Re: Murania Audio


Thanks Dave!  Just time for the 4H kid's build, we're finishing up Monday night.
I love this radio stuff.
On 7/27/2018 7:30 AM, nm0s_qrp via Groups.Io wrote:

I had a chance to check out a Murania that one of out builders had put together, that he reported low audio.  On examining it, I found that the regeneration loop was too large, and the receiver was in full oscillation.

When the receiver is oscillating, it makes a large RF signal that is detected in the receiver IC, and drives down the AGC voltage.  This cuts the gain of the IC.  So, to set up the regen, the loop needs to be about the diameter of a pencil, no larger, and exactly perpendicular to the board, and to the ferrite rod.  That is neutral feedback.  If you then twist it slightly either way, it will increase or decrease the feedback.  It is hard to hear a change in volume with strong stations, because the AGC flattens out the volume.  If you hear whistles as you turn the tuning knob, it is oscillating, and the regeneration is too high.

Hopefully this helps some other builder!

73 Dave NM0S

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