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

[Courtney Duncan]

Thanks Scott,  I just ordered one of the VHF LNA kits from Down East  
(which, apparently, is now "south east") and a Tohtsu relay to switch  
it in and out.  I'll probably tower mount one of these days, but for  
now I'll just eat the extra 1-1.5 dB in cable loss and have it in the  
shack where I can watch it work.  Still, it will be a lot better than  
the straight front end.

73, Courtney



"Duct Tape / Swiss Army knife / ... the emergency repair kit.  If you  
can't fix it with those two items, it's a major repair and shouldn't  
be attempted in the field!"

	Paul Wade, w1ghz, QST 2008 August, p. 93

Courtney Duncan, n5bf/6
144.200, 7.040
n5bf at amsat dot org





On Sep 8, 2008, at 3:16 AM, Scott wrote:

> Here is one source of preamps, both kit and assembled  
> versions...they are receive only, which means you will have to come  
> up with relays to switch them in and out of the line (they are meant  
> to be tower mounted)
>
> http://www.downeastmicrowave.com/Catalog.htm#BM2M
>
> Scott
> N0EDV
>
> Courtney Duncan wrote:
>
>> 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
>>>> _______________________________________________
>>>> DSP-10 mailing list
>>>> DSP-10 at mailman.qth.net
>>>> http://mailman.qth.net/mailman/listinfo/dsp-10
>>>>
>>> _______________________________________________
>>> DSP-10 mailing list
>>> DSP-10 at mailman.qth.net
>>> http://mailman.qth.net/mailman/listinfo/dsp-10
>>
>>
>> _______________________________________________
>> DSP-10 mailing list
>> DSP-10 at mailman.qth.net
>> http://mailman.qth.net/mailman/listinfo/dsp-10
>>
>>
>
> -- 
> Scott
> http://corbenflyer.tripod.com/
> Flying Corben Junior Ace - Building RV-4
> Gotta Fly or Gonna Die
>
>
> _______________________________________________
> DSP-10 mailing list
> DSP-10 at mailman.qth.net
> http://mailman.qth.net/mailman/listinfo/dsp-10