This Month in QEX -- September 1992

     Digital signal processing is the "hot ticket" today in
amateur radio--and other communications technologies. A
fascinating look into DSP filtering techniques is presented in,
"Using The LMS Algorithm for QRM And QRN Reduction," by Steve
Reyer, WA9VNJ and Dave Hershberger, W9GR. This article is a
companion piece to an article published this month in ARRL's
flagship publication, QST. We hope to do more such companion
pieces in the future, allowing authors the opportunity to expand
on the technical niceties of their projects in QEX when QST page
space limitations don't permit detailed coverage there.
     Long-time amateur satellite operators may remember the
4$X3$X5 mode-J filter used with OSCAR 8. The advent of later
mode-J birds, such as AMSAT's microsats, has reawakened interest
in this design. This month, ARRL Technical Advisor and AMSAT
stalwart Dick Jansson, WD4FAB, describes a new kit implementation
of the filter in, "The 4$X3$X5 Filter--Revisited."
     AM lives, and synchronous detection promises to help it live
a fuller, richer life as ARRL Laboratory Engineer Mike Gruber,
WA1SVF, reports in, "Synchronous Detection of AM Signals." Mike
presents a complete theoretical discussion as well as practical
circuits.

This month in QEX -- October 1992

     Continuing our coverage of the DSP25 plug-in DSP board
introduced in January, 1992 QEX, John Albert, WA9FVP, and Will
Torgrim, N9PEA, give us "Developing Software for DSP." This
article looks at some of the design considerations that go into
making a flexible, practical, DSP-based packet system.
     In "Lightning--Your Home and Ham Gear," Stu Gurske, K9EYY,
shows us one route to protecting ourselves from the dreaded
effects of lightning strikes. It can be done!
     Ken Wickwire, KB1JY, wraps up his four-part series, "The
Status and Future of High Frequency Digital Communication," with
a look at where we go from here.
     Zack Lau's "RF" column looks at some portable microwave
station design considerations, and Geoff Krauss chimes in with
some devices suitable for portable--and other--"VHF+" uses. This
month's "Gateway" includes a brief report on KITSAT, the most
recent addition to the amateur space program. That it is a
valuable addition is demonstrated by the KITSAT image reproduced
on this month's cover!

This Month in QEX -- November 1992

     John Champa, K8OCL, shares with us some of his expertise in
the developing world of digital video systems. It's a technology
that amateurs can exploit!
     Making the computer do the work is one of the obvious trends
in amateur development. James Vandiver, WB4LHG, follows this
trend with his "Multi-Mode Computer/Radio Interface." Although
implemented on an obsolete computer, the techniques he describes
are applicable to any platform.
     In this month's "Components" column, Mark Forbes rounds up
some handy hardware, software and "bookware" for your
consideration. "Gateway" this month reports on the results of a
recent meeting between the ARRL Digital Committee and operators
of the HF automatic-forwarding STA network.

This Month in QEX -- December 1992

     Power supplies, especially those using the ubiquitous 723
regulator chip, have been published ad infinitum, but Dennis
Connole shows us in "Twin-Bridge Power Supply" that there is
still fresh ground to be plowed on the subject.
     In "An Audio Peak Filter with Noise Reduction Effect for CW
Reception," Yoshiharu Mita, JH1XEO, exploits the common-mode
rejection of an op amp to differentiate noise from a signal using
bandpass filters.
     Gregory Glass, N2MOH, wants us to experiment with video
image processing, and in "The Video Experimenter" he shows us how
easy it is to set up a video lab and describes some simple
experiments to get us started.
     This month, Zack Lau's "RF" column describes a 10-GHz preamp
Zack designed and shows us some of the trials and tribulations of
building and measuring 10-GHz equipment. Harold Price kicks off
his "Digital Communications" column by looking at how HF packet
evolved to its present state and how it could be improved using
existing techniques.