[Elecraft] (OT) Recommendations for Testing

[Joe Subich, W4TV]

> For a more detailed analysis take a look at G4AON's Simple Spectrum
> Analyzer at http://www.astromag.co.uk/ssa/. While the mixer should
> have a +7 dBm LO input, it should be usable with the XG3 0 dBm output
> (or build up an MMIC board with 7 dB gain.)

SDR-IQ with SpectraVue or another SDR application will do everything
G4AON's "Simple Spectrum Analyser" will do.  The only thing I would
add to the SDR-IQ is a directional Coupler (Elecraft CP-1) with the
appropriate coupling factor.

The resistive tap used by G4AON is also usable (SDR-IQ connects where
he shows the SBL-1) but a directional coupler will give more accurate
measurements in the presence of SWR.

If you're measuring outputs of more than 100W you will need more than
30 dB of coupling factor in the directional coupler or resistive tap.
I would keep the input to the SDR-IQ substantially below 0 dBm.  -50
dBm (~S9 + 20 dB) is a good target; you can get there using both
the coupling factor in the CP-1 and fixed attenuation between the
sample port and SDR-IQ.

Finally, if you are measuring amplifiers above 30 MHz you will need
a converter ahead of the SDR-IQ.  Make sure your sample level is
within the signal handling range of the converter.

73,

    ... Joe, W4TV


On 3/17/2012 3:38 PM, Don Wilhelm wrote:
> Ed,
>
> No Spectrum Analyzer?  You do have your SDR-IQ that will do that task on
> a narrowband segment.  For a more detailed analysis take a look at
> G4AON's Simple Spectrum Analyzer at http://www.astromag.co.uk/ssa/.
> While the mixer should have a +7 dBm LO input, it should be usable with
> the XG3 0 dBm output (or build up an MMIC board with 7 dB gain.)
>
> 73,
> Don W3FPR
>
> On 3/17/2012 3:19 PM, Edward R. Cole wrote:
>> I will be testing some amplifiers, soon, and would like advice or
>> links to info on making IMD and harmonic level tests on HF amplifiers.
>>
>> I can generate two-tone modulation and monitor spectrum up to 196 KHz
>> width with my SDR-IQ, but do not have a spectrum analyzer.  I have a
>> scope, power meters, 500w coaxial load, XG3, and a couple DMM, plus
>> analog 30v and 30a dc meters..
>>
>>
>> 73, Ed - KL7UW, WD2XSH/45
>> ======================================
>> BP40IQ   500 KHz - 10-GHz   www.kl7uw.com
>> EME: 50-1.1kw?, 144-1.4kw, 432-QRT, 1296-?, 3400-?
>> DUBUS Magazine USA Rep dubususa at gmail.com
>> "Kits made by KL7UW" http://www.kl7uw.com/kits.htm
>> ======================================
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