[Elecraft] [K3] IF output

[Alan Bloom]

Brett,

Those numbers are similar to what I measured on my K3.  It varies by
band, but before modification I was getting in the neighborhood of -6 dB
with preamp on and -17 dB with preamp off.  After modification I
measured +4.5 dB with preamp on and -6.5 dB with preamp off (at 10 MHz).

A 0603 resistor should be fine.  It's not dissipating significant power.

Alan N1AL


On Fri, 2010-01-15 at 22:44 -0800, Brett Howard wrote:
> Ok so I decided to do the IF mod as the P3 will be ordered when it comes
> out and I'd like the increased sensitivity.  I'm copying elecraft and K3
> support cause I wanted to ask a simple question (as well as share the
> results).  First my question, I didn't have any 13K ohm resistors in
> 0805 size.  So I put an 0603 resistor on the same pads.  Will this be
> ample or should I replace it with an 0805 for power rating reasons?
> 
> I made measurements before and after the modification and collected
> results which I figured I'd share. 
> 
> Signal Generator was a Rhode and Schwartz (sp?) model number unknown.
> This signal generator was uncalibrated.  However the spectrum analyzer I
> was using was a very recently calibrated N9020A which our cal report
> gave a clean bill of health and an absolute accuracy of 0.009dBm at
> -50dBm.  Agilent didn't specify the accuracy at -70 but it was getting
> tighter as the amplitude went lower.  I did not engage the preamp in the
> analyzer.  
> 
> I was making my measurements at -70dBm as its a "common ham amplitude".
> I injected the signal at 7.040Mhz (cause I use that w/ my XG2 a lot) @
> -70dBm.  This input was verified on the spectrum analyzer at the end of
> my cable to calibrate cable losses out of the system.  I then measured
> the output at the IF OUT port at 8.215Mhz. 
> 
> Before
> PreAmp off: -88.2dBm
> PreAmp on:  -77.0dBm
> 
> After
> PreAmp off: -77.9dBm
> PreAmp on:  -66.9dBm
> 
> Looks like there is a tad bit of loss with the PA off (7.9dB) but then
> again there is 3.1dB of gain with the PA on...  Hopefully this jives
> with intended results.  If not hopefully its a useful data point.
> 
> Respectfully
> 
> ~Brett (KC7OTG)