[TowerTalk] Mosley..again.

[Jim Thomson]

Since the 70s,  at least a dozen times we have helped swap a Mosely TA-33 jr to 
something else, usually a Hy-gain 204BA.   The difference on 20m is the usual 10 db.
Think about it, 12 times that has been done locally.  The former mosely owners
said the reason they bought the mosely ta-33 jr was  everything from  super high
gain figures,  superb FB, superb FS, low cost, light in weight, cheap to buy,
simple rotor, only one coax, no balun required  and most of them...including the local radio inspector
at the time,  bought the 33jr...cuz of its outstanding swr curves !! 

The problem with traps is they always put the 10 and 15m traps in the same casing..nose to tail. 
On 10m it’s a 10m trap.  On 15M, the  10m trap is now a loading coil on 15m.  problem is that 15m
loading coil is at the end of the 10m ele.  If ur gonna build a shortened 15m tapped, monoband yagi,
and used coils, you would not place the coils more than  half way out each ele half.   On 20m,
the 10 and 15m traps are now loading coils for 20m. 

The only way the swr ends up flat on all 3 bands is cuz of a trap fudge.   the feedpoint Z is obviously
way less than 50 ohms on both 20 + 15m.  But with the trap losses thrown into the mix, the feedpoint
Z ends up closer to 50 ohms... and presto, flat swr.   Several local folks had the infamous wilson 
system 1 back in the day..trapped tribander.  It used a hairpin match.   Now someone explain to me how the hell  you
can make a hairpin match work on 3 bands ???  

A fellow 140 miles north of me installed a Mosely PRO-96.   What a gong show, and then some.   I looked at the 
PRO-96 myself, years ago.  After talking to Mosely reps at the factory, I find out its really only good for 600W
on rtty..and that’s only in the middle of each band, where swr is flat.   They said NOT to run 1.5 kw rtty into it,
on any band = kablamo. 

Some trapped yagis  have worked fairly well for a lot of folks.   The problems  start after a few years..and the 
coil connections at each end of each trap start to deteriorate.   Then the losses increase even more, meanwhile
its has same or better swr, good fb and good fs.   Local friend has the big trapped tribander..up 80 ft.   I could literally
talk right over top of him on 20m, with my f-12  5-el 20m, monoband yagi up 40 ft.   That’s into EU  from the west coast. 

Another local fellow had the big 6 el telrex 20m monoband yagi  up 80 ft.   After 10 yrs of use, he swapped to the big
telrex triband trapped yagi.   He gained 2 bands, but was no longer the kingpin on 20m, he lost a carefully measured 6db.

Fact is a simple F-12 C3, with only 2 els per band will out do most trapped yagis.   trapped yagis provided 3 bands..and 5 bands
with later models..which is a lot more bands than any 204BA.   Trapped yagis  provide for several bands with just one yagi. 
These days  you can get  6 bands with one ant..and no traps.   F12  5BA for example.  Or the 40-10m f-12 ants.  or any of the
optibeam yagis.   IMO, it would really be silly to spend $$  on trapped yagis in 2015,  esp when they can easily be out performed. 

Jim   VE7RF