[DSP-10] Noise Figure (finally) measured.

[Courtney Duncan]

Hey Mike,

That's good news.  Your measurement is consistent enough with mine  
that I believe my measurement and I don't think there are any gross  
errors in assembly.  I've made hundreds of 2 meter contacts on the  
thing, so I didn't really think anything was wrong -- but this does  
explain why I sometimes can't hear guys who are hearing me pretty well.

So, a good preamp is next on the list then.  Anybody have any advice?

73, Courtney, n5bf/6


On Sep 6, 2008, at 10:07 PM, kd7ts wrote:

> Hi Courtney,
>
> I measured mine at 11.5 db noise figure. That was just measuring at  
> the antenna terminal. It is used as the IF for 10 GHz.
>
> Works fine.
>
> 73 Mike KD7TS
>
> At 07:55 PM 9/6/08 -0700, you wrote:
>> My noise source was built, works fine, and was calibrated at NoiseCom
>> in May.  Today I finally got to measuring the receiver performance of
>> the DSP-10.
>>
>> Using F = ENR / (Y - 1) with Y = (noise on) / (noise off) calculation
>> did several measurements using several calibrated fixed attenuators  
>> in
>> the setup.  Also compared the direct measurement to one done with all
>> of the amplifiers and the Bird wattmeter in line.  The results across
>> all tests are consistent, about 12.0 dB, that is 4300 K.
>>
>> This is somewhat higher than I was expecting so I scrutinized Sabin's
>> article and the equations and played with them in a spreadsheet until
>> I decided they are probably right.
>>
>> I was expecting more like 600K - 1000K for this.  It's no wonder I'm
>> not seeing EME2 as quickly as expected, even at 70 watts, but I'm
>> wondering now how I ever saw anything at 7 watts, even with 10,000~
>> seconds of integration.
>>
>> Certainly, a nice low noise preamp is higher on the list now.
>>
>> Continuing to investigate.  Anyone have any ideas?
>>
>> Courtney, n5bf/6
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