Date: Wed, 25 Feb 2015 18:23:34 -0800
From: Jim Brown <jim@audiosystemsgroup.com>
To: towertalk@contesting.com
Subject: Re: [TowerTalk] Mosley Antenna Question
On Wed,2/25/2015 6:08 PM, David Gallatin via TowerTalk wrote:
> Kelly, could you please give some examples of the antennas you are talking
> about that are "a smaller, computer-modelled, trapless
> interlacedmulti-monobander"
I'm not Kelly, but I'll some. The Force 12 C3, C3S, C3SS, C31XR, C19XR,
and C4XL, are well respected antennas. The oldest of these designs date
from the late 90s. Force 12 has recently changed hands (the original
owner is a much better engineer than businessman), and is now owned by
InnovAntennas America.
http://www.force12inc.com/categories/beam-antennas/classic-c-series-multi-mono-triband-yagi-beams.html?sort=pricedesc
73, Jim K9YC
## heres the latest from F12. 20-15-10 all on barely a 10 ft boom.
http://www.force12inc.com/products/xr3-compact-6-element-20m-15m-10m-multi-mono-contest-yagi.html
## heres the latest and greatest..with booms shrunk by 30%. The old C3, xr5
etc line up has been upgraded to the newer format.
http://www.force12inc.com/categories/beam-antennas/all-new-xr-series-multi-mono-hf-yagi-beams.html?sort=pricedesc
## BTW, I see n6bt wrote an entire section on trapped yagis in his book,
array of light. . Turns out I was correct. By encasing the coils with AL
tube, the coil Q drops down to just 20-30.
feed Z rises to close to 50 ohms..cuz of the excessive losses by the high esr
of the low q coils. He mentioned that one maker of trapped verticals used a
ceramic core to wind the coils on,
so it would handle the extreme temps.
## He also mentioned about HF yagis using the T match...and the 200:50 ohm
coax balun. Several of them had the main lobe canted off to one side by 20
degs ! The fix was to replace the T
match with a conventional hairpin setup. He did not mention the brand, but I
suspect it was telrex... the only co I know of that used a T match. Why the
lobe ended up skewed 20 degs to one
side is beyond me. He mentions fixing several of them.
## One of the hams 140 miles north of me had a trapped yagi..dunno which
brand, but it was not a 33 jr. More like the hygain explorer series or
similar. His neighbour was walking the dog after lunch and
noticed the ant was literally on fire ! Pounded on the front door to get his
attention. He had been using his henry 4 k with the single 8877 cranked to
max on 20m ssb with processor on. The end caps on the traps had melted and
caught fire, along with the polystyrene tube that the coil is wound on. All 4
x traps on the DE had flamed on virtually simultaneously. This was back
around mid 90s. This flaming glop came dripping down onto his roof like
naplam.
he was a nice fellow, and manager of the local rs at the time. never did find
out what he replaced it with. The folks in EU that he was rag chewing with at
the time, all got a good laugh out of it.
## When I blew the traps in my trapped vert back in the mid 70s, it simply
shorted, with sky high swr. it didn’t like the 1900 w out on cw from the
4-1000 amp. Swr on the very bottom of 40m was on the high side a bit, like
2.2: 1
Jim VE7RF
_______________________________________________
_______________________________________________
TowerTalk mailing list
TowerTalk@contesting.com
http://lists.contesting.com/mailman/listinfo/towertalk
|