[AMRadio] Thank You and Toroidal transformers


Brett gazdzinski brett.gazdzinski at verizonbusiness.com
Fri Dec 29 10:10:38 EST 2006


The peak voltages are an issue, but more of
a problem is the duty cycle.
Running 300 watts carrier with 1200 watts pep
has a much higher duty cycle then 2000 watts pep
in ssb service.
I think even 100 watts of AM has more of a duty cycle
then 2000 watts pep ssb.

I gave up a long time ago on traps and baluns, coils
are ok, like the butternut vertical, or loading
coils on a dipole, but any cap needs to be something
like 10 or 20 kv to hold up.

While running experimental antennas through an antenna 
tuner, I have had the rg214 get HOT, set fire to the
balun in the heatkit antenna tuner, etc.

I am trying to come up with a multiband antenna that will fit
my lot (100 feet between trees), and the only thing that
would work well at my power levels would be open wire
line into a balanced antenna tuner.
A tuner to handle my power would be huge, with massive
coils that would be hard to make out of copper tubing,
very large caps and switches, etc...

I found a very good design in an old arrl handbook,
1966 I think, but its LARGE and states its good
for 500 watts of AM I think, or maybe less.

The other idea is a G5RV, with very little coax
between the balanced line and the tuner, and careful
tuning of the length.

I might be able to put a G5RV up next to the 40 meter dipole
and test its operation..

Brett
N2DTS






 

> -----Original Message-----
> From: amradio-bounces at mailman.qth.net 
> [mailto:amradio-bounces at mailman.qth.net] On Behalf Of Ed Sieb
> Sent: Friday, December 29, 2006 8:48 AM
> To: Discussion of AM Radio in the Amateur Service
> Subject: RE: [AMRadio] Thank You and Toroidal transformers
> 
> Yup, I zapped and zorched a "300 Watt" antenna tuner with my 
> DX-100!   100W
> of well modulated AM equals 400W PEP! More if your running over 100%
> positive peaks! 125% positive=500WPEP!  Few small tuners will 
> handle that,
> and a TH3Jr or TA33Jr  tri-bander certainly won't!
> 
> Ed, VA3ES
> ------------------------------------------------------
> 
> 
> Brett gazdzinski wrote:
> My guess is the hardline will work fine without
> any matching, most Pi nets will match it fine.
> I also don't like toroids or baluns on AM,
> high power (or even medium power) AM tends to overload
> and/or cook anything like traps or baluns in short order.
> Many antennas rated for 2kw plus pep crap out with 100
> watts of AM on them....
> I blew out traps in a trapped dipole and in a vertical
> antenna with a DX100 (100 watts out).
> 
> 
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