[TowerTalk] 2-el 15/20 meter duobander

[Jim Thomson]

Date: Tue, 28 Nov 2017 17:14:40 -0800
From: "AA6DX - Mark" <cqdx at suddenlink.net>
To: "TT" <towertalk at contesting.com>
Subject: Re: [TowerTalk] 2-el 15/20 meter duobander

<In the wayback, (70S), I contested/dxed using a DB-54 Wilson on a 40' 
<boom -- was interlaced 20/15 --  and, the 4 15M elements were inside the 
<20M. If memory serves me, this design was in the QSTreet magazine..n'est-ce 
<pas? Had it on a W-67 tower, which bit the dust, after I added a 6el Wilson 
<for 10M on the tippy-top -- an educating experience!  B U T  -- in the 
<meantime, worky-worky!
<73 -- Merry Christmas -- Mark  AA6DX

##  we had several of the interlaced wilson yagis here in town back in the 70s.
None of em worked worth a damn.   The higher freq always suffered badly. 

##  I had a wilson 5 el  15m yagi, on a 26 ft boom, it too was a dud.   My conclusion
was Wilson had no clue as to what they were actually doing.   Nobody had a clue how to handle
swedged eles back then.   Another local buddy also had the wilson 5 el 15m, and 4 el on 10m
yagi.   You think my wilson 5 el 15m monobander was bad, adding 4 els to it  for 10m  was even worse.
15m was severely de-graded, and 10m portion was a total write off.   The wilsons would sorta work, provided
you installed them up high , like  70-100 ft, and stuffed several kw into them. 


## My last version of YO  was called  YO-7.05     YO would not do a 2 el yagi, only 3 els and more. 
The only way around that was to make the boom  super extra long, like say  150 ft or more... to put the
director way out at the end of the boom, so the REF and DE  did not  ..see  the  DIR. 

##  YO would not design any interlaced yagi, only monobanders.     YO would also not allow you to design
any OWA yagi either.  YO software  would not allow any 2 els to get closer than .09 wavelengths, so that killed
any notions of any OWA  design right there.   YO had a limit on how long..or short each ele could be..in any 
monobander.   Trying to tweak a gamma or oemga match on a DE that was way out on the boom was a trick in itself. 
Ditto with any version of a HB hairpin. 

##  another contester buddy  had the 3 el 20m telrex..on a 26 ft boom.   The boom was  way too long for just
3 els.  Els  are fixed on any telrex, so the best I could do was to tweak the tip lengths, which made a huge 
impact for his application. 

##  I forget how I handled swedged eles in YO, it was a real bitch.  I believe  I had to take each swedge and  segment
it down into smaller segments, where each swedge was.   Im talking about where the ele reduces from  say 
1.25 inch OD...down to 1.0 inch.   With each ele having loads of swedges, the design is easily messed up. 

##  These days, I use tubing that slides into the next, or if having to jump diameters, use inserts that still allow for tubing
to slide easily into the next section... no swedges.       

##  some of the..yagi designs back in the 70s  were totally off the wall.   Then along comes telrex with its  6 equally
spaced els  for their 6 el on a  46 ft boom.   Ditto with their 8 els on 15m, also on a 46 ft boom..... and ditto with their
10 el on 10m, also on a 46 ft boom.   Again, the best I could do was to tweak the tips, since eles were fixed. 

##  back then, loads of triband, trapped yagis, with the usual issues of lousy, int trap connections, melted traps, blown
baluns, mosely baluns, etc.   One local fellow had the  big telrex tribander..that used  traps that consisted of  a coil,
plus a doorknob cap in parallel with the coil, then the entire mess covered in heat shrink.   Caps were typ replaced in 
the DE  every 2 years. 

##  then a bunch of us decided to stack 20-15-10m monoband yagis on the same mast, in various xmas tree configs.
Typ the interaction between yagis resulted in  a net loss of gain and fb... negating any benefits from using monobanders
in the 1st place.   Then several locally used the infamous hygain  402BA.   The small, short spacers they used for the LL,
some were at HV points, and would either short out, carbon arc, or self destruct..and were replaced on a regular basis. 

##  I never owned any quads, but helped a lot of folks install them , or repair them..usually after a 70 mph wind, and or 
ice or snow loading.   After a  half dozen  repair jobs, I decided I would never entertain the thought of owning a quad, or
delta loop etc.   If you want a real laugh, stuff some of these old yagi designs from the 60s and 70s  into NEC-4.  Then
you will see why a lot of em did not work as advertised. 

##  The old days were fun, but a real pita.   The only thing that worked correctly back then was my small  prop pitch,
until it got water in it..and my  3 hb amps.   Ok, end of rant. 

Later... Jim   VE7RF