Return-Path: Received: from mtain-mk02.r1000.mx.aol.com (mtain-mk02.r1000.mx.aol.com [172.29.97.134]) by air-ma03.mail.aol.com (v129.4) with ESMTP id MAILINMA031-b4f74d4ea8202f1; Sun, 06 Feb 2011 08:54:40 -0500 Received: from post.thorcom.com (post.thorcom.com [195.171.43.25]) by mtain-mk02.r1000.mx.aol.com (Internet Inbound) with ESMTP id 6F83238000144; Sun, 6 Feb 2011 08:54:38 -0500 (EST) Received: from majordom by post.thorcom.com with local (Exim 4.14) id 1Pm53t-0002Bw-Vj for rs_out_1@blacksheep.org; Sun, 06 Feb 2011 13:53:57 +0000 Received: from [195.171.43.32] (helo=relay1.thorcom.net) by post.thorcom.com with esmtp (Exim 4.14) id 1Pm53t-0002Bm-CH for rsgb_lf_group@blacksheep.org; Sun, 06 Feb 2011 13:53:57 +0000 Received: from mail-iy0-f171.google.com ([209.85.210.171]) by relay1.thorcom.net with esmtp (Exim 4.63) (envelope-from ) id 1Pm53r-00069k-0d for rsgb_lf_group@blacksheep.org; Sun, 06 Feb 2011 13:53:57 +0000 Received: by iyh42 with SMTP id 42so713300iyh.16 for ; Sun, 06 Feb 2011 05:53:48 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=gamma; h=domainkey-signature:mime-version:in-reply-to:references:date :message-id:subject:from:to:content-type; bh=6+MvaZNZzAIHxVDvXXv+qvDLRyIoF7T8Q3vQU/kQ73M=; b=HRvE1SKp1QOcqhVE3IgjJUwz5ciVmhWnDlR5ssBa3kYsjPMuSDkq2v9xG2VKPJvsi5 S5h7A9YW6YjdX0Vfe8Te5QlIEMFpmaUSAuOx+ci56An3zBZbfWJk6yyGHsinaSU1fLe8 sVVzHETnWaU+PhCU41F6uAcFmGh8DXGSAJbug= DomainKey-Signature: a=rsa-sha1; c=nofws; d=gmail.com; s=gamma; h=mime-version:in-reply-to:references:date:message-id:subject:from:to :content-type; b=RJLo0HQOWw2dt9mtodsBt27DcIbiNrqZ7yq7uWcxdjVEhb2SQZFsUtbBheM+O7aYWT JuUmuBpTwkJ7VKQWmM3EeSSnUVoXf4cLU1Lg4k2X5h+z439mpnL1nkJ02LRg/f0rxFQ4 HwUhxHAjuyWcRAv9RFrq4HgNmFTEolrjOYkqo= MIME-Version: 1.0 Received: by 10.231.199.76 with SMTP id er12mr8345501ibb.72.1297000428730; Sun, 06 Feb 2011 05:53:48 -0800 (PST) Received: by 10.231.199.4 with HTTP; Sun, 6 Feb 2011 05:53:48 -0800 (PST) In-Reply-To: References: <4D4E8A68.4060601@freenet.de> Date: Sun, 6 Feb 2011 13:53:48 +0000 Message-ID: From: Andy Talbot To: rsgb_lf_group@blacksheep.org, sub9khz@yahoogroups.com DomainKey-Status: good (testing) X-Spam-Score: 0.0 (/) X-Spam-Report: autolearn=disabled,HTML_MESSAGE=0.001 Subject: Re: LF: Simple PIC based DDS for VLF Content-Type: multipart/alternative; boundary=90e6ba4fc4a2d3fb6d049b9d7102 X-Spam-Checker-Version: SpamAssassin 2.63 (2004-01-11) on post.thorcom.com X-Spam-Level: X-Spam-Status: No, hits=0.0 required=5.0 tests=HTML_MESSAGE autolearn=no version=2.63 X-SA-Exim-Scanned: Yes Sender: owner-rsgb_lf_group@blacksheep.org Precedence: bulk Reply-To: rsgb_lf_group@blacksheep.org X-Listname: rsgb_lf_group X-SA-Exim-Rcpt-To: rs_out_1@blacksheep.org X-SA-Exim-Scanned: No; SAEximRunCond expanded to false x-aol-global-disposition: G X-AOL-SCOLL-AUTHENTICATION: mail_rly_antispam_dkim-d016.1 ; domain : gmail.com DKIM : pass x-aol-sid: 3039ac1d61864d4ea81d629e X-AOL-IP: 195.171.43.25 X-AOL-SPF: domain : blacksheep.org SPF : none X-Mailer: Unknown (No Version) --90e6ba4fc4a2d3fb6d049b9d7102 Content-Type: text/plain; charset=ISO-8859-1 All done.... 5 minutes to do the PIC code, .. and an hour or so to test and update the documentation. http://www.g4jnt.com/PIC_DDS.zip now also contains PIC code " cohFSKsrc " that generates FSK by switching between two continuously running oscillators. The DDS clock now has to run at Fosc / 256, but with a 10MHz input, that's still just about OK for generating a 9kHz waveform. With 20MHz input, no problem and the PIC can be overclocked up to 40MHz - well, mine could anyway, and survived. Also managed to considerably shrink the size of the. PDF http://www.g4jnt.com/PIC_DDS.pdf - no more 5 Meg download just to get hi-res pictures embedded Tnx for the idea, Wolf.... Andy G4JNT On 6 February 2011 12:05, Andy Talbot wrote: > That's a very good point - having suffered this FSK-losing-coherence > problem once before. > It could all be done inside the PIC, maintaining two accumulators and then > using one or the other to address the sine lookup table. As you say, there > will be a discontinuity, but hopefully not a big problem. > > The interrupt routine is at maximum capacity, so the sampling rate will > have to come down a bit to allow nearly double the instructions, but it > should be possible - I'll think about it :-) > > And something a DDS chip like the AD985x can't do ! > > Andy > www.g4jnt.com > > > > On 6 February 2011 11:47, wolf_dl4yhf wrote: > >> Thanks Andy, nice project.. maybe I should dig out the PIC programmer >> again... ! >> >> One suggestion for VLFers: A PIC doesn't cost a fortune. Build two of >> these generators, and clock them with the same source (GPSDO or OCXO). For >> the FSK simply flip between both generators. This has the *big* (cannot >> emphasize this enough..) advantage that if the signal is to weak to be seen >> as DFCW etc, we can still dig it out through a long FFT because each of the >> two carriers remains coherent, and can be coherently averaged as long as >> necessary (much longer than a single DFCW symbol). I noticed this on >> Stefan's signal today : With the very slow settings, all you see is a >> rounded hump in the spectrum because the signal isn't coherent. No chance to >> detect it for "DX" receivers. >> >> Of course flipping the (FSK-) switch may cause a heavy click then >> (depending on the momentary phase shift between the two carriers) but I >> think a robust PA will survive this. >> >> Have a nice sunday, >> Wolf . >> >> Am 05.02.2011 19:57, schrieb Andy Talbot: >> >> 9kHz OPs may be interested in this DDS suitable for audio/ VLF using just >> a 16F628 PIC, , R-2R ladder and op-amp filter. It can generate frequencies >> up to about 40kHz with typical DDS high resolution / frequency steps, >> (higher if you overclock the device) offers two-tone FSK operation by >> toggling a single input line (ideal for DFCW), The two frequencies are >> stored in non-volatile memory and are user-programmable from an RS232 >> interface using ASCII text based commands. >> >> See www.g4jnt.com/PIC_DDS.zip for full details. >> >> Andy >> www.g4jnt.com >> >> >> >> >> > --90e6ba4fc4a2d3fb6d049b9d7102 Content-Type: text/html; charset=ISO-8859-1 Content-Transfer-Encoding: quoted-printable
All done....
=A0
5 minutes to=A0do the PIC code,
.. and=A0an hour or so=A0to test and update the documentation.
=A0
http://www.g4jnt.com/PIC= _DDS.zip=A0=A0 now also contains =A0PIC code " cohFSKsrc "= that generates FSK by switching between two continuously running oscillat= ors.=A0=A0=A0 The DDS clock now has to run at Fosc / 256, but with a 10MHz= input, that's still just about OK for generating a 9kHz waveform.=A0= =A0 With 20MHz input, no problem and the PIC can be overclocked up to 40MH= z - well, mine could anyway, and survived.
=A0
Also managed to considerably shrink the size of the. PDF=A0 http://www.g4jnt.com/PIC_DDS.pdf= =A0-=A0=A0 no more 5 Meg download just to get hi-res pictures embedded
=A0
Tnx for the idea, Wolf....
=A0
Andy
G4JNT

On 6 February 2011 12:05, Andy Talbot <andy.g4jnt@gmail.com<= /a>> wrote:
That's a very good point -=A0having suffered this FSK-losing-cohe= rence problem once before.=A0=A0
It could all be done inside the PIC, maintaining two accumulators and= then using one or the other to address the sine lookup table.=A0=A0 As yo= u say, there will be a discontinuity, but hopefully not a big=A0problem.=
=A0
The interrupt routine is at maximum capacity, so the sampling rate wi= ll have to come down a bit to allow nearly double the instructions, but it= should be possible - I'll think about it :-)
=A0
And something a DDS chip like the AD985x can't do !
=A0
Andy


=A0
On 6 February 2011 11:47, wolf_dl4yhf <dl4yhf= @freenet.de> wrote:
Thanks Andy, nice project.. mayb= e I should dig out the PIC programmer again... !

One suggestion for= VLFers: A PIC doesn't cost a fortune. Build two of these generators,= and clock them with the same source (GPSDO or OCXO). For the FSK simply= flip between both generators. This has the *big* (cannot emphasize this= enough..) advantage that if the signal is to weak to be seen as DFCW etc,= we can still dig it out through a long FFT because each of the two carrie= rs remains coherent, and can be coherently averaged as long as necessary= (much longer than a single DFCW symbol). I noticed this on Stefan's= signal today : With the very slow settings, all you see is a rounded hump= in the spectrum because the signal isn't coherent. No chance to detec= t it for "DX" receivers.

Of course flipping the (FSK-) switch may cause a heavy click then (dep= ending on the momentary phase shift between the two carriers) but I think= a robust PA will survive this.

Have a nice sunday,
=A0=A0 Wolf= .

Am 05.02.2011 19:57, schrieb Andy Talbot:=20
9kHz OPs may be interested in this DDS suitable for audio/ VLF using= just a 16F628 PIC, , R-2R ladder and op-amp filter.=A0=A0 It can generate= frequencies up to about 40kHz with typical DDS high resolution / frequenc= y steps, (higher if you overclock the device) =A0offers two-tone FSK opera= tion by toggling a single input line=A0(ideal for DFCW),=A0 The two=A0freq= uencies are stored in non-volatile memory and are=A0user-programmable=A0fr= om=A0an RS232 interface=A0using ASCII text based commands.
=A0
See ww= w.g4jnt.com/PIC_DDS.zip for=A0full details.
=A0
Andy
=A0
=A0



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