General Comments for
 Experimental Methods in Radio Frequency Design


(update 12 June 07)  

  DSP Easy-Kits from Analog Devices have been the basis for Digital Signal Processing experiments reported in EMRFD and for the earlier DSP-10 "Software Defined Radio"  described by Bob Larkin, W7PUA.   Unfortunately, the price on the Easy-Kits has been increasing.   There is now a solution, a board using the Analog Devices ADSP-2185N.   This board is a real gem.  It's small and does not even use an excess of current.  And the board is fully compatible with the DSP-10 SDR as well as the 18 MHz Transceiver described in EMRFD, p11.12.   The board was designed by KK7P and is available from TAPR. Click on Lyle's call to get to his web site with more information on this board.   You will also find links to TAPR in Lyle's web site.    

This new board is not an exact replacement for the present Easy-Kit from Analog Devices.  However, the differences seem to be minimal.   Lyle has done software conversions on several of the routines that required modifications and discusses this on his web page with the link listed above.

We want to express our gratitude to Lyle Johnson, KK7P, and to the gang at TAPR for all of their help and activity with DSP.  TAPR has been a major force for experimental activity within amateur radio for a long time now and we applaud their efforts. All three of us (w7zoi/kk7b/w7pua) recently (well, it was a few years ago by now [2006]) attended the Microwave Update Conference in Everet, WA, and got to meet Lyle.

Update:   I got to spend some more time with Lyle at FDIM07 (Dayton, Ohio May 2007) and really enjoyed the experience.   Again I want to extend my thanks to Lyle for his contributions as well as for the kind words re EMRFD in his FDIM07 presentation.  I think that we can even forgive Lyle for his excursion to "the dark side" of design with his efforts on a commercial product, the Elecraft K3.

We will be adding additional information here regarding software updates for the DSP-10 and the book DSP transceiver.  The experimenter is referred to   W7PUA - DSP-10 Transceiver.

 Dual Gate MOSFETs:    Chapter 6 includes considerable information on IF and RF amplifiers for receiver applications.  Some of the circuits use dual gate MOSFETs, a component that was popular about 20 years ago, but not in common use these days.   The dual gate FETs are still available and are highly recommended for AGC amplifiers, or for low noise applications.   I got a very interesting note recently from Mark, WU0L.   Mark had purchased some BF998 surface mounted dual gate MOSFETs from Bob, KE6F, Via EBay.   I also got some of these parts from Bob.   Mark beat me to the punch and has built the AGC IF amplifier that was used in the Progressive Communications Receiver.   This circuit, from QST, November, 1981, is included on the EMRFD CD.    Mark reports "good gain and no stability problems" with his version of the circuit.   He did his own circuit board.  Many thanks for the info Mark, and many thanks to Bob for supplying the parts.     A data sheet for the BF998 is available from the Philips web site at:   http://www.semiconductors.philips.com/    Update, April 4, 2004:   We finally did an experiment here.  See A SMT Dual Gate MOSFET Preamplifier for 50 MHz

Discontinued Transistors:    Within a few days of publication, we saw the discontinuation of a transistor used in a project.   This one was in Chapter 1 where we used a 2N5321 as a power amplifier in a 2 watt transmitter.    This is going to happen, but we hope that the information is fundamental enough that it will transcend these details.  For this example, we discovered that a MJE181 from ON Semiconductor makes a great power amplifier at 7 MHz.   This device provided an output of 2.6 watts with a drive of 230 mW, a power gain of just over 10 dB.    The 2N5321 was running a gain of 13.3 dB at the same output.    The MJE181 price is only $0.55 each from Digi-Key (in lots of 10) and the parts are robust.  See Fig 1.35 and Fig 1.39.    To get a data sheet for the part, go to the Digi-Key catalog, look up the part, and then follow the links to download the information.     25 Jan 05         
Another good part for RF power amplifiers is the Panasonic 2SC5739.   At less than $1, it can produce an output of 10 watts.    See my paper using this part, QST, April, 2006, p28.      3 April 06           

Which Book Printing do you have?    To check your copy of the book to see what printing you have, go to the title page plus one.   Go to the bottom where it says "First Edition."   If you have a second printing, it will say "First Edition, Second Printing."    But if it just says "First Edition," you have the first printing.   Some folks have sent emails asking when a Third Printing will occur.   We have no idea at this writing (Oct, 06).

CD Problem:     On Jan 25, 2004 we discovered a problem with compact discs distributed with the 2nd printing of the book. It appears that text is missing from all of the QST/QEX/HR/Microwave-Update articles in the collection, only to be replaced by a page from another article.  The CDs with the first printing are generally OK.  The ARRL folks have fixed this problem and the books being shipped are good.  This problem was only present with the 2nd printing of the book.  The CD with the 2nd printing has a silver cover.   The replacement CDs will be blue.  If you have a defective CD, you should contact ARRL and ask for a replacement.  

Please let us know about the errors that you discover.  Just drop any of us a note at w7zoi@arrl.net, kk7b@arrl.net, or w7pua@arrl.net.   Let us know which printing you are reading.    Page numbers and position on the page would also be useful when you write.    We really do seek and appreciate your feedback!     Many thanks!

We also want to extend our thanks to Steve Ford, WB8IMY, and the other folks on the ARRL Headquarters Staff for their work in keeping the manuscript up-to-date.