Jim and Bill,
Thank you for the compliments. I'm having more fun with this little SDR tool that just about anything I've played with in a long time. I just got started looking at EMI coming off of the CAN-Do module and I've already made an interesting discovery. I made a hairpin single-loop sniffing coil a while ago out of a piece of coax to sniff the internals of the receiver and I already knew that it would also work at the low noise fundamental frequencies that we're seeing from the CAN-Do module, so I pressed it back into service.
Holding the sniffer near the CAN-Do's inductor I see this:
As we already know, I can set the fundamental frequency by varying the input voltage, so I set it to 50 kHz by adjusting the input to 13.69 volts. I then captured this display. To my surprise the module jumps briefly to about 57 kHz at regular intervals of about 3 seconds. I think this has to do with it resetting because it’s not happy. I’ve forgotten the details. My next plan is to probe all 40 pins by using a 10x scope probe. I’ll start another log called CAN-Do Noise and start posting there as I start on this task.
From: [email protected] [mailto:[email protected]] On Behalf Of Jim Sanford
Sent: Sunday, June 10, 2007 7:46 PM
Cc: [email protected]
Subject: [eagle] Re: Jim's Phase Noise Number!!
-110 dbc/hz at 10khz offset is what I REMEMBER in my response to the
question, "What is a good phase noise number to shoot for in a microwave
narrowband (ssb/cw) system?"
My memory may very well be WRONG, which was the point of asking my question.
I agree with you, looks like -90dbC at 10 KHz, but given what Juan's
already said about his sources, and the uncertainties of the SDR-IQ,
that may be VERY good!
Do you have a different answer to my original question, "What is a good
phase noise number to shoot for in a microwave narrowband (ssb/cw)
system?" If so, I'd like to engage in that conversation, both for
Eagle and for my terrestrial microwave station.
I agree with your assessment of Juan's work -- ABSOLUTELY EXEMPLARY!!!!!!
Thanks & 73,
> Where did the -110 dBC/Hz at 10 KHz come from? And at what frequency?
> That's pretty aggressive using straight forward VCO's and PLLs. >From
> Juan's data with his snappy SDRIQ, it looks like that the 70 cm is
> doing about -90 dBc/Hz at10 KHz. I thought that's what I read from his
> early HP8566B dtata.
> My straight forward S2 RX downconverter PLL LO does -100 dBc/Hz at 10
> We'd better get a good read on this since, if real, it forces more
> sophisticated LO designs.
> Great work Juan!!
> Regards...Bill - N6GHz
> Jim Sanford wrote:
>> I think I remember Bob's answer as -110dbc at 10 KHz offset.
>> Thanks & 73,
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