[eagle] Re: Jim's Phase Noise Number!!

Juan Rivera juan-rivera at sbcglobal.net
Sun Jun 10 20:04:20 PDT 2007


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.

 

73,

 

Juan

WA6HTP

 

 

-----Original Message-----
From: eagle-bounces at amsat.org [mailto:eagle-bounces at amsat.org] On Behalf Of
Jim Sanford
Sent: Sunday, June 10, 2007 7:46 PM
To: Bill Ress
Cc: eagle at amsat.org
Subject: [eagle] Re: Jim's Phase Noise Number!!

 

Bill:

-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,

Jim

wb4gcs at amsat.org

 

 

Bill Ress wrote:

 

> Jim,

> 

> 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 

> KHz.

> 

> 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,

>> Jim

>> wb4gcs at amsat.org

> 

> 

> 

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