----- Original Message -----

From: Jim Sanford

To: [email protected]

Cc: [email protected] ; Bdale Garbee ; Bill Ress ; Dave Black (Home) ; Dave Black (Work) ; Dave hartzell ; David Smith ; Dick Jannson ; Don Ferguson ; John B. Stephensen ; Juan.Rivera (Work) ; Lyle Johnson ; Phil Karn ; Robert Davis KF4KSS ; Robert McGwier ; Samsonoff@Mac. Com ; Stephen Moraco ; 'Steven Bible' ; 'William A Schmitt'

Sent: Monday, June 11, 2007 00:44 UTC

Subject: Re: 70 cm Receiver Spur Source Found

Juan:
Can you "sniff" the various lines from CAN-Do! to get an idea of which is the source?

Also, my memory is that we still have an open issue with the passband ripple -- or did that get resolved and I missed it?

Again, thanks for all you're doing.

73,
Jim
[email protected]


Juan Rivera wrote:

All,

The source of the spurs in the 70 cm prototype receiver is the CAN-Do module.

This is the receiver IF output as designed

(powered from pins 39 and 40 of the CAN-Do Module)

This is the receiver running off of a separate power source

(bypassing the CAN-Do Module +13 volt output on pins 39 and 40)

This is the same configuration as above, but with the CAN-Do module shut down

From the above it appears that:

<!--[if !supportLists]-->1.    <!--[endif]-->The CAN-Do module is the source of all the spurs that I see

<!--[if !supportLists]-->2.    <!--[endif]-->None of the spurs are being generated by the receiver’s internal power supplies

<!--[if !supportLists]-->3.    <!--[endif]-->Some, but not all, of the noise is entering the receiver via the switched +13 volt CAN-Do output on pins 39 and 40

<!--[if !supportLists]-->4.    <!--[endif]-->The remainder of the noise could be entering the receiver on other CAN-Do pins, or being radiated to receiver components or traces in close proximity

See my log for all the intermediate steps I took to reach these conclusions.

Remaining RF issues:

<!--[if !supportLists]-->1.    <!--[endif]-->Phase noise

<!--[if !supportLists]-->2.    <!--[endif]-->Microphonics

73,

Juan

WA6HTP