Nh

Address

City

State

$3.00 enclosed for one

Coax Handbook, postpaid.

e Inexpensive

FM to AM

J. R. Popkin-Clurman, W2BK 134 Wheatley Road, BrookviUe Glen Head, LJ., New York 11545

Scan TV and

The heightened interest in slow scan TV and facsimile has brought forward a need for a converter to change the frequency shifted (FM) video or facsimile transmitted signal information into amplitude signals for feeding to a tape recorder, a slow scan TV monitor, a cathode ray oscilloscope (z axis modulated) with a photographing camera, or a facsimile machine. So far, the only available piece of gear appearing in surplus suitable for the above mentioned purposes has been the CV 172-172 A/U, Frequency Shift Converter.

The CV 172-172A/U consists of the following elements, (Fig, 1): L Input

2. A band pass input filter

3. A limiter

4. Driver for the discriminator

5. A discriminator

6. A tuning indicator

7. A sound channel

8. Output i he tuning indicator, a dual ''magic eye/* defines the limits of the channel used, 800 cycle shift for black and white. The frequency limits in the CV 172 are 2300 (white) to 1500 cycles (black). A built-in monitor speaker is also included with the audio channel.

Analysis of the CV 172 reveals that many

View of satellite APT receiving equipment position; Tape recorder to right; FAX machine to far right; converter on right side of table.

of these elements can be dispensed with, since they are incorporated into a modern high selectivity receiver of the type used for SSB and R i I V. i he irreducible minimum, then, consists of the input, limiter, driver, and discriminator (Fig. 2).

This simple converter is built from parts out of the junk box and uses two silicon diodes and one transistor (Fig. 3). In its quiescent state, it draws approximately 100 micro-amperes from the 9 V dc battery and approximately one milliampere under signal conditions. It would thus seem that the

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