EMRFD Message Archive 2213
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, WA5BDU2215 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 toNewer DDS chips like the AD9951 or the AD9912 have much lower level spurs than the
> 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
>
AD9851. Also, the Si570 is very good. I just happen to sell boards for all three.
Dave - WB6DHW
<http://wb6dhw.com>