[Lowfer] Bogus WSPR decodes

[Paul Daulton]

Off topic a bit, but I am impressed with the WSPR mode.
I wonder if you know John Taylor K1JT. I am thinking of writing him and 
asking if a SuperWSPR could be written for our needs on 2200 and 1750 
meters. If the 200 hz bandwidth could be compressed down to 10 or 20 hz 
would we approach the sensitivity of QRSS 30? With the upload feature of 
WSPR reporting would be much simplified. Several have suggested WSPR for 
1750 meters but I wonder if it is practical at the 80mw erp level. I have 
been sucessful with your WOLF on 137 at high power but no luck with lower 
powers. How does WOLF bandwidth compare with WSPR?

Just thinking out loud.
Paul
----- Original Message ----- 
From: "John Andrews" <w1tag at charter.net>
To: "Discussion of the Lowfer (US, European, &amp;UK) and MedFer bands" 
<lowfer at mailman.qth.net>
Sent: Sunday, March 07, 2010 12:30 PM
Subject: Re: [Lowfer] Bogus WSPR decodes


> Paul,
>
>> But with WSPR, BPSK, WOLF and other
>> modes phase shift at a single freq on audio would be easy.Would it be a
>> practical project to make a phasing exciter for single tone or a narrow
>> audio bandpass? I know simple designs exist for simple SDR exciters but I 
>> am
>> thinking of  a stand alone unit? What do you think?
>
> Yes, you can definitely make an accurate audio phase shift network more
> simply for a narrow BW than a wide one. A good free design program for
> op-amp all-pass filters is:
> http://www.werewoolf.org.je/apf.htm
>
> With that program, you can play with the component values to your
> heart's content. 30 dB opposite sideband rejection is trivial. 40 dB can
> be done with standard 1% tolerance parts. 50 dB requires accurate
> measurement of actual 1% parts values, and a pile of parts from which to
> choose. At the 1 watt transmitter output level, 30-40 dB suppression
> should be plenty. I would suggest FET-input op-amps like TL072/074 or
> TL082/084. Avoid antiques like LM324's or 741's.
>
> With WSPR requiring 1400-1600 Hz tones, you could probably restrict
> yourself to the 1000-2000 Hz range. This would mean setting WOLF or PSK
> up for 1500 Hz or so, no problem.
>
> JA
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