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 Post subject: On AM radio alignment the bands end and begin dont match dir
PostPosted: Nov Sun 26, 2017 5:19 am 
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Location: shirley NY...Long Island
On alignment of the AM radio, dont matter which one, the alignment instructions always say to set the radio at the end of the band, which is around 1600-1630 and to set it at the lower end of the dial around 500-530. When I do this the bands are always wrong...and the stations dont match the dial setting..so I set it to what the back of the radio says..like 1600-500, then it matches...

Kenny KE4HVE


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 Post subject: Re: On AM radio alignment the bands end and begin dont match
PostPosted: Nov Sun 26, 2017 12:51 pm 
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After aligning the IF to the specified frequency using an RF signal generator (generally 455 kHz in single conversion transistor radios), I always start with the low end first using the slug in the oscillator coil. With the tuning cap fully meshed, I use 530 kHz because I can receive a station in Canada at that frequency. Then I set the tuning dial to 1600 and use the oscillator trimmer cap to hear a semi-local station on that frequency. This usually needs to be done several times to get the dial to track at both ends of the band. I use same procedure for RF sensitivity tracking.

Dave


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 Post subject: Re: On AM radio alignment the bands end and begin dont match
PostPosted: Nov Sun 26, 2017 1:06 pm 
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The general rule:
Low end: adjust mechanical linkage, inductance, or a padder capacitor.

High end: adjust a trimmer capacitor.

A trimmer cap is in parallel with the tuner, whereas a padder is in series.

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 Post subject: Re: On AM radio alignment the bands end and begin dont match
PostPosted: Nov Sun 26, 2017 9:18 pm 
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Use what the manufacturer says. He printed the dial scale to those figures, any other frequencies will shift the scale slightly, probably not noticeable but....

....sometimes I think that data from publications other than the manufacturers are suspect. I don't recall the radio now, but one of the web pages told me to align very low and very high, the scale extremes, but this made the centre of the scale high in frequency. Eventually I found the true figures and it all came in well - much higher at the low end and low at the high end. Ironically I have sometimes found discreet little marks on either the scale or on the backing sheet!

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 Post subject: Re: On AM radio alignment the bands end and begin dont match
PostPosted: Nov Mon 27, 2017 2:10 am 
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Location: shirley NY...Long Island
Thanks..all...If I adjust to the specs of the diagram..the scale is way off...meaning the high end is adjusted to like 1650...and when I tune across the band the stations are all off...and I mean like a station at 1100 will be like 1400..also on the last adjustment it usually says to set the radio and the generator to 1400 and there is no way to do this, doing it the way of the diagam. So I have done it my way....I set it to the range written on the radio itself, and it seems to be alot closer....I listen to a station like 900 CHML, and 1010 WINS from NY...cause I live on Long Island NY....The radio is a CM Sanyo 6515A and it says on the label 540~1600Kc/s.

Seems like there should be a (standard) setting of 530-1600kc/s and that would seem to cover all radios..

Kenny


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 Post subject: Re: On AM radio alignment the bands end and begin dont match
PostPosted: Nov Mon 27, 2017 2:16 am 
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majoco wrote:
....sometimes I think that data from publications other than the manufacturers are suspect.
I have found this to be true on numerous occasions including Sams. I sometimes even suspect the manufacturer's recommendations. I've found that, over the years, a person can develop his own techniques that work best for him. I've always maintained that alignment of radios is an "art" based on scientific principles.

Dave


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 Post subject: Re: On AM radio alignment the bands end and begin dont match
PostPosted: Nov Mon 27, 2017 2:28 am 
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Location: shirley NY...Long Island
I use same procedure for RF sensitivity tracking.????

Dave...What do you mean by this?...Im kinda new to the aligning thing, but not to electronics..

KNY


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 Post subject: Re: On AM radio alignment the bands end and begin dont match
PostPosted: Nov Mon 27, 2017 2:42 am 
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Where are you getting those frequencies from? You said the schematic. If it is actually the schematic and not the alignment instructions, they probably indicate the tuning range of the circuit and not the alignment points. The separate alignment instructions specify what frequencies to use. If that is what you are using, they aren't very good instructions.

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 Post subject: Re: On AM radio alignment the bands end and begin dont match
PostPosted: Nov Mon 27, 2017 3:28 am 
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Here are the alignment instructions for the 6515 (there is no information for an A suffixed model), straight out of a Channel Master service manual.


Attachments:
Channel Master 6515 align.jpg
Channel Master 6515 align.jpg [ 225.84 KiB | Viewed 337 times ]

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 Post subject: Re: On AM radio alignment the bands end and begin dont match
PostPosted: Nov Mon 27, 2017 4:05 am 
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Location: shirley NY...Long Island
Jim....why would you align a radio to outside of the tuning range? I did the alignment as per the instructions that fifties...and when setting it to 1650 and not the max range of the radio at 1600 when I went adjust the 1400 setting the dial was off...and it will be. That is why I set the align, top and bottom the freq range of the radio..is this wrong?

Its like step 4. when you set it for 600 on the generator...the dial will not be at 600 on the radio...so you will not hear the signal...and if you set it that way, both the same...then the upper end will be wrong...
How are you going to hear the signal of the generator, at 1650 when the radio wont go tune that high..it stops at 1600?

The range is 540~1600


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 Post subject: Re: On AM radio alignment the bands end and begin dont match
PostPosted: Nov Mon 27, 2017 4:22 am 
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Kennynva wrote:
How are you going to hear the signal of the generator, at 1650 when the radio wont go tune that high..it stops at 1600?

The range is 540~1600

OK, consider that in step one, with the tuning gang fully closed, it's ideally at about 540 Kc, BUT the generator is set to 455. The radio's RF circuits can't tune that frequency, but you can still get tone, and adjust the IF cans for the loudest audio.

The same would occur at the top of the dial, tuner fully un-meshed. At that frequency, about 1600 Kc per design, you would again ideally be able to receive a tone, even though the generator is set 50 Kc higher. For that, it's only adjusting the trimmer on the tuner, to set the upper frequency.

At 600 Kc you are adjusting the oscillator, which would be primary for establishing correct dial positions. At 1400, you are peaking the set's sensitivity.

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 Post subject: Re: On AM radio alignment the bands end and begin dont match
PostPosted: Nov Mon 27, 2017 4:49 am 
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I hear absolutely nothing when I tune the generator to 1650, and the radio to 1600...zero


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 Post subject: Re: On AM radio alignment the bands end and begin dont match
PostPosted: Nov Mon 27, 2017 4:53 am 
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Kennynva wrote:

Its like step 4. when you set it for 600 on the generator...the dial will not be at 600 on the radio...so you will not hear the signal...

This is where I suggest you start (after being sure the IF's are all correctly set at 455 Kc), setting the radio's osc slug to match 600 on the generator. Then advise how far up the dial tracking is correct, and how high it will tune.

BTW, are you certain that the generator is putting out valid frequencies? Have you verified it with a digital radio, or freq counter?

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 Post subject: Re: On AM radio alignment the bands end and begin dont match
PostPosted: Nov Mon 27, 2017 5:02 am 
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Location: shirley NY...Long Island
Yes I used an oscilloscope that has the measurements on it..of course anything can be out of calibration..but it is very close..
I have got it right...I was just asking why it was this way....
If the gen..is set to 540 and I set it there, it will be right at the other end...
It is strange how the 455 goes thru the radio, and the others dont..


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 Post subject: Re: On AM radio alignment the bands end and begin dont match
PostPosted: Nov Mon 27, 2017 5:15 am 
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I don't like using a 'scope for frequency measurements unless it has a digital readout and even then I'm sceptical.

Quote:
I hear absolutely nothing when I tune the generator to 1650, and the radio to 1600...zero


It doesn't tell you tune the gen to 1650 and the dial to 1600. It tells you to unmesh the tuning cap fully, ie. to the endstop. Set the sig gen to 1650 and then with the oscillator trimmer tune in the signal and tune to max.

The scale range may be 540 to 1600 but the maximum physical range can be greater than that.

Quote:
It is strange how the 455 goes thru the radio, and the others dont..


That is exactly the function of the IF amplifier - it does amplify only 455kHz +/- say 10kHz either side to accept only the station you select plus it's sidebands and reject all others

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 Post subject: Re: On AM radio alignment the bands end and begin dont match
PostPosted: Nov Mon 27, 2017 5:35 am 
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Location: shirley NY...Long Island
Yes it has a digital readout for freq...

The front for the radio starts at 540 and ends at 1600. That is the physical range.

Here is the range on the dial...and if I set the top range to 1650 it will be way off at say 900


Attachments:
IMG_1531.JPG
IMG_1531.JPG [ 169.49 KiB | Viewed 316 times ]
IMG_1530.JPG
IMG_1530.JPG [ 201.72 KiB | Viewed 316 times ]
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 Post subject: Re: On AM radio alignment the bands end and begin dont match
PostPosted: Nov Mon 27, 2017 12:09 pm 
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That dial is confusing.....I assume that you have to go by which of the small dashes the pointer is on. IOW, in your second picture, it's actually set pretty close to 1600.

As it sits right now, what frequency is received at each end of the rotation? ( not the dial reading, but the setting on the signal generator?)

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 Post subject: Re: On AM radio alignment the bands end and begin dont match
PostPosted: Nov Mon 27, 2017 12:33 pm 
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I've noticed that the dial markings on most consumer grade transistor radios only approximate the stations' actual frequencies. I think it's more important to get the best sensitivity tracking rather than the frequency tracking as long as the entire band is covered. Today, the AM broadcast band actually extends to 1700 kHz at the high end.

Open frame tuning caps often have bendable tabs on the outer rotor plates to adjust dial frequency tracking but this radio does not have that type of tuning cap.

Dave


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 Post subject: Re: On AM radio alignment the bands end and begin dont match
PostPosted: Nov Mon 27, 2017 12:34 pm 
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The way I read the adjustments, you have 2 for the LO and 4 for RF peaking.

The 2 for the LO are the only ones to adjust when setting the dial tracking: A4 at the low end, and A5 at the high end.

Watch out for images and harmonics. Eg, if the dial is set at 600, you can get a response at both 600 and 1510 (generator setting). More generally, there can be a response whenever the difference between generator and LO (or their harmonics) is 455. If the "peaking" adjustments are way off....or the generator level is too high....images can be more of a problem.

Also, how are you coupling the generator to the radio?

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 Post subject: Re: On AM radio alignment the bands end and begin dont match
PostPosted: Nov Mon 27, 2017 7:55 pm 
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Location: shirley NY...Long Island
Pixellany, it has already been adjusted so couldn't tell you the high and low end...there is a dot at the top near 540, and that is where you set the indicator to so it will be right and I guess track as close as it can...
I set the low end to 530 and the high end to 1600, and tuned to a freq around 1000 to set the trimmer on the antenna. I mostly listen around 900 and 1010. Setting it this way made the indicator track very close...and the middle of the band is right and as loud as I can get it.

I was just looking at the dial again..and thought of something...If you put the pointer on the larger dash by 1600, it moves a little farther than the dash, maybe that is suppose to be the 1650. Its moves like an eight of an inch past the larger dash. But it still dont matter I cant hear it at 1650 with the dial all the way open.

Im ok with it now...I just wanted to ask how some people would do this.

Kenny KE4HVE


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