Question about Uniden Bearcat Pro PC68XL CB Radio

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How to turn up modulation on uniden PRO 510xl? I noticed it has tuneable vr4, I used vr4 to turn up the modulation on my cobra 29 ltd bt but are they the same on all cb radios?

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No they are different. the pro 510 doesn't have a variable like the 29.
just trace the audio wire back to the audio transformer there should be a transistor on that section. best is to change the value of the resistors controling it to increase modulation.. if you take it out.. it will be wide open.. and can cause issues like splattering on adjacent channels. same goes for cutting the audio limiting diode, will cause the same issues. leave the parts in the circuits just change the values to achieve 100% modulation on a scope or wattmeter with a modulation function.

Posted on Oct 21, 2013

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Posted on Jan 02, 2017

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Mechanic688
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SOURCE: modification of frequency output of uniden pro 510xl

deweyp, hi, if you are wanting to turn the power up some on the radio, do this; tune L4, L5, L6, L9 for
maximum RF forward output. There are 2 versions of the radio, and both are listed as 510xl. If you are wanting to expand the freq's or add channels, then no, there is no mod for that radio. If your going to tune the radio for more power, make sure you have a power meter to watch the output. It is preferable to tune into a dummy load so your not broadcasting over the air. You tune the radio for peak output, using a steady awwww sound in to the mic. Just be careful as that radio has a fairly small driver and final transistor. Don't want to let the factory smoke out of it,,,
Here is what the little variable adjustments are for and what they control;
VR1 Squelch
VR2 TX Meter
VR3 RX Meter
VR4 RX IF Gain
Hope this helps you out, let us know,, Mechanic

Posted on Feb 19, 2008

tparsenault
  • 170 Answers

SOURCE: Uniden Pro 510xl can send but not receive

If you look on the solder side of board you shoud see a straight line of 5-7 solder joints, look on the other side the audio vhjp is a bmack thin retangular ic chip. Not to worry you wont hurt anything by doing this. Its an old cb tech trick to test audio chips.GOOD LUCK.

Oh one other thing does the radio have same same problem in either vehicle? A insulating washer on the antenna bracket can cause this also,
Happy New Year , Tom

Posted on Dec 31, 2008

  • 1 Answer

SOURCE: UNIDEN UH-011 UHF CB RADIO

i have just printed off a hard copy of this manual it was on Http//.www.uniden.com.au/ RESOUCES main/pdf/uh011.pdf If that isnt helpfull i could post it out to you.

Posted on Aug 09, 2009

Benimur
  • 6966 Answers

SOURCE: CB Radio

Hi and welcome to FixYa,

Have you tried VR5? Not much on the mods other than adjusting L8-10 for AM power.

Good luck and thank you for asking FixYa.

Posted on Aug 15, 2009

  • 14 Answers

SOURCE: I have a Uniden Pro

chk mic, lose cable in **** plug test with other mic .. also test with Ext speaker.. do u get any reading on meter / LED display during RX? does PA work? otherwise your sound chip is dead

Posted on Jan 04, 2011

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Cobra 29 ltd modulation problen


You need to check the modulation on a modulation meter. Just because the meter doesn't peg, doesn't mean the modulation isn't working. Usally a meter pegging, means the swr's are too high or the meter is misadjusted. If in fact the modulation is low, their is a pot inside the radio (VR4) that will add gain to the modulation circuit. This setting is legally supose to be set by a qualified technician.
Good Luck
Ed Meshechek ( Radio Man )
NC Electronics
PO Box 1696
414 6th St.
Mills, Wyoming
82644
307-266-4675
wyoed1@aol.com

Nov 24, 2008 | Cobra 29 LTD CB Radio

1 Answer

Cobra 29 Ltd


Hi,

Appreciate the direct "Ask Me" again.

The initial posting would still hold true, best would be:
  • remove TR18;
  • replace 2SC2069 with 2SC1969; and
  • adjust L12, 13 & 14.
Hope this be of initial help/idea. Pls post back how things turned up or should you need additional information.

Good luck and kind regards. Thank you for using FixYa.

Sep 07, 2008 | Cobra 29 LTD CB Radio

2 Answers

Cobra 29 Ltd Classic


In most cases just turning up VR4 is more then enough. Replacing the final, tr14 with another transistor requires changing many more parts to get it to work.

With a new 29, there is no need to change the final. Just turn vr4 all the way up and you will see around 20 - 25 watts. L13 won't gain you a single watt. L12 will raise the dead key, and usually you want a lower dead key for good swing. L14 will gain you a few watts, but don't adjust this unless you have a watt meter. You turn it out to increase wattage, but too much will over bias the final and shorten its life.

You hook it to a watt meter with a dummy load. Then say a steady AHHHH into the mic while keyed. Turn the slug out until the needle stops going up, then back it down to where it stopped.

The easy thing to do, and you will be pleased is just to turn VR4 up. Now, Up is counter clockwise. Its a variable resistor, so the less resistance, the more modulation. So you want to turn the VR down.

that will be more then enough.

Sep 06, 2008 | Cobra 29 LTD CB Radio

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