[Elecraft] KPA500 - just 500 watts?

[Jim Brown]

On 1/25/2011 8:59 AM, N2TK, Tony wrote:
> Having the capability to go to 1500W in these situations may make the difference between working a "new one" and not working the "new one".

I used to be one of those "100 watts is plenty" guys -- licensed for 55 
years now, I bought my first amp in 2004. Now I use it almost all the 
time.  The main reason is RF noise on the other end.  I live in the 
mountains with fairly low population density, so most of the time I have 
a local noise level of less than S3 (on a calibrated K3 meter). It's 
common for guys living in towns or cities to have an S7-9 noise level. 
When I lived in Chicago my noise level was rarely below S7.

On a calibrated S-meter, the difference between S3 and S7 is 24dB. S3 to 
S9 is 36dB.  The difference between 100W and 500W is 7db; 500W to 1.5kW 
is another 4.7dB. So the short answer is that the 500W amp gives you a 
one S-unit boost to get over the other guy's RF noise, and the 1.5kW amp 
gives you two S-units.

Dollar cost of the power amp is only part of the equation.  As others 
have noted, you'll need to run 240V into your shack to run most 1.5kW 
amps effectively.  That costs money.  The power supplies for most 1.5kW 
amps are big and HEAVY -- as we get older, it gets tougher to lift them 
(or transport them), and it can get very expensive to ship them.  The 
tubes used in most big power amps require a 3-minute warm-up, while most 
500W solid state amps are instant-on.  I've missed more than a few DX 
contacts in that 3-minute cycle.

73, Jim K9YC