LBS Update

Spent a huge amount of time working on the pre amplifier. Between reading up on how to calculate impedance's for the input and output of the pre and bilateral amps, along with determining turns on cores to make the transformers and learning LT Spice, it has been quite an exercise. While I have a better idea on matching transformers, I still will need to go back and study this topic a little more.

Re-winding the transformer has made all the difference. Sweeping the original transformer with my SNA, showed a flat response across the 40 meter band, good, but an swr of a little over 3.  The core is a FT37-43 with 16Turns for the primary and 2 Turns for the secondary. The secondary also showed an impedance of 23 ohms.  The new transformer works quite well, so that good. We are on the right track. A sweep showed again a flat response but a little less loss, and the swr went way down into the -350 range.  I never thought about a negative reading for swr.  Considering the performance of the transformer, I guess its a good number.  Testing of the core surprisingly, still has the impedance quite low.  It now measures about 22 ohms.

Here's a video of the pre-amp doing its thing. The station is from the US Virgin Islands. I switched back to the pre amp mode just before the end of the video.

For the audio end of things, I think a different speaker is in order. I have distortion when turning up to a level of volume needed. I also have a small amplifier board ready to go to replace the original audio amp, but I think I'll change the speaker first.  Now just have to find one.