Re: ND6T AGC implementation for uBIT-X
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On 29/04/18 1:45 PM, Kees T wrote:
I've been looking at
the ND6T website and find several interesting, useful, and focused
on minimalist circuits.
1) The AGC circuit which we're discussing here. I have a board
layout which is 980mils x 980mills and it seems to fit nicely. It
offers jumper selection of 4 Hold times and AGC OFF......using 0
ohms for AGC OFF, "a" ohms, "b" ohms, "c" ohms, "d" ohms. It's a 2
sided board which you can attach with double sided tape to the
back of an RF gain pot (5K) or wherever you want. The reason for
mentioning the RF gain pot is that it's a recommended good idea
and you wire it to the uBITX board using small coax. This is also
explained by ND6T in the "Adding an RF Gain Control to the uBITX".
2) T/R Click Fix is a board half the size of the AGC board and
contains the circuit defined by ND6T. I refer you to his write-up
3) The Polite Antenna Tuner also caught my eye and has a really
simple minimalist technique using a broadband noise generator to
tune the antenna and listen with your receiver for a null (when
you are matched to 50 ohms). Seems to fall right in line with QRP
rigs and tuners. And you don't require transmitting to get
"close". Believe you me, a high BITX antenna SWR will take out an
IRF510 in a heartbeat .....not so much for a RD16HHF1 RF MOSFET.
Sounds like another ~ 1 sqin board.
73 Kees K5BCQ
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