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Kid_vicious
Advanced Member
Username: Kid_vicious
Post Number: 862
Registered: 9-2004
| | Posted on Sunday, November 20, 2005 - 3:28 am: | 
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i hope this is the right place to post this; it seems to be a nice quiet spot.
After being in the hobby for a few years; the more ambitious and less prudent of us start to venture beyond the knobs on the faceplates of our precious CB radios. The results are usually somewhere between extremely lucky and extremely regretful.
For some, this first attempt is the last, and for others, it is just the beginning.
this thread is for the latter.
Anyone with a background in radio maintenance would probably discourage any layperson from potentially damaging their expensive toys, and their advice is to be heeded.
HOWEVER, with the understanding that part of the draw of this hobby is experimentation; i believe that everyone should have access to any and all information on the subject and should form their own assesment of their desires versus their skills.
With that in mind, i offer to you all, "the golden screwdriver's guide to aligning your own radio equipment."
i say "your own equip." because i mean specifically the equipment that you own and dont mind voiding the warranty on. (because you will)
under no circumstances should you use this knowledge to align your friends' radios unless you are willing to buy them another or dont mind losing a friend.
here we go:
LESSON 1- what do i need?
most of us are led to believe that we need a bunch of expensive test equipment to properly align our CB radios. IT IS TRUE! to properly align a CB radio you need to have an oscilloscope, a spectrum analyzer, and about $3,000 worth of other peripheral gear.
can you say, not gonna happen? i can! i am not a technician. i do not claim to be one to anyone anywhere. i am a radio hobbiest and a die hard do-it-yourselfer. the techniques i will show you are a bit "down and dirty" by professional standards, but they will allow you to buy a used CB radio, and align the PLL, the reciever, and the transmitter to within specs. this is the first step of most repair centers, and they wont even start troubleshooting until they do an alignment first. (the alignment can also make a problem show its face)
the equipment you will need is easily available to you on the used market and even new, it is quite affordable. the popular auction site is a great place to look!
The first piece of test equip. to buy is a voltmeter. i like to have a digital and an analog one for different things, but for starters, just get a digital one. you should spend between $20 and $60 on yours. better to stay away from the $10 grocery store special. your meter should have the capability to measure AC and DC volts, DC milliamps, and if possible 10amps DC.
more on its use later.
next most important thing is a frequency counter.
it needs to be the kind with a BNC connector on the front, not the add on ones for exports; those are frequency displays; not counters.
i paid $55.00 for mine on the auction site. make sure it is made for freqs. up to 100mhz or so. (most are) when you get your freq. counter, you need to verify that it is calibrated correctly or your adjustments will be meaningless. more on this later, just get one that works).
next is a signal generator. this seems complicated and it is, but for our purposes, a basic unit will work. the newer the better here, and i have seen brand new ones for $160.
i paid about half that. make sure it is an RF signal generator as there are other ones specific for audio testing. the generator you get should cover from 1 to 30 mhz in different frequency bands, and should be able to internaly create a 1000hz tone. it should have an adjustable output level and binding posts for hookin up test leads.
mine is a LEADER LSG-16. do a search to find a pic.
thats it for tonite. gotta go to sleep. i'll post more tomorrow.
start saving your pennies!
matt |
Kid_vicious
Advanced Member
Username: Kid_vicious
Post Number: 864
Registered: 9-2004
| | Posted on Monday, November 21, 2005 - 12:56 am: |
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princess!!!? dont make me get vicious on you! J/K!
LESSON 1 continued:
so have you bought anything yet? just kidding!
honestly, i spent less than $200 for the stuff i have, and i do just fine.
The next things to buy are test probes, or you can make your own.
you will need to make or buy three different sets of test probes. one for the voltmeter (other than the ones included), one for the sig. gen. and one for the freq. counter.
for the freq. counter, you dont need to have an elborate storebought probe, (they're nice though!)
what you need is some shielded cable, (doesnt have to be coax) and a male BNC connector. the center conductor of the cable should be 18ga. or bigger.
solder the cable to the BNC connector, and solder an alligator clip to the other end on the shield.
solder the tip of a test probe to the center conductor. now you can check different test points inside the radio for exact freq. adjustments!
The probe for the signal generator is pretty simple. if the sig. gen. has binding posts then all you need is stripped wire on the end that fits in the binding posts. cut the red test probe about 4-6" from the sig. gen. end. add a .01uf 1000volt ceramic disc capacitor in series with the red probe. (add the cap in between the wire you just cut) this will make sure you dont load the circuit you are trying to test. use heat shrink tubing on the cap connection to prevent shorts.
cut the tip off of the black test probe and add an alligator clip instead. (this tip will work nicely for the tip you need for the freq. counter probe)
now for the voltmeter. the probe we will need for this is a bit more complicated then the others, but dont worry; we'll get through it. we need to convert our DC voltmeter to an RF voltmeter.
to do this, we need whats commonly called an RF probe. the circuit is simple as heck to build, but hard to explain without pictures. so for the sake of keeping things simple; i'll tell you to do a search for "RF probe" and build any one of the dozen or so designs that you will find. my favorite is the one that uses a pen for the body, but you can just as easily solder the few parts to a breadboard and use wires coming out of it.
when using this probe, you will hook it up to the test leads on the voltmeter and use the wires coming out of it to go to the circuit you are testing.
the numbers will not be accurate using this method, but that really doesnt matter for our purposes. when you are using your RF probe, you will be tuning coils for max. RF voltage. this is where the analog voltmeter would come in very handy. its alot easier to judge the peak on an analog meter. i will try to draw up a simple diagram for an RF probe later.
the next step is to make sure that your test equip. is calibrated correctly. you can have this done somewhere, or you can build a frequency standard for very cheap. the most expensive part is the crystal, and they are like $10. i'll try to draw up a diagram, but for now, do the search thing for "frequency standard" and build any of the circuits you find. this neat little device will put out a singal that is exactly, say, 10mhz.
so you look at you freq. counter and it says, 10.0005. you find the calibration screw inside, and turn it slowly until the counter reads exactly 10.0000mhz. again, they are easy to build.
now you need to get a good set of alignment tools. they must be ALL plastic. NO metal. if you are planning on using jewelers screwdrivers for your tune ups, you might as well stop right here, because there is no point in buying real test equipment if your measurements are not going to be accurate anyway. (and they WONT!)
you can order them online, or get them from Rad Shak. you really need to get two sets, as they are kinda cheaply made nowadays, and you'll need a spare eventually. (not good to need one in the middle of a midnight tune up!)
OK, thats enough for tonite. go start bidding on some stuff to get started. more to come tomorrow.
matt |
Kid_vicious
Advanced Member
Username: Kid_vicious
Post Number: 865
Registered: 9-2004
| | Posted on Monday, November 21, 2005 - 11:53 pm: |
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howdy, i almost forgot to mention that you are going to need a wattmeter. pretty much all wattmeters are also SWR meters. this you should buy new and NEVER turn any of the pots inside it. anyone can make a radio "look" like it puts out 50 watts by messing with a meter. buy one new.
the last two pieces of test equipment are very important, one is a bench radio. this is a radio that has all the capabilities of the radios you will be working on. the choice is yours, but i do recommend a brand new or completely stock radio that has been aligned. (you can do an alignment without the bench radio, they just help when you want to check certain things. trust me, you'll find a use for it)
The last, but most certainly not least piece of equipment is SERVICE INFORMATION! you cant do anything without this. if the radio is new, chances are you can find the alignment procedure online, but if the radio is older, you'll have to hunt down a SAMS PHOTOFACTS book for your specific radio. SAMS at one time had service info on almost ALL CB radios in production. the alignment will be on the first few pages of the service manual. We will use a practical example to familiarize ourselves with the procedure and the terminology used.
since it is a classic, and i have more experience with them; we will use the venerable 148/2000gtl chassis that so many of us love.
sorry, out of time again! tomorrow... the procedure!
matt |
Kid_vicious
Advanced Member
Username: Kid_vicious
Post Number: 874
Registered: 9-2004
| | Posted on Thursday, November 24, 2005 - 12:11 am: |
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gonna have to wait a few days for the alignment procedure, i keep forgetting to bring the manual to work with me. sorry!
for now, here is my best attempt at drawing a schematic of an RF probe that you can build. (yes you can!)
OUTPUT__________________________________INPUT
+ ---|(---/\/\/\------------------ +
________D
________I
________O
________D
________E
- ------|----------------------- -
the input is the voltmeter, the output is the circuit you are testing.
this symbol means a capacitor, and the value is .01uf (microfarad)
--|(---
this symbol means a resistor, and the value is 4.7M ohms (mega ohms)
---/\/\/\---
the diode is labled as "DIODE" because i couldnt draw a picture of it. so, the diode is a 1N34A.
(this is commonly known as a germanium diode)
the diode will have one banded end. this end should go in between the cap and resistor, and the unbanded end to the negative lead.
this RFprobe will work best with a digital voltmeter as they generally have a higher input impedance.
the site where i got this from can be found by doing a google search for "rf probe".
build one and you too can align your own PLL for max. RF out.
just as a disclaimer, i know the correct tool to use here is an oscilloscope, but most people that end up actually buying one, never learn how to use it, and hence, never use it. this info is for the people that want to do the best they can with what they've got.
good luck,
matt
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Kid_vicious
Advanced Member
Username: Kid_vicious
Post Number: 883
Registered: 9-2004
| | Posted on Friday, November 25, 2005 - 11:59 pm: |
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one more piece of test equipment you will want to have, and should want to build is a dummy load.
to build your own, use this formula. (its simple)
ohms=value of resistors (divided by) number of resistors
we will always want 50ohms to be the impedance because that will be a match for the CB.
meaning we will have a 1.1 to 1 SWR. this way, we can tune our transmitters without causing interference on the air, and you can rule out an antenna problem by substituting the dummy load inline.
for example:
50ohms=150ohms(divided by) 3
150/3=50
so, use three 150ohm resistors in parrallel and you have a 50ohm load.
i used three 25 watt resistors so my dummy load can handle 75 watts continuously, and about 300 for short durations. (long enough to make my adjustments)
300/6=50
1000/20=50
get it?
get a small aluminum box and mount an SO-239 on one end. twist the ends of your resistors together so that it looks like one big, bulky resistor.
solder one end to the center pin of the SO-239 connector and the other end goes to a screw in the case. (ground)
try to space the resistors apart a bit to increase heat dissapation.
thats it! now you have a neat little accessory to impress your friends with next time they cant figure out whats going on with their mobile antenna. |
Kid_vicious
Advanced Member
Username: Kid_vicious
Post Number: 884
Registered: 9-2004
| | Posted on Saturday, November 26, 2005 - 12:58 am: |
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finally, here is the alignment.
this is from the factory service manual for the 2000GTL, but it should work with the 148gtl, the new grant, the new madison, and the tramD300 among others.if your radio has an MB8719 or MB8734 chip in it and a dual conversion receiver, then this alignment procedure should work for you.
for any other radio, you will have to find the specific service info for that radio. DO NOT USE THE NUMBERS IN THIS ALIGNMENT TO ALIGN OTHER RADIOS. YOU WILL SEVERELY DAMAGE THE RADIO!
when looking for sevice info, the internet is your best friend. you can often find the manuals on the auction site for a fair price.
if the radio is older than say, 10 years, then you should be able to find a SAMS PHOTOFACT for your radio. these were made by the Howard W. sams company. they are no longer made but you can find them around if you look. YOU MUST HAVE THE SERVICE INFO FOR THE RADIO YOU WISH TO ALIGN. DO NOT ATTEMPT THE ALIGNMENT WITHOUT THE SERVICE INFO AND THE TEST EQUIPMENT!
here we go:
1. input of frequency counter to TP13 (test point 13) IC1 pin 8.
radio on ch.19 am. clarifier in center pos. NB and ANL off.
check for 10.240mhz.
this means that you will hook the alligator clip rom the shield (-) or the freq. counter and clip it to PC ground. i like to use the tuning cans as they are all grounded. just clip right to the can, or if there is a wire soldered to it, clip to that. make sure the place you clip to is true ground. (connected to the big foil trace) and also make sure you dont use the metal case of the radio or "chassis ground" this is not the same as the PC board ground and will not work.
now take the probe from the freq. counter and touch the tip to pin 8 of IC 1. look at the freq. counter, it should read 10.240mhz. (if you get no reading and the radio seems to work correctly, then you have either hooked something up wrong or your freq. counter is set wrong or doesnt work.
2. input of RF voltmeter to TP10
radio on ch. 19am. clarifier centered.
adjust L21 for maximum RF out.
this means that you will clip the negative lead of your RF probe to where you had the freq. counter hooked to and the positive tip will go to TP10 (location found in service manual)
adjust the can SLOWLY for the maximum voltage. you will notice the volts rise to a point and then start to fall again, go back and forth until you find the peak point and leave the can set there.
3. input of DC voltmeter to TP9
radio set on ch. 40am
adjust L19 for 3.20 volts. check channel 1 for 2.45 volts.
this means set up the same way as before except dont use the RFprobe and set the can for 3.2 volts and leave it there.
4.input of RF probe to TP1.
radio set on ch.19am
adjust L20 for maximum voltage. (you may have to use the mV setting on the voltmeter for this one.
this is done the same way as in step 2.
5. input of freq. counter to TP1.
radio at ch.1 am
adjust L23 for 34.7650mhz + or - 20hz (try to get it exact)
6.input of freq.counter to TP1
radio at ch.1 USB
adjust L59 for 34.7665mhz.
7. input of freq. counter to TP1
radio at ch.1 LSB
adjust L22 for 34.7635mhz.
8. input of freq. counter to TP10
radio at ch.1am
check for .790mhz
9.input of freq. counter to TP3
radio at ch.19USB
adjust CT2 for 7.8015mhz
10. input of freq. counter to TP3
radio at ch.19LSB
adjust L30 for 7.798mhz
11.input of freq. counter to TP14 (IC3 pin 7)
radio at ch.19 AM TRANSMIT (key mic with no modulation)
adjust L31 for 7.800mhz.
12. input of freq. counter to TP15 (FET 1 gate1)
radio at ch.19am
check for 7.345mhz.
13.input of freq counter to antenna input (so-239)
radio at ch.1 AM TRANSMIT
adjust VR5 for 26.965mhz.
thats it for the PLL section.
tomorrow, the receiver,
matt |
Kid_vicious
Advanced Member
Username: Kid_vicious
Post Number: 890
Registered: 9-2004
| | Posted on Tuesday, November 29, 2005 - 12:15 am: |
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so here is the reciever alignment procedure.
for this you will be using your signal generator.
make sure you have a .01uf cap in series with the positive test lead.
to set the s-meter and the squelch; you will need a voltmeter that measures microvolts. i do not have one of these, and therefore, i cannot do an accurate adjustment on these two pots.
this is where the bench radio comes in handy.
the bench radio i have has an analog meter on it, and after performing a tune up on a radio, i will find a local with a steady carrier, and match the radio im tuning to the S-meter on the bench set.
same with the squelch. (you wont need to adjust this ever, unless someone has turned the pot by mistake, and then, its not the most critical adjustment on the radio)
for this radio, the squelch range is VR3, the AM s meter is VR1, and the SSB meter is VR2.
YES, i realize that this is not entirely accurate, and i do not claim it to be. if you want it completely perfect, you will have to take it to a tech with a higher quality signal generator.
you could buy a better one yourself, but i dont feel the need for it, and can always find something else to buy with that ammount of money.(more radios!)
here we go:
FOR ALL RECEIVER ADJUSTMENTS: RF GAIN MAX. CLARIFIER AT CENTER, SQUELCH AT MINIMUM, NB OFF, ANL OFF, TONE MAXIMUM CLOCKWISE.
1. output of signal generator to TP16 (TR15 emitter)
7.8mhz
radio at ch.19USB
adjust L14,12,10,9,8,7 in that order for maximum s meter reading.
so, set your sig gen at 7.8mhz, clip the negative lead to PC ground, and the positive lead to TP16.
adjust the output of the sig gen so that the S meter on the radio reads about S-3. (no more)
slowly turn the coils, starting at L14 and working down. you will notice that they cause the S meter to move up or down as they are turned. turn the coils SLOWLY until you find the peak reading. leave the coil in that position and move on to the next.
2.output of sig. gen. to TP15 (FET 1 gate 1)
455khz.
radio at ch.19AM
adjust L15,13,3 for max. s-meter reading.
same as last step.
3.output of sig. gen. to antenna input
27.185mhz.
radio at ch.19AM
adjust L6,5,4 for max. s-meter reading. readjust L7,8,9,10 for max. in that order.
i also adjust L1,and L2 at this time. these are the NB coils, and should be adjusted using an oscilloscope and very high quality signal generator.
at this point, its up to you whether or not to mess with them. if you are doing a tune up on a radio that you know the history of, then there is no need to adjust them. if, however, you happen to be working on a garage sale special that you want to get working; then adjust them for max. s-meter reading using the set up from the previous step. this is how i do it on my radios, and my ear cant tell the difference.
matt |
Coyote
Advanced Member
Username: Coyote
Post Number: 608
Registered: 11-2004
| | Posted on Tuesday, November 29, 2005 - 11:14 pm: |
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Well Matt, the time I did hear you, your radio sounded excellent. 
But you were make'n to many contacts to hear my mudduck station.
CEF-443 |
Kid_vicious
Advanced Member
Username: Kid_vicious
Post Number: 896
Registered: 9-2004
| | Posted on Tuesday, November 29, 2005 - 11:51 pm: |
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and finally, the transmitter alignment.
you should use a dummy load for these tests, if you dont, you will be causing malicious interference, and generally being a jerk. and your results wont be as accurate. dont do it!
hook up a wattmeter between the radio and the dummy load.
radio should be on ch.19
1.radio at ch.19 AM
key the mic, and say "aaahhhhh" in a steady natural voice tone. using a two tone generator here can be very helpful. there are numerous designs around on the net, and they are simple to build. i use one. do not tune the coils for max. deadkey, as this will weaken the modulation to a great extent, sometimes making the output power actually DECREASE when you are speaking. (downward modulation)
while speaking into the mic, adjust L47,48,46,45, and L38 in that order for max. peak (modulated) power. on one or more of these coils, you will notice that there is a waxy substance covering the opening. carefully pick this away, and then, right before you make your adjustment, put your soldering iron on the ferrite core for just two seconds. be careful not to melt the plastic threads on the edges. this will allow the core to turn easily. if you dont do this, you can break the core, and then you'll have to scrounge another one from a different radio which may or may not work as well. be careful, dont turn anything fast, and never force anything.
2.ch.19USB mike gain at minimum.
adjust VR4 for 0 watts. (no carrier)
3. ch.19USB mike gain at minimum.
insert DC ammeter at TP8. (driver bias)
this means that you need your DC volmeter set to milliamps on a scale that can read 200ma (milliamps).
this hook up is not the same as voltage testing! when you test for current, you hook the voltmeter in series with the lead under test.
so, pull the wire off of TP8, and clip the negative lead to the end. touch the positive lead to TP8. key the mic and adjust VR9 for 30ma.
reconnect the wire to TP8.
4. ch.19USB mike gain at minimum
pull wire off of TP7 and clip negative lead of voltmeter to it.
touch positive lead to TP7.
key the mic and adjust VR8 for 60ma.
reconnect the wire to TP7.
VR11 is your SSB power out. set it wherever you want it. if you are running an amp after the radio, you should set it for no more than 15 watts.
i set mine at 12 watts.
VR7 is the mod control in the 148 chassis. in the 2000 chassis its VR12.
i just set this at max and use the front panel mic again to adjust the modulation. (you wont have to run the mike gain all the way up anymore)
VR10 is the AM carrier power. this is where people blow up their radios. they say, "wow! how cool! the manufacturer put in an easy adjustment for more power out!" dont be fooled! most radios cant handle the increased wattage for very long when this is turned up.
if you are running an amp; set this control for 2-3 watts and NO MORE! otherwise you will sound very quiet coming out of your amp, and you may just smoke it!
if you are running barefoot, then set it for about 5 watts. this is safe, and no one can tell the difference between 5 and 8 watts anyway. your radio will last for a very long time if you keep this control under control. if you get the power bug, you will be buying transistors that are getting more expensive every day.
finally, adjust VR6 so that the S meter on the radio agrees with the wattmeter.
well, thats pretty much it, except for the 50 flaming posts ive got coming my way for condoning such cheap and dirty tricks.
make no bones about it. this is not as accurate as sending your radio to a good tech shop, but if you wanted to do that, you wouldnt have read this far would you!
good luck, and please feel free to point out any mistakes or bad advice that you see. all quesitons are good questions.
have fun,
matt
CEF410 |
Kilowatt
Intermediate Member
Username: Kilowatt
Post Number: 245
Registered: 2-2004
| | Posted on Sunday, August 26, 2007 - 9:14 pm: |
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Thanks for the information, Kid Vicious! I always appreciate tech "pointers" and information on my favorite chassis - the MB8719! |
Lester_elm
Member
Username: Lester_elm
Post Number: 54
Registered: 12-2007
| | Posted on Sunday, May 30, 2010 - 2:39 am: |
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Realizing that this thread is over two years, old at this time, I would like to offer one tidbit of information to the excellent procedural posts so meticulously posted by Matt (Kid Vicious).
It is ALWAYS a wise step to make sure that your body, the radio being aligned and all test equipment are at the same ground potential. Components such as FET's and IC's can be easily destroyed by static discharge. Just wear a grounded wrist strap or similar device when servicing your equipment and make sure the strap is connected to a ground source. I learned this the hard way.
CEF #964 HAM #276
Let's play radio!
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Low_boy
New member
Username: Low_boy
Post Number: 1
Registered: 12-2010
| | Posted on Friday, December 17, 2010 - 10:13 pm: |
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Kid Vicious ( Matt ) Great work, Very interesting. |
Silvercreek
New member
Username: Silvercreek
Post Number: 1
Registered: 6-2013
| | Posted on Sunday, June 09, 2013 - 1:06 pm: |
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I wish I was close to someone that could do a proper alignment on my DAK Mark IX. The transmit works great. It's the receive that sounds like it could use some fine tuning. |
Tech237
Moderator
Username: Tech237
Post Number: 1681
Registered: 4-2004
| | Posted on Monday, June 10, 2013 - 9:04 am: |
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Some addendum to the above posts.
1)Although a lot of "amateur" tech use ahhhh to test a radio, the word "four" actually hold more speech power than ahhh.
2) Ground Potential - I have power plugs with just teh black wire on then connected to my bech ground plate, which in turn is connected to the outside ground via a THICK braided strap.
3) If you DO NOT have the proper gear, or are NOT competent, DO NOT attempt this. It is the best way tio get a bad sounding, over-modulated distorted radio around.
Tech237
N7AUS
God made me an athiest, who are you to question his wisdom?
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Keithinatlanta
Advanced Member
Username: Keithinatlanta
Post Number: 994
Registered: 3-2003
| | Posted on Friday, February 28, 2014 - 6:19 pm: |
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Ok, here is another lesson learned. In reading about using the word four. How about that. I will pass that on to others. Thanks!!
Keith in Atlanta
CEF 150 |
Mslisaj
New member
Username: Mslisaj
Post Number: 2
Registered: 12-2015
| | Posted on Saturday, December 12, 2015 - 11:20 am: |
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Thanks Kid vicious for these detailed instructions. I have a copy of Sam's Photofacts for this radio but being I'm not a tech it was very confusing. Thanks to your explanations and instructions you have made this process comprehensible. Right now I am in the process of accumulating the equipment I need to do this. I have a recently calibrated six digit frequency counter. I have an RF Probe kit that I have to build for my Fluke DVOM. I also have to build a probe with a cap to work with my freq. counter. Then the RF signal generator and I'll be ready to try all this.
Bottom line, thank you for all the effort to write up and post this. Much appreciated.
73's
Lisa |
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