[Elecraft] Gamma Research Very Small Switching Power Supply

[John Buck]

My test data indicates that my K2 / 100 is happy with the Gamma power 
supply.
The K2/100 is specified to run ok down to 11 volts. The K2 is more 
tolerant than many rigs when run at supply voltages down to 12 volts 
minus line drop.

As I stated, the Gamma does run 100 watt cw with the K2/100.  The Gamma 
specifications will not support long Key Down at 100 watts.  I have not 
run sufficient testing to see how conservative the Gamma 5 amp steady 
state, or 22 amp 25% duty cycle is.  In my operation, even at 100 watt, 
cw my average periods of transmission tend to fit in the specified 
limits of this supply.  I believe that about 85 watt CW fits within the 
specification of this power supply.

Karl, you bring up the subject of heavy compression.  If your 
compression is to effectively limit voice peaks so you can have higher 
average speech the average current will increase.  The compression 
should be adjusted so that background noise is not driving the 
amplifier.  If so adjusted, I suspect that the average power will still 
be less than CW.  Since the Supply can handle the peak currents easily, 
the main question is the true average power over a longer time.
Uncompressed SSB is about 20% and CW is about 40% per the RF Safety table.
It has been my experience that heavily compressed SSB is much less 
intelligible than moderate compression even though the S meter moves 
higher.  In all of my experiments with compression I have ended up using 
much less than I initially thought would be useful.

Digression aside, I am happy with my Gamma Research power supply for 
portable use with my KPA/100.

Aloha,
John KH7T

Karl Larsen wrote:
>
>    Hi John, I bet the company will not provide the tests you give us 
> here. I summarize your work as proving this power supply is properly 
> specified by the maker and when you draw high current at 12 VDC the 
> voltage goes down.
>
>    For the low duty cycle of SSB at 100 Watts it will work fine. For 
> the higher duty cycle of CW you can't run 100 Watts. I run serious 
> compression on my 100 Watt rig and the duty cycle on SSB is much 
> higher. I wonder if that will work with this supply.
>
>    The power supply has no RF noise output so that is a sure plus.
>>
>> John KH7T
>> no affiliation, just a happy customer.
>