Hi Bob,
If I understand the question correctly, yes. The DMTDs that I've encountered
so far use a zero-crossing detector and a TIC. I wanted to build sort of a
hybrid system that has a DMTD front end and an SDR back end. It seemed to me
that that would be sort of half way between a DMTD and a Timepod. But whereas
the Timepod digitizes 4 RF signals, this would digitize 2 audio signals. It
may be that it suffers all the disadvantages of both and has the advantages of
neither, but I thought I'd build it and see where it leads.
As to the 1 to 10 Hz range, doesn't that depend on the heterodyne frequency you
choose? I mean, you don't have to use a 10 Hz offset, do you?
Bob
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From: Bob Camp <[email protected]>
To: Discussion of precise time and frequency measurement <[email protected]>
Sent: Thursday, August 11, 2016 3:13 PM
Subject: Re: [time-nuts] Low cost SDR suitable for phase noise measurement?
Hi
Just to clarify:
You are looking for a way to digitize the output(s) of the mixer(s) in a DMTD.
The
“target signal” is in the 1 to 10 Hz range.
Is that correct or are you looking for something to use instead of a DMTD?
Bob
> On Aug 11, 2016, at 3:29 PM, Bob Stewart <[email protected]> wrote:
>
> Hi Brooke,
> It looks like I've asked a question poorly, yet again. So, let me try again.
> I have this idea of combining a DMTD with an SDR. So, said that way, it
> looks like what I really need is a 2-channel audio SDR. And having said
> that, maybe what I'm looking for is an external USB sound card. Those I can
> find. I can probably even figure out how to convert them to DC and supply
> them with a disciplined oscillator, if needed.
>
> Bob
> -----------------------------------------------------------------
> AE6RV.com
>
> GFS GPSDO list:
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>
> From: Brooke Clarke <[email protected]>
> To: Discussion of precise time and frequency measurement <[email protected]>
> Sent: Thursday, August 11, 2016 1:36 PM
> Subject: Re: [time-nuts] Low cost SDR suitable for phase noise measurement?
>
> Hi Bob:
>
> The SDR-IQ has a lower frequency limit of 500 Hz.
> http://www.prc68.com/I/Bats.shtml#SDRIQ
>
> There is a mod that replaces the on board 66 MHz oscillator with one locked
> to 10 MHz.
>
> --
> Have Fun,
>
> Brooke Clarke, N6GCE
> http://www.PRC68.com
> http://www.end2partygovernment.com/2012Issues.html
> The lesser of evils is still evil.
>
> -------- Original Message --------
>> A number of posts have appeared about Zynq SDRs on the "Shera revisited"
>> thread. So, I'd like to ask the more general question: Are there any low
>> cost SDRs that are suitable for measuring phase noise when coupled with a
>> DMTD? I believe what I'm looking for is something with enough bits to work
>> in the audio range down to DC. Yes, I could use a modified sound card, but
>> I'm really looking for something not sound card related. My thought was to
>> use a DMTD with a heterodyne frequency of maybe 5KHz.
>>
>> Bob -----------------------------------------------------------------
>> AE6RV.com
>>
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