Pegleg CB Radio
360 Earrusso st
Cocoa, FL 32926
HOURS 9:AM 11:PM
321 639-0463
http://www.angelfire.comfl2/cbradiorepair/
f2h1@aol.com
I receive calls from baffled radio users, with the same
complaints : "My microphone shocks me when I key up!", "Radio hums on high power or with the amplifier on", "My SWR increases when I turn up the power" or "I have low SWR, but can only talk a half mile". Most of the time these symptoms all point back to the same problem, improperly configured coax cable and RF grounds. This is an especially crucial issue when you are using an amplifier as well.
There are a few common mistakes individuals (and shops) make when installing antenna systems, most are easily remedied. First, and probably the most common; extra coax cable is coiled in a circle or loop.
This is not a good idea as the coil then becomes an extra loading coil, sending RF energy into the cab or other location other than the antenna. This is probably the biggest producer of microphone sparks, and definitely the most painful (speaking from personal experience).
To correct this, try to run the coax differently stretching it out. If you still have excess, make a large figure eight or zigzag pattern. This will offset the magnetic fields, which cause the problem. Second: make sure all PL-259 connections are well soldered, especially the grounding points. Never trust a crimp on connector.
Third: if your antenna is mounted to any moving body part (door, trunk lid) connect a short wire from that part to the body when possible, this will assure a good ground especially in instances where you must contend with weather-stripping and other poor conductors. Following these few simple rules will make installing and tuning your total system much easier, and occasionally, less painful.
For all of you golden screwdrivers out there that think that clipping the limiter is going to make your radio better, "DO NOT DO IT!" Your just going to make your radio exceed 100% modulation, sound distorted and produce all kinds of harmonics.
When you "clip" the limiter, you remove it from the mic input circuit, and in doing so, cause the radio to be very sensitive to RF and causing (squeal).
In some of the earlier radios clipping the limiter was the only way to improve the modulation, and even then, it did not make the radio exceed 100%.
I have received lots of questions about "how can I tune my radio for more power?" You can't, It takes more than just turning a few pots. Strangely enough, there are many "truck stop hacks" that do just that and call it a "peak and tune" and charge $20.00 to $35.00 to do it.
Well, it takes more than just a few twists to tune up a radio, it takes proper equipment like an accurate Frequency Counter, RF Signal Generator, Oscilloscope, a good VOM (volt/ohm) Meter, a 50 ohm/1000 watt Dummy Load, a good quality RF/SWR Meter and lastly a frequency reference like a receiver that tunes WWV in Ft. Collins Colorado, to calibrate your Frequency Counter.
Every month we take in hundreds of repairs for customers, Many of these items are sent in with power input related damage. In particular, on base station amplifiers and radios:
In this tip I will cover the basics of AC spikes, and not the more detailed problem of electrical damage resulting from antenna line spikes, such as caused by lightning. AC line voltage in the US is usually around 110 to 120 volts, as it is supposed to be.
However, due to weather conditions, or line equipment failure, these AC lines can transmit well above the acceptable voltage to your radio or amplifier's power supply circuitry. In most cases, each unit has a built in supply that rectifies 120Volts AC to DC voltage, to be used by the internal circuitry. All RCI and Galaxy base stations are built in such a fashion, as are many others.
These devices normally come with AC circuit-side fuses, and DC circuit-side fuses, some may be internal. This is your last stage or protection, and it is crucial that you used the rated fuses for these devices. To further protect you device, always use the third prong on the devices that come with them, this allows for the case of the device to be grounded to you homes electrical system.
Do not use extension cords that bypass this third prong. To make absolutely certain your expensive equipment is protected, the ideal means is a Personal Computer type UPS system. This rectifies the AC to DC, and back to AC, making it almost impossible to force an electrical spike through this type of device, and it will also allow you to use your radio equipment in the event of a power outage, for a brief period until the internal batteries are depleted. These devices are rather expensive, but are an excellent idea to protect your equipment, and for emergency preparedness.
A less expensive and more easily obtainable protection device is a standard Computer Surge Protector, available at any general merchandise store (such as Wal-Mart). Make sure that you choose one with an Insurance Option; basically theses refund you the price of your equipment if it's damaged by electrical surges, while their product is in use. These are slightly more expensive, but well worth the small investment. Simply fill out the card included with the purchase, and mail it in with the details of your equipment. Combined with proper maintenance, and tuning, your equipment should last through many years of service with the proper electrical filters such as the above.
I am sure you all know this, but just to be on the safe side, when there is a storm its better to be safe then sorry. I disconnect all my equipment. I have seen over the years too many radios, including equipment, linears, antennas, and an entire radio room totally destroyed by lighting.
