[Amps] rich Richard - tiny antenna

[Jim Thomson]

Date: Mon, 10 Apr 2017 15:24:51 +1200
From: Steve Wright <stevewrightnz at gmail.com>
To: amps at contesting.com
Subject: [Amps] rich Richard - tiny antenna

On 10/04/17 14:20,  Catherine James <catherine.james at att.net> wrote:
> Instead, you need an expensive auto-tuner and protection circuitry, whereas a tube radio is fine with a manual transmatch.  I use an ATR-30, which will tune just about anything.
>  

What is the fixation on this list with antenna tuners?  You lot are
starting to sound like a bunch of rich appliance operators!  Almost
every thread has reference to a verrry expensive antenna tuner!

Surely most multi-band yagi's, 1/4y verticals, plain ol' dipoles, and
any other competitive HF antenna that you would WANT to poke some
horsepower into is gonna have <1.5:1 SWR?  Maybe you alligators want to
tune up your half size g5rv on 160M or similar?

It's almost as baffling as the fixation with IMD..  Isn't the goal to
get on the air, work some DX and bend some jealous locals' S-meters?

And yet, a ACTUAL constructor asks a question about a GS-35b 2M amp and
doesn't ANY comment whatsoever!

Cmon people..  Make a resonant antenna already!


S

##  You  have to be a rich appliance operator to spend $7K   ( $9k + tax + shipping  in canada)   for a 
lousy 1.5 kw.   I wouldnt spend that kind of money on any amp..that has air variable 
tune + load caps either.   We added up the total parts cost for that  3CX-6000A7
amp I designed for a buddy a few years back, and with mostly new, and some used parts
it came out to aprx $7 K.   Manual tune, takes  45 secs to dial it up by the pre-sets,  and swap bands from
upper hf...to  160m.   The new 253 lb hypersil dahl xfmer had risen in price though.  $1600.00
I paid  $1400  for the same one, 2 years before.   Rated at  15 kva  CCS.   Full qsk, covers
warc + 60m too.  Does an easy 13 kw out.  At least he can say he got something for his $$.

##  hams  put the tuner at the wrong end of the coax.   My upper hf yagis are all flat, non issue.  The 40m
yagi is less than 2:1  across the band..up to 7280 khz.   Installed some vac relays + 1 inch wide
silver plated strap coils in a nema box at the feedpoint, and now its dead flat across the 300 khz. 

##  the 80m rotary dipole is only 70 khz wide.  Came up with this scheme to use a motor driven vac  cap,
but its heavy, and also had to use PWM, to slow it down, plus other issues.  The original plan was
a mess of  dpst relays and coils to provide for 8  segments.  Tossed that too, then went to plan C, and
installed a seco tornado drive, which is just a pair of motor driven compressible .25 inch OD plastic
tubing coils.  Each coil goes from 6.25 uh  to 12.5 uh... a  2: 1  ratio.    T bar capacity hats do the main
loading.   Ok, now, on paper at least, it will cover from 3300-4000 khz with a flat swr, problem finally solved.
Digital readout controller, + 10 x pre-sets, + manual up /down tuning.  

##  If the SS wonder amp wont deliver full power into a 2:1  swr  without  requiring the use of a tuner,  its not
designed correctly.    If an amp wont do 1.5 kw cxr out... CCS, then  its not the real deal.   Its an icas rated amp.
Being a SS amp, the switching power supply is not the issue, they are cheap.   The diplexer is not
the issue either.  Its probably a cooling issue. A water cooled heatsink  will be the ticket to cool these SS 
amps, as is already being done in several cases. 

## $9k  for lousy imd, on a par with a sweep tube amp  from 1972 is not in the cards for me.   Nor is junk like
a K3  xcvr with equally lousy TX IMD..deal breaker right there.. at –23 dbc.   I also looked at the yaesu 9000 xcvr, the 400watt
version, and it has the absolute worse IMD  of any xcvr ever produced bar none, well below any sweep tube amp. 
-13 dbc  for  IMD-3 .    Wtf are they playing at ?     

##  You had better have deep pockets if you have to ship any of the above outside the country to get it repaired.  

Jim  VE7RF