Nothing Special   »   [go: up one dir, main page]
Scribd Logo
Upload

Welcome to Scribd!

  • 35 views

    Increasing Amplifier Relay Speed: Bob Wolbert, K6XX

    Uploaded by

    Taufiq Fahlifi Yfzerobrr
    This document describes a circuit that can speed up the relay switching in radio amplifiers. It works by briefly applying twice the normal voltage to the relay coil when first activated, causing it to engage faster. This helps prevent problems like signal clipping or transmitter power reductions caused by slow relay switching. The circuit uses a capacitor, diode, and transistor to provide the initial voltage boost to the relay before it decays back to normal. It has been successfully used to improve performance in amplifiers with sluggish relays, without apparent harm to the relays.

    Copyright:

    © All Rights Reserved
    Download as PDF, TXT or read online from Scribd

    Increasing Amplifier Relay Speed: Bob Wolbert, K6XX

    Uploaded by

    Taufiq Fahlifi Yfzerobrr
    35 views1 page
    This document describes a circuit that can speed up the relay switching in radio amplifiers. It works by briefly applying twice the normal voltage to the relay coil when first activated, causing it to engage faster. This helps prevent problems like signal clipping or transmitter power reductions caused by slow relay switching. The circuit uses a capacitor, diode, and transistor to provide the initial voltage boost to the relay before it decays back to normal. It has been successfully used to improve performance in amplifiers with sluggish relays, without apparent harm to the relays.

    Original Description:

    Original Title

    Untitled

    Copyright

    © © All Rights Reserved

    Available Formats

    PDF, TXT or read online from Scribd

    Did you find this document useful?

    Is this content inappropriate?

    This document describes a circuit that can speed up the relay switching in radio amplifiers. It works by briefly applying twice the normal voltage to the relay coil when first activated, causing it to engage faster. This helps prevent problems like signal clipping or transmitter power reductions caused by slow relay switching. The circuit uses a capacitor, diode, and transistor to provide the initial voltage boost to the relay before it decays back to normal. It has been successfully used to improve performance in amplifiers with sluggish relays, without apparent harm to the relays.

    Copyright:

    © All Rights Reserved
    Download as PDF, TXT or read online from Scribd
    Download as pdf or txt
    35 views1 page

    Increasing Amplifier Relay Speed: Bob Wolbert, K6XX

    Uploaded by

    Taufiq Fahlifi Yfzerobrr
    This document describes a circuit that can speed up the relay switching in radio amplifiers. It works by briefly applying twice the normal voltage to the relay coil when first activated, causing it to engage faster. This helps prevent problems like signal clipping or transmitter power reductions caused by slow relay switching. The circuit uses a capacitor, diode, and transistor to provide the initial voltage boost to the relay before it decays back to normal. It has been successfully used to improve performance in amplifiers with sluggish relays, without apparent harm to the relays.

    Copyright:

    © All Rights Reserved
    Download as PDF, TXT or read online from Scribd
    Download as pdf or txt
    of 1

    Increasing Amplifier Relay Speed

    Bob Wolbert, K6XX

    The first element of all of my transmissions T/R Out


    was shortened when running the amplifier. Worse,
    the transmitter ALC swung high, which automati- NPN
    cally reduced transmitter power for several sec- 1N4001 (Voltage and
    current rating
    onds. Both problems were traced to a slow acting 1k suitable for
    relay used)

    T/R relay in the amplifier.


    The circuit (Figure 1) speeds the relay by T/R In
    blasting it with twice the normal coil voltage when
    47 F
    first activated. The coil voltage decays to normal 1N4001
    within a few milliseconds (decay time is propor-
    tional to the capacitor size; 47µF is a good start-
    ing point). This circuit was designed by Tony,
    K1KP. Figure 1. Relay Accelerator Speeds Your Amplifier
    This circuit only does its magic with ampli-
    fiers that switch a relay coil to transmit. Also, the
    relay must use a DC coil. Suitable amplifiers in- Circuit Operation
    clude the Drake L4B and L7, Ameritron amps, When the amplifier is initially powered up,
    and the TL-922. the T/R Out voltage rises, charging the capaci-
    Does this harm the relay? I don’t think so. tor through both diodes. When T/R In is pulled
    For example, W6CYX has modified the relay sup- low (to about zero volts), the emitter of the NPN
    ply voltage in his TL-922 (which has an excep- transistor suddenly falls to a negative voltage—
    tionally sluggish relay) so that it is double its de- nearly equal in magnitude to the open key volt-
    sign voltage full time. He has run it every day for age (VOPEN) on T/R Out. The transistor turns
    several years without problems. ON and the instantaneous voltage on T/R Out
    After adding these parts to the T/R cable from is –VOPEN. The relay coil sees twice VOPEN across
    the rig to the amplifier, my AL-1200 no longer it and closes faster than normal. As soon as the
    truncates leading dots, even at high speed. If your capacitor discharges, the relay coil only sees
    amplifier has slow T/R switching, try installing VOPEN, so coil power dissipation remains nor-
    this simple circuit in the T/R line! mal.
    When T/R In goes high, T/R Out stays low
    only until the capacitor charges up again—a
    very short while. The 1kΩ base resistor is
    needed to prevent the transistor from clamping
    the negative spike to only –0.7V (and also
    avoids destructively high base currents).
    Before you select a transistor, measure
    VOPEN and the short-circuit (key down) current
    through T/R Out. The Ameritron relays gener-
    ally run 12V at about 100mA. The L4B switches
    50V at 50mA. Make sure your transistor can
    handle both the open circuit voltage and the
    short circuit current. The capacitor must have a
    voltage rating above VOPEN.

    You might also like