[DSP-10] 1st EME2 test -- nil

[Bob Larkin]

Hi Courtney,

Interesting tests, and yes, I agree, positive results are not expected with 
6W, 12 el and 886 points!

I think I posted the results of 5W, 4x12 el and 6743 points for which the 
signal was statistically a high probability.  That test was done before the 
narrower DFT was available, i.e., it used 9.4 Hz BW and Hamming window. 
Going to 1/4th the BW, and using no window will improve the sensitivity. It 
is just over 3 dB improvement, I believe, as the coherent BW is 6 dB 
better, but the amount of non-coherent averaging is down by 4.

The only easy way to save between sessions is to use the Home key to stop 
EME2 and then do nothing until the next session!  Changing modes or 
shutting down will lose the data.

But, I believe there is provision for saving the EME return data to a file. 
This does not have a corresponding processing program to use the data, so 
is probably of no use. If you want more information on this let me know, or 
look in UHFA.C for the details.

With linear polarization, half of the power, on the average, will be lost 
to incorrect Faraday rotation. Circular polarization  will work around 
this, picking up 3dB in exchange for the mechanical complexity of having 
antenna elements pointing everywhere!

Yes on the 575 ms.

I don't think it is as bad as 450,000 points!  You can pick up some part of 
that with the reduced coherent BW.  My test gives you a starting point to 
see what is needed, but it was with 4 yagis.

General comments-  It is really useful to have 100W+ available for seeing 
that everything is working. It gives quick results.  Also, 2-meters is a 
tough band because of interference. For most of living in an urban area, 
noise becomes a factor, even when pointed to the sky.  Also, those 
apogee/perigee dB on the Moon can be a factor.

Stay with it and let us know how it goes!

73,
Bob Larkin  W7PUA

At 07:14 PM 5/9/2006 -0700, Courtney Duncan wrote:
>Well, after my first hour-long EME2 test, 886 points, I am unambiguously 
>seeing -- nothing.
>
>Which is what I think I expect to see from a single 12 element beam at 6 
>watts.
>
>Without being able to steer in elevation, I think an hour is about all 
>that I will get unless I go crank the fixed elevation up to about 15 
>degrees.  Then I could get maybe two hours.
>
>So, here are a few questions:
>
>- Is there a way to save the contents of the Alt-A box, the yellow line, 
>and the underlying running averages from session to session? If I could 
>load what I have tomorrow and add another ~1000 points, maybe I'd 
>eventually see something, but wouldn't want to leave it sitting, 
>untouchable all the time between sessions.
>
>- What is the meaning of the dly_emet2r parameter?  Is this instrumental 
>delay through a transverter or lock up or something? Maybe in my case 
>(DSP-10 to Brickette) it should just be 0?  ... and that would presumably 
>make some difference.
>
>Oh, wait a minute, maybe 575 milliseconds is the time after 2.00 seconds 
>after transmission start before the leading edge of the echo begins to 
>arrive back at the antenna.  It's close, according to my 
>calculations.  And the software would adjust for variation in actual moon 
>distance.  If this is correct, never mind.
>
>- I'm guessing that a station at a KW with four of my 2M12s would hear 
>themselves on CW.  That's 28 dB above this.  Does this mean I need like 
>450,000 measurements to see something?  That's a lot, hundreds of hours worth!
>
>- Is linear polarization (horizontal) hurting?  What is the return 
>polarization on a moon echo.  I know it reverses circular but don't know 
>what it does to linear.
>
>Still fun, though.  If it were easy where would be the accomplishment in that?
>
>Courtney, n5bf/6
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