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LSB/USB ending frequency for alignment ???
- Thread starter 1iwilly
- Start date
so that is the offset you would see on a counter installed in the VCO section on TP1 that had an internal offset of 7.8mhz. like those little counters they sell on ebay.
Like Mike said, follow the procedure, as it sounds to me like you are mixing up two parts of the alignment.
first, don't try to use the radio's own counter for the alignment. it will just screw you up.
you need an external counter that you can trust, the kind with a BNC connector on the front.
sounds like you have one.
so, connect that counter to TP1 over near the VCO chip.
set radio to AM, channel 20, and tune for 35.0050 mhz.
now set USB for 35.00650, and LSB for 35.00350.
that sets the VCO freq to where when you mix it with the 7.8mhz IF alignment that comes next, the radio will mix the two frequencies together to get the 27mhz signal.
AM is easy.
if you have an RF sampler in line then you can just key into your dummy load with no modulation and read the 27mhz signal directly. Tune the AM IF can so that the counter reads 27.20500 coming out of the antenna socket.
(if you dont have a sampler then you can do a trick here. just pull the TP 7 and TP 8 wires from their pins near the main filter cap. this will keep voltage from going to the driver and final, but the radio will still output a tiny bit of signal so you can clip your test leads right to the antenna socket on the radio. be careful though! keying your radio into the counter this way with those wires connected is a recipe for a new counter)
once you get AM done, the idea is to get the SSB offsets set so that voice quality is the best it can be.
yes, you can set the SSB IF cans to the freqs listed in the service manual, but that assumes that the crystal filter in your radio is perfectly centered between those offsets.
that is very doubtful. more likely that filter is off just a bit and it is hard to tell where and how much.
so, instead of doing it the service manual way, try this:
do you have a signal generator that produces a 1khz tone for the receive alignment?
connect it to the radio, and input the 1k tone on channel 20. clarifier centered.
listen to that tone on AM.
now switch to USB.
is the tone higher or lower than the AM tone? switch back and forth so you know the difference in tone, and tune the USB IF can so the tones match.
now do the same thing on LSB. as you switch your mode switch back and forth through the modes, the idea is to get all the tones to sound the same.
(helps if you are musically inclined LOL)
that is your preliminary adjustment.
the final tune is best done with a good well known on frequency radio, like a modern ham radio. if you dont have one, maybe you have a friend that does that can transmit to you on SSB while you adjust the two SSB IF cans for best voice quality.
since you already pre-tuned them, they will require very little tweaking.
if you do have a known good radio to listen to yourself on, then just key the mic, and listen to yourself on it.
you will hear whether or not you sound more like Donald Duck or Darth Vader on that radio, and you will turn the appropriate can for that mode until you sound like you again.
do the same for the other mode and you're all set.
no, it doesn't sound that scientific, but as long as you can trust the radio you use for your reference, you will sound great on anyone else's radio that is on freq.
LC
Like Mike said, follow the procedure, as it sounds to me like you are mixing up two parts of the alignment.
first, don't try to use the radio's own counter for the alignment. it will just screw you up.
you need an external counter that you can trust, the kind with a BNC connector on the front.
sounds like you have one.
so, connect that counter to TP1 over near the VCO chip.
set radio to AM, channel 20, and tune for 35.0050 mhz.
now set USB for 35.00650, and LSB for 35.00350.
that sets the VCO freq to where when you mix it with the 7.8mhz IF alignment that comes next, the radio will mix the two frequencies together to get the 27mhz signal.
AM is easy.
if you have an RF sampler in line then you can just key into your dummy load with no modulation and read the 27mhz signal directly. Tune the AM IF can so that the counter reads 27.20500 coming out of the antenna socket.
(if you dont have a sampler then you can do a trick here. just pull the TP 7 and TP 8 wires from their pins near the main filter cap. this will keep voltage from going to the driver and final, but the radio will still output a tiny bit of signal so you can clip your test leads right to the antenna socket on the radio. be careful though! keying your radio into the counter this way with those wires connected is a recipe for a new counter)
once you get AM done, the idea is to get the SSB offsets set so that voice quality is the best it can be.
yes, you can set the SSB IF cans to the freqs listed in the service manual, but that assumes that the crystal filter in your radio is perfectly centered between those offsets.
that is very doubtful. more likely that filter is off just a bit and it is hard to tell where and how much.
so, instead of doing it the service manual way, try this:
do you have a signal generator that produces a 1khz tone for the receive alignment?
connect it to the radio, and input the 1k tone on channel 20. clarifier centered.
listen to that tone on AM.
now switch to USB.
is the tone higher or lower than the AM tone? switch back and forth so you know the difference in tone, and tune the USB IF can so the tones match.
now do the same thing on LSB. as you switch your mode switch back and forth through the modes, the idea is to get all the tones to sound the same.
(helps if you are musically inclined LOL)
that is your preliminary adjustment.
the final tune is best done with a good well known on frequency radio, like a modern ham radio. if you dont have one, maybe you have a friend that does that can transmit to you on SSB while you adjust the two SSB IF cans for best voice quality.
since you already pre-tuned them, they will require very little tweaking.
if you do have a known good radio to listen to yourself on, then just key the mic, and listen to yourself on it.
you will hear whether or not you sound more like Donald Duck or Darth Vader on that radio, and you will turn the appropriate can for that mode until you sound like you again.
do the same for the other mode and you're all set.
no, it doesn't sound that scientific, but as long as you can trust the radio you use for your reference, you will sound great on anyone else's radio that is on freq.
LC
thanks loosecannon the re-aligment came from putting the clarifier back to stock it was open i never had talk on LSB/USB so i won't be to picky with that as long as is what it calls for i have a 148 i can listen on if need be actually i have 3 counters a b&k 6 digits a dosy FC50P 6 digit and a EF-1000-7 DIGIT once again thanks i sent you a pm for that 5 pin mike jack
Attachments
@1iwilly - Just be patient.
Remember that the VOLUME of your 1kHz tone, has to be pretty small - they say about 30% when you measure.
Why?
What does this mean?
There is a bit of physics and math here but you have to at least be aware of this...
A Frequency counter - in order to work correctly, needs a reference oscillator - a known frequency to compare the counts it sees, to what it knows it can use to divide them by.
That's one crystal used for the counter.
The others are in the radio - one for the PLL - your "main reference" whether it'd be 10.240 or 11.325 MHz or something in between - there's another Crystal.
Then there's the intermediate frequencies...7.8MHz and your 10.69MHz
The last one is what your radio uses in SSB mode, your AN612 uses it, the audio from your 1kHz tone uses it, and it too gets combined into all of this.
So, really, you can have up to 4 crystal references all working against each others' own and any others externally.
So, don't make this harder, I find with all the different crystals, their "differences" between the one known reference it uses, and all those other external ones, why mess with that?
Just use (don't tune) the Good radio as your benchmark and tune your test radios using it make them all sound the same - and you'll be far better off.
Your situation of noticing all these different numbers and thinking that they all have to match up - your missing the point - or at least joy, of using SSB.
It's also why I have sold off the (only) one Cobra 148F-GTL I had
Remember that the VOLUME of your 1kHz tone, has to be pretty small - they say about 30% when you measure.
Why?
- well the radio can over-amplify the signal - start compressing it - making the signal more of a square wave or at least not as much a sine wave, as a skewed wave.
What does this mean?
- It means you can get goofy readings because the counters are "locking onto" what they think is a good frequency - what you're doing and what they read - may be two different things.
There is a bit of physics and math here but you have to at least be aware of this...
A Frequency counter - in order to work correctly, needs a reference oscillator - a known frequency to compare the counts it sees, to what it knows it can use to divide them by.
That's one crystal used for the counter.
The others are in the radio - one for the PLL - your "main reference" whether it'd be 10.240 or 11.325 MHz or something in between - there's another Crystal.
Then there's the intermediate frequencies...7.8MHz and your 10.69MHz
The last one is what your radio uses in SSB mode, your AN612 uses it, the audio from your 1kHz tone uses it, and it too gets combined into all of this.
So, really, you can have up to 4 crystal references all working against each others' own and any others externally.
This includes other radios
- - so the more you pay attention to making the tune up better using the "Good radio" you have for monitoring, the better off you are, because everyone else is using this "Good Radios'" circuitry like it, to listen to you.
- So the more effort you place in making your "test radio" work with your "Good Radio" - the one you tune that other radio to and make the two communicate - then you're in better condition than to settle for what 3 different signals referenced back to three different crystals and the external one on top of that for your 4th.
- - you can see where one error, can multiply itself by a factor of 4 and make it even a bigger mess.
So, don't make this harder, I find with all the different crystals, their "differences" between the one known reference it uses, and all those other external ones, why mess with that?
Just use (don't tune) the Good radio as your benchmark and tune your test radios using it make them all sound the same - and you'll be far better off.
Your situation of noticing all these different numbers and thinking that they all have to match up - your missing the point - or at least joy, of using SSB.
It's also why I have sold off the (only) one Cobra 148F-GTL I had
- - because of it's own desires to be different than anything else - took away from my enjoyment of radio because too many people are focused on the numbering results than the simple conversation you could be having.
thanks andy the confusion was on lsb/usb does it end i LSB-27.3840
or 27.3835 and USB 27.3860 or 27.3865
or 27.3835 and USB 27.3860 or 27.3865
Now, I must ask, what Frequency Counter are you using?
This becomes important because - a "simple external Counter - is only going to show what you put thru it. So it will see something.
Say you're on Channel 38...27.385 (AM)
Your counter seeing your 1kHz tone - would show 27.386/5/6/7/8/5 - fluttering - if you have a 5-digit counter.
Now, if you're using a INTERNAL counter - like Galaxy - they have an OFFSET programmed in - and you use the radios IF to do this trick.
1kHz tone in...
If the radio tuned to 38 - USB - will show 27.386/7/6 - flutter.
If the radio tuned to 38 - LSB - will show 27.385/4/5 - flutter
If the radio tuned to 38 - AM - Will show 27.385...- steady
Now, unkey, turn tone off.
Rekey radio - just throw dead carrier - no audio - and repeat doing the above...
Internal counter with Offset will show 27.385 - ALL modes - no audio.
External counter would show 0 (or close to) on USB
External Counter would show 0 (or close to) on LSB
External Counter would show 27.385 (your channel) on AM
So if you use INTERNAL counter and had to wire in Offset lines (Mode switch USB/LSB/AM) you're IF takes care of this frequency to display, and the counter OFFSETs to show you your "base" or starting Frequency.
External - needs a signal.
Internal - has a signal - calculates using OFFSET
They're all the same - you just have to focus on MODE...
This becomes important because - a "simple external Counter - is only going to show what you put thru it. So it will see something.
Say you're on Channel 38...27.385 (AM)
Your counter seeing your 1kHz tone - would show 27.386/5/6/7/8/5 - fluttering - if you have a 5-digit counter.
Now, if you're using a INTERNAL counter - like Galaxy - they have an OFFSET programmed in - and you use the radios IF to do this trick.
1kHz tone in...
If the radio tuned to 38 - USB - will show 27.386/7/6 - flutter.
If the radio tuned to 38 - LSB - will show 27.385/4/5 - flutter
If the radio tuned to 38 - AM - Will show 27.385...- steady
Now, unkey, turn tone off.
Rekey radio - just throw dead carrier - no audio - and repeat doing the above...
Internal counter with Offset will show 27.385 - ALL modes - no audio.
External counter would show 0 (or close to) on USB
External Counter would show 0 (or close to) on LSB
External Counter would show 27.385 (your channel) on AM
So if you use INTERNAL counter and had to wire in Offset lines (Mode switch USB/LSB/AM) you're IF takes care of this frequency to display, and the counter OFFSETs to show you your "base" or starting Frequency.
External - needs a signal.
Internal - has a signal - calculates using OFFSET
They're all the same - you just have to focus on MODE...
Also it's important to know that the counter is accurate meaning that it has been calibrated recently or you will never know if the measurements you are taking are correct and you could be making the radio worse.
Channel 35 SSB with the 1000hz tone should transmit LSB at 27.354 Mhz and USB at 27.356Mhz. Receive, of course would be the same frequency. The baseband frequency is 27.355Mhz so you deduct 1khz for LSB and add 1khz for USB
Goodluck