[DSP-10] A Brickette mostly thought experiment

[Courtney Duncan]

Still puzzled why I'm getting only 5 watts out of the Brickette, I did 
the following:

For DSP-10 power levels of 71 - 83 where I measured 0.1 to 1.65 watts 
out on the Bird wattmeter, I calculated what linearized values should be 
over that range then found a DSP-10 power setting that would correspond 
to one Watt.  This was 80.61 and the noise in the fitting process was 
about 0.5 dB.

Extrapolating downwards from there, I determined what the amplifier 
power outputs should be for DSP-10 drive levels of 70 down to 50.  51 
should yield about 1.1 mW out of the Brickette, for example

Using my Figure 12. RF power detector (through a TNC to phono adapter) I 
measured amplifier (not exciter) power outputs through this same range.

I then interpolated those (extrapolated) results to see what those 
original measurements from the exciter really meant.

 From this "one and a half significant digit" data, I reached the 
following conclusions about my particular setup.

1.  My Figure 12 RF detector is 3 dB below the one in QST:

   Mine     Fig. 12
mW    mV      mV
20   253     491
10    67     225
  5     8      66

The only big difference is that I used a 47 ohm load resistor rather 
than a 51.  I supposed there could be a lot of difference in diodes, 
other low tolerance parts, or construction substrate.  3 dB worth?

2.  My DSP-10 exciter is putting out plenty of power.  Nearly 40 mW full 
bore (level 100) and about 20 mW in nominal operation (level 95).

3.  This particular amplifier module has about 28 dB gain, a 1 dB 
compression point of 2.5 W, and saturates just above 5 W (which is what 
it does for all drive levels above 93 ~= 15 mW).

Also, I double checked that my module is a M57732L, as specified and the 
data sheet says it should go to over 7 watts for 20 mW drive and 12.5 
VDC input. I've measured 12.4 V Vcc1 and Vcc2 and 4.93 V Vbb at full 
output.  (At 1.35 A, that's 30% efficient.)  I tried different drive 
cables and it changed a little, but only a few percent and the 
saturation level didn't change at all.

I guess I'm willing to call this done and just say that I have a high 
gain, low saturation level module.  Does anyone have much experience 
with these parts, or any other related thoughts on this?

Operationally the difference between 5 and 7 watts isn't much.  It's 
really just a curiosity.

If someone is really interested in all this, I can forward the Excel 
spreadsheet.

73, Courtney, n5bf