[DSP-10] Sun Noise Measurement

[Bob Larkin]

Thanks Mike.  Those are not the ones, so here goes.  I don't think this 
got written down :-)

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In the FM mode, the data-dump file written by the ALT-F command (a 
toggle) is named UHFA_1.DAT.  This file is appended to when used, and 
never cleared.  So, you get to manage the data on the file, including 
deleting it to keep the size more manageable.  HFM records are appended 
to the same file as other ALT-F data saves.

A record is written every time the the spectral averaging (ALT-F3, 
ALT-F4) time is up, which is every 0.6 seconds or more.  The 19 fields 
of the record are comma separated and as follows:

HFM           Identifies record type, differentiates
                  from HL records
year          as 2016
month         1 to 12
day           1 to 31
hour minute   0 to 2359, UTC Time
second        0 to 59 Seconds
fft_bw        DFT noise bandwidth always 2
rf gain       0 to 6, 0=full gain or 100
noncohave     Number of DFT in ave*
do_window     window type, 0 to 3
2ndLO         Not Used
mode          Not Used
0             Not used
0             Not used
0             Not used
16            Not used
fm_log_power  S-meter power, dBm
deltaf        Discriminator output, Hz**, every 0.6 seconds or more. 
The 19 fields of the record are comma sep
fmf           Received freq, Hz

* The DFT overlap 50% to minimize windowing losses.  Thus, the number of 
DFT being averaged is twice the number that time would allow.

** The discriminator output will not usually be zero with no signal 
present.  This is due to asymmetries in the crystal filter passband. 
However, as the S/N increases, the correct deviation from tuned 
frequency will be shown.

Note that the Sigma-Delta ADC is inherently extremely linear, and the 
power measurements can be used over a wide dynamic range.  Likewise, the 
phase measurements used in the "FM discriminator" are accurate to better 
than a Hz across the +/- 6 KHz, assuming adequate S/N.

------------------------------------------------------------------------

73, Bob

On 10/15/2016 12:49 PM, Mike wrote:
> On Sat, 15 Oct 2016 10:47:48 -0700
> Bob Larkin <boblark at proaxis.com> wrote:
>
>> In addition, the ALT-F3, ALT-F4 averaging also applies to this
>> measurement, so you can adjust the averaging time from 0.6 sec on up.
>
>
> Hi Bob,
>
> Maybe this relates ?
>
> Data Record - The logged power data after non-coherent integration can be saved directly to disk. This is toggled on and off by the Alt F command. It is saved to a file called UHFA1.DAT and if the file exists, it is appended to the end of the existing data. The data is time and date stamped for future use. It is not compacted, though and can produce some big files. To reduce the file size increase the non-coherent integration (Alt F4). The beginnings of a companion program EDFILE01.C and EDFILE01.EXE is available. It reads the data file and replays the data allowing additional smoothing as well as Doppler slope correction and various other feaures. EDFILE is not documented except through the C listing, but the program listing comments do much to describe the operation.
>