Expo Kit FAQ (Frequently Asked Questions)
Q. Installing a model A expander kit, sometimes I have trouble getting the channels on the upper or lower bands to work properly. I have tried adjusting the VCO coil with no results.
A. The injection point (White wire) into L22 is sometimes critical. Try re-adjusting L22 and then re-align your trimmer caps to set the proper frequencies. Also try changing the 22pf capacitor (included in the kit) to a 10pf and re-adjusting L22.
Q. On an A Kit A Installation High and Low Frequencies work but Normal Doesn't.
A. Adjust the 15.360 Mhz coil in the unit slightly clockwise (L22 in Cobra 29LTD Classic) should cause the unit to resume Normal operation. Also try adjusting the VCO coil slightly further clockwise. Sometimes the receive will take slightly more adjustment than the Transmit to lock in property.
Q. Using the A+ kit on a PC-76XL, I have noticed on the lowest few channels (1 through 6 on the Low band) seem to transmit ok but the receive is not working.
A. It may be necessary to re-adjust the VCO coil L13 until receive pops in at these frequencies. Even though the transmit works ok, the receive sometimes lags behind at the lower frequencies.
Q. Installing a S kit on a PC-33, I have some channel bleedover from the regular CB frequencies. If I am on channel 19 Lower
band, and someone loud is on 19 regular CB, I can hear them.
A. Try adding a 10pf capacitor in series with the kit's Green wire. Also separate the kit's White and Green wires to cut down on crosstalk. Re-align the 10.695 first mixer coil for best receiver performance.
Q. What can I do to increase the Lower frequency range of the VCO coil?
A. Solder a 10pf capacitor across the VCO coil terminals and re-adjust for maximum range.
Q. What can I do to increase the Higher frequency range of the VCO coil?
A. Solder a 10k ohm resistor across the VCO coil terminals and re-adjust for maximum range.
Q. The VCO still will not reach the frequencies I wan't to use, What now?
A. If the VCO is an outboard circuit (not a module such as UC0005) it will have a small varactor diode connected across the VCO
coil. Replace this with a "Super Diode" or a varactor diode with a wider range. Sometimes it is even possible to actually
cut into the side of the molded VCO modules (UC0005) and solder a diode across the existing one.
Q. How can I increase the frequency of the crystal on the kit if it won't adjust any higher?
A. Remove the small 22pf capacitor soldered across the trimmer capacitor on the kit.
Q. How can I make the crystal on the kit lower after adjusting the trimmer to maximum?
A. Solder a 10pf or 15pf capacitor across the crystal legs (not the trimmer). If the range is still not low enough, it is possible to cut the trace between the crystal and trimmer cap. and solder a small rf choke (5.6uh or 10uh) across the cut.
Q. On an Cobra (Korean) 148GTL: Problems with unit draping power level shortly after moving out of the normal 40.
A. Solder pins 10 and 11 of the S042P IC chip together. Solder a 100 ohm 1/4 watt resistor from the two soldered pins back to circuit board ground. Cut resistor R181 (270 ohm).
Q. Odd Channel Operation: Using AM units on the odd frequency offset channels by adding a 10 Khz switch.
A. Cut one side of the 10.240 Mhz xtal trace, and solder a 22 pf capacitor across the cut. Also solder a wire on each side of the cut back to a SPST switch. The switch will allow most units to shift 10 Khz upwards without affecting the kit, or Normal, operation.
Q. PC-122 Hints: Helpful changes to make performance and frequency tuning easier.
A. Change C66 (5pf) to 8pf. Change C67 (7pf) to 12 pf. Change C72 (47pf) to 100 pf. Add 22 pf capacitor across High Xtal of the N kit.