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Message |
    
Audiophile73
Member
Username: Audiophile73
Post Number: 85
Registered: 5-2004
| | Posted on Tuesday, April 04, 2006 - 10:09 am: | 
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Hello i had my radio turned down locally. It keys up at about 2 watts and swings to about 4. It seems like it just hits a brick wall. But it's strange because the modulation pot is up all the way. If anybody knows which pots i can adjust for am power that would be great. It looks the same as a 29 on the inside. Also someone told me if I adjust those coils (spread them out) it changes the frequency of the radio and that has to be adjusted to. Any help would be good.
Tech 833 adds: Spreading coils will NOT change the frequency of the radio, unless those coils are in an L-C section near the PLL circuit. The RF tank coils are adjusted BY changing the coil spacing.
If your radio hits a 'brick wall' at 4 watts, perhaps your final output transistors are only capable of that power level. Check the transistor bias and supply voltages, then the devices themselves. |
Kid_vicious
Senior Member
Username: Kid_vicious
Post Number: 1371
Registered: 9-2004
| | Posted on Tuesday, April 04, 2006 - 10:07 pm: |
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do not spread any coils in the final amp section.
it may show more power on the wattmeter (like 1 watt more), but the wattmeter does not know that the extra watt is on a harmonic of 27mhz and is not helping you get heard.
is about the way the person who turned your radio down did it.
they may have lowered the overall output, rather than modifying the radio to have a lower deadkey and still swing up to its fullest potential.
im not sure if this is possible with this radio or not, as i have never opened one up.
try doing an internet search for "uniden PC78elite mods", and if you find something that you think might work; post it here.
good luck,
matt |
Moonraker
Intermediate Member
Username: Moonraker
Post Number: 192
Registered: 3-2005
| | Posted on Wednesday, April 05, 2006 - 1:22 am: |
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Does it swing to 4 watts rms(average) or pep? With the radio facing you (bottom cover off) look at the final, look about 1/2 twards you. If you see a 220 uf cap with a resistor soldered across it on the other side of the board, someone has put in a "swing kit" as kid vicious mentioned. If you only see a jumper, that part is stock. You will also see a barrel about the size of a pencil eraser with copper wire coiled around it and a tuning slug inside, this adjusts your dead key. I think there are 2 of these, if so don't adjust the one with the fewer coils that is closer to the ant. plug because it it the tvi trap. I don't have any info on this radio so I can only do my best to describe it to you.
I know that is a poor description, but I hope it helps. GOOD LUCK |
Audiophile73
Member
Username: Audiophile73
Post Number: 86
Registered: 5-2004
| | Posted on Wednesday, April 05, 2006 - 3:57 pm: |
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well, this radio has the same board as a cobra 29 ltd, any help would be good |
Goat373
Intermediate Member
Username: Goat373
Post Number: 197
Registered: 3-2005
| | Posted on Wednesday, April 05, 2006 - 10:48 pm: |
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look in my pics post for the diagram of the darlington swing/variable power kit...if you need instructions...let me know, i can post them too |
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