, it is probably easier to get the ends higher using a shorter antenna.  Plus, for a FIXED antenna, attempting to obtain a narrow pattern with longer legs resulting in deep nulls elsewhere is not a good idea for local AM work.


Frank, I'll be curious how your L system works out. Be sure to insure you are using a reference antenna (the 160M ant?) and they are not coupling, giving false readings. That will be hard to prevent due to their near proximity.  A min 300'-400' separation is required OR they need to be at perfect right angles from one another (or collinear, not broadside) OR one needs to have a reflector separating the two to keep interaction minimal.  If you see little difference between the two, I wud be suspect.  Obviously, making a meaningful determination between the driven array and L will not me possible if the driven is down since condix change minute to minute.

Tom, K1JJ

[WA1GFZ]

Tom,
I will be able to compare it to the dipole in the woods. The ends will be close to each other but they will line up  If it doesn't work it will be the new dipole required to get the phased array working again. I keep coming back to the CF inverted L every time I get into simulation. 30 to 60 degrees TO is not bad and still OK at 90 degrees. It just keeps coming up as a winner. I want to play with spacing from the tower. I have not tried putting it broadside to the tower which would put it 90 degrees from the reference. That may be an even better test. There is plenty of room in the yard to put it either way and up at least 70 feet.
I also want to try phasing a pair of them. The nice thing about that is it only takes 65 by 65 feet.
Also tried a 2 wire cage with a BW good 3.5 to 3.9 MHz at 2:1 VSWR.   

[K1JJ]

Sounds like you gots it covered, Frank.

A pair of phased L's is very worthwhile, assuming your ground conductivity is OK. Otherwise I'd switch back to the proven horizontal phased dipoles.

Another way to test it is we can get down in the DX window and do a series of comparison tests into Europe over a coupla nights. If I run exactly the same set up each time, you will start to see a very close difference number that can be used when you try the next ant, etc.  It's amazing even with changing condix how the differential between two stations remains pretty close, esp for long haul DX.  Local tests are much more difficult and unreliable in comparison.

T

[WA1GFZ]

I was looking at a Cebik article and he also says the ground effects are less with a CF inverted L compared to base fed. I guess comparing a vertical GP to a vertical dipole.
Yup, if it doesn't work no harm done just hang it horizontal in the woods.

[W2PHL]

Well I just got down from the roof.  The Jackite mast does not function well as an inverted V center support.  The gusty winds today were snapping it around like a whip. Mission aborted.

As some have already implied, I will have to use something more substantial. 

Thanks guys.

[WA1GFZ]

well, WX too good becuse  I just gave the CF inverted the last yank to pull it into place and a ceramic end insulator snapped at the top of the tower.
I didn't even see it break. I was about to tie off the vertical lead and looked up and the other 1/2 of the antenna was missing. Dropped the whole thing back down and got another insulator. (the old one must have been dropped because that never happened before). Then the sky opened up. Weird warnings for twisters and the sky is a funky color.

[WA1GFZ]

what a dope I am. The high winds would have cleared the branches for me had I not given that last yank. I could be on the air with the new ant testing tonight,. The end was off the ground and I wanted more.

No place like homer out there tonight

[WA1GFZ]

well got the CF inverted L up but had to put the feed point near the tower. Just too many branches in the way. End is a good 80 feet and feed point about 60. Vertical  is on a slight angle. Faces West. AWA net Herb K2VH is about even money with the diople but most others louder on the reference.

[WA1GFZ]

WX not bad enough. Simulation shows VSWR messed up and pattern screwed with feed point near tower. I did notice a tree fell in the woods that was blocking the new position of phased array. Maybe it is time to go back to it.