Subj:  Hy-Gain 204BA
Date:  Thu, May 18, 1995 9:12 PM CDT
From:  0005543629@mcimail.com
X-From: 0005543629@mcimail.com (David & Barbara Leeson)
Sender: owner-cq-contest@tgv.com
Reply-to: 0005543629@mcimail.com (David & Barbara Leeson)
To: fish@crl.com (Bill KM9P), cq-contest@tgv.com (cq-contest)

The Hy-Gain 204BA seems to be the standard of comparison in short 
monobanders for 20m.  Some folks have suggested extending the boom, but 
making the 204BA longer runs you into the weird behavior of antennas that are 
near 1/2 wave boom length (you either get gain or F/B, but not both).  This 
happens for 20m boom lengths from 30-36 feet, although I do have a design for 
the 205BA at 34 feet (I've never been sure that F/B is worthwhile for 
contesting, and we designed the HC8A ants specifically not to have much F/B, 
around 10-15 dB, so we can hear and be heard in both directions).  Also this 
note will give you some ideas about reinforcing the elements if you need that 
for higher winds.

Here's a set of tip dimensions that work great over the whole band:

Refl      53"
Driven    50.75"
Dir 1     49.5"
Dir 2     49.5"

Other dimensions including Beta match are as standard per the manual.

To reinforce the elements for much higher wind, you need two inserts for the 
existing element:  Get some 1" x .035 or .049" wall tube, open each element 
at the joint between 1 1/4" tube and 1 1/8" tube, stick the 1" tube all the 
way down to the boom inside the 1 1/4" tube plus enough additional length to 
extend 15 1/2" out into the inside of the 1 1/8" tube (slides over, back to 
original position).  The length is different for each element, but you get 
the idea.  When assembling, in addition to hose clamp at this joint, drill 
and tap for 8-32 pan head stainless machine screw through all three tubes, 
just inside the location of the clamp, so the joint won't ever fall apart the 
way it usually does, and the reinforcement won't slip out of place.  Use 
plenty of NoAlox or other hateful goop on assembly to prevent oxidation later.

The only other piece that needs reinforcing is the 7/8" OD section, which 
needs 3/4" x 0.028 wall tubing 12" long, set flush with the inner end of the 
piece.  Drill for a 1/8" all-aluminum or all-stainless pop rivet at the outer 
end of the reinforcing section, so the reinforcement will stay in place, 
using plenty of goop on all joints.

Last, I support the boom by running a back guy out to each end of the boom, 
connecting at or outside the reflector and last director.  Attach the guy to 
mast about 24-30" up from boom.  I use a muffler clamp with a long U-bolt, 
tighten 1/2-height nuts to hold it to the mast in the right position, then 
slip the eye of a turnbuckle bolt over U-bolt legs, add a big, thick washer 
and another nut (Nylock is best)...I also use right and left hand lock nuts 
on the turnbuckle eye-bolts, so when it's adjusted for level boom I can lock 
the whole shebang (this is easier on a flat-top tower where you can really 
get up to the upper mast).  Since the boom and elements are symmetrical, I 
don't worry about wind balance on the 204BA. 

This setup will have great SWR, gain and F/B over whole band with stock Beta 
match, and will last through 120 mph winds.

73 de Dave, W6QHS