[TowerTalk] Vertical comparison question

[Jim Thomson]

Date: Sat, 6 Apr 2013 03:17:15 -0000
From: "John G." <af5cc at fidmail.com>
To: "Dan Hearn" <n5ardxcc at gmail.com>
Cc: towertalk at contesting.com
Subject: Re: [TowerTalk] Vertical comparison question

Hi Dan

How lossy are traps really?  I have seen so many diffrent figures on how bad they are or aren't

73 John AF5CC

##  I literally melted two trap vert ants  back in the mid 70s. .... with 1900 w out on cw. 
A buddy had a TA-33 jr... thay went screwy one day..so we took it down off his tower.
Slid the covers off the traps on the DE...and the forms that the coils  are wound on, were
completely melted !    It look like somebody had run a propane torch up and down it.
He was using a SB-220  at the time...1200 w pep out, ssb only. 

##  telrex used fixed HEC / centralab style  HV, NPO TX caps on their trapped  yagis...and they
too are a pita.   Phil, K5pc, was always getting Telrex to send him more caps, etc.

##  fixed ceramic vac caps and 6 ga  cu wire  or .187”  tubing might work for traps, but heavy.

##  The real answer is probably the  multiband  stepir  verticals. No traps, and it can be tuned dead on
right across the entire hf spectrun, like 7-54 mhz.   But it would require radials. 

##  seco systems makes motor driven compressible  coils, with a 2:1  uh range.  IE:  6-12,  10-20, etc. 
These are used on verticals to resonate anywhere within ONE band, like 80m.  they also make em, so
when the coils are fully expanded, they short out each coil, taking it right out of the circuit !   that way, it
will work on a 2nd band, like a monoband vert. 

##  resonant  radials, esp for 40m,  can be a pita in some cases.   back in the 70s,  I used a 20’  tv mast
on the roof, and the trap vertical above that.  Then loads of room for 40m radials.  But the roof was 29’ tall,
and the very top of the vertical was 70’ above ground.   No easy feat, but doable. 

the step IR vert is worth checking into.... but again, requires radials.   radial laid on a roof can also be bent at the
ends to make em fit in.  that works,  but I used insulated wire for the radials. 

F-12  also makes some lossless vert arrays, with T bars.....  capacity hats. 

Jim   VE7RF