EMRFD Message Archive 2135
Message Date From Subject 2135 2008-09-26 06:33:30 Eduardo Alonso micro R1 receiver with RA3AAE mixer // CAPACITIVE COUPLING HELLO RICK, CECIL AND GROUP
>>Muy Bueno Eduardo,THANKS YOU FOR YOUR WORDS.
>>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
I LEARNED A LOT FROM YOUR DESIGNS AND I RE-READ EMFRD OFTEN
THE THIRD PART OF THE SPANISH ARTICLE WAS PUBLISHED IN SPRAT AND CAN BE READED
ON LINE IN http://ea3ghs.googlepages.com/VERY-SIMPLE-SOFTWARE-DEFINED-DSB-RAD.doc
>>Note that the input double tuned circuit values in Eduardo's 40 mI AM NOT VERY HAPPY WITH MAGNETIC COUPLING IN THE PRESELECTOR FILTER.
>>version are appropriate
>>for the microR1 schematic that I posted.
THE SCHEMATICS ARE AMBIGUOUS WITHOUT COUPLING COEFICIENT AND Q,
LATTELY I USE CAPACITIVE TRANSFORMERS. TAKE A LOOK TO MY CALCULATOR
http://www.rootshell.be/%7Eea3ghs/ctrafo.php
> I like circuit #1, and #2, I have always liked balanced mixers butHELLO CECIL,
> 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
THE CIRCUIT #1 IS FROM http://www.b-kainka.de/HF.htm
I LIKE #3 VER VERY VERY MUCH. IT IS MY SIMPLEST RECEIVER AND
I SPEND A LOT OF HOURS UNDERSTANDING HOW REALLY WORKS
AND HOW CAN I DO A BETTER VERSION.
(AND LISTENING PSK31 SIGNALS WITH IT!)
HERE I PUT HAND NOTES:
http://ea3ghs.googlepages.com/verysimpledsbrx-newideas.pdf
> but it works slightly better. Good choice on the BC547 transistor,BC547 IS A UBIQUITOUS TRANSISTOR IN THIS SIDE OF THE WORLD
> that is a very low noise transistor but inexpensive, very few
THE BC549 IS A FACTORY SELECTED BC547 LOW NOISE VERSION.
> Is the over-coupling of the two input tuned circuits so you can haveSORRY I DON'T UNDERSTAND YOUR QUESTION. I ADJUSTED THE PRESELECTOR
> broader bandwidth?
TO CRITICAL COUPLING "MODE" WITH THE HELP OF AN NETWORK ANALYZER.
> The one thing I question is the diodes clipping the output to +- .7VYES, YES IS TRUE.
> 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.
I TRY TO DO THE SIMPLEST CIRCUIT AS POSIBLE.
I BROKE ONE SOUND CARD PLAYING WITH IT (ESD?).
SINCE THEN I PUT TWO OVERVOLTAGE PROTECTION DIODES.
THIS CIRCUITS HAVE VERY LITTLE AMPLIFICATION AND THE SIGNALS ARE -60dB
OR MORE(LESS) UNDER
THE FULL SCALE.
THE #3 CIRCUIT, FOR EXAMPLE, THE DIODE RECEIVER HAVE NOT AMPLIFICATION
AND THE RECEIVER
NOISE (QUANTIZATION FROM ADC) IS HIGHER THAN ATHMOSFERIC NOISE.
> Very good circuits.THANKS YOU AGAIN
73/DX Eduardo
ea3ghs @qrp.cat