Lafayette Telsat 140 alignment question

[Lkaskel]

Hi Gang,
I hope everyone had a wonderful Christmas holiday!!!
He is my challenge. I am aligning an SSB 140 recapped and fully stock. The clarifier is not even unlocked. When I go through the synthesizer alignment I am able to get it aligned perfect. The challenge is that once it's complete the transmitter is 200 low (27.184801) on channel 19 and all others. In this procedure you are adjusting the frequency on receive only. My freq counter is an HP5370B, 11 digit, calibrated at a lab in March of this year so I really trust the counter. Also, I have contacted a few folks on air, one with a Yaesu rig and he was able to track my transmit at 48 as well. The receive seems to be dead on as everyone sounds good with the clarifier centered. When aligning the synthesizer you are setting it to 10.240, 10.0525 and 10,695 for USB so you are not aligning it to a 27.185 like you would for some Uniden chassis for example. Can anyone explain what would cause the transmit to be off like this? Other parts of the alignment for both the receive and transmit are not adjusting to a frequency so I am unsure what to look for. Learning can be fun if you can keep it from driving you nuts

Thanks!!

 

[oldtymer]

200 cycles off in a radio that old is pretty good.
on AM it don't mean squat & on SSB they can tune you in.
Use it & enjoy the old gear, could just be parts aging & changing value.

 

[Lkaskel]

200 cycles off in a radio that old is pretty good.
on AM it don't mean squat & on SSB they can tune you in.
Use it & enjoy the old gear, could just be parts aging & changing value.

** I agree that it is possibly an effect of age and in the end it is ok but I am also interested in learning something here. I actually refurbish them (radios) and sell them as well so I want it to be as perfect as possible. In the end, if there is no way to figure this out or make the necessary changes it will be ok but it would also be nice to understand it.

 

[Robb]

Not familiar with the chassis you are working on. However, most SSB radios have a TX freq adjust VR on the board and is a part of the alignment procedure. Where did you find the alignment for it? Link?

BTW, just because the radio seems to be on freq to those you are listening to, it does not they are on freq. Chances are, one of them just tuned to the other using an unlocked clarifier.

 

[Lkaskel]

Not familiar with the chassis you are working on. However, most SSB radios have a TX freq adjust VR on the board and is a part of the alignment procedure. Where did you find the alignment for it? Link?

BTW, just because the radio seems to be on freq to those you are listening to, it does not they are on freq. Chances are, one of them just tuned to the other using an unlocked clarifier.

Hey Rob, a few of the folks I talk with locally use high end radios and I trust what I hear. Besides, I do compare it to other radios I have. I am sure that the receive is on and the transmit is off 200. I have the Sams manual for the radio as well as the owners manual that contains the alignment procedure for it. Both procedures are the same. Also, the board in this radio is the same one that is in a few others that I own like the GE side band mobile. This particular board does not seem to have a specific transmit freq adjustment. Some of the Uniden boards do so I will say that for this particular issue that would be helpful.

All The Best,

 

[Robb]

200hz is unacceptable.
I'd find a clarifier mod and then realign - IMO.

 

[todd chase]

Hi Larry,
I would try swinging the radio above your head in your right hand while hopping up and down on your left foot and spinning in a circle counter clockwise at the same time. This should solve all your problems.........I couldn't help myself lol
Todd

 

[Lkaskel]

Hi Larry,
I would try swinging the radio above your head in your right hand while hopping up and down on your left foot and spinning in a circle counter clockwise at the same time. This should solve all your problems.........I couldn't help myself lol
Todd

Seriously Todd? How would you think this was helpful? I did as you suggested I swung it by the power cord. The cord came out and the radio hit the ceiling fan. The ceiling fan fell onto the floor and broke into pieces. I had to lie to my wife and tell her that I was trying to peak the radio and I did such a great job that when I keyed it up it shot off of the table and did that damage. Now I need to repair the radio, replace the ceiling fan, clean up the mess and the radio is still 200 low. Thanks a lot buddy!!!!!

 

[Larry A McClanahan]

If you move it to a higher shelf that should solve the problem

 

[Lkaskel]

200hz is unacceptable.
I'd find a clarifier mod and then realign - IMO.

Robb, I agree that your suggestion would most likely fix it. I still want to understand why though. I WILL get this figured out. It is probably a resistor out of tolerance or something.

 

[nomadradio]

Newer models will have a trimmer pot that gets activated in transmit mode. It takes the place of the front-panel clarifier in transmit. That knob is only active in receive mode.

That's how the FCC rules require the manufacturer to build it. The rules say that only two knobs can control transmit. The channel knob and the mike gain. A knob that changes the transmit frequency is not allowed on the outside of the radio. Only on the inside, under a cover secured with screws.

If it had that "transmit" side trimpot, you would simply set to to agree with the frequency you get with the clarifier at 12 o'clock. But you would still be stuck transmitting to that frequency. No way to line up your transmit frequency with another station on the channel.

This radio just takes two fixed resistors and divides the clarifier voltage to around half the voltage that feeds to the clarifier in receive mode. You could monitor the radio's internal PLL frequency and turn the clarifier knob to agree with the transmit frequency.

This is one reason that modifying the clarifier to remain active all the time makes sense for this kind of radio.

For this kind of radio, we mount a tiny 8-Volt voltage regulator on the back of the clarifier control, and remove R24 and D5.

Don't have a 'how2' with detailed steps or pictures.

73

 

[Inquietude]

After looking over the schematic, I would absolutely agree with the above post and unlock. No TX adjustment present, so now you understand! A quick question for ya......what kind of power output does that rig have on SSB? My experience is that chassis has always been lackluster.Thanks.
73,
inquietude