• You can now help support WorldwideDX when you shop on Amazon at no additional cost to you! Simply follow this Shop on Amazon link first and a portion of any purchase is sent to WorldwideDX to help with site costs.

backward swing


Most amplifiers are not directly compatible with a stock legal 40-channel CB. The amplifier tends to exaggerate the carrier, and limit the audio peaks. There are two ways to fix it. One is to turn down the amplifier if it has a High/Low or H/M/L switch. This is the cheap fix, but not so popular. It limits the wattmeter reading. The other way is to reduce the radio's carrier wattage. If it's done correctly this will restore a balance between carrier and audio power and restores the forward swing that the radio had when run barefoot. But so much depends on which radio and which amplifier. They are not all created equal.

73
 
  • Like
Reactions: Eldorado828
You can try different lengths of coax jumper cable.

It should be significantly less than 6 feet, or significantly more than 7 feet.

11ft, 4 inches of RG58 (with hard, clear center insulation) will often fix the swing on the amplifier.

You can coil up the jumper to keep it out of the way.

The high / low switch is a trick to switches out the impedance balance in the feed input of the amplifier.

This causes the watt meter to show slightly higher power, but causing the impedance to change greatly when modulated.

Switching the high / low switch to Low, switches in the designed feed balance of the amplifier.

In the old days, the amplifiers had this balance circuit, but didn't have a switch on it and it was designed by the transistor makers as part of the amplifier.

So if there is a high / low power switch, place it in Low and try some different length coax jumper, between the radio and the amplifier.

As the radio sees an impedance change while modulated, the radio protection circuit will reduce the power output of the radio, so it is important to keep the drive impedance balanced.
 

dxChat
Help Users
  • No one is chatting at the moment.
  • @ heartbreaker3473:
    Hello gentlemen and Ladies. I have the dreaded RCI-2990 receive issue where my radio gets distorted when people get close to my location. I found the C90 Capacitor, but I can not for the life of me find the C89 capacitor. Can or does anyone have a picture of the exact location of C89 ? Thank you in advance, Wes
  • @ AudioShockwav:
    Wes, it's better if you start a thread on the main forum, more people are going to see your question.
  • @ heartbreaker3473:
    Okay, sorry, will put in a forum
  • @ heartbreaker3473:
    I put it in the general disscution help area and started a new thread. Thank you for letting me know.