Thursday, June 24, 2021

Simple SSB Xcvr Mic Amp build & AF amp layout

 I had decided to build most of the transceiver using perf board.  I prefer the double sided plated through hole variety to the bare variety.  For me it just makes it easier to solder the part in place, and then route the leads as needed.  Also if you have to replace a part, you can usually just  clip it off on the top and solder in a replacement without changing the connections on the bottom. 

This type is available in various sizes. You can find small kits with several small sizes for around $10.  You can also get larger size boards and cut to the size desired.

After I received the kit, I changed the layout to fit one of the sizes in the kit.  The extra time spent making an exact layout template really saves time, and frustration in the long run.  I also did the layout in ME Pad  and Muppet format, and all are available at

https://www.dropbox.com/sh/v9rr5cqg9a788qe/AADuZN4t4wCLGh8orBzdFUwTa?dl=0

When I first started building some of my projects, I used many components I had salvaged from junked equipment, or surplus supliers.  Anyone remember 'PolyPacks' ?  Because of this I got into the habit of always measuring the value of the components as I used them. Time spent doing this also paid for itself many times over.  Now I use better quality parts, but still test them before use.  Getting harder to read the values on these small parts for some reason. 

For this I use one of the inexpensive component testers available through the usual suppliers. The one usually use is similar to this one, and has pads for use in testing SMC components.  They are available with or without cases for $10 - $20.  Most of them measure R,L,C, along with diodes, transistors and FETs.  For the seimconductors, they give pinout along with values such as gain and internal capacitance depending on type being tested. The first one I bought did not have a case so I found the design for a 3D printed one.

Following the template, it only took a little while to do the actual construction.  For audio and  digital boards I use either straight or right angle header pins for connectors.  This allows me to use JST style jumpers for wiring for DC and control signals.  You  can also add connectors to shielded cable if needed.  Or, you can easily solder wires directly to the pins if desired.  For much of my test gear, I have adapters made up so I can use JST jumpers for ease of testing modules.

Now that this module is finished, I did a layout template for the AF amplifier.  Since the premap half of the AF amp is nearly identical to the Mic amp, I could just move components over a little to make room for the LM-386 and associated components. 






It turned out like this. This was fairly crowded on this size board, so I did another template using a slightly larger board in the kit.  This one allows plenty of room for components.  Either version will work.  Just up to the builder to choose the one they prefer.

I also did a ME Pad template for those that like that construction method. but only for the smaller size board.  They are available at

https://www.dropbox.com/sh/ia55ghqyibs5iur/AAAlbEp8ARKuvKQ38VONz5zMa?dl=0


Next time I will have the AF Amp board finished, and will describe the simple test gear and software I use for checking audio frequency stages.









1 comment:

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