Fine-tuning the Yaesu FT-891 Reference Oscillator
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- Опубліковано 15 жов 2024
- The Yaesu FT-891, like other Yaesu radios on the market today, has a menu option that allows us to find tune the reference oscillator. If you don’t have access to a frequency counter, this video shows a “poor man’s” way to check the accuracy of your reference oscillator, by checking it against WWV. The resolution of the FT-891 goes to 5 Hertz increments, so adjusting the reference oscillator using this method will get your radio within 5 Hertz accuracy. I hope you find this video informative and helpful.
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73, de N4HNH
Thanks for the video Doug - I just picked my first HF radio which happens to be the FT-891. I don't have much to compare it to but from my research I think I've got a radio to last me a long time! This feature is one of those things nobody would think to make a video on. 73 W0KNI
Thanks for reaching out, Stephen! I’m always glad to know that the videos have helped. 73, de N4HNH
@@n4hnhradio Yesterday I gave this a try. I found the tone on 15Mhz and pressed the Zero In option in the CW menu. It moved about +4 Hz. I went to calibration menu item and moved it up to max (25). I tried a few things but could only get to within +2 Hz of 15.000.000. Any thoughts? Or should I just move on and not really worry about it. 73
Stephen Payne, within 2 Hz is pretty good. The maximum offset is 25. On one of my 891’s I had to set to 25 to get to 1Hz. Be sure you have pitch set to 300, Also be sure that Fast isn’t enabled. Enable the ZIN LED, menu 02-06. Go to CW mode and adjust the VFO for the most blue from the LED.
@@n4hnhradio Thanks Doug, I'll give all that a try. Love this radio! Got it used for $400, and really happy with it.
That’s a great price, Stephen! 73, Doug
The General Test for the Amateur Radio License it states that an attenuated RF output of the transmitter is connected to the vertical input of an oscilloscope in order to check the RF envelope patter of a transmitted signal. Is the attenuated RF output the frequency counter? How can a connection take place to a device such as an oscilloscope?
The attenuated RF signal means that you lower the power of the transmitter to less than the maximum power that the oscilloscope allows.
At Motorola I used something called a service monitor. I could transmit directly into it as long as I did not exceed 125W. It could accurately display power, frequency, modulation envelope, etc. It was calibrated and certified for accuracy.
So let’s say that you are using an oscilloscope that has a 50-Ohm input rated for 0.5W. Let’s say that you are testing an HT that has a low power setting of 1W. You need 3dB of attenuation between the radio and the oscilloscope, in order to drop the power to 0.5W.
A dedicated frequency counter can detect a carrier in its vicinity. It will then display the actual carrier frequency. This frequency can be created by multiplying or dividing the frequency of the reference oscillator, so it is vitally important that the reference oscillator be accurate and stable. With the Yaesu FTdx10, for example, the reference oscillator is aligned by placing a frequency counter test probe directly to TP1097 (test point 1097). Then you go into the “secret” service menu and adjust for 250.000000 +/-20Hz. That’s the official method used by Yaesu. My on-air method works from the final Radio Frequency backwards, toward the reference oscillator. The “public” menu available to the operator allows for minor tweaking. That’s the method used in my video. No special equipment required. We are calibrating directly against the National Institute of Standards. Like I said in my previous post, the worst case is that the Beat Frequency Oscillator might be 1 or possibly 2 Hertz off. That is negligible.
How do you adjust the RF power? My 891 has no ears?
Are you referring to transmit power? That is in the menu, near the end. Long press the function button. There are separate settings for SSB, AM, CW, and 50MHz.
If you are referring to RF Gain, the default is the the our ring at top left, the ring around the volume knob, is RF Gain. But there is a menu choice to make it adjust squelch instead.
73, de N4HNH
@@n4hnhradio menu 16-1 through 16-3 ssb power, am power and hf power. Hf power controls the power on FM. I believe digital modes as well although I have not tested it yet.
I can't seem to get the blue light to stay on steady. It keeps flashing no matter what I do.
The stronger the signal, and the closer you are to the frequency that will produce your desired sidetone (CW pitch), the more steady the blue LED will illuminate. The ZIN function can automatically adjust the receiver for you.
But, remember don’t use ZIN on 60m. It can move you off frequency and inhibit transmit. Use APF to fine tune a CW station on 60m.
73, de N4HNH
@@n4hnhradio Okay that explains why you were monitoring the clock. I'll try that. I was on a Clear Channel. 73 DE N3QQB..
hi Doug GREAT WIDEO 4 ME FRECUANCY IS 14.090 AND 19.098 That IS ROMANIA Sibiu CIty
That’s interesting to know. Very different than our reference frequencies.