Message	Date	From	Subject
2213	2008-10-08 19:23:18	Nick Kennedy	first sound ...
I've been working on a receiver around various circuits familiar to emrfd readers since December and tonight it's playing the sweet sounds of 40 meter CW. Lots of fun. I decided to build a receiver after building the HYCAS board. My IF is 8 MHz. I built a 6-pole 500 Hz crystal filter (Butterworth) to go with it. The LO at present is an AD9851 board from NJQRP. I'm currently using an AVR Butterfly controller board with software by Steve Weber which I modified to add rotary encoder frequency control and a few other things. I used a spare R1 receiver board for the product detector and audio stages, reducing the gain of some of the stages and omiting the (expensive) L/C audio filtering stages. I inserted a diplexer based on a design on VE3BPO's QRP homebrewer page after my ADE-1 product detector. The BFO is from emrfd, one with a 74HCxx buffer to which I added a DC bias control to adjust the duty cycle. The mixer is another ADE-1. I don't have any front end filtering yet, that's next. Naturally, I'd like it to evolve into a transceiver at some point. And if DDS birdies prove to be a problem, I may go to a PLL/VCO for the VFO using a DDS for its reference. I also need to build a SSB bandwidth filter. 73- Nick, WA5BDU
2215	2008-10-08 19:40:47	brainerd@wildblue...	Re: first sound ...
On 8 Oct 2008 at 21:23, Nick Kennedy wrote: > I've been working on a receiver around various circuits familiar to > emrfd readers since December and tonight it's playing the sweet sounds > of 40 meter CW. Lots of fun. > > I decided to build a receiver after building the HYCAS board. My IF > is 8 MHz. I built a 6-pole 500 Hz crystal filter (Butterworth) to go > with it. The LO at present is an AD9851 board from NJQRP. I'm > currently using an AVR Butterfly controller board with software by > Steve Weber which I modified to add rotary encoder frequency control > and a few other things. > > I used a spare R1 receiver board for the product detector and audio > stages, reducing the gain of some of the stages and omiting the > (expensive) L/C audio filtering stages. I inserted a diplexer based > on a design on VE3BPO's QRP homebrewer page after my ADE-1 product > detector. > > The BFO is from emrfd, one with a 74HCxx buffer to which I added a DC > bias control to adjust the duty cycle. The mixer is another ADE-1. I > don't have any front end filtering yet, that's next. > > Naturally, I'd like it to evolve into a transceiver at some point. > And if DDS birdies prove to be a problem, I may go to a PLL/VCO for > the VFO using a DDS for its reference. I also need to build a SSB > bandwidth filter. > > 73- > > Nick, WA5BDU > Newer DDS chips like the AD9951 or the AD9912 have much lower level spurs than the AD9851. Also, the Si570 is very good. I just happen to sell boards for all three. Dave - WB6DHW <http://wb6dhw.com>

On 8 Oct 2008 at 21:23, Nick Kennedy wrote:

> I've been working on a receiver around various circuits familiar to
> emrfd readers since December and tonight it's playing the sweet sounds
> of 40 meter CW. Lots of fun.
>
> I decided to build a receiver after building the HYCAS board. My IF
> is 8 MHz. I built a 6-pole 500 Hz crystal filter (Butterworth) to go
> with it. The LO at present is an AD9851 board from NJQRP. I'm
> currently using an AVR Butterfly controller board with software by
> Steve Weber which I modified to add rotary encoder frequency control
> and a few other things.
>
> I used a spare R1 receiver board for the product detector and audio
> stages, reducing the gain of some of the stages and omiting the
> (expensive) L/C audio filtering stages. I inserted a diplexer based
> on a design on VE3BPO's QRP homebrewer page after my ADE-1 product
> detector.
>
> The BFO is from emrfd, one with a 74HCxx buffer to which I added a DC
> bias control to adjust the duty cycle. The mixer is another ADE-1. I
> don't have any front end filtering yet, that's next.
>
> Naturally, I'd like it to evolve into a transceiver at some point.
> And if DDS birdies prove to be a problem, I may go to a PLL/VCO for
> the VFO using a DDS for its reference. I also need to build a SSB
> bandwidth filter.
>
> 73-
>
> Nick, WA5BDU
>

Newer DDS chips like the AD9951 or the AD9912 have much lower level spurs than the
AD9851. Also, the Si570 is very good. I just happen to sell boards for all three.

Dave - WB6DHW
<http://wb6dhw.com>