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Old 1st Jan 2017, 2:04 am   #14
Herald1360
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Join Date: Feb 2007
Location: Leominster, Herefordshire, UK.
Posts: 16,528
Default Re: Two or three IF stage Chinese radio kits.

I'd check the current on VT4 is in the 2-5mA range suggested- too high and the TX may start to saturate which won't help! R5 will adjust- it's only controlled by the gain of VT4 and the current through R5. For the output stage, I think a pair of AC176s might help, they'll have a bit more headroom for signal. Raising the values of R7, R9 bias resistors to compensate for the lower Vbe will be necessary.

Could be fun to play with, just to squeeze performance it was never designed for out of it!

Possibly the best mod would be to increase the supply voltage and add some low value emitter resistors in the output stage. The feed tor the front end can be kept down by increasing R6.
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