[Amps] ALS-1300... IMD ??

[Joe Subich, W4TV]

> What is the TX  IMD on this amp, when running full bore  at  
> 1200 w pep out ??    I suspect it won't be good.   The 
> ALS-600 is only -25db   

The ALS-1300 is effectively two ALS-600 amplifier boards in 
parallel with splitter/combiner on the input/output. There 
are some minor changes in bias and control but they should 
not effect operation/performance. 

> I wonder if this new ALS-1300.. or any of the existing  KW 
> output  SS amps   have the same reduction in eff... when 
> power reduced.   

That's inherent in a fixed tuned (e.g. "broadband") design. 
The voltage remains the same while the current changes so 
the input/output impedances become significantly higher 
than the design point.  Try tuning your tube amplifier 
for 1500 Watts into a dummy load then reduce the drive by 
75% without retuning and calculate efficiency ... you will 
see a similar decrease in efficiency. 

73, 

   ... Joe, W4TV 
  



> -----Original Message-----
> From: amps-bounces at contesting.com 
> [mailto:amps-bounces at contesting.com] On Behalf Of Jim Thomson
> Sent: Wednesday, December 30, 2009 6:19 AM
> To: amps at contesting.com
> Subject: [Amps] ALS-1300... IMD ??
> 
> 
> Gents
> 
> I understand the  new ALS-1300 uses  8 x finals.     Are 
> these  MRF-150's ??      At 1200 w pep out... that's   150 w 
> pep out per device.      That's a bunch. 
> 
> What is the TX  IMD on this amp, when running full bore  at  
> 1200 w pep out ??    I suspect it won't be good.   The 
> ALS-600 is only -25db   
> 
> 
> On a similar note,   I noticed that  the eff on my  1000-MK 
> -v  is  aprx  50%... at 200 w out.       With power reduced 
> to 100 w...... eff is down to 36%     
> 
> At 50w, it's worse still.  
> 
> I'm not impressed with the SS  finals so far.... eff wise.   
> 
> I wonder if this new ALS-1300.. or any of the existing  KW 
> output  SS amps   have the same reduction in eff... when 
> power reduced.   
> 
> Tnx......... Jim   VE7RF
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