[Lowfer] OPDS 32 tonight 2230-06-0700...

[jrusgrove at comcast.net]

Garry

Known issue for strong signals.

Jay


----- Original Message ----- 
From: "Garry Hess" <k3siw at sbcglobal.net>
To: "lowfer list" <lowfer at mailman.qth.net>
Sent: Wednesday, October 30, 2013 11:04 AM
Subject: Re: [Lowfer] OPDS 32 tonight 2230-06-0700...


> Bob, your signal was so strong it brought out flaws in the opds code 
> and/or my SDR-IQ receiver. I was out of town but got back last evening 
> and fired up to look at 136 kHz with an e-probe. After the standard very 
> long acquisition period, I got decodes for WE2XEB and VO1NA around 
> 0300Z. However, the WE2XEB decoded line was clearly amiss - it quoted 
> the snr as -99.9 and only indicated 93% correlation. On the spectrum a 
> very big peak from WE2XEB was present (but also very wide, perhaps the 
> source of the problem), along with a smaller peak from VO1NA. A few 
> minutes later opds changed VO1NA to -99.9 snr also:
> 
> sdr-iq1, eprobe1
> 2013-10-30 03:26:55 VO1NA   2836km 137555.014Hz  30mHz -45.6dBOp  57% 15.3dB
> 2013-10-30 02:58:29 WE2XEB   934km 137533.971Hz 233mHz -99.9dBOp  93% 20.2dB
> 
> Followed by:
> sdr-iq1, eprobe1
> 2013-10-30 03:31:25 WE2XEB   934km 137533.978Hz 185mHz -99.9dBOp 100% 18.9dB
> 2013-10-30 03:26:57 VO1NA   2836km 137554.971Hz 192mHz -99.9dBOp  88% 18.4dB
> 2013-10-30 02:58:29 WE2XEB   934km 137533.971Hz 233mHz -99.9dBOp  93% 20.2dB
> 
> Next, I fired up opera1.4.7 and got decodes for both WE2XEB and VO1NA at 
> sensible snrs. WE2XEB was roughly 2 dB better with a loop aimed at 
> VO1NA, but strangely VO1NA never decoded with the loop.
> 
> opera1.4.7
> 06:57   136 VO1NA Op32 -35 dB    sdr-iq1, eprobe1
> 06:16   136 WE2XEB Op32 -13 dB
> 05:43   136 WE2XEB Op32 -11 dB   sdr-iq1, loop at VO1NA
> 05:10   136 WE2XEB Op32 -16 dB
> 04:37   136 WE2XEB Op32 -18 dB   sdr-iq1, eprobe1
> 04:36   136 VO1NA Op32 -28 dB
> 
> When WE2XEB went QRT I returned to opds32 and then also got sensible 
> snrs. The values ran perhaps 9 dB lower than those using opera1.4.7, a 
> difference that has been noted previously by others.
> 
> sdr-iq1, eprobe1
> 2013-10-30 09:17:11 VO1NA   2836km 137554.993Hz   3mHz -38.8dBOp  99% 19.1dB
> 2013-10-30 08:07:06 VO1NA   2836km 137554.993Hz   6mHz -42.5dBOp  99% 18.3dB
> 
> I don't know what the last dB numbers in the decode lines represent.
> -- 
> 73, Garry, K3SIW, EN52ta, Elgin, IL
>


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