[Lowfer] Homebrewed SSB Filter question - Clarification

[PAUL DAULTON]

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  
 
 
Andy - KU4XR wrote:  
> Jim & All:  
>  
> In this experiment, I have absolutely everything to learn. Allow me  
> to give some reason on my thinking. I read an article on the web  
> recently by Alberto discussing JASON, and in his article, he said  
> that JASON could be ran thru a Non-Linear PA due to the fact that  
> no audio tones ever overlapped ( I'll say here that I may be like  
> an anxious runner jumping the gun ). But with that in mind, after  
> reading his article, my understanding was that ( in simplistic  
> understanding ) all I have to do is find a way to drop the carrier,  
> and modulate the PA with the JASON audio tones, and that's where  
> the MC1496 DBM comes in. The carrier is there, but -65dB below  
> the DSB audio. Then I need to get rid of the LSB component,  
> with a USB filter so that the only thing left is the attenuated  
> carrier with the audio tones appearing on the USB. Now the  
> simplicity stops, and reality slaps me hard upside the head; I  
> like you Jim, have no idea what will happen if you mix a sine wave  
> audio tone, with a square wave carrier, and then feed it into a  
> switching PA. If I even make it that far, I think that's what I'll  
> be trying to do. I may be trying to build a better mouse trap.  
>  
>  
> Andy - KU4XR - EM75xr - Friendsville, TN.  
> LOWfer Beacon " XR " @ 184.322 KHz ( QRSS-60 )  
> Coordinates: N: 35* 43' 54" - W: 84* 3' 16"  
> http://www.myspace.com/beaconxr  
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