QEX

By Dick Jansson, WD4FAB 1130 Willowbrook Trail Maitland, FL 32751-4837 Those amateurs who have been communicating through the OSCAR satellites long enough to remember OSCAR 8, will well remember experiencing some of the problems in operating their 70-cm receivers. This was caused by being desensed by their 2-m transmitters, when operating in Mode J. There are two basic phenomena at work in this particular ailment (to be discussed forthwith) and several cures that could be applied. With...

Info

Sampling rate are all determined, it remains to verify that the LMS algorithm is operating as expected through simulation. Results of these simulations are presented here. These simulations were performed by executing the actual TMS320C10 code developed for the hardware in the QST article mentioned earlier, using a developmental TMS320C10 simulator which runs on IBM PCs, Fig 3 shows the LMS software in the autonotcher mode in response to a burst of signal at 1000 Hz followed immediately by a...

Arrl Board Recommends Creation Of Unattended Digital Stations

Complying with the recommendations of the ARRL Committee on Amateur Radio Digital Communications, the ARRL Board of Directors adopted the following motion at their July meeting It was moved by Director Comstock, seconded by Director Heyn, that the General Counsel, with the assistance of the Executive VP and the staff, is authorized to prepare a draft Petition for FCC Rulemaking to permit the operation of a new category of amateur station, unattended digital station, on RTTY data frequencies...

Synchronous Detection Of Am Signals

By Mike Gruber, WA1SVF ARRL Laboratory Engineer Interest in synchronous detectors seems to be on the rise. This phenomenon is no doubt due in part to the commercial availability of synchronous detection in a popular, moderately priced short-wave receiver, the Sony ICF-2010. Simplified implementation utilizing current IC technology now makes synchronous detectors easier than ever for the experimenter to build and use. A firm understanding of amplitude modulation is essential before being able to...

How It Works

The input to the sync detector is an AM signal as shown by the phasor diagram in Detail A. The I and Q locally generated carriers are shown by Details B and C, respectively note the 90-degree phase shift in the Q channel. These carriers are then mixed with the original AM signal to produce the outputs shown by Details D and E. Although these signals are at audio frequencies, the USB and LSB components at this point are not in correct phase for proper audio recovery. A 90-degree audio phase...

Phasors For An Am Signal About Common Point

Same phasors are also depicted about a common point in Fig 3B. The resultant is determined as follows 1 0 Degrees The LSB and USB are 180 degrees apart from each other and, therefore, cancel each other out. The carrier level at this point is unaffected by the sideband components and is the same as if the carrier were unmodulated. 2 90 Degrees The USB, the LSB and the carrier are all in alignment and, therefore, reinforce each other. The RF envelope is the sum of both sidebands and the carrier....

September

EX The ARRL xperimenters' Exchange merican Radio Relay League 25 Main Street ewington, CT USA 06111 L.L. Grace introduces our latest product, the DSP-12 Multi-Mode Communications Controller. The DSP-12 is a user programmable, digital signal processing DSP based communications controller. L.L. Grace introduces our latest product, the DSP-12 Multi-Mode Communications Controller. The DSP-12 is a user programmable, digital signal processing DSP based communications controller.

Psn Amp Pn

I first became acquainted with selectable sideband synchronous detection when I purchased a new Sony ICF-2010 several years ago. The ability of this feature to reduce or eliminate certain types of distortion and interference was quite remarkable. It quickly became an indispensable asset to my shortwave listening enjoyment. I soon began to desire an outboard sync detector for my other radios. To this end, albeit several years later, I built the unit described in this article. It has been used...