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Aligning Cobra 148. Help please.

longhaireddwb

W9WDX Amateur Radio Club Member
Oct 8, 2008
555
30
38
Colorado Springs, CO
I've got the service manual.
Anyway, what I'm trying to do is align the TX and RX. According to what I read in the manual, you can adjust the RX frequency but I'm not seeing any way to adjust the TX on LSB. And the RX is adjusted with two pots? Can anyone explain how this is properly done? The manual is not making sense to me. Not sinking in to my head as they say. ha. Normally I can find a pot to adjust for RX and one for TX but not with this 148. Thanks for any help you can offer.

Jerry...
 

Aligning RX and TX are two separate operations and do not affect the radio's frequencies. Best to do the PLL and output oscillators alignment first; this puts your radio on freq. Apples and oranges.

Adjusting the receive is another can of worms and is best left alone unless one has the right gear to do that part of the operation. Requires an accurate (and expensive) signal generator and a SINAD meter for best results. Aligning the TX requires a dummy load and a lab-grade freq counter and is far less expensive to get into.
 
Problem I'm having is fixing what a golden screwdriver did. Someone had been trying to find more power, like usual, and knocked this thing off freq. Of course AM being so wide it dont mater much so that didn't bother the golden screwdriver. The TX and clarifier is not even close to being right. Wont TX on freq. I have a sig gen so no problem there. I just dont see what pots I need to adjust to get the TX right. Then what pot to adjust to center the clarifier so that its right.

I'm not making sense out of the manual. Nothing unusual about that for me.

VCO Alignment says to adjust L22 for LSB RX, Then Carrier alignment says L30 for LSB RX. But nothing on adjusting TX. And why the two pots for RX?

I'm not trying to squeeze every once of power out of it nor trying to modify it to splatter everywhere. Just want it on freq.
 
Then Carrier alignment says L30 for LSB RX. But nothing on adjusting TX. And why the two pots for RX?

You see; this makes no sense at all. The Service Manual treats RX and TX/PLL in different sections. For that matter, this is also true of any Service Manual I've looked at. They are two distinctly different operations. One is not done at the same time as the other. Perhaps you can show an example/quote?
 
just read the service manual and it tells you what to do. put the clarifier in the center position when aligning the radio. do you even have a freq counter to set the radio properly.?
Robb has explained what you are asking. . maybe you should take the radio to some one that knows what to do before you really get it messed up. I left you the service manuals from cobra. just follow them one step at a time and if you have all the equipment to adjust a radio you will have it on freq. stop trying to set tx before you have all the adjustments made.
 
Sorry guys. Been out of town. I drive truck. Finally got back home. I do have a HP Frequency counter and an HP signal generator. Old stuff but it works well and was calibrated not too many years ago. Its gotten me by and I do well with them. I will start from the beginning and go step by step. Guess I was looking for a short cut but will do all the steps and hope all turns out like it should. Why wouldn't it, right? Thanks for the help and I'll reply after I get this done and let you know the outcome.

Have a great holiday and remember all that died and served our country!

Thanks for the reply's!
 
I will start from the beginning and go step by step. Guess I was looking for a short cut

....just like the last person who was in it....

Quite funny you complain about a golden screwdriver whilst wanting to do the same. You cannot shortcut alignment procedures.
 
OK, Went thru the alignment steps. Had to compare my book to the online info and bow was the book off. Had an issue on a couple places but after I was done I finally got this thing TX and RX on freq.

Now I got an audio check and two people say its sounds tinny or pinched. Any ideas?
 
Yea, I should have stated that I did that. I put a second mic on it. I had made an adaptor years ago for 4 to 5 pin and gave that a go and the guy I was chatting with said it didn't change at all. Odd I thought. Changing to a different mic should have made a difference. I'm starting to think maybe it was just him or the band conditions. I turned on my FT-1000MP and turned on the ATT so I didn't smoke it and the audio sounded pretty good to me for a CB anyway. Its not like the 148 has a bandwidth adjustment so I dont have a clue on what it could be. Double checked everything and just dont see what it could be.

I did find out I need a new Test probe for my Freq counter/scope. I guess this one just finally gave up the ghost.
 
OK, Went thru the alignment steps. Had to compare my book to the online info and bow was the book off. Had an issue on a couple places but after I was done I finally got this thing TX and RX on freq.

Now I got an audio check and two people say its sounds tinny or pinched. Any ideas?
If it is the old 5-pin 148; then it may well be high time that your recap it. Failing caps will have a nasty effect on audio and the radio in general. Remember, that radio is close to 40 years old now.
 
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