[Lowfer] 495.9 last nite

[jrusgrove at comcast.net]

Mike, Dex & All

In WSPR (and other digital modes) i-f filters narrower than the 'standard' ~2.5 kHz used for USB 
reception only serve to artificially inflate the reported s/n ... weak signal reception is not 
enhanced. The width of the individual FFT bins are significantly smaller than the width of any i-f 
filter.

Jay W1VD  WD2XNS  WE2XGR/2


----- Original Message ----- 
From: "Michael Sapp" <wa3tts at verizon.net>
Cc: <lowfer at mailman.qth.net>
Sent: Thursday, November 01, 2012 2:14 PM
Subject: Re: [Lowfer] 495.9 last nite


> Dex & All:
>
>>Also seeing a signal at 1500 Hz but no decode?
>
>
> Dex
>
> That was WF2XXQ on 495.9 in EL95 at +17 WSPR mode. I was seeing another station 25 Hz below him on 
> the waterfall which I assumed was JT9 but obviously no decode here in WSPR mode.
>
> I was testing my 300Hz Collins filter in the FT-847 last nite set on 495.05 for the 650Hz BFO 
> offset and then shifting the IF bandpass up 850Hz
> to be on 495.9 using XXQ as the test beacon signal. So far lowest SNR -30 captured versus a 
> few -33 SNRs I have had with the InRad 1800 Hz xtal filter previous evenings. -60 dB skirts on the 
> 1800Hz filter at 2862 Hz vs 850Hz at the -60 skirts point for the 300Hz Collins filter.  The 
> signal levels come up a few dB overall with the narrower IF filter. Waterfall shows weaker signals 
> there with the narrow filter below the lowest decode level, but did not decode them.  Waterfall 
> image from the night B4 with a -28 SNR decoded and last nights XXQ's data decodes attached. XJM 
> went to WSPR at 0736 til near sunrise on 495.850....Just an experiment,  as the FT-847 could use 
> some extra gain at 500 kHz and I have not built an external 2n5109 preamp yet. The IF gain comes 
> up 4~5 dB with the narrow Collins filter.
>
> 73  Mike wa3tts
>
> Oct 31 waterfall
>
> http://s1296.beta.photobucket.com/user/wa3tts/media/xxq31nar.jpg.html?sort=3&o=1
>
> Nov 1 data
>
> http://s1296.beta.photobucket.com/user/wa3tts/media/xxq111nr.jpg.html?sort=3&o=0
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