[Amps] New SGC Mini Lini Uses Class E Technology

[Bill Fuqua]

     My point was, that if the band modules were only passive devices why 
cooling at all? And then I realized the Power MOSFET must be in the band 
module.  Tuning is critical in Class-E amplifiers and perhaps each one has 
to be tuned to match its own Power MOSFETs .
     Here is the thing about envelop restoration that troubles me.  Once 
you clip the input signals you have produced the worst case (nightmare) IMD 
generator that will make loads of IMD products. The harmonics will, of 
coarse,  be eliminated by the output filter.  The trick is that you are 
going to modulate the envelope in such a way as to produce other sidebands 
that have just the right phase relationship to the undesired ones as to 
cancel them out while making the others the right amplitude.  This may be 
trivial and once the Balance is made it is just fine. But, it seems to me 
that maintaining that balance may be difficult over the life of the product 
or after a RF semiconductor is replaced. Alingment may require instruments 
that many hams do not normally have today.
     If anyone happens to get more detailed information of that inner 
workings of this amplifier. Please let me know and send me copies.

73
Bill wa4lav


At 05:20 PM 7/3/2005 -0400, you wrote:
>In a message dated 7/2/2005 8:25:03 PM Eastern Standard Time, 
>wlfuqu00 at uky.edu writes:
>I have some questions.
>Why does the plug-in band module need so much cooling air and what are the 
>drive requirements?
>You realize that this adds to the DAF discussion. Which practically does 
>the same thing.  I have had some nagging issues with the DAF circuit.  One 
>is if you are amlifing AM for example and eleminate the envelope and 
>restore it that would work just fine. But, if you have multiple 
>frequencies of different amplitudes that you clip and then restore the 
>envelope, how does each seperate frequency get assigned it's approprate 
>amplitude?
>These last question has nagged me for some time.
>
>73
>Bill wa4lav
>
>Hi Bill,
>        On the SGC Mini Lini, I don't think it requires a huge amount of 
> cooling air. I believe the amplifier plug-in modules are the size of a 
> small cube maybe 3 x 4 inches and they have a small fan mounted right 
> behind the heatsink  for good cooling. That allowed them to make the 
> heatsink smaller and lighter and keep the size and weight of the 
> amplifier down. Otherwise they would have had to use a heatsink maybe 4 
> or 5 times bigger and heavier that weighed several pounds on its own. I'm 
> not sure what do the letters DAF stand for? The drive requirements would 
> be small since all they have to do is sample the driving signal - they 
> would probab;y only need a few volts of signal. There is probably a dummy 
> load resistor at the input of the amplifier and you would only need a few 
> watts of drive to sample the signal, maybe 5 or 10 watts if that much 
> depending on how far down you can throttle the exciter.  You need 2 
> channels in an EER amplifier. One channel samples the amplitude 
> information using a diode-type detector. This is the fuzzy-sounding audio 
> you would hear in a receiver without the BFO turned on if you were 
> listening to a SSB signal. The other channel samples  the phase 
> information using a hard-limiter so you are left with a 
> constant-amplitude but phase-changing low-level carrier I believe. The 
> phase-changing carrier is amplified directly by the Class-E amplifier. 
> The audio amplitude information is amplified by a PWM audio amplifier and 
> it high-level modulates the Class-E amplifier like you would an AM 
> transmitter. When the signals recombine it  cancels out the carrier and 
> you are left with a reconstituted high-level SSB signal. That is how I 
> best understand how the system works. I think you get a delay in the 
> audio signal when it is amplified so you have to use some kind of delay 
> in the phase channel of the signal so when they recombine the signal is a 
> perfect copy of the original. I'm not sure how it would sound if you 
> didn't do this - it would either sound totally weird or perhaps very 
> distorted? 73 Todd WD4NGG