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307
| | Posted on Friday, November 30, 2001 - 10:19 pm: | 
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A thing or t two about internal echo boards....
If you are the one of several thousand people who have internal echo boards installed inside your CB radio and the controls are located outside the CB , this little article is for you . I have to be quite direct about this and do not want to offend any CB repair shop but I constantly get radios with echo boards that are just dropped into the radio with bubble wrap , black tape , sandwich bags , I have even had them rapped in foil . If your tech does not understand how to install your echo board the CORRECT way then hand him a copy of this article as a guide line to help him along .
First of all , remember to always use 8 volts for the supply and make sure it is regulated . I see them hooked up to 12 volts right at the power connector and most techs do not understand EMI/RFI protection . Sometimes noise enters the radio from the power cord and the first thing it enters when the echo board is tied to the power plug is echo board . Some of the circuitry that is on the echo board are high gain audio amplifiers that are susceptible to very low noise . Some of you may already be experiencing a rumble sound in your echo board now and this is one of the problems .
The NUMBER ONE no-no when installing echo boards is the techs are to lazy to make the coax cables (input and output) as short as possible . They mostly let the coax wires as long as they come in the package and this is just like an antenna and will pick up all kinds of noise . When installing an internal echo board make ALL wires as short as possible . Always keep the shield rapped around the wire just up to where the center wire is attached . Techs add wire to the center wire and strip back the shield inches away from the attach point . This defeats the whole purpose of having shielded wire in the beginning .
The next thing about installation is to remember that the case of the radio is capacitivly coupled to the circuit board and that the shields of the echo input / output cable should be twisted together and attached DIRECTLY to the microphone plug shield or return line . NOT the chassis or the cabinet of the radio . I have actually seen where some tech has taped the shields to the inside cabinet of the radio where solder will not stick .
If your internal echo board is installed the CORRECT way , you will be able to turn it up all the way and will not have any noise , rumble or squeal . If you have any of these symptoms then you need to go to the copy machine , make a copy of this page and give it back to the shop that installed it and tell them to do it correct using this article . |
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