[TowerTalk] Magic Length for 160-40 vertical?

[Kirk Kleinschmidt]

Regarding the top-loaded doublet idea: I planned to do this, and I have the relays and the goodies on hand to implement it. My potential problem is, the 35-foot support tower is bracketed to the side of my garage... The yardarm at the top of the tower stands the center insulator about 4 feet "away" from the garage, but that puts the feed point only about 5 feet away from the side of the building.
My plan for the doublet is to drop the open-wire feed line straight down to my SGC autocoupler, which is mounted on a short T-post.
The small side yard has a 30 x 50 area suitable for radials. I planned to use a galvanized hardware cloth ground screen there for the first season, adjusting as necessary after winter fades. As it stands that would put the feed point of the vertical only five feet from the garage side of the radial screen.

I could mount the autocoupler in the "middle" of that radial space, "slanting" the open-wire feed line at a 25-degree angle (roughly).
But the 1-acre back yard has nothing in it but short grass... I was reading an article by one of the radial and grounding gurus the other day (Rudy?), and he suggested that a 30-foot "fat" vertical over a 500-square-foot ground screen (or an appropriate radial field) would make for a decent short vertical on the low bands. A 6-inch aluminum pipe that's 30-feet long seems nice and fat! It's also free, as in beer, so the price is right....
If I knew that the top-loaded doublet would work on the low bands (installed next to the garage of my wood-frame house over a heavily lopsided ground screen), I'd leave it at that. Maybe it will be okay...but maybe not. I have heard nothing but negative anecdotal reports about using verticals mounted close to houses, especially on the low bands.
So, knowing more details, do you think the top-loaded doublet will work? 

I've spent 13 seasons in a townhouse with an indoor attic antenna, so I need to work on my low-band DX and state totals! I managed to work ZL and VK on 80 CW with 5 W...and two Caribbean stations on 160 with 5 W (both using that attic-mounted 40-meter horizontal loop), but let's just say that wasn't the norm! On 20 and up it was a killer antenna (considering)...but I need to give some attention to the low bands....
Thanks,
--Kirk, NT0Z

My book, "Stealth Amateur Radio," is now available from www.stealthamateur.com and on the Amazon Kindle (soon) 

    On Friday, November 4, 2016 12:12 PM, Steve Jones <n6sj at earthlink.net> wrote:
 
 

 I second Rick's suggestion.  I have an 80M dipole up about 80 feet fed with
open wire line.  On 160M I short the feedline together in the shack, and
with an antenna tuner use it as a top-loaded vertical.  

I plan to eventually put up a stand-alone vertical over a radial system, but
for now this improvised antenna works well on 160M.  

Only drawback is I need to avoid touching bare metal in the shack when
transmitting to avoid RF burns!

73,
Steve
N6SJ


-----Original Message-----
From: TowerTalk [mailto:towertalk-bounces at contesting.com] On Behalf Of
Richard (Rick) Karlquist
Sent: Friday, November 04, 2016 8:40 AM
To: Kirk Kleinschmidt; Towertalk Reflector
Subject: Re: [TowerTalk] Magic Length for 160-40 vertical?

Tie the feed wires together and operate the existing antenna as a top loaded
vertical.  Forget about all the other ideas you mentioned.

Rick N6RK

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