[Amps] Amplifier Vs Plate Modulated

[Gary Schafer]

The amp is only going to be 60% efficient at 1500 watts. At 375 watts
carrier only, it will be around 30% efficient.

73
Gary  K4FMX

> -----Original Message-----
> From: Amps [mailto:amps-bounces at contesting.com] On Behalf Of Fuqua, Bill
> L
> Sent: Sunday, November 29, 2015 12:59 AM
> To: Roger (K8RI); amps at contesting.com
> Subject: Re: [Amps] Amplifier Vs Plate Modulated
> 
>   I did not deal with plate dissipation. 562.5 Watts power is the
> average power out for 1500 Watts PEP and
> 100% sinewave modulation. Now at 60% efficiency that amounts to 375
> Watts Plate Dissipation. So there are two limits.
> One is the PEP output the amplifier can produce at low distortion, the
> second is the plate dissipation. You would have
> to chose the lowest of the two. However, most amplifiers will be PEP
> Power Output limited not plate dissipation limited.
>   Please check my math.
> 73
> bill wa4lav
> 
> ________________________________________
> From: Fuqua, Bill L
> Sent: Saturday, November 28, 2015 7:29 PM
> To: Roger (K8RI); amps at contesting.com
> Subject: RE: [Amps] Amplifier Vs Plate Modulated
> 
>   By putting all the sideband power into one sideband you have a 3dB
> advantage over traditional AM because you could go to
> a 3kHz IF filter rather than 6kHz.
> 73
> Bill wa4lav
> 
> 
> ________________________________________
> From: Fuqua, Bill L
> Sent: Saturday, November 28, 2015 7:26 PM
> To: Roger (K8RI); amps at contesting.com
> Subject: RE: [Amps] Amplifier Vs Plate Modulated
> 
>    Lets see, for legal limit you will be limited to 1500W PEP/4 or 375
> Watts of carrier.
> Sideband power for will be half of that if you are running constant
> sinewave tone into your exciter so add another 187.5 Watts.
> The total power output for 1500W PEP 100% plate modulated by sinewave is
> 562.5 Watts average power.
>   Taking that into account I'd think most any modern full gallon
> amplifier could handle it.
> You could half the bandwidth but still have the same effective
> modulation by running 375W carrier and 187.5 Watts into
> one sideband only rather than split between two.
> 73
> Bill wa4lav
> ________________________________________
> From: Amps [amps-bounces at contesting.com] on behalf of Roger (K8RI)
> [k8ri at rogerhalstead.com]
> Sent: Thursday, November 26, 2015 1:27 AM
> To: amps at contesting.com
> Subject: [Amps] Amplifier Vs Plate Modulated
> 
> I've posted the following on two group. They are not cross posted.
> Please do not cross post answers.  If you must post to both groups,
> please cut and past rather than cross posting.  Thanks!
> 
> OK, I understand, there's less iron in an amp Vs plate modulation, but
> how about a low level carrier driving a legal limit, plate modulated
> stage Vs a low level AM signal into a linear amp?.  Which is
> preferable?  Not many commercial ham amps can stand up, to long winded,
> AM transmissions and from my experience most AMers tend to be long
> winded, me included.  I talk like I write<:-) However Plate modulated,
> or linear amp, the power out limit is the same. With the new power
> limitations, AM appears to be the only loser,
> 
> So, what is the advantages and disadvantages for each.  Yes, I
> understand that many of today's rigs will run a nice clean  AM signal of
> relatively low amplitude (25 to 75 watts, bearing in mind that the
> dissipation in class A is driving the amp right to its limit.
> 
> I haven't run AM since the old plate modulated days. OTOH, I do run the
> 5000MP in class A to drive a Tetrode to the legal limit.  The 5000MP amp
> only gets warm when run this way.  It gets hot if I reduce the drive.
> Class A runs the maximum dissipation with no signal input to the final.
> 
> Thoughts?
> 
> 73
> 
> Roger (K8RI)
> 
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