>
>From: Peter Chadwick <Peter_Chadwick@mitel.com>
>
>First, I agree that receiver intercept is hardly an issue unless
>someone leaves a noise blanker on or has too much front end gain.
>
>The largest problem is by far the very very poor transmitter IMD
>specs tolerated, and poor operation of conventional linears.
>
>One fellow who LOVES the G2DAF'fy self-biased keeps bugging
>Ameritron to build cathode driven tetrodes with the DAF circuit
>because they are "good enough for Hams".
>
? Part 97 allow any amount of in band splatter within amateur service
bands as long as it does not interfere with emergency communications.
>The G2DAF design he tested measured about -25 dB below PEP,
? the two I tested had a total IMD that was c. 22db down.
>which is -19 dB below one tone of a two tone test in a commercial
>type test. A standard pair of 3CX800's measures in the -46 dB
>range in amateur type testing, and -40 dB or better in normal
>testing.
>
>Even 811 tubes pushed to the limit are much cleaner than a
>conservative Daffy circuit.
>
>I can see no reason to downgrade the poor IMD standards we
>tolerate even more.
>
>> The assumptions made and not stated (something you shouldn't do on this
>> reflector!) are that we are talking about an SSB bandwidth, 10dB noise
>> figure, and HF operation.
>
>and as proof to that statement, let me keep the spirit going.....
>
>You said:
>> triode pushing a couple of watts input. It drifts like Kon Tiki, pulls
>> like a Union Pacific Big Boy, has more FM when modulated than KFOX, gives
>> hernias when you lift it. But it's good on phase noise.......
>
>The 4-8-8-4 Big Boy's because of its lighter weight on the drivers,
>actually had less tractive effort than the Allegheny 2-6-6-6. IMO,
>that generator pulls like a Allegheny 2-6-6-6, and weighs almost as
>much as one.
>
>By the way, the Big Boy had a problem you may not have heard of.
>The basic problem with the Big Boy was a parasitic resonance in
>the drivers, causing massive boiler explosions when parked in the
>Sun. The root cause was high energy stimulated emission of
>steam caused by photon bombardment of the steam recovery
>pumps. This caused a sharp peak in pressure, causing the drivers
>to ring like a gong. This happened even while the engine was in
>standby, with a cold fire box (called a "Hillery" in US railroad slang).
>
>In the 70's USA automobiles were made with recycled steel, some
>of which was from the Big Boy drivers. Pinto's used this metal in
>gas tanks, and when the car was gently tapped from the rear the
>tank would go into an uncontrolled oscillation and explode.
>
>Ford changed the tanks to material recycled from the Allegheny 2-
>6-6-6, and that cured the problem. Very few tanks have exploded in
>1979 and newer Pinto models. Rumor has it that the side mounted
>fuel tanks in GM trucks also used Big Boy driver steel.
>
>
? and remember kids, just say no to drugs.
Rich...
R. L. Measures, 805-386-3734, AG6K, www.vcnet.com/measures
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