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More on Aligning the FT101 TX and Rx

FT-101/B/E/F Carrier Frequency Alignment Instructions

 

13 April 2006

 

Here is something you may want to add to your FT-101

instruction/maintenance manuals:

 

As another ham pointed out to me, neither the Instruction Manual

nor the Maintenance Service Manual for the FT-101 series of radios

seem to include alignment instructions for setting the

carrier-insertion frequencies for USB, LSB, AM/CW.  Normally,

they don’t need re-alignment, but sometimes they can go out if

someone has adjusted them hoping to correct some other problem

with the radio.  If these three oscillators are misaligned,

they can cause the quality of the transmitted and received

audio to sound bad.  Also, a misaligned carrier frequency can

leave an annoying carrier on your transmitted signal.

 

Other Yaesu radios include alignment instructions for these

oscillators.  My FT-101ZD, FT-901DM and Tempo One include them;

however, the information is also missing in my FTdx-560 manual.

If you have a digital frequency counter with a resolution of

100 kHz or better, and you can find the right sampling point,

you can get these oscillators pretty close by simply using the

frequencies printed on your schematic.

 

However, to do it properly, they really should be set to the

response curve of the crystal band-pass filter being used.

Not all of these filters are the same.  Aftermarket filters

often have steeper skirts or a narrower pass-band than OEM

filters and all of them can change slightly as they age.

 

Here are the cut-and-paste carrier frequency adjustment

instructions for the FT-101/B/E/F circuits as adapted from

the FT-101ZD manual.  The parts in brackets are where I made

the changes from the original FT-101ZD manual to fit the different

IF frequency, part numbers and circuit layout of the FT-101/B/E/F

series.  Notice that the carrier adjustment can mess up the carrier

balance on sideband as well, so don’t forget to make that your

final adjustment.

 

* * *

 

A.  SSB Carrier Point

 

1.  Tune up the transmitter on 20 meters,

LSB mode, into a dummy load.  Apply a

1 kHz audio signal to the microphone

input, and adjust the audio generator

output until the transmitter power output

is 60 watts, as indicated on the dummy

load wattmeter.

 

2.  Shift the audio generator output

frequency to 300 Hz, without changing

the output level.  Adjust [TC3] for a

power output reading of 15 watts on the

wattmeter.

 

3.  Shift the MODE switch to USB.

Adjust [TC2] for an identical 15 watt

reading on the wattmeter.

 

4.  Recheck the LSB adjustment, as

well as the carrier balance adjustment,

after performing the carrier point

alignment.  The background noise,

when switching between USB and LSB,

should not change.

 

B.  Carrier Balance

 

[This description is essentially the same

as the one in the FT-101/B/E/F instruction

and maintenance service manuals, so you

can just insert that part here.]

 

C.  CW Carrier Point

 

1.  Connect a frequency counter to

[a test point on circuit board PB-1183,

at the common junction of C11, C12,

R8, R9, D3, and D4.  The lower end of

C11 should be the easiest tap point.]

Place the MODE switch in the TUNE

position.

 

2.  Adjust [TC4] for a frequency counter

reading of exactly 3179.3 kHz.

 

3.  When using the optional CW filter, a

substantial loss on transmit, when in the

[CW] position, may indicate the need for

adjustment as indicated in steps 1 and 2.

 

* * *

 

If you don’t have a calibrated audio signal generator,

there seem to be a lot of software programs on the

internet that use the soundboard in a personal computer

as a calibrated audio generator.

 

If anyone has any comments, suggestions, additions or

alternative methods of carrier alignment for these radios,

let me know and I’ll try to do an update to this file from

time to time.

 

 

— John (N0BUP)     (jpkiljan atsymbolthingy yahoo.com)

 

(file:  101CarrierAlign.doc)

 

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