EMRFD Message Archive 2008
Message Date From Subject 2008 2008-09-06 00:39:56 richj_focus Direct Conversion Radio Group:
I am a novice at radio construction but know a thing or two about
I would like to gain experience building and using direct conversion
radio receivers. I want to build an analog phasing rig however to
start with, i was thinking of a direct conversion, no side-band
suppression simple rig. My question, is it worth the time to build
the simple rig? Or should i just jump in with the side-band
suppressing phasing rig like the miniR2?
Looking for advice from experienced builder and radio operators.
2009 2008-09-06 07:12:41 James Duffey Direct Conversion Radio Rich - You asked:
"My question, is it worth the time to build the simple rig?"
Yes, you should build the simple rig. You will learn a lot building a
simple direct conversion receiver. The phasing rig is a bit more
difficult and the simple rig will help if you understand the basics
A direct conversion receiver, despite its performance quirks, has all
the building blocks that a more complex receiver has, either DC or
superhet. It has filters, a mixer, a oscillator, and audio amplifier.
With those four building pieces you can build any more complicated
receiver, and for that matter, by adding an RF amplifier (which some
DC receivers have), a simple transmitter. It is easy to understand
what is happening from stage to stage.
To get the most from the your first DC receiver build experience you
should build as much of each stage as possible from scratch. Eschew
ICs and prewound inductors. As you are on this list, I assume that you
have a copy of EMRFD. The information on direct conversion receivers
is excellent. There is a simple DC receiver in the DC receiver chapter
that KK7B built and designed. It is all built from discrete parts and
you will learn a lot from building and troubleshooting it. While you
are at it, read Wes's comments (philosophy?) on building and
operating. Build what you operate, operate what you build.
You may wish to take a step back and build a simple crystal radio.
There is no better way to learn about bandpass filters and impedance
matching. Then perhaps a regen? But that is for another post.
Whatever you do, keep us informed on your progress and ask questions
if you have them. There is no better way to learn and the resources on
this list are vast. - Duffey
Cedar Crest NM
2012 2008-09-06 11:14:20 Alberto I2PHD Re: Direct Conversion Radio richj_focus wrote:
>My suggestion is to go the SDR route, where e.g. the phasing network is replaced by software code (no tight tolerance
> I would like to gain experience building and using direct conversion
> radio receivers. I want to build an analog phasing rig however to
> start with, i was thinking of a direct conversion, no side-band
> suppression simple rig. My question, is it worth the time to build
> the simple rig? Or should i just jump in with the side-band
> suppressing phasing rig like the miniR2?
problems, no component value aging, etc.)
Give a look at this series of very inexpensive kits :
73 Alberto I2PHD
2014 2008-09-06 13:07:40 Alberto I2PHD Re: Direct Conversion Radio Alberto I2PHD wrote:
>An additional link could be this one :
> My suggestion is to go the SDR route, where e.g. the phasing network is replaced by software code (no tight tolerance
> problems, no component value aging, etc.)
> Give a look at this series of very inexpensive kits :
73 Alberto I2PHD
2016 2008-09-06 16:41:57 WA0ITP Re: Direct Conversion Radio As usual JIm's right on.
Building a DC receiver from scratch is indeed a learning experience, can be
humbling, but is well worth the effort. Luckily there's a wealth of info on it
in EMRFD to jump start the process.
I'm fussin with one now, and currently it's deaf as a post. I wound a simple
(?) trifilar mixer on an FT37-43 core, added a coupla 1N4148's, and an audio amp
for some gain.. Maybe not enough gain tho, since I read somewhere that about a
100 dB is needed. I also think I need more LO energy in the mixer.
Here's the plan:
Add an audio preamp with some AGC (a lot of AGC if I can get it)
Change the oscillator to get more output (add a buffer or build a Butler)
Add a bandpass filter on the front end.
Investigate an rf amp ahead of the mixer
Maybe change the mixer core material (6 or 2 material?)
Maybe use another mixer (diode ring, Schottkey's on the same chip?)
etc, etc, ... whatever it takes.
We learn best by doing, plus it's a lot of fun!
I love this radio stuff !
72, 73 Terry, WAØITP
----- Original Message -----