Topband: 160M Helical Vertical

[GERRY]

Another thing to keep in mind is that at legal limits the voltage at the 
base of a short loaded vertical can be very significant and might short 
between windings. Also the tape clearly has to handle the high current and 
not negatively impact radiation efficiency by adding significant element 
resistance.

73, Gerry VE6LB/VA6XDX
VE6 QSL Bureau Team
DXCC Field Checker
ve6lb at telus.net
403-251-0384
http://www.qsl.net/ve6lb

--------------------------------------------------
From: <k3bu at optimum.net>
Sent: Thursday, March 31, 2011 3:33 PM
To: "paulkb8n" <paulkb8n at aol.com>
Cc: <topband at contesting.com>
Subject: Re: Topband: 160M  Helical Vertical

> Here some info on loading coils and current distribution in loaded 
> resonant antennas.
> http://www.k3bu.us/loadingcoils.htm
> In the nutshell: efficiency is roughly proportional to the area under the 
> current curve along the radiator.
> It is better to have loading coil or top loading than distributed helical.
>
> Yuri  K3BU.us
>
>
> ----- Original Message -----
> From: paulkb8n
> Date: Thursday, March 31, 2011 2:36 am
> Subject: Topband: 160M Helical Vertical
> To: topband at contesting.com
>
>> I've read a lot about the K6MM vertical and may be forced to go
>> that route, as the Neighborhood Association has received some
>> complaints on my current 160M dipole and I may be forced to
>> remove it.
>>
>> Somehow, I feel that the K6MM design might be improved. I've
>> been testing an 80M version using some military-style fiberglass
>> mast poles with my helix made out of copper foil tape. This has
>> resulted in a much more tidy and easier way to construct the
>> helix. I also believe the 1.5 mil foil has less capacitive
>> losses between turns than the wire that is used by K6MM. I am
>> using a one-quarter inch wide foil tape on my 80M version, and
>> with fairly close spacing and a small capacitive hat, I can
>> squeeze the antenna size down to only 8'.
>>
>> I've been testing this antenna indoors in my attic, and it seems
>> to work remarkably well. I've gotten decent reports around the
>> states, and have worked some modest DX.
>>
>> I have no idea how the foil tape helix could be modeled. I have
>> built several working helical segments using various diameter,
>> tape size and pitch, and measurements suggest that using a half-
>> wave of foil tape in the helix will yield a quarter-wave of
>> electrical length. Every design I've tested seems to show nice
>> usable bandwidth against a fairly decent ground (center screen
>> and 12 radials). I am wondering how the flat foil tape will
>> perform compared to a regular round conductor? Also, what width
>> of foil tape would be adequate for 160M use? Has anyone modeled
>> or experimented with this? Can the
>>
>> My 80M version's performance gives me hope that a short 160M
>> helical vertical might work effectively as well. Any thoughts
>> or suggestions will be appreciated.
>>
>> Thanks, Paul, K5AF
>> _______________________________________________
>> UR RST IS ... ... ..9 QSB QSB - hw? BK
>>
> _______________________________________________
> UR RST IS ... ... ..9 QSB QSB - hw? BK