The ripple problem is not resolved, but is likely to be in concert with reducing power dissipation in adjacent components. The SAW filters need to be kept warm (-35 C) during eclipses so the second mixer needs to be replaced with something that dissipates less power. This will raise the input impedance and make the matching circuitry less critical.
----- 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

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.

[email protected]

Juan Rivera wrote:


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 receiverís 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