The Yaesu Mk V in class A, on the other hand is astoundingly clean.
http://nc0b.com/documents/NC0B-Contest-U-2008-9.pdf
Joe Subich, W4TV wrote:
>
>
>> As a general rule if you can reduce your amp driving power in
>> half you gain a 3db reduction in the transceiver IMD.
>>
>
> This is one of those "general rules" that is very wrong when it
> comes to solid state transceivers. Almost all modern power
> transistors have a "saddle shaped" IMD curve. When power output
> is reduced significantly below the optimum point IMD increases.
> If power is increased above optimum IMD increases rapidly.
>
> For example, look at the 2SC2879 used in the Yaesu Mark V Field:
> http://www.datasheet4u.com/download.php?id=71199. The IMD vs. Power
> Output curves show a "sweet spot" around 55 to 65 watts per transistor
> before filter and transformer losses of about -38 dB. With the losses
> in the transformer, lowpass filter and antenna tuner, this represents
> just about the transceiver's rated 100 watt output. Decreasing power
> to 40 watts per transistor (1.4 dB) increases IMD by more than 6 dB!
> Increasing power output to 80 watts per transistor (~1 dB) results in
> an 8 dB IMD increase and pushing to 100 watts (~2 dB) per transistor
> results in a nearly 14 dB increase in IMD.
>
> If your amplifier requires substantially less drive than your
> transceiver produces you are better off using an attenuator on
> its input rather than reducing the drive in the transceiver.
>
> 73,
>
> ... Joe, W4TV
>
>
>
>
>
>
>> -----Original Message-----
>> From: amps-bounces@contesting.com
>> [mailto:amps-bounces@contesting.com] On Behalf Of Robert Kirkland
>> Sent: Sunday, August 31, 2008 9:04 AM
>> To: amps
>> Subject: [Amps] IMD and driving power
>>
>>
>> As a general rule if you can reduce your amp driving power in
>> half you gain
>> a 3db reduction in the transceiver IMD. Less in, less out. Bob,w5pvr
>>
>> _______________________________________________
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>> Amps@contesting.com http://lists.contesting.com/mailman/listinfo/amps
>>
>
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