A Simple Superhet by John E. Post, March 2008

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redrocker
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A Simple Superhet by John E. Post, March 2008

Post by redrocker » Sat May 24, 2008 7:59 am

I do not understand how to connect the antenna (L1) to the SA602's input amplifier. The problem is that the antenna is depicted as a transformer (see schematic below) when in reality it is an inductor. In other words, the antenna is a two-terminal device, not a four-terminal device.

Image

Here are some recommended input configurations from the SA602's datasheet:

Image

Even if the antenna (inductor) and the variable capacitor were to be placed in parallel across the input amplifier's inputs, the problem is that one of the differential inputs would be directly tied to ground. The datasheet contains no examples of such an arrangement.

If anyone has any idea what the author's intent was, please inform me.

sghioto
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Post by sghioto » Sun May 25, 2008 7:27 am

Use figure "a" single ended tuned input. I don't see any problem with this arrangement. However, if you look at the end of the article on page 47 "From Here", you can wind a secondary coil over the primary as the author suggest.

Steve G

redrocker
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Post by redrocker » Sun May 25, 2008 1:43 pm

Thanks, sghioto. I entirely missed that part of the article. Would 30 AWG wire wrap wire be a suitable substitute for magnet wire?

sghioto
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Post by sghioto » Sun May 25, 2008 3:31 pm

Don't know for sure would just have to try it. Might just need a few extra turns. The magnet wire is usually better because it allows the windings to be closer together due to the lack of the vinyl insulation.

Steve G

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