Which cans were you turning at which time? Could you explain what you were looking for at the VU meter? It seems like they were flailing up and down at random then you said they were good. I couldn't tell what you were looking for. Thanks.
I am not "him" but I would like to take a try at explaining what you are seeing. The over-all idea is that.... when you feed a modulated RF signal into the antenna jack on a radio... the ultimate "end" is that the demodulate audio gets sent to the speaker. However, BETWEEN the antenna jack and the demodulator are a varying number of "tuned circuits" that, as the name suggests, "tune" each of those stages to "peak" the signal passing THROUGH that stage. When you have successfully tuned ALL stages.... the audio signal that goes to the speaker will be "maximized". So, as you tune the stages... you are looking for the maximum "audio" out to the speaker. A point to be made before proceeding....while our ears can certainly hear the audio getting "greater" and "lower"... they have a little trouble detecting VERY SLIGHT changes in level. So what he has done is to build an "audio power meter" with sufficient sensitivity to "catch and display" audio power levels... and you can SEE the power level changes on the meter... EVEN when your ears can't hear a change. Note that he is NOT looking for calibrated levels.... this process only needs "relative measurement". You only need to know the "MAX level". Accuracy is NOT as important as "finding the highest peak". So to start, he hooks his audio power meter to the speaker jack. The power meter has an 8 ohm resistor inside to "fake" a speaker. At this point the needle on the meter goes up to show that audio is being sent out. As he describes... he just sets the volume control so that the needle is somewhere near "mid point" on the meter as a starting point. Then he steps through the various stages of the radio, he is adjusting each tuned circuit. As he tunes and "bumps into the peak" the audio needle goes up and then DOWN as you pass it. At that point he reverses the adjusting "direction" to bring the needle back to the peak. This process may require SEVERAL back and forth passes... and THAT is why the needle bobbles up and down. At some point, he will get the circuit he is working on adjusted to that the needle is at it's very highest point. THEN he moves on to the next circuit and starts adjusting it. Each stage behaves the same way.....needle moves up..... PAST the peak point and starts going down again... so you back up and try to hit the peak again and again.... it is kind of "back and forth" as you find the peak. At some point the needle may get so far UP or DOWN the meter..... so he uses the radio's volume control to bring the needle back to the middle. Also note that you often have to go BACK to previously adjusted stages a few times and repeat the process. THIS PART is just something that you have to "develop a feel for" and the only thing that will help is "practice". Just doing it.... will make you better at it. In the end, you will hit a point where each and every adjustable stage is set so that the RF passed on through is at it's maximum and can not be improved. THIS means that the receive side of your radio is precisely adjusted to create the fullest audio signal for the faintest of RF input signals. ALSO NOTE: it is best to perform this alignment with the RF generator output as LOW AS POSSIBLE at any given time. The reason for this is that there is circuitry in the radio (AGC) that works to KEEP the signal maximixed FOR YOU. If you overpower the radio with too much RF... you will be SO FAR IN to the AGC action.... that the RF will keep automatically adjusting the signal..... and you will NOT be able to see the tiny little changes as you tweak the individual transformers. So only bring up as much RF s you need to be able to hear the modulation tone (or SEE IT on the meter) but don't bring it up TOO high. Hope you find this useful/helpful. Bob
I did the best I could with what I have. I have never seen any videos out there on how to do a "receiver alignment" so I figured I'd make one. Then all these people saying how I'm doing it wrong and blah blah. Let's see how you do a receiver alignment! Post video link in comments. Thanks
I have an old beat up 29 that had horrible receive. Can i tun in the pots while listening to someone or is that too rough of a guess? Thanks for the vid 👍
I sure miss rat shack. Everything went downhill when they stopped selling all their ham and cb gear. Thats a cool power supply I once owned that same one
So you just have a regular VU meter with a 8 ohm resistor with a audio cord attached to the back of the vu meter and that’s it ? I just ordered one on eBay it’s just a plain old vu meter no driver circuit or anything will that work
Did you ever post how to's on the VU meter to use or simulate a speaker. Would it just be the 8ohm resistor in line with 1 of the wires from the extension jack on back of radio? thanks
Can YOU make a short Video on how to make, or what You did to transform your Meter into a meter to mimic a speaker??? Or where I can go to learn how to do as YOU did??
@@stansmith6343 Define receive pots? They are not pots (potentiometers). It's adjustable inductors (tank circuits) . And the cans you tell to keep off is not 455 Hz, It's 455 KHz IF filter cans
@@user-su5sq5ib3i yep. I built mine out of an inductor i wound with about 10 turns and the signal wire going through the middle of it, and put in a pot to use as a variable attenuator for the sample output then threw it all in a metal box. Works great
@@user-su5sq5ib3i I believe it is 25 ohm, I used what I had on hand. Its a variation on TRX Bench's design on his channel, search youtube for TRX Bench RF tap. I built it so that I could hook up a HP 8591 spec analyzer to the ant output, and it makes it easy to hook up a scope as well. The 25 ohm pot I'm using is good for anywhere from 0 ~ 32 db of attenuation, and i use it in combination with another 14 db attenuator and a DC block.
After the alignment, how many microphones of signal did it take to produce a barely audible tone in the receiver? If you where to turn the generator down to its lowest point and still be able to hear a sound coming from the speaker?
So you normally do a sinsativity test and siniad measurement..normally a ref is 12 siniad is standard . Bigger the siniad better or larger - dbm facter better the sinsativity... 73s from 9lb hammer Oklahoma
@@justinruth9729No way he can go to -120dbm at 30% modulation and read -12db on a sinad with a cobra 29. -110dbm would be really good for a Cobra 29. 👍
Yesterday, I was having an issue receiving from someone who was maybe a mile or so ahead of me but, i could hear the other guys that were closer, I have a Cobra 29LTD Classic. I use an external speaker. I just brought it in the house to see if I could hear me transmit on my handheld on the classic and I cannot hear a transmission. I just really need to know if my radio and antenna are working. WHen I key the mike, I a little more that 2.5 watts but when I key the mike on the handheld, the needle on the classic pegs all the way to right and I cannot hear the transmission. Any ideas?
Butterfly Taxi DFW check tr7, d5, d6 and d24. Or just replace them. Give it a good visual and use your finger and press around the board to find a bad solder joint or connection.
That would be a rf sampler. It basically just takes a sample of the rf power so it can be viewed on an oscilloscope. If you hooked directly up to a scope with a radio, you would blow the scope up.
What are the alignment tools, you don't tell them, the camera is constantly in motion, something is not understood, it is a useless video, if you calmly explain what you are doing, we will understand something, you do not tell what cable you connect to the test tools, is it a secret, how will we know what the electronic components in a closed box are? A video made in vain If you are going to be useful to people, you should prepare a video that people can understand, you made a video from the story.
I had to give YOU a thumbs down because watching your demonstration was making ME dizzy and YOU did not show what cans YOU adjusted as some of the others who commented wanted to know as well.... A good Demonstration is in the details given and shown...
Thanks, much appreciated James! I was showing how "I" do a receiver. I assumed that people attempting a receiver alignment would at least know the cans to adjust with a quick google search on " cobra 29 ltd alignment procedure".
Which cans were you turning at which time? Could you explain what you were looking for at the VU meter? It seems like they were flailing up and down at random then you said they were good. I couldn't tell what you were looking for. Thanks.
I am not "him" but I would like to take a try at explaining what you are seeing.
The over-all idea is that.... when you feed a modulated RF signal into the antenna jack on a radio... the ultimate "end" is that the demodulate audio gets sent to the speaker. However, BETWEEN the antenna jack and the demodulator are a varying number of "tuned circuits" that, as the name suggests, "tune" each of those stages to "peak" the signal passing THROUGH that stage. When you have successfully tuned ALL stages.... the audio signal that goes to the speaker will be "maximized". So, as you tune the stages... you are looking for the maximum "audio" out to the speaker.
A point to be made before proceeding....while our ears can certainly hear the audio getting "greater" and "lower"... they have a little trouble detecting VERY SLIGHT changes in level. So what he has done is to build an "audio power meter" with sufficient sensitivity to "catch and display" audio power levels... and you can SEE the power level changes on the meter... EVEN when your ears can't hear a change. Note that he is NOT looking for calibrated levels.... this process only needs "relative measurement". You only need to know the "MAX level". Accuracy is NOT as important as "finding the highest peak".
So to start, he hooks his audio power meter to the speaker jack. The power meter has an 8 ohm resistor inside to "fake" a speaker. At this point the needle on the meter goes up to show that audio is being sent out. As he describes... he just sets the volume control so that the needle is somewhere near "mid point" on the meter as a starting point.
Then he steps through the various stages of the radio, he is adjusting each tuned circuit. As he tunes and "bumps into the peak" the audio needle goes up and then DOWN as you pass it. At that point he reverses the adjusting "direction" to bring the needle back to the peak. This process may require SEVERAL back and forth passes... and THAT is why the needle bobbles up and down.
At some point, he will get the circuit he is working on adjusted to that the needle is at it's very highest point. THEN he moves on to the next circuit and starts adjusting it.
Each stage behaves the same way.....needle moves up..... PAST the peak point and starts going down again... so you back up and try to hit the peak again and again.... it is kind of "back and forth" as you find the peak.
At some point the needle may get so far UP or DOWN the meter..... so he uses the radio's volume control to bring the needle back to the middle.
Also note that you often have to go BACK to previously adjusted stages a few times and repeat the process. THIS PART is just something that you have to "develop a feel for" and the only thing that will help is "practice". Just doing it.... will make you better at it.
In the end, you will hit a point where each and every adjustable stage is set so that the RF passed on through is at it's maximum and can not be improved. THIS means that the receive side of your radio is precisely adjusted to create the fullest audio signal for the faintest of RF input signals.
ALSO NOTE: it is best to perform this alignment with the RF generator output as LOW AS POSSIBLE at any given time. The reason for this is that there is circuitry in the radio (AGC) that works to KEEP the signal maximixed FOR YOU. If you overpower the radio with too much RF... you will be SO FAR IN to the AGC action.... that the RF will keep automatically adjusting the signal..... and you will NOT be able to see the tiny little changes as you tweak the individual transformers. So only bring up as much RF s you need to be able to hear the modulation tone (or SEE IT on the meter) but don't bring it up TOO high.
Hope you find this useful/helpful.
Bob
Bud Light cans 😅😅😅
I did the best I could with what I have. I have never seen any videos out there on how to do a "receiver alignment" so I figured I'd make one. Then all these people saying how I'm doing it wrong and blah blah. Let's see how you do a receiver alignment! Post video link in comments. Thanks
I have an old beat up 29 that had horrible receive. Can i tun in the pots while listening to someone or is that too rough of a guess? Thanks for the vid 👍
I'd love to see more videos like this
Can YOU show a Vedio how to make a VU Meter as the one YOU used in this Video??? Parts and layout
I sure miss rat shack. Everything went downhill when they stopped selling all their ham and cb gear. Thats a cool power supply I once owned that same one
Dude please make a video on how to align transmit section!
So you just have a regular VU meter with a 8 ohm resistor with a audio cord attached to the back of the vu meter and that’s it ? I just ordered one on eBay it’s just a plain old vu meter no driver circuit or anything will that work
Can you show us how you made your VU meter? Schematic and inside view.
Did you ever post how to's on the VU meter to use or simulate a speaker. Would it just be the 8ohm resistor in line with 1 of the wires from the extension jack on back of radio?
thanks
You can make an audio watt meter very easily. www.circuitstoday.com/audio-wattmeter-circuit
Can YOU make a short Video on how to make, or what You did to transform your Meter into a meter to mimic a speaker??? Or where I can go to learn how to do as YOU did??
You betcha james, are you going to give me another thumbs down though? lol
I would also like to see the VU Meter set-up and is there anything inside your input Tee connector.
William Colvin the input tee is irrelevant to the receiver alignment. I use the tee for transmit only.
Hi RF, did you use a bridge rectifier setup or a single rectifier in your circuit? What about a capacitor? Thanks for sharing the vid!
Which cans exactly did you adjust?
Thanks!
I adjusted L2 through L9
L2,3,4,5,6,7,8,9 are the receive pots
@@stansmith6343 Define receive pots? They are not pots (potentiometers). It's adjustable inductors (tank circuits) .
And the cans you tell to keep off is not 455 Hz, It's 455 KHz IF filter cans
@@mikaelkarlsson9945 bet you have lot's of friends 🤦♂️
Do you use 30% modulation at -73dBm and 100mv?? If not what settings do you use in the sig gen
What is the box on the back of the 29? Homemade attenuator?
Its likely a rf coupler/sampler, you can build one.
@@Sloxx701 yeah they arent hard to build. Heck even a coax position switch does the trick
@@user-su5sq5ib3i yep. I built mine out of an inductor i wound with about 10 turns and the signal wire going through the middle of it, and put in a pot to use as a variable attenuator for the sample output then threw it all in a metal box. Works great
@@Sloxx701 good idea, what value potentiometer resistance did you use?
@@user-su5sq5ib3i I believe it is 25 ohm, I used what I had on hand. Its a variation on TRX Bench's design on his channel, search youtube for TRX Bench RF tap. I built it so that I could hook up a HP 8591 spec analyzer to the ant output, and it makes it easy to hook up a scope as well. The 25 ohm pot I'm using is good for anywhere from 0 ~ 32 db of attenuation, and i use it in combination with another 14 db attenuator and a DC block.
He doesn't show where the adjustment points are for watt control
After the alignment, how many microphones of signal did it take to produce a barely audible tone in the receiver? If you where to turn the generator down to its lowest point and still be able to hear a sound coming from the speaker?
-120 dbm
So you normally do a sinsativity test and siniad measurement..normally a ref is 12 siniad is standard . Bigger the siniad better or larger - dbm facter better the sinsativity... 73s from 9lb hammer Oklahoma
@@justinruth9729No way he can go to -120dbm at 30% modulation and read -12db on a sinad with a cobra 29. -110dbm would be really good for a Cobra 29. 👍
Yesterday, I was having an issue receiving from someone who was maybe a mile or so ahead of me but, i could hear the other guys that were closer, I have a Cobra 29LTD Classic. I use an external speaker. I just brought it in the house to see if I could hear me transmit on my handheld on the classic and I cannot hear a transmission. I just really need to know if my radio and antenna are working. WHen I key the mike, I a little more that 2.5 watts but when I key the mike on the handheld, the needle on the classic pegs all the way to right and I cannot hear the transmission. Any ideas?
Butterfly Taxi DFW check tr7, d5, d6 and d24. Or just replace them. Give it a good visual and use your finger and press around the board to find a bad solder joint or connection.
Replace receiver pre amp. Might have got blown by a big radio close by.
Tr7
what is that gray box u have that connects to antenna jack on cb
That would be a rf sampler. It basically just takes a sample of the rf power so it can be viewed on an oscilloscope. If you hooked directly up to a scope with a radio, you would blow the scope up.
thank you
Where u adjusting
Very good video.
He is trying to sound like a tech pro, We beginners and novices don't get that effing lingo.
What are the alignment tools, you don't tell them, the camera is constantly in motion, something is not understood, it is a useless video, if you calmly explain what you are doing, we will understand something, you do not tell what cable you connect to the test tools, is it a secret, how will we know what the electronic components in a closed box are? A video made in vain If you are going to be useful to people, you should prepare a video that people can understand, you made a video from the story.
Hey!
Leave this type of adjustment to professionals or at least follow proper tuning instructions provided by manufacturer.
sent me to fucking sleep
I had to give YOU a thumbs down because watching your demonstration was making ME dizzy and YOU did not show what cans YOU adjusted as some of the others who commented wanted to know as well.... A good Demonstration is in the details given and shown...
Thanks, much appreciated James! I was showing how "I" do a receiver. I assumed that people attempting a receiver alignment would at least know the cans to adjust with a quick google search on " cobra 29 ltd alignment procedure".