Wouldn't you need another oscillator to heterodyne it with? And a 150 MHz comparator to hard-limit it? and then a counter (possibly a Johnson counter) to generate the I/Q switching waveforms? That's at least three more parts, and counters that'll run that fast aren't easy to find, or cheap. Neither are 150 MHz comparators. There are a lot of ways to skin this cat. We can debate it forever, and that's probably a good thing.
--- In [email protected], "Rotten Robbie" <rottenrobb...@...> wrote: > > If I were doing it (and I might in the near future) I would use the DDS > somewhere in mid range and heterodyne it up to the necessary 4X frequency. > > Bob Macklin > K5MYJ > Seattle, Wa. > "Real Radios Glow In The Dark" > > ----- Original Message ----- > From: Bob Camp > To: [email protected] > Sent: Sunday, January 24, 2010 2:13 PM > Subject: Re: AW: AW: AW: AW: [soft_radio] Re: LD-1 Discussion on > Garage-shoppe.com Blog > > > > > Hi > > > A full wave rectifier can also be used as a simple broad band doubler. > > > > The problem with the output of the DDS is that without filtering it is far > from symmetrical in the upper octave. Some use bandpass filtering to get > around the problem, but that usually is not an option on a wide band radio. > > > Bob > > > > > On Jan 24, 2010, at 5:08 PM, Rotten Robbie wrote: > > > > For this application Nyquist does not matter. It is just used as a > clock.And > what you need for the detector is a square(rectangular) waveform. > > If the waveform is reasonably symetrical you can use both edges for > frequency doubling. It just takes a few inverters for a time delay and an > exclusive OR. > > Bob Macklin > K5MYJ > Seattle, Wa. > "Real Radios Glow In The Dark" > ----- Original Message ----- > From: "Dave Wade" <g4...@...> > To: <[email protected]> > Sent: Sunday, January 24, 2010 1:56 PM > Subject: Re: AW: AW: AW: AW: [soft_radio] Re: LD-1 Discussion on > Garage-shoppe.com Blog > > > > > > > k5nwa wrote: > >> At 12:04 PM 1/24/2010, you wrote: > >>> > >>> Thanks for your explanations, Bob! > >>> > >>> I understand the principles of driving the mixer with a squarewave > >>> signal and that you use a comparator to change sine to squarewave. > >>> > >>> Where I'm failing at is the trick how to receive 30 mhz with a DDS > >>> that make 37 MHz max without getting problems with nyquist. Can you > >>> use a comparator to double your VCO frequency without getting > >>> problems at the duty cycle? > >>> > >>> > >>> Stephan > >>> > >> > >> This is a mixer, you are not trying to digitize the 30MHz signal > >> where you would need a minimum of two samples, instead you are mixing > >> it down to the base band. > > > > No but the DDS chip is synthesising a sine wave from samples, and > > Nyquist bite both ways. However some DDS chips (I don't know about this > > one have on-board frequency multipliers... > > > > > >> > >> > >> Cecil > >> k5nwa > >> www.softrockradio.org www.qrpradio.com > >> < http://parts.softrockradio.org/ > > >> > >> Never take life seriously. Nobody gets out alive anyway. > >> > >> > >> > >> ------------------------------------ > >> > >> Yahoo! Groups Links > >> > >> > >> > >> > > > > > > ------------------------------------ > > > > Yahoo! Groups Links > > > > > > >
