[Lowfer] Homebrewed SSB Filter question - Clarification

[Ed Phillips]

  For a very good program to design quadrature networks for SSB go here 
and download free:

< http://www.tonnesoftware.com/quad.html>

Then go back to:

<http://www.tonnesoftware.com>

and look at all the other FREE goodies they have to offer. Great stuff!

Ed

"PAUL DAULTON wrote:

>Steve and Andy
>I have read your posts about the usb filter. Steves comments brought to
> mind the ease of generating a ssb signal
>with phasing technique. Better yet is the SDR technology that enables us
> to send and rec multimodes with the aid 
>of a computer sound card and downconver. At a set freq the osc signal ( 4x
> carrier freq) is divided into quadraqure
>elements of 0,90,180, and 270 degrees. Then the mixers provide I and Q
> signals to the computer sound card.
>With simple r/c components at a fixed frequency this can be accomplished
> with a very simple circuit. See http://www.qrz.lt/ly1gp/SDR/
>for a simple 80 meter circuit. It is an 80m sdr rec with a variable osc.
> If we replaced the vfo with a 4060 chip and a 11.0mhz divided by 32
>xtal we would have a center freq of 171.8 khz. The sdr soft ware generally
> has a +/-  range of 1/2 the sound card sample rate.
>Most are 48khz so we would have 171 +/- 24khz. Resonate the tuned circuits
> at lowfer freq and calculate the phase shift
>caps and res and we are in business.
>Note the simple Tiny SDR circuit can be turned around and generate any
> mode in the same manner. Feed the proper i/q signals 
>in and you have a phasing type modulator. There are programs such a Rocky
> which can generate I/Q signals for transmitt 
>as well as demodulate  rec. With R/C phase shift 30 db of sideband(image)
> supression is easily realized. With digital 60 to 70 db is 
>often the norm.
>This weekend I attended the Ozarkcon 4sqrp convention in Branson ,MO. I
> brought back a Softrock lite 80m rec and an 80meter
>RXTX v6.2 tranceiver. Both these I intend to convert to lowfer. In kit
> form these were $11 and $30 respectively. Now obsolete
>they have been replaced with newer versions.
>Keep posting this is a very  interesting thread.
>Paul Daulton k5wms
>-----Original Message-----
>From: Steve Dove <dsp at hifidelity.com>
>Sent: Thu, 30 Apr 2009 02:37:51 +0000
>To: ku4xr at yahoo.com, "Discussion of the Lowfer \(US, European, &UK\) and
> MedFer bands" <lowfer at mailman.qth.net> 
>Subject: Re: [Lowfer] Homebrewed SSB Filter question - Clarification
> 
> 
>Hi Andy,  
> 
>Just a thought here: since Jason is actually very narrow band with the  
>several tones close together a *very* simple phasing-type exciter would  
>work.  
> 
>Simple, because the has-to-be-accurate quadrature phase shift of the  
>audio source (which is ordinarly in analogue a pain to get right over  
>the full audio band) only has to be right at effectively a single  
>frequency; it could be achieved with just an equal RC / CR pair to make  
>the +/-45 degrees for the quadrature pair, centred at whatever frequency  
>Jason pops out of the soundcard.  
> 
>Smells like a handful of bits in the ever-popular Altoids tin.  
> 
>Thinking this through a bit further, a single crystal as a bandpass  
>filter acting as a sideband filter would work, too, since the required  
>bandwidth is small. No need for anything elaborate.  
> 
>73,  
> 
>Steve  
>