EMRFD Message Archive 201
Message Date From Subject 201 2006-11-18 10:17:49 Stan Looking for help with PIXIE mixer stage
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Help - I am working on a modern version of a PIXIE. The basic
concept has been around for well over 10 years. I plan on using a
modern cell phone part for the audio section. My hang up is in the
mixer section.
Currently it uses the transmitter output stage as the mixer. The
received RF (1 10 uV) is fed to the collector, the drive osc stage
outputs 20 100 mW to the base and the audio is taken off of the
emitter (across a 10 k resistor).
The PIXIE has a couple good features 1) it is simple 2) it
works but it has some bad features also a) BCI break
through b) poor weak signal detection
I have brain stall with the mixer action. I can not bring myself
to understand what I consider up side down operation. Hi
Anyhow, I would like to know if any one has any suggestions, or if
anyone has every done a LTSpice model of the circuit.
My plan is to do a SMD PCB in micro size once I get everything
updated. And the problem area is the receive mixer section at
present. The osc and audio stages are under control.
Suggestions, etc appreciated
De Stan ak0b202 2006-11-18 13:10:42 michael taylor Re: Looking for help with PIXIE mixer stage
> I have brain stall with the mixer action. I can not bring myselfIf you are not too tied to making it as minimal as the Pixie, you
> to understand what I consider up side down operation. Hi
> Anyhow, I would like to know if any one has any suggestions, or if
> anyone has every done a LTSpice model of the circuit.
could use the Philips/NXP BF991/2/8 dual-gate MOSFET [1] (avail from
Digikey in single quantities) and use a 40673 style mixer circuit as
shown in EMRFD [2] or W1FB's QRP or Design Notebooks.
[1] <http://www.nxp.com/pip/BF991_2.html>
[2] <http://users.easystreet.com/w7zoi/emrfd.html>
-Michael Taylor, VE3TIX203 2006-11-18 15:40:20 Stan Re: Looking for help with PIXIE mixer stage
the final RF stage transistor for the dual purpose of mixer I have
not thought of a way to do the dual functi204 2006-11-18 20:47:11 michael taylor Re: Looking for help with PIXIE mixer stage
> I would like to end up with the same or fewer parts now require forI am the sort who is happy if my oscillator works, period, let alone
> a PIXIE but still have an improved LPF plus some BCI protection.
trying to decide super minimal circuits using "short-cuts" such as
using a power amplifier transistor also as a mixer, and I'm a
confirmed gold-plater [1] when it comes to software design ideas. But
I assume the normal way to design minimal circuits is to start with a
simple basic circuit, so in this case with multiple transistors or
MOSFETs, one for each of the separate stages, and from there you do
Muntzing [2] and then try short cuts of making a single component do
double duty.
[1] <http://www.stevemcconnell.com/rdenum.htm> #28
[2] <http://www.national.com/rap/Story/0,1562,17,00.html>
-Michael Taylor, VE3TIX