Bill: I believe Christos is asking about the Brainerd (WB6DHW) 995X PIC/DDS/QSD board, and how far it will REECEIVE SIGNALS up to, not just a 995x DDS chip output frequency. We both have the same Brainerd board, I think, and my original response was related to receiving 2 Meters on SDR hardware (hence my assumptions).
The Brainerd 995X board uses an 18F2550 PIC to drive an AD995x series DDS. We regularly use 125MHz oscillators with the DDS PLL set to X4, giving a DDS clock of 500MHz. Many will lock up OK at 625MHz (X5), and some hams have driven it directly with external oscillators as various frequencies up to 500MHz. The great part of the Brainerd 995X board is that it also has a high- speed I/Q clock generator(X2 or X4), and a QSD receiver using very fast switches. This QSD easily works to 6 meters. Some careful attention needs to be paid to regarding spurs at the higher freqs, however. Also, the QSD should have an external bandpass filter preceeding it, as it seems to pick up FM broadcast and possibly even low-VHF TV stations as subsampled signals. Incidentally, we are testing a new Brainerd board that uses an AD9912, to 1GHz. It has the PIC and DDS chip, but no QSD. The initial PIC code has just been released, it is definately a work in progress. Both PICs are driven from the host computer via USB, no stand-alone controller yet. that is one difference from the I0CG designs. I0CG also uses a external clock multiplication, which may be better than the internal DDS PLL. His techniques could easily be applied to the Brainerd 995X board as well. There is also a prototype Brainerd QSE that is being worked on, which can generate up to about 1/2W, and takes clocking signals from the 995X PIC/DDS/QSD board. And, there is also a six-filter BPF that uses FST3251 switches for filter selection. Check out WB6DHW.COM, and the dds_controller Yahoo group. Other than writing some support software for the Yahoo group, and enjoying the Brainerd designs a lot, I have no connection with David. (top post to keep message flow) Terry WB4JFI --- In [email protected], "Bill Carver" <[EMAIL PROTECTED]> wrote: > > BAD TYPING !! > I0CG SELLS AD9951......... > I am clocking mine at 536 MHz, output 73-100.4 MHz, which I divide with ACMOS to get HF frequencies.......... > Bill W7AAZ > > > -----Original message----- > From: "Bill Carver" [EMAIL PROTECTED] > Date: Thu, 08 May 2008 17:52:53 -0600 > To: [email protected] > Subject: [softrock40] Re: softrock for 2m? > I0CG sekks AD9951 DDS products clocked at 500 MHz. > I am using one with 536 MHz clock with zero problems. > Bll W7AAZ > > > > > -----Original message----- > From: "Christos Nikolaou" [EMAIL PROTECTED] > Date: Thu, 08 May 2008 15:54:18 -0600 > To: [email protected] > Subject: [softrock40] Re: softrock for 2m? > > Hi Terry, > > How high can the 995x actually go? > Although the parts on it seem to have something like 350MHz or so > limits, I could not get it go beyond 60MHz. >
