Tuesday, May 4, 2021

Mounting to Perfboard and Scope Test

I was happy to finish out my normal duties last night (training, practice my lute, etc.) and move the MMM to a more permanent perfboard. In the case of this mounting, I did my best to preserve the layout of the schematic if at all possible. I checked continuity after mounting each component, etc. Everything seemed to be going great. But I couldn't get any signal at 3.579 MHz. Damn. Truly, I didn't beat myself up about it. Instead, i headed back upstairs after the youngest went to bed and did some reading. 

I have the circuit another look on a short work break. Tested I connected the battery and heard the slightest amount of oscillation. Hey! And I noticed significant shifts in oscillation when I fooled with the L1/L2 coils. 

Troubleshooting: I'm not sure why this would occur. I understand that touching the coil would change the inductance. Ought I need to fix this before moving forward? Exactly how would I do this?

This feedback from Bill Maera: 

Yes, or you could go with a toroidal coil   Aside from the value in uH  you have to pay attention to the tap -- and make sure that you are tapping from the correct side (usually X number of turns up from the bottom).  Try it. 

If it doesn't work, take a look at the coil and the tap.  

You are mentioned on the SS blog.   With a link to your site.<--the real cool part

I then put the MMM on a scope shown below. 

Next steps:

  1. Better understand the coil issue.
  2. Build a low pass filter (LPF) to pass frequencies below 4 MHz. 

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