Lafayette 99 90375

0+9V MOD

OX ose 50 MHz

Ql-ftCA SK 3019

MODULATOR-LAFAYETTE CAT NO. 99E9037& + 9V

CJ -32 oF Rl-470 TO Itct for desirtd voice I*ve0

C2 - SO DF OSt-iNT XTAL "OX" SERIES HI FREQ. LI- 10T MO. 22 AWG ENAMEL ON 1/4 m DlA CERAMIC SLUG TUNED FORM

L2-2T NO. 22 AWG ENAMEL ON BOTTOM {COLO END) OF Lr Tl-MIN MIKE XFMR-LAFAYETTE NO 99E60345 T2-M\N MOD XFMR-LAFAYETTE TYPE AR/S2

Fig. J. Modulator - Laiayette Cat. No. 99E90375. Parts: Ql: RCA SK3019; CI: 22 pF; C2: 50 pF; RFC: Z-50; LI: 10T No. 22 enamel on Ya in. iron core, ceramic slug tuned. L2: 2T No. 22 enamel on bottom LI ; Tl: miniature microphone transformer (Lafayette 99E60345); T2; miniature modulation transformer (Lafayette type AR162); SI: 2PZT; OSC; internationai Crystal OX osc. Series HI freq. ; Rl: 470-820^1 Select value for desired voice levei miles with an S-9 signal. The QTH is located in a poor VHF location so the results are more than satisfactory. The transmitter has not been on the air during skip conditions, so we are waiting for an opportunity to give it a try. This transmitter is on the air nightly and local contacts are routine. Remember, when using QRP power the choice of frequency and the band activity is important in making contacts. We have been very successful in making contacts when the band is quiet or when very few stations were on. We have had our greatest success later in the evening. If your interest is low power, give this little rig a try. The cost is small, and the results are exciting. Good luck in your QRPing.

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John J. Schultz W2EEY/1 c/o RLC Inc. 30 East 42nd St New York NY 10017

Rf level speech clipping tor SSB transmitters, where the SSB signal is clipped and then re filtered to remove distortion products, is generally conceded to be the most effective type of speech processing that can be applied to a SSB transmitter.

1 Uis system is employed in the more expensive amateur equipment designs as well as in many military and commercial SSB designs instead of simpler audio compressor or ale circuits. Material has been written before on the building of such clippers as accessory item or modifying existing transmitters for rf speech clipping. The main drawback to such designs, particularly those intended as independent accessory items to a transmitter, has been the expense involved because of the need to use two sideband filters of either the crystal or mechanical type.

The cost of the necessary filters alone could run to $70 or more if new filters were purchased.

This article presents an rf speech clipping unit which can function as a completely separate accessory item for use with any

SSB, AM or FM transmitter, has 99% of the performance capability of the more expensive designs but yet can be built for a total cost of $20 - 30 including the necessary filters. One can also still use an available speech compressor as part of the unit if such a unit is available and one now wants to upgrade the speech processing used to include rf speech clipping.

Basic Unit

The basic functions of the rf speech clipping accessory unit are shown in block diagram form in Fig. 1. it consists of a basic SSB generator as would be found in any SSB transmitter, 1 he SSB signal is formed by the sideband filter following the balanced modulator. The signal is then amplified, clipped, and again amplified. A second sideband filter is then used to pass only the original sideband signal and remove the spurious signals generated during the clipping process. The filtered signal is then demodulated by a simple ring diode demodulator and is audio fed into I he microphone input of any 1 ransmitter

Fig, i. BJock circuit diagram of rf dipper unit. Use of various modules and diode array packages considerably simplifies construction.

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