[qrptech] Facsimile of the MC1350 IF Amp.


Hi Bob...you have some nice questions. I'll try to answer the questions below...

I'll review the questions again after I finalize the empirically engineered circuit.

Actually, I bet y'all can do a better job at testing since I'm kind of limited  by my test equipment.

That's why I hire prototype testers...they do the job for me...a great job too.

-Diz, W8DIZ

On 1/11/21 4:20 PM, Bob N1RC wrote:
Nice job! 

Having worked for a semiconductor company and in particular on the AD600/AD602 and AD603 Data Sheets, here are a few questions that come to mind:

1. What are are input and output clipping levels in Volts at minimum and maximum gain?
No clue...only tested with 100uV P-P (50 ohms) input but noticed some distortion on scope with 20mV P-P AGC-OFF

2. What are the second and third order intercepts or distortion vs. input vs. gain voltage?
Idunno...may need some help here...

3. Have you plotted a curve of AGC voltage vs. gain vs. clipping levels vs. bandwidth?
Nope...not yet...but AGC action seems smooth using a POT to ground.

4. Have you tested operation at 9V, 13.6V, and 20V?
Only at 6 volts...Gain is reduced by 6 dB...which I think is "nice"

5. Have you checked the power dissipation of the transistors you used?
2N3904 for now...may change to 2N2222A...seem OK

Did you use matched pairs where possible?
Nah...matching is for sissies...actually the transistors are all from the same manufacturing lot...so just crossing fingers.


Bob, N1RC

Thanks for the feedback Bob...this project has been a lot of fun so far.

Building 2nd generation circuit this week...guess you can call this version the Alpha...next is Beta :)

73, DIz, W8DIZ

On Mon, Jan 11, 2021 at 9:38 AM w8diz via groups.io <w8diz=kitsandparts.com@groups.io> wrote:

Howdy all,

Here is the first attempt at creating a simple version of the old popular (balanced I/O) MC1350 IF Amp

Bias circuits are a bit simpler; lots of empirical design here.

Balanced Input Z was measured at 660 Ohms; Balanced Output Z measured at 2800 Ohms

First measurement using 50 ohm 100uV P-P Input was 2.5V P-P Output with 50 ohm load.

Looks like at least 66 dB gain at 9 MHz. Amp look stable and clean.

Will fine-tune circuit values this week.; then order prototype PCBs.

Would love some comments on usefulness of such a project.

73, DIz, W8DIZ

Bob Clarke
M: 978.337.2720