UW3DI transceiver upgrade. Scheme, description

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ENCYCLOPEDIA OF RADIO ELECTRONICS AND ELECTRICAL ENGINEERING
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UW3DI transceiver upgrade. Encyclopedia of radio electronics and electrical engineering

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Encyclopedia of radio electronics and electrical engineering / Civil radio communications

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To operate in AM mode on the UW3DI transceiver, many radio amateurs use the modulation of the final or pre-terminal stages. In this case, difficulties arise associated with the manufacture of a separate modulator.

The UA4LAB radio uses the same transceiver stages that operate in SSB mode to receive the AM signal. For this, two additional relays are introduced (see Fig. 1). Through the contacts P1 / 1 and the capacitor C1 during AM operation from the cathode of the lamp L6 of the reference oscillator to the grid of the lamp L 12 of the amplifier. DSB RF voltage is applied. In order to avoid frequency-phase distortions, the relay contacts P2 are shunted by the EMF capacitor C2. This results in an AM signal that is no different from the AM signal obtained by modulating the final stage.

UW3DI Transceiver Upgrade
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It should be noted that during AM operation, the gain should be slightly reduced using the R73 potentiometer.

The switching of the relay (another P2g board is added to the switch of the type of work P2) is shown in fig. 2. Both relays - RES-15, passport RS4.591.001.

UW3DI Transceiver Upgrade
Ris.2

On a transceiver with AM obtained in this way, a large number of short and long distance communications were carried out. All correspondents noted the good quality of the modulation.

Author: A. Korolkov (UA4LAB) Dimitrovgrad, Ulyanovsk region

In the absence of a 500 kHz quartz resonator in the reference oscillator, you can use two RF quartz, the frequencies of which differ by 495-505 kHz, and isolate the difference frequency signal. A diagram of such a generator is shown in fig. 3.

UW3DI Transceiver Upgrade
Ris.3

The required frequency value can be set by slightly erasing a layer of silver with an "inky" student's rubber band (and thereby increasing the frequency) of one of the quartz, or by drawing strokes with a simple pencil (lowering the frequency) of another quartz.

When choosing quartz, care should be taken that there are no side combination frequencies near their difference frequency ns. I used quartz at 4544 and 4044 kHz (from the 10-RT radio station), I also tried quartz at 2900 and 2404 kHz.

Coils L1 and L2 are wound in the SB-12a core, the first contains 60, the second - 120 turns of PEL 0,1 wire.

Author: A. Kochetov (RM8MBC) Frunze; Publication: N. Bolshakov, rf.atnn.ru

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