[TowerTalk] Re: [antennaware] Re: Hygain Hytower

[K7GCO@aol.com]

In a message dated 06.02.00 18:20:31 Pacific Standard Time, dx@swipnet.se 
writes:

<< 
 > Looking for any mods on the old Hy-Gain 18HT Hy Tower.  I read that there
 > were some that increased the length to 63 feet...if anyone can help
 > would be greatly appreciated.  thanx   Tim  WB8OWX
 
 The K7GCO Modified HT-18 Hy-Tower, CQ September 1971, page 28.
 
 73 ...Thomas, SM6CNS [DU7CC] >>

Thomas: You are a sharp observer.  That goes back 29 years and there is more 
of them. 
Tim: My modification added a top loading inductor and a 10' or so tip for 
160M.  The Hy-Tower can be base loaded to 160 but it doesn't work as well.  
This is current fed on 160M.  I resonated it lower than the operating 
frequency which makes it inductive, added a certain Xc across the feedpoint 
when of certain values creates an L network matching the 25 ohms to 50.  This 
technique is used on mobile whips.  On 80/75M, it's a voltage fed 1/2 W with 
an L network with good bandwidth.  It's top loaded with the high current at 
the top--the ideal configuration.  It's an upside down ground plane and the 
most effective configuration for 1/4 WL high. The DX called me.  No big 
radial system is needed with this configuration. On 40M it's voltage fed 
again with a L network and it's 1 WL long.  The top 1/2 wave is out of phase 
and short.  It's close to an equivalent 1/2 wave in performance.
     It was hinged and I could tip it up all by myself.  The top section 
needed 4 way bracing.  I have built an improved much better looking model 
using a 40' length of 3" irrigation tubing (instead of 24' of tower) with the 
necessary extensions without extra bracing and also hinged at the base.  This 
worked electrically the same way.  I then added another design of 5/8 wave 
radiating lengths for 10, 11, 12, 15, 17&20M in a novel way.  It used current 
feed on 40&75M as a 1/4 wave.  It used a variable inductor driven by a selsyn 
at the base for broadbanding and no capacitors.  This is a very practical 
design with a couple of new techniques, easy to build and will be written up 
for one of the mags.  It's been well tested.  K7GCO   
 

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