EMRFD Message Archive 2103
Message Date From Subject 2103 2008-09-22 09:43:17 ter753 micro R1 receiver I have mislaid my copy of emrfd and was wondering if anyone could post
or e-mail me the schematic.Thanks!, terry. email@example.com
2105 2008-09-22 19:33:54 timshoppa Re: micro R1 receiver 2108 2008-09-22 21:39:08 Rick Re: micro R1 receiver The August 1992 article describes the original R1 receiver. It is considerably more complex
than the simple microR1 described in chapter 8 of EMRFD. I occasionally re-read both
descriptions, and often learn something new while thinking about them--even though I
wrote them. I always learn something when I re-read Wes and Bob's sections of the book.
I approach direct conversion receivers the same way I approach playing scales on the violin:
the simplest ones are always worth reviewing, and there are more complex ones that I am
not ready to tackle, yet.
I have played with the microR1 circuit many times over the years, and each time I build it a
little differently. I just posted a new file on this site that describes a recent variation I built
for my RF Design class at Portland State University. The new file does not include any
information on the input double tuned circuit, because that was left as a design exercise for
my students. Note that the link on the output of the double-tuned circuit is the DC return
for the diodes in the mixer, so if you change the input circuit be sure to provide a path to
ground at that point.
2111 2008-09-23 05:12:36 ea3ghs micro R1 receiver with RA3AAE mixer Hello,
Maybe can be interesting for someone.
In my local QRP club we have only 7030khz xtals.
I was very interested in digital modes in the 20
meters band, 14070 kHz.
One year ago I copied the Rick's receiver but
with the RA3AAE or/and Marvin Cohn from Westinghouse
The schema can be seen here: (page 6)
I have received an Australian station (20000km!!) with a small dipole
in MFSK16 mode.
2116 2008-09-23 10:34:35 Rick Re: micro R1 receiver with RA3AAE mixer Muy Bueno Eduardo,
This is an excellent, well-written article with many interesting ideas and insights. I highly
recommend it to anyone in the group with any Spanish at all. Even if you don't read
Spanish, the schematics are well worth studying. There are some ideas here I will try the
next time I build a simple receiver.
Note that the input double tuned circuit values in Eduardo's 40 m version are appropriate
for the microR1 schematic that I posted.
Muchas Gracias y 73,
> The schema can be seen here: (page 6)
> I have received an Australian station (20000km!!) with a small dipole
> in MFSK16 mode.
> 73/DX Eduardo
2117 2008-09-23 11:24:37 k5nwa Re: micro R1 receiver with RA3AAE mixer At 12:34 PM 9/23/2008, you wrote:
>Muy Bueno Eduardo,I like circuit #1, and #2, I have always liked balanced mixers but
>This is an excellent, well-written article with many interesting
>ideas and insights. I highly
>recommend it to anyone in the group with any Spanish at all. Even if
>you don't read
>Spanish, the schematics are well worth studying. There are some
>ideas here I will try the
>next time I build a simple receiver.
>Note that the input double tuned circuit values in Eduardo's 40 m
>version are appropriate
>for the microR1 schematic that I posted.
>Muchas Gracias y 73,
> > The schema can be seen here: (page 6)
> > I have received an Australian station (20000km!!) with a small dipole
> > in MFSK16 mode.
> > 73/DX Eduardo
> > EA3GHS
generally I make it more complicated than #1, the author was looking
to simplify the circuit and he succeed. In place of the 47 ohm
resistor in the emitter I like to use a FET circuit being a constant
current source, that increases the gain of the mixer. Usually I feed
the differential RF signal to both bases and the LO as a separate
circuit to the FET in the emitters. It's quite a bit more complicated
but it works slightly better. Good choice on the BC547 transistor,
that is a very low noise transistor but inexpensive, very few
circuits use that transistor in the U.S. which is a shame. I have
about 500 of the BC550 and BC560 transistors. (even more quiet) The
2N4401, and 2N4403 are also excellent and underused.
Is the over-coupling of the two input tuned circuits so you can have
The one thing I question is the diodes clipping the output to +- .7V
that is way too low so it limits how strong a signal the circuit can
handle, the sound card can usually handle about +- 1.25V.
Very good circuits.
"Blessed are the cracked, for they shall let in the light."
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