The January 1983 issue of QEX carried an article by Ivo Chladek, ZS6AXT, on the "Microwave Alignment Probe." A number of individuals questioned the list of references given in that article. One letter summing up the situation follows:

The January 1983 issue of QEX contained a very neatly packaged "Microwave Alignment Probe" by ZS6AXT. In that note, the author referenced an article and comments contained in several issues of RSGB Radio Communication. These references ostensibly contain the heart of the recommended procedures for alignment and noise figure measurement of vhf/uhf receivers. In the U.S., and certainly in central Florida, the reference is rather obscure. It would be appreciated if QEX would reproduce the heart of the methods expounded in RAD COM. - Dick Jansson, WD4FAB, 1130 Willowbrook Trail, Maitland, FL 32751.

As you can guess, we are running the reprints from RAD COM in this issue. They can be found starting on page 5.

Antenna Compendium

The League will publish a special Antenna Compendium in May 1984. Potential contributors of unpublished papers on any aspect of Amateur Radio antennas are invited to send a one-page, double-spaced abstract describing the paper to Paul Rinaldo, W4RI, at Hq. Authors will be notified of acceptance and provided preparation guidance. Deadlines are December 2, 1983 for abstracts, March 15, 1984 for manuscripts.

Amateur Radio Satellite Symposium '83

AMSAT will hold an Amateur Radio satellite symposium in conjunction with its annual meeting on Saturday, November 12, 1983. Located at the John Hopkins University Applied Physics Laboratory just off 1-95, the planned programs include: How to get on the new OSCAR 10 satellite, tracking OSCAR 10 with and without a computer, a report on the W5LFL Space Shuttle operation, PACSAT and much more!

Admission is free, but advance reservations are required. For further information and reservations, contact AMSAT, P. 0. Box 27, Washington, D.C. 20044, or call (301) 589-6062.

Low-Cost Solution

The July 14, 1983 issue of Electronics magazine has an article on "Ceramic-Filled Resonators" as a low-cost solution to building filters for 800-MHz land-mobile applications. It uses six 10mm varisonators for a receiving filter, four for a transmitting filter. The two filters can be com

bined to make a duplexer. The author, Tomoki Uwano, of Matsushita, Osaka, Japan, says that the filters could be supplied in the $1 to $2 range, with duplexers under $20, in mass production.

APPLE Computer Program Transmits/Receives Teletype

A recent news release crossed QEX desks from Cotec. The company announced the latest in its line of APPLE II software for communications. The following is direct text from their release.

RTTY MACHINE, like its Morse Code predecessor, is designed to minimize the interface hardware. Audio tones fed into the APPLE cassette input are demodulated and decoded in software, and sent to the screen as text. Keyboard input is encoded to Baudot and sent to the cassette output as MARK (2125 Hz) and SPACE (2295 Hz) tones. A pair of audio cables with the necessary connectors between the speaker output and microphone input of an ssb or fm transceiver and the cassette ports of the APPLE is all that is necessary to run standard TTY.

The receive portion of the program has two modes of operation. For afsk, which is typical of vhf/uhf operation, the program is operated in the absolute mode: 2125/2295 MARK/SPACE. For use with an hf transceiver, a second mode can be used to match the software discriminator frequency to the center of the receiver audio passband so that increased selectivity may be used. A novel real time tuning indicator at the top of the screen assists the operator in making tuning adjustments.

The transmitting portion also has two modes of operation. In the first mode, each character is sent as a key is pressed. This is similar to the way the standard mechanical TTY machines operate. The second mode allows the sender to prepare and edit a message before sending it. A number of automatic formatting features are built in for operator convenience.

In addition to the cassette port interface, dc output through the Game 1/0 connector is available to drive frequency shift keying circuitry and transmit/receive switching. Two printer drivers are also included in the software which converts the received signal to ASCII for generating hard copy.

Written in machine language for the APPLE II, APPLE 11+, or APPLE //e using DOS 3.3, RTTY MACHINE comes double sided on a 5.25 inch diskette with full instructions for installation and use. RTTY MACHINE is available for $29.95 including postage and handling. No C.O.D. orders, foreign orders add $4.00 and California residents add sales tax. The manufacturer's address is: COTEC, 13462 Hammons Ave., Saratoga, CA 95070.

QEX October 1983

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