1. BITX20@groups.io

Re: AE7EU Top Level PCB Mod

Diver Martin <diver.martin@...>
 

I suspect we'll find out.  The one thing about a PIN attenuator is that the attenuation range is lower to my understanding (I could be totally wrong though).  Right now I'm mostly hoping the detector/etc circuitry works okay overall, and that the nonlinearities aren't too bad.  It's really unfortunate to me that the radio doesn't have AGC of any kind, otherwise a mod like this wouldn't even been necessary.  But, such is the spirit of the uBitx's I guess!

On Tue, Jan 16, 2018 at 7:25 PM, Jerry Gaffke via Groups.Io <jgaffke@...> wrote:
I suspect a pin diode attenuator would produce less non-linearities than the ADE-1.
So less intermodulation distortion, less harmonics created.
The charge carriers can stick around for microseconds, so at RF it looks more like a resistor than the ADE-1's diodes.

The ADE-1 like diode ring mixer at the front end of the uBitx does not have the same issues
as an ADE-1 used as an attenuator, because the mixer diodes are driven very hard by the VFO,
and so are either on or off.  Perhaps use the NXP BAP64Q: 
    https://groups.io/g/BITX20/message/32056



On Sat, Jan 13, 2018 at 02:55 pm, Diver Martin wrote:
Jerry, if I had my druthers, that's where I'd put it, and /or I'd also derive the signal level post 12MHz bandwidth crystal. 




--
Martin Held - AE7EU
http://ae7eu.com/
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