[Boatanchors] Using a SG-230 tuner on AM

[Gary Schafer]

Hi Carl,

You can't combine powers directly. You must first add the voltage of each
and then calculate the total power.

At 100% modulation it requires the plate voltage to double. 

As Mac says if you look at a scope on the output of the AM transmitter and
set it to read say 2 centimeters with carrier, then modulate it 100% you
should see 4 centimeters of voltage at the peaks of the audio waveform. You
have doubled the transmitter output voltage with 100% modulation. 
Since power is equal to the square of the voltage over resistance you will
have 4 times the power at the modulation waveform crests.
Peak envelope power is defined as the average power at the peak of the
modulation envelope over at least one RF cycle.

Now if you were to use some negative peak clipping or phase the mike to
where the positive modulation peaks are greater than the negative peaks you
could run even greater than 400 watts PEP out of the 100 watt out AM
transmitter, provided the finals could handle the extra power without
flattening out.

As to the tuner, if I remember right that was originally designed  for the
150 watt PEP marine radios. In the AM mode they ran around 40 watts of
carrier or so. 
You might get away with it with some loads where the current and or voltage
was not too extreme in the tuner but you are probably asking for a zapped
tuner. 

73
Gary K4FMX

> -----Original Message-----
> From: boatanchors-bounces at mailman.qth.net [mailto:boatanchors-
> bounces at mailman.qth.net] On Behalf Of Carl
> Sent: Sunday, August 09, 2009 2:56 PM
> To: D C *Mac* Macdonald; boatanchors at mailman.qth.net
> Subject: Re: [Boatanchors] Using a SG-230 tuner on AM
> 
> Its rated at 200W PEP.
> 
> However I still have a hard time understanding how you get  4X PEP on AM.
> 
> For 100% modulation it requires 50% of the RF plate input power. So thats
> 50W of audio on a 100W input final. At 70% efficiency thats 70W carrier
> and
> 50W of total audio using a rather conventional 1:1 modulation transformer
> ratio.
> 
> For a Viking I at 100W out that is 140W input which requires 70W audio.
> That
> comes out at 170W PEP in my book.
> 
> Carl
> KM1H
> 
> 
> ----- Original Message -----
> From: "D C *Mac* Macdonald" <k2gkk at hotmail.com>
> To: "KM1H Carl Huether" <km1h at jeremy.mv.com>;
> <boatanchors at mailman.qth.net>
> Sent: Sunday, August 09, 2009 3:26 PM
> Subject: RE: [Boatanchors] Using a SG-230 tuner on AM
> 
> 
> 
> Carl and otherson the boatanchors list:
> 
> I believe the SGC-230 is rated at 125 Watts PEP.
> 
> Since the Viking, DX-100, 32V-*, B&W, etc. ran
> close to 120 Watts carrier, 100% modulation would
> cause PEP output to be 400-500 Watts.
> 
> I don't believe it advisable to risk running that
> sort of power into the SGC.
> 
> I'm pretty sure most list members are aware of that
> fact but I believe that it bears refreshing.
> 
> 73 - Mac, K2GKK/5
> Oklahoma City, OK
> 
> 
> ----------------------------------------
> > From: km1h at jeremy.mv.com
> > To: boatanchors at mailman.qth.net
> > Date: Sun, 9 Aug 2009 14:30:11 -0400
> > Subject: [Boatanchors] Using a SG-230 tuner on AM
> >
> > Has anyone tried running a 100W output AM rig thru one of these?
> >
> > Id like to be able to be able to run a Viking I or II thru one using a
> 160
> > and 75M dipole in parallel for 160-20M.
> >
> > Carl
> > KM1H
> >=
> 
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