Re: AM demodulation

To all who gave me good ideas and insights,

Thank you for your help. Based on all of your comments, I have a new and
improved AM receiver which automatically corrects small tuning errors.
Attached is a picture of the flowgraph.

Best regards,
---
Barry Duggan KV4FV


On 2019-10-28 12:21, Albin Stigö wrote:
> Last time I looked I found the AM demod block less than ideal so I just
> used a complex to mag and a DC blocker and found that worked better for
> my
> experiments.
>
> 73 Albin SM6WJM
>
> On Mon, Oct 28, 2019, 16:43 Barry Duggan <barry@dcsmail.net> wrote:
>
>> Hi Albin,
>>
>> Hmm.. Good to know. I had tried a frequency translating filter to
>> create
>> a 10khz IF, but it didn't seem to make any difference. I need to take
>> another look at that.
>>
>> Thanks!
>> ---
>> Barry Duggan KV4FV
>>
>>
>> On 2019-10-28 11:32, Albin Stigö wrote:
>> > A direct conversation SDR receiver like the funcube dongle pro plus has
>> > a
>> > large DC spike, it's not the carrier, it will mask your carrier
>> > though.. IQ
>> > correction will remove it, but that will also remove an AM carrier at
>> > 0Hz
>> > so it's common practice to offset a bit with a frequency translating
>> > filter.
>> >
>> > On Mon, Oct 28, 2019, 15:24 Barry Duggan <barry@dcsmail.net> wrote:
>> >
>> >> Hi Albin and Volker,
>> >>
>> >> I added a PLL Carrier Tracking block to take care of the tuning
>> >> problem.
>> >> See the revised
>> >> https://wiki.gnuradio.org/index.php/File:FunCube_AM.png
>> >>
>> >> Albin, that 'spike' is the carrier! This is AM ;)
>> >>
>> >> Thank you both for your suggestions.
>> >> ---
>> >> Barry Duggan KV4FV
>> >>
>> >>
>> >> On 2019-10-27 07:13, Albin Stigö wrote:
>> >> > Hi Barry,
>> >> >
>> >> > Some thoughts:
>> >> >
>> >> > You have a large DC spike at the center, try using the frequency
>> >> > xlating
>> >> > fir filter to tune an offset frequency.
>> >> >
>> >> > Why don't you decimate at the channel filter?
>> >> >
>> >> > Try observing the signal at various points using the frequency sink.
>> >> >
>> >> > Good luck,
>> >> > Albin SM6WJM
>> >> >
>> >> > On Sat, Oct 26, 2019, 21:02 Barry Duggan <barry@dcsmail.net> wrote:
>> >> >
>> >> >> Hi,
>> >> >>
>> >> >> I've been working on a gnuradio AM broadcast receiver, and have found
>> >> >> that the tuning is very critical to obtaining clear audio. My
>> >> >> flowgraph
>> >> >> can be seen at
>> >> >> https://wiki.gnuradio.org/index.php/File:FunCube_AM.png.
>> >> >> Are there any alternate demodulation methods which are not so
>> >> >> sensitive
>> >> >> to exact tuning?
>> >> >>
>> >> >> Thanks,
>> >> >> --
>> >> >> Barry Duggan KV4FV
>> >> >>
>> >> >>
>> >>
>>