Yaesu FT-301 CW filter install
However, after installation, when I transmit on CW the power output is only 20W when the compressor is switched ON. When it is switched off it is 0W !
I thought the installation would be straight forward, what's going on?
The filter is in the RX IF stage, it has nothing to do with transmission.
Are you sure you didn't disturb something else?
Brian.
Yes sure I guess. It works fine on RX, although I noticed a very high pitch when switching the unit to the FSK option now that the CW filter is installed. It may be relevant it may not.
The filter unit has bridged the CW and AM pads with the SSB filter before, so that the SSB filter is used instead. At this point the TX was output 100W on CW. Now I just cut the CW bridge and installed the filter there. It works on RX because I can notice the noise difference and the CW signals passed, but no TX output on the CW setting.
Isn't the CW filter used for TX as well? Maybe it is not aligned with other parts of the circuit?
All the XF filters (including XF90C) are used on both, RX and TX.
In TX SSB mode, the DSB signal from the DSB modulator (D503, 504, 505 506) is going to the gate of the source follower Q403, and from there (through D405) exit the PB-1436C IF unit on pin 14 (RX IN/TX OUT), and from there to pin 17 of the Filter Unit (PB-1435). After filtering, the TX signal exit the filter unit on pin 6 (TX out).
In CW mode the DSB modulator is not used. The IF 9MHz CW signal is generated by CW OSC Q409, and after that is using the same source folower as the SSB path (Q403). From Q403 (the same as in SSB) the CW signal goes to the Filter Unit (pin 17).
If the TX power is low in CW, have to check using a scope the signal path in CW and maybe compare the levels to SSB path.
If the levels are the same (SSB and CW) at pin 17 of the filter unit, could be something wrong with the new filter (higher insertion loss, which you may not notice in RX mode).
Or the central frequency of the new XF90C doesn't match the CW carrier frequency (Q409).
Excellent, thanks a lot for the info!
I notice also that the mode, when set to RTTY, the audio is like there is a HPF, tinny.It might be the central frequency, I will check the things you mentioned and let you know.
Exactly. TC401, the trimmer that tunes the CW osc. It is also marked on the settings panel inside the radio as FREQ. (CW).
I tuned it for maximum TX power, which is now about 80W, so problem solved!
Do you think that the CW OSC is used at another point? I do not think so, but just to make sure it was not a mistake to tune it that way.
Sorry for my misinformation about being RX only. I've been hospitalized for a while with only my mobile phone so reading Yaesu schematics hasn't been easy!
It seems either the filter is slightly off frequency or more likely the CW oscillator has drifted over the years. Anyway, it seems fixed so 'well done!'.
Brian.
Brian, I hope it was not covid19. Either way, I wish you good luck with your health man!
Probably the second case a drifted crystal in the oscillator. But it may be common practice to do this frequency trimmer setting after installing a new CW filter. It is just this was not written in the manual. But in the plastic cover above the oscillator, there was clearly a marking for it for CW, so I bet it was a common thing to do.
The CW OSC signal is not going in other place. The Digital Display Circuit is using a different crystal reference oscillator.
The reason that you get a bit less power in CW (80W instead 100W) is because CW filters usually have a bit more insertion loss than SSB or AM ones (1dB up to 3dB more).
Yaesu should compensate somehow for this loss on TX path, but this is a very old transceiver, which otherwise it has a pretty quiet receiver.
Wish good health to everybody on this forum...
I got around 100W finally. I had to set the selector and the processor to on. It works just great and thank you, really helpful.
The receiver of the FT-301 is much quieter than the IC-728. I immediately noticed that when used the 301 for the first time. How can simple discrete devices offer better performance than ICs... Perhaps the fact that despite a decade or so older, the 301 was not an entry level set like the 728 was a decade later.
Just for the story, I have done this http://qrp.gr/ft301vfo on another set I have (the qrp S version) and it works well as a general coverage RX.
FT-301 was first built in 1976, more than four decades ago. Was the first solid-state HF transceiver in the world.
It is true, even if the new HF transceivers claim very low noise floor of -142dBm (some of them), nothing can beat the quietness of the old solid-state radios.
I mention "old solid-state radios", because also the old tube-radios were noisier than an "all dual-gate MOSFET" receiver. Here can be mentioned a long list of HF radios from that generation made by Yaesu, Kenwood, ICOM, JRC, Collins.
This would be interesting to know. And this can be told from people that have worked such radios and compared to new ones. Does it really have to do in general with the type of semiconductors used (dual gate mosfets) or is it some kind of ingenious discrete engineering from great engineers?
If it is the first, maybe in our hobbyist circuits we could use more and more these mosfets rather than bjt or ICs. Now this is very general, I know, but a clue would be useful.
I really wish it was Covid19! It's cancer I'm afraid.
Actually I was quite lucky, the hospital stopped all admissions the day after I left so it could be prepared to take Covid19 patients.
Brian.
Man, it's hard but try to relax. They say good psychology really makes a difference, it lets the body accept medicine better or heal itself in some cases. I am sure you have your own people, but we are here in this forum for anything we can do to make you feel better and recover well. That's the least we can do from 4.000 Km away!
Yours
Kostas sv3ora
Thanks for your good wishes Kostas.
I was diagnosed just over a year ago but this last trip was for biopsy to see how far it has spread. Too many needles for my liking!
I'm OK, still functioning normally but a little uncomfortable. Hopefully I've got a few years left to go!
On a plus point - I now know a lot more about anatomy... and how MRI scanners work!
Brian.
To cheer out, next time in the MRI scanner, hide a small ball neodymium magnet in your pocket. That will be fun! Not for the doctors though :))))
You kidding! - look at this: https://www.youtube.com/watch?v=6BBx8BwLhqg
It's bad enough that it rearranges your molecular spin, I think a magnet might take the short route from the pocket, straight through you.
Brian.