Is this what receive alignment means ?

[Limeybastard]

Was basically listening earlier on AM and some local on ch 27,2850 , sounded good but when I adjusted my frequency display to 27,2870 he sounded a bit better.

How does one know if their receive or transmit is out of whack , or cant they? Earlier, I was playing around on lsb 27,7900 , they guy I made contact with said I was on the wrong frequency or something, I dont recall his exact words but i think he said they were a few Hz higher or lower than what I was dialed in ( 27,7900 ) , i think he said he was on 277890 or something.

 

[Robb]

Center freq in any radio is setup in the TX circuit, and the receiver uses that freq to receive,

So your radio may be out of alignment if what you said is true.

But I doubt it is as far out as you said, otherwise you wouldn't even hear him and talk to him at all.

Probably off a few hundred Hz.

 

[nomadradio]

What you saw is pretty ambiguous.

Was the station you heard transmitting off frequency?

Only way to establish if your receiver is off frequency is to feed the correct frequency into it. A weak signal is best, so you can hear the noise along with your AM signal. When the pitch of that noise is at its lowest, you are tuned on frequency. Shifting the radio's clarifier will cause the pitch of that noise to rise on either side of the receiver's internal center frequency.

But you did not have an accurate reference to compare. Like I said, the other guy might have been off frequency.

But that's the only way I know to test the accuracy of a receiver's frequency. With a signal you know to be on frequency, to feed into it. A calibrated signal generator is the usual test-bench method.

The term "alignment" generally refers to all the variable adjustment components inside the radio. Only some of them set the receiver's frequency. Other adjustments are "peaked" to optimize the sensitivity of the receiver, and to set the range of frequencies it will cover before the sensitivity falls off.

It's always possible for a radio to transmit on frequency, and the receiver to be 'offset' to one side or the other of that frequency. All radios are not created equal, so this will depend on its internal design.

More than once we have seen radios built by RCI that use a black-plastic "ceramic" IF filter in the 455-kHz section AM-only of the receiver. Sometimes that filter will be off frequency by as much as 2 kHz. Just a possibility. If you have a signal generator that can feed 455 kHz into the radio, this is easy to determine. And if you don't, there's no good way to tell.

73

 

[Limeybastard]

What you saw is pretty ambiguous.

Was the station you heard transmitting off frequency?

Only way to establish if your receiver is off frequency is to feed the correct frequency into it. A weak signal is best, so you can hear the noise along with your AM signal. When the pitch of that noise is at its lowest, you are tuned on frequency. Shifting the radio's clarifier will cause the pitch of that noise to rise on either side of the receiver's internal center frequency.

But you did not have an accurate reference to compare. Like I said, the other guy might have been off frequency.

But that's the only way I know to test the accuracy of a receiver's frequency. With a signal you know to be on frequency, to feed into it. A calibrated signal generator is the usual test-bench method.

The term "alignment" generally refers to all the variable adjustment components inside the radio. Only some of them set the receiver's frequency. Other adjustments are "peaked" to optimize the sensitivity of the receiver, and to set the range of frequencies it will cover before the sensitivity falls off.

It's always possible for a radio to transmit on frequency, and the receiver to be 'offset' to one side or the other of that frequency. All radios are not created equal, so this will depend on its internal design.

More than once we have seen radios built by RCI that use a black-plastic "ceramic" IF filter in the 455-kHz section AM-only of the receiver. Sometimes that filter will be off frequency by as much as 2 kHz. Just a possibility. If you have a signal generator that can feed 455 kHz into the radio, this is easy to determine. And if you don't, there's no good way to tell.

73

Thanks for explanation, must admit didnt understand all of it, but some of it , better than none of it ;-)

So when i scroll through the SSB frequencies, sometimes i hear the fast pitched or slow pitched audio, i turn my clarifier knob and adjust it okay, but sometimes no matter what turning of the clarifier , the audio sounds slow or fast pitched. Im assuming they are either A out of range or B I'm not on the correct frequency to hear them, so in turn I select the sht button move my cursor on the frequency display to Hz and adjust up or down to fine tune it, but still cant get them sometimes. Albeit this wasnt my original question/ query.

 

[nomadradio]

Still haven't told us what kind of radio.

They're not all the same.

73

 

[Robb]

IF the clarifier is unlocked; then it will be on the same RX freq as the TX freq.

CB radios come from the factory with the clarifier locked.

Export radios have an unlocked coarse clarifier and a locked fine clarifier.

 

[Limeybastard]

Still haven't told us what kind of radio.

They're not all the same.

73

Its a RCI 2970n4

 

[StrangeBrew]

....
More than once we have seen radios built by RCI that use a black-plastic "ceramic" IF filter in the 455-kHz section AM-only of the receiver. Sometimes that filter will be off frequency by as much as 2 kHz.
....

I see aftermarket 455kHz crystal filters for shortwave filters are available, could one of these be used as an upgrade in a CB and/or export?

 

[Tallman]

Send it off for repair. The radio I adjusted for the reading below took me 30 minutes to achieve this near perfect reading. It's just ONE HERTZ off from perfect.

 

[Limeybastard]

So I was listening to SSB channel a few moments ago, the guy talking sounded a little fast pitched on first image so when I adjusted the frequency to the second image frequency he sounded relatively normal. Bearing in mind the clarifier knob is central. 2Khz? Then again, he was the strongest signal, but other weaker signals sounded "normal" on 27,3850.
I assume if he was ON frequency attempting to communicate with him on frequency 273848 would render me off frequency for tx?

EDIT: This is getting more confusing, there was about 2 or 3 others on the above channel SSB, some sound normal on 273850 but some high pitched, adjusting the frequency to 273848 made those sound normal but then the one I could here normal before on 273850 no longer was normal LOL

 

[rabbiporkchop]

There's more to a receiver alignment than turning screws. changing resistor values to alter AGC timing, and changing capacitors to alter frequency response of the incoming signal are a couple things involved.

 

[Limeybastard]

There's more to a receiver alignment than turning screws. changing resistor values to alter AGC timing, and changing capacitors to alter frequency response of the incoming signal are a couple things involved.

I appreciate that, and I wouldnt dream of turning those screws. A no tools and equipment and B no knowledge lol

Was hoping someone could explain what it occuring. Or possibilities of what is happening.

 

[StrangeBrew]

With an AM signal the carrier is transmitted with the signal, since the carrier and modulated signal come from the same source they will usually be where they need to be in relation to each other.

On SSB in order to increase efficiency the carrier is filtered out at the transmitter so all available TX power can be used for modulated output, then a carrier is generated within your receiver and mixed with the incoming signal. Since the carrier and modulation are now coming from two different sources they may not be where they need to be in relation too each other and adjustments need to be made, this is why you use a clarifier on SSB but not AM.

When receiving multiple signals from multiple sources it gets interesting because you can only tune your clarifier to one at a time, how good other signals that are being received sound will depend on how close they happen to be to the station your clarifier is tuned to.


PS: This probably isn't 100% accurate from a pure technical standpoint but should give you an idea of what's going on.

 

[Limeybastard]

With an AM signal the carrier is transmitted with the signal, since the carrier and modulated signal come from the same source they will usually be where they need to be in relation to each other.

On SSB in order to increase efficiency the carrier is filtered out at the transmitter so all available TX power can be used for modulated output, then a carrier is generated within your receiver and mixed with the incoming signal. Since the carrier and modulation are now coming from two different sources they may not be where they need to be in relation too each other and adjustments need to be made, this is why you use a clarifier on SSB but not AM.

When receiving multiple signals from multiple sources it gets interesting because you can only tune your clarifier to one at a time, how good other signals that are being received sound will depend on how close they happen to be to the station your clarifier is tuned to.


PS: This probably isn't 100% accurate from a pure technical standpoint but should give you an idea of what's going on.

Cheers, so the caller 169 from tennessee, he sounded better than most on 27,3850 his voice was ever so speeded up tiny bit even with my clarifier knonb at 12 o clock, but when i adjusted my freqency to 27,3848 it sounded spot on to me, but the weaker signals of the other folks speech was faster pitched now.

 

[StrangeBrew]

It doesn't take much of a frequency shift to effect the pitch of received voice communications, and even the fancy pants ham rigs ain't perfect.

On another note you'll hear a lot of arguments on the air about who's off frequency, try not to get involved in that stuff. Learning to use a clarifier is a part of the game, AM is the place to be if you just want to select a channel and talk.