Hello Andy
We do need to refer back to my original posts here.
Yes OP8 decodes but almost always either equal S/N or worse.
After that Graham asked for what I meant by worse.
I have been keen to run some tests because I have never been monitoring
and seen the expected 3dB advantage of OP8 over OP4 on 500kHz. Seeing
repeated OP4 then OP8 results when OP8 does not decode but OP4 does, put
me in doubt of my PIC timing. Regularly seeing OP4 produce between 3dB
and 7dB stronger reports than OP8 when both were de-coding at low signal
levels I considered made all OP8 reports invalid, and confused the
theory.. (On 500kHz on the paths tried)
Surely this is QSB, visible on some transmissions, hence the shorter OP
modes win over on 500kHz.
Eddie
On 09/02/2012 21:20, Andy Talbot wrote:
The reported S/N (normalised to 2500Hz) for each mode should be the
same; the decoding threshold is different in proportion to teh speed.
If the reported value is consistently and systematically out, either
there's a big mistake in the software decoding, or there are other
factors coming into play.
'jnt
On 9 February 2012 21:11, James Moritz<[email protected]> wrote:
Dear Eddie, LF Group,
So what you are saying is that the actual SNR at the decode/no decode
threshold is the same for Op8 and Op4, but that the SNR indicated by Op8 at
this level is 3dB lower than that indicated by Op4?
Cheers, Jim Moritz
73 de M0BMU
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