Re: AE7EU Top Level PCB Mod

Diver Martin <diver.martin@...>


Can you point me towards which chip/board you're going to try out?

On Jan 10, 2018 11:05 PM, "Dave Bottom" <ars.kd6az@...> wrote:

Looks good so far.

I have one of the Mic AGC amplifiers coming, so I will let you know how it works out.  I think a set and forget gain control will be fine.  It should be set so as not to over drive and be left alone.  Almost all cell phones use these 3 stage low noise AGC amplifiers for the Electret Mic so I’m expecting it to work well here too.

Dave WI6R

Sent from my iPhone

On Jan 10, 2018, at 10:39 PM, Diver Martin <diver.martin@...> wrote:

So, I've finally got a rough draft of what I'm thinking for my uBitx top PCB mod.  Features at this point are:

No modifications required to uBitx board itself (not to say a 470uF anti-pop mod might be bad, or other things couldn't be done)
ATU: 7-inductor, 8-capacitor with Hi-Z/Lo-Z switch.
Selectable Power output (two power input connectors)
Brain transplant:  Teensy3.2 96MHz ARM processor
All connections on side edges - no wiring to enclosure
Front panel with pushbutton switches
DSP Audio (Via Teensy32, would require headphones or amplified speakers)
Solderless AGC modification (Attenuator at the front end switched in during RX)
Realtime clock (via Teensy32)
Linear amplifier control (just a reed relay on a 3.5mm header, sorry, not an RCA, but you could easily change it...)
Top side only construction (would make assembly cost lower)

BoM cost:  Probably way higher than it should be.  Needs optimization, and I still need to enter in costs.
Complexity:  Probably way more than it should be.
Layout:  An ugly mess of routing.  I can't say I like it, but the constraints I put on myself made it really hard to route.  There's lots of open areas to cross with lots of signals going all different directions.

Picture of the layout and schematic PDF attached, along with a 3D view.

I think the one modification that I still need to consider is a microphone preamp.  But, I have no flippin' clue where on the PCB I'd put the gain control knob!  Might have to be an internal potentiometer....

Martin Held - AE7EU
If there aren't any questions, then what is there to learn?

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