Re: Antenna


Howard Fidel
 

Gordon:
Thanks for the feedback. Back in my youth, I had a 15 meter 3 element yagi at one QTH and a 3 element 15 meter cubical quad at another QTH, and 15 meters was wide open. The house the quad was on was a 20' wide attached row house. The antenna was more then 20' on the diagonal so I always parked it so it didn't hang over the neighbors when I wasn't on the air. Never had a complaint about the antenna. Everyone had over the air antennas for TV back then, so I did get 1 or 2 complaints about interference, but never anything about my antenna. I'll post a picture later.

Howard

On 4/30/2018 10:44 AM, Gordon Gibby wrote:

fan dipoles work fine and I've used them several times in my life, as did the fellow who mentored  me in WINLINK gateway construction --- good performance without a tuner!  By all means, post some photos!!!


My current favorite however is either a non-resonant dipole (140 feet is nice) fed with 300 ohm window line (harder to see) to a 1:1 or 4:1 balun (whichever works best) and then an LDG auto-tuner.    These have done 2+ years' service at my automated WiNLINK gateway(s).  


An alternative has been an off center fed style with balun works either in the center, or after a length of 300 ohm window line to a more protectected location....and then the auto-tuner.   


With both types there is often one frequency band that is tough to match --- and I stick in a coax-based trap (or two) in the antenna line tuned to just the difficult frequency, to change the effective length around there....and then it can tune basically any frequency from 3 - 30 MHz.   That sort of performance is necessary for the SHARES DHS winlink gateway system.


Antennnas are a hoot, and there are a zillion ways to succeed at it, so more power to you!!!!


Before I bought the 5-acre property in my gated HOA semi-rural community (target practice can frequency be heard around us) I got them to agree that a wire antenna was acceptable.   They basically didn't want huge antenna towers and huge yagi's.    Since I prefer thin little dipoles, they can hardly see mine.    Then I made a big thing about how they are part of a government backup communications system and also to help ships at sea --- and I've never heard a single complaint.   Another ham moved into the neighborhood and immediately threw up an end-fed long wire with an auto-tuner and is having a blast, just like me.   


Many people have published ways to hide antennas --- anything from bird houses (my neighbor actually put up a Bue Martin birdhouse that would be PERFECT) to invisible wires inside trees.  


From: BITX20@groups.io <BITX20@groups.io> on behalf of Howard Fidel <sonic1@...>
Sent: Monday, April 30, 2018 10:16 AM
To: BITX20@groups.io
Subject: [BITX20] Antenna
 
At my QTH we have restrictions on antenna height, no more then 7' above the roof line. My property is such that I did not have a place to put up a 40 meter dipole. I was hoping to put a multiband dipole. To achieve this, I combined two different antenna designs I found online. For the 40 meter part I adopted W5VM's shorty 40 design, which is under 38' long. From the same coax I added additional dipoles for the 20 15 and 10 meter bands using a modification the classic fan construction. 
The antenna is hung from the top of my chimney, about 25' of the ground to a tree on the property edge mounted at a point about 7' lower then the chimney mounted end. There were 2 surprises when I tested this. According to W5VM, the loading coil should be tapped 3 turns from the center for the drive point.  I designed the coil so I could test this tap, and 1 turn more and 1 turn less. All of these had SWRs over 2 to 1. Since it was easy to try, I moved the drive point to the end of the coil, and the SWR came down to an acceptable 1.6 to 1. The second surprise is that the SWR on the high end of the 80 meter band is also quite usable at as low as 1.5 to 1. 
The other unorthodox thing that I did was use 75 ohm RG6 coax, which if very inexpensive, I picked up 100' for $6. My design notes are attached on a spreadsheet. If anyone is interested I can post pictures.
Howard


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