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Re: FT-301D: Transmit audio quality

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Oh. And PS. I modified a few of the IF boards per Roland. He’s a smart guy, has a doctorate in electronics! Way smarter than me but the IF mod didn’t work right. Had a side effect so I put all of them back to stock. I think he’s close with his theory that there is an impedance issue with the filter board

On Feb 19, 2025, at 10:16 AM, atlasstuff via <g4fph@...> wrote:

Digging into this a little more today.
?
Using my SDR transceiver as a narrow-band, RF spectrum analyser, I checked the DSB TX IF signal going into the Filter Unit. Audio fidelity from the mic. I selected as best match to the '301 (an old Astatic MOD. 575-M6) was very good, with modulation sidebands extending to at least 4 kHz either side of the (suppressed) carrier, and with some signs of roll-off from around 3.3 kHz. So, I think the issue is likely to be the response of the second crystal filter on the NB (/ RF Processor) Unit.
?
Even with the processor turned off, the (now SSB) TX IF signal still passes through this second filter, which seems like an odd decision by the Yaesu design engineer(s). I see references in the service manual that the filter is optional, but I think it is present in all three of the transceivers (one -301 and two -301D) that I own. It's not listed as an option in the English brochure that I have a PDF of.
?
Later this week, I will pull a complete NB Unit from another '301 and try it instead of the one I have been using. Depending on results, I may even try removing the filter on the NB Unit to see what difference it makes. I assume it is present principally to clean up artifacts arising from the RF clipping process, so it would be nice to retain it for that. Perhaps a modification is possible...?
?
I note that 'ELcon' () published a modification for the Filter Unit that better terminates the filters in order to improve the response on USB. My testing has all been on LSB so far.
?
Regards,
?
Mark, G4FPH.
?
Re: FT-301D: Transmit audio quality

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The filter on the NB board is only on the hi power models. Forget the computer stuff. You need a tone generator and a signal generator. I use a IFR 1200S and a Motorola two tone generator to adjust the SSB osc's. That is an EXCELANT mic!! Very valuable today. I used to sell them in my store for about sixty bucks. I have a few. With a stock mic I get people asking what mic I’m running? I run 301’s on all bands using transverters and Swiss displays and VFO stabilizers. Whens the last time you worked AM on 220 mhzs? Hi hi
Do you want a copy of the 9mhz alignment? There never was a service manual and the latest owners manual was obsolete when it was printed and can’t be trusted. The key is to listen to the receive signal on USB and LSB. They won’t be the same. That’s the problem. Your on it but it takes a bit of doing to tune it up right.

Dave

On Feb 19, 2025, at 10:16 AM, atlasstuff via <g4fph@...> wrote:

Digging into this a little more today.
?
Using my SDR transceiver as a narrow-band, RF spectrum analyser, I checked the DSB TX IF signal going into the Filter Unit. Audio fidelity from the mic. I selected as best match to the '301 (an old Astatic MOD. 575-M6) was very good, with modulation sidebands extending to at least 4 kHz either side of the (suppressed) carrier, and with some signs of roll-off from around 3.3 kHz. So, I think the issue is likely to be the response of the second crystal filter on the NB (/ RF Processor) Unit.
?
Even with the processor turned off, the (now SSB) TX IF signal still passes through this second filter, which seems like an odd decision by the Yaesu design engineer(s). I see references in the service manual that the filter is optional, but I think it is present in all three of the transceivers (one -301 and two -301D) that I own. It's not listed as an option in the English brochure that I have a PDF of.
?
Later this week, I will pull a complete NB Unit from another '301 and try it instead of the one I have been using. Depending on results, I may even try removing the filter on the NB Unit to see what difference it makes. I assume it is present principally to clean up artifacts arising from the RF clipping process, so it would be nice to retain it for that. Perhaps a modification is possible...?
?
I note that 'ELcon' () published a modification for the Filter Unit that better terminates the filters in order to improve the response on USB. My testing has all been on LSB so far.
?
Regards,
?
Mark, G4FPH.
?
Re: FT-301D: Transmit audio quality

[email protected]
 

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The 301 had a couple of bugs out of the gate. One is the “crab walk” problem on the pre-mix board and the other major one is the one your working on. I wrote an a alignment procedure for the one your on. Seems like an impedance mis match going onto the filter board. As you indicated ?the carrier point that is how I resolved that. Built many of them and they all sound great with good audio reports. To long to go into but can forward alignment instructions if you wish. No need to change anything just realign. I have many parts and spare radios. I thought they would be worth something someday but was wrong. Today, if it doesn’t have a computer connection, what good is it. The Elcon library is a good place to look also.
Dave

On Feb 19, 2025, at 3:18 AM, atlasstuff via <g4fph@...> wrote:

Hi to all in the group!
?
I'm close to the end of repairing an FT-301D transceiver and trying to get the transmitted audio quality sounding anything like 'nice'. It's proving surprisingly challenging.
?
Looking at the transmitted RF spectrum, one issue would seem to be that the SSB filter response is very narrow - more like 2.0 kHz rather than the supposed 2.4 kHz. I've tried moving the carrier point around and different microphones, all with no real improvement. This morning, I grabbed a Filter Unit from my spare radio and tried that. No real improvement:-(
?
I imagine it's possible that the crystals in both SSB filters I have tried have aged the same way and their responses have degraded. If that is the case, then I'm stuck with the problem. I do have a minVNA and could remove the filter to test it, but it would be nice not to have to. The receive audio response with either filter sounds generally OK.
?
I'm wondering whether aged coupling capacitors in the mic. amp. could also be a factor. I've not looked into that as yet.
?
Any experience out there of this issue?
?
Regards,
?
Mark, G4FPH.
?
Re: FT-301D: Transmit audio quality

 

Dave,

Thanks for the mails.

Yes, please send a copy of your alignment procedure. You clearly have a lot of experience with these old things.

Agreed, no service manual, as such (not like for the FT-221R and FT-101E). I was following the alignment in the back of the regular / user manual.

I've tried setting the carrier oscillator frequencies to their book values. The LSB one nets just fine, but the USB one doesn't quite get there - it's about 100 Hz shy. I'll look at that in due course. I also tried varying the LSB one to give optimum audio, but made no real improvement - still sounded cruddy to my ears.

Interesting that the extra filter was only on the qro version (which all mine are). I've sketched out a simple mod. that would bypass this filter when processor = off, if needed.

Regards,

Mark.

‐‐------------------------------------
Mark Hill - G4FPH


Sent from a mobile device
------‐-------------------------------
On 19 Feb 2025, at 18:47, n0eds@... wrote:

The filter on the NB board is only on the hi power models. Forget the computer stuff. You need a tone generator and a signal generator. I use a IFR 1200S and a Motorola two tone generator to adjust the SSB osc's. That is an EXCELANT mic!! Very valuable today. I used to sell them in my store for about sixty bucks. I have a few. With a stock mic I get people asking what mic I’m running? I run 301’s on all bands using transverters and Swiss displays and VFO stabilizers. Whens the last time you worked AM on 220 mhzs? Hi hi
Do you want a copy of the 9mhz alignment? There never was a service manual and the latest owners manual was obsolete when it was printed and can’t be trusted. The key is to listen to the receive signal on USB and LSB. They won’t be the same. That’s the problem. Your on it but it takes a bit of doing to tune it up right.

Dave

On Feb 19, 2025, at 10:16 AM, atlasstuff via <g4fph@...> wrote:

Digging into this a little more today.
?
Using my SDR transceiver as a narrow-band, RF spectrum analyser, I checked the DSB TX IF signal going into the Filter Unit. Audio fidelity from the mic. I selected as best match to the '301 (an old Astatic MOD. 575-M6) was very good, with modulation sidebands extending to at least 4 kHz either side of the (suppressed) carrier, and with some signs of roll-off from around 3.3 kHz. So, I think the issue is likely to be the response of the second crystal filter on the NB (/ RF Processor) Unit.
?
Even with the processor turned off, the (now SSB) TX IF signal still passes through this second filter, which seems like an odd decision by the Yaesu design engineer(s). I see references in the service manual that the filter is optional, but I think it is present in all three of the transceivers (one -301 and two -301D) that I own. It's not listed as an option in the English brochure that I have a PDF of.
?
Later this week, I will pull a complete NB Unit from another '301 and try it instead of the one I have been using. Depending on results, I may even try removing the filter on the NB Unit to see what difference it makes. I assume it is present principally to clean up artifacts arising from the RF clipping process, so it would be nice to retain it for that. Perhaps a modification is possible...?
?
I note that 'ELcon' () published a modification for the Filter Unit that better terminates the filters in order to improve the response on USB. My testing has all been on LSB so far.
?
Regards,
?
Mark, G4FPH.
?

Re: FT-301D: Transmit audio quality

 

Digging into this a little more today.
?
Using my SDR transceiver as a narrow-band, RF spectrum analyser, I checked the DSB TX IF signal going into the Filter Unit. Audio fidelity from the mic. I selected as best match to the '301 (an old Astatic MOD. 575-M6) was very good, with modulation sidebands extending to at least 4 kHz either side of the (suppressed) carrier, and with some signs of roll-off from around 3.3 kHz. So, I think the issue is likely to be the response of the second crystal filter on the NB (/ RF Processor) Unit.
?
Even with the processor turned off, the (now SSB) TX IF signal still passes through this second filter, which seems like an odd decision by the Yaesu design engineer(s). I see references in the service manual that the filter is optional, but I think it is present in all three of the transceivers (one -301 and two -301D) that I own. It's not listed as an option in the English brochure that I have a PDF of.
?
Later this week, I will pull a complete NB Unit from another '301 and try it instead of the one I have been using. Depending on results, I may even try removing the filter on the NB Unit to see what difference it makes. I assume it is present principally to clean up artifacts arising from the RF clipping process, so it would be nice to retain it for that. Perhaps a modification is possible...?
?
I note that 'ELcon' () published a modification for the Filter Unit that better terminates the filters in order to improve the response on USB. My testing has all been on LSB so far.
?
Regards,
?
Mark, G4FPH.
?
FT-301D: Transmit audio quality

 

Hi to all in the group!
?
I'm close to the end of repairing an FT-301D transceiver and trying to get the transmitted audio quality sounding anything like 'nice'. It's proving surprisingly challenging.
?
Looking at the transmitted RF spectrum, one issue would seem to be that the SSB filter response is very narrow - more like 2.0 kHz rather than the supposed 2.4 kHz. I've tried moving the carrier point around and different microphones, all with no real improvement. This morning, I grabbed a Filter Unit from my spare radio and tried that. No real improvement:-(
?
I imagine it's possible that the crystals in both SSB filters I have tried have aged the same way and their responses have degraded. If that is the case, then I'm stuck with the problem. I do have a minVNA and could remove the filter to test it, but it would be nice not to have to. The receive audio response with either filter sounds generally OK.
?
I'm wondering whether aged coupling capacitors in the mic. amp. could also be a factor. I've not looked into that as yet.
?
Any experience out there of this issue?
?
Regards,
?
Mark, G4FPH.
?
Re: Vox circuit problem

 

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Hi Chaz

?

The problem is known to occur with the VOX-UNIT on a >40 year old device.

Q604 is only a comparator that switches the relay RL-1 (TX) when pin6 is LOW.

?

This can have the following causes:

  1. the ANTI TRIP circuit has no effect on the comparator getting a LOW level on Q604/Pin6.
    It is rather the opposite if e.g. C620 (10uF) makes a short circuit.
  2. the VOX AMP circuit is more likely to be a fault candidate. For example, C613 (2.2uF) can leak,
    and pull the level to GND via R639 (1k) on Q604/Pin6.
  3. also keep an eye on the transistor Q603 (2SC373). If this has a short circuit C-E,
    then the level at Q604/Pin6 is pulled to GND.

?

Good luck and best 73 de Roland, HB9GAA

?

?

?

HB9GAA
Brunnhaldenstrasse 8
3510 Konolfingen
Switzerland

Tel: 41 (0)31 792 04 60
Mail: hb9gaa@...

?

Von: [email protected] <[email protected]> Im Auftrag von Chaz Smith via groups.io
Gesendet: Samstag, 11. Januar 2025 03:18
An: [email protected]
Betreff: [yaesuft301d] Vox circuit problem

?

Hi, all, I see there was some other thread about a vox problem, but no resolution posted. ?I’ve been tracing the schematic and reading the manual and taking measurements, but I’m having an issue that my vox is always on no matter what. ?This came on suddenly, one time I powered on the radio and it went straight into continuous tx and will not exit to rx. ?The big Rl-1 clicks and it goes straight to tx on power up every time.

?

To use the radio, I found that I can disconnect pin 4 of Q604 on the vox card. ?This is the output of the SN 72560 level detector. ?With this disconnected, the radio receives as normal, and transmits on keying the mic.

?

I replaced that Q604 chip, but still have the same problem.

?

This is where I’m getting confused: if I measure the voltage to ground of the blue mic wire (it normally connects to pin 4 of Q604) without Q604 connected, it is at 13.8v on rx and 0v on tx. ?So it would appear that the 604 chip would need to hold that line at 13.8 or similar volts to not close the RL-1 relay and send the unit into tx mode. ?However, the supply voltage to Q604 is only 6 volts. ?So how does a 6 volt supply turn off the relay? ?With that chip connected, the unit goes straight to tx mode, and the voltage on the output of Q604 goes to about 3.5 volts.

?

Monitoring the input to Q604, it drops when I speak in the mic and goes up again when quiet, so the mic side of the vox would seem fine.

?

Wonder if anyone else has had issues like this, or can suggest a possible solution.

?

Thanks in advance…

?

Chaz, KC3ZPB
Vox circuit problem

 

Hi, all, I see there was some other thread about a vox problem, but no resolution posted. ?I’ve been tracing the schematic and reading the manual and taking measurements, but I’m having an issue that my vox is always on no matter what. ?This came on suddenly, one time I powered on the radio and it went straight into continuous tx and will not exit to rx. ?The big Rl-1 clicks and it goes straight to tx on power up every time.
?
To use the radio, I found that I can disconnect pin 4 of Q604 on the vox card. ?This is the output of the SN 72560 level detector. ?With this disconnected, the radio receives as normal, and transmits on keying the mic.
?
I replaced that Q604 chip, but still have the same problem.
?
This is where I’m getting confused: if I measure the voltage to ground of the blue mic wire (it normally connects to pin 4 of Q604) without Q604 connected, it is at 13.8v on rx and 0v on tx. ?So it would appear that the 604 chip would need to hold that line at 13.8 or similar volts to not close the RL-1 relay and send the unit into tx mode. ?However, the supply voltage to Q604 is only 6 volts. ?So how does a 6 volt supply turn off the relay? ?With that chip connected, the unit goes straight to tx mode, and the voltage on the output of Q604 goes to about 3.5 volts.
?
Monitoring the input to Q604, it drops when I speak in the mic and goes up again when quiet, so the mic side of the vox would seem fine.
?
Wonder if anyone else has had issues like this, or can suggest a possible solution.
?
Thanks in advance…
?
Chaz, KC3ZPB
Re: 10 watt amp finals needed

 

Thanks !!!? This morning I found one on ebay and if it is a dud, I will get back to you.

Bob..KH2BR
Re: 10 watt amp finals needed

[email protected]
 

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I’ve probably got some driver boards untested. I have lots of parts, Bob. I’m just about to fire up this 301s ?7 H xxxxxx

On Jun 18, 2024, at 8:07 AM, Robert Holsti via <kh2br.w6@...> wrote:

Does anyone have or know of a substitute for the 10 watt amp finals ??
the original part number is a s10-12

Rober KH2BR
10 watt amp finals needed

 

Does anyone have or know of a substitute for the 10 watt amp finals ??
the original part number is a s10-12

Rober KH2BR
Re: To Dave Bohlen CW filter.

 

It is a FT301 analog that needs the amp and is arriving thursday. It may need other things so I better wait so please reserve a 600hz filter for me and the amp if you have one. I could use my Juma amp if not. Here is my direct e$mail and you will have to
remove the ft301 from the start and end plus replace AT with the @ symbol and Dot with a period.

FT301rholstiATicloudDOTcomFt301? here is my p$hone number and the same thing?
remove ft301 from the start and end and remove the @ symbol.? FT3019516@439026FT301.
Thanks and 73's,
Bob KH2BR
Re: To Dave Bohlen CW filter.

 

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I undestand completly Bob. I have a 600 khz filter as I had mentioned. 25 bucks.. I have also RF decks if you wish to put it on the back of the one you have coming. Make sure it isn’t an SD. SD’s were a stripped down version and were only 10 watts. Those are valuable because you can run a Ukrainian kit ?tranverter off of them easily. They can be upgraded but it is a bit of work. I’d swap you a high power one for it if it’s an “SD”. The SD does not have the plug on the back for the RF deck to plug into. Well it does but is covered by a hard to find SD cover.
Good luck on the new one. I wouldn’t buy anything with a serial # earlier than 77 G xxxxxx . ’76 and real early 77’s had the early filter board among other things. Some of them work ok. 77G xxxxxx and on are the best ones.
73Dave

On Jun 3, 2024, at 4:36 PM, Robert Holsti via <kh2br.w6@...> wrote:

[Edited Message Follows]

I have? radio number one that has only a ssb filter and it is strapped to the AM and CW position.

The problem with a ssb filter being used in CW is that strong stations near my operating frequency produce agc action and I have difficulty copying that weak cw station due to agc pumping. Thats why a cw filter is necessary. It? is very noticeable while there is a contest going on.

The radio number two has all 3 filters installed but the 250hz cw filter in the cw slot is to narrow. I like it but there are some guys that dont know how to zerobeat be so I dont hear them at all.?

I would never use a 250hz filter in AM mode, its to narrow.

The sotabeams filter works like a champ but you still suffer from agc action since it is hooked up to the earphone jack.

I have another FT301 arriving this week but it does not have the amplifier on the back
and the insides will be a mystery box with good or bad surprises.?

Bob KH2BR

?


--
Dave Bohlen
Re: To Dave Bohlen CW filter.

 
Edited

I have? radio number one that has only a ssb filter and it is strapped to the AM and CW position.

The problem with a ssb filter being used in CW is that strong stations near my operating frequency produce agc action and I have difficulty copying that weak cw station due to agc pumping. Thats why a cw filter is necessary. It? is very noticeable while there is a contest going on.

The radio number two has all 3 filters installed but the 250hz cw filter in the cw slot is to narrow. I like it but there are some guys that dont know how to zerobeat be so I dont hear them at all.?

I would never use a 250hz filter in AM mode, its to narrow.

The sotabeams filter works like a champ but you still suffer from agc action since it is hooked up to the earphone jack.

I have another FT301 arriving this week but it does not have the amplifier on the back
and the insides will be a mystery box with good or bad surprises.?

Bob KH2BR

?
Re: To Dave Bohlen CW filter.

 

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Not sure I follow Bob. Did you strap the SSB filter to the CW filter slot on the filter board? I actually have a mod to ?select all there filters on the front panel but it’s a lot of work. AM filter 250! Ouch. But CW filters are common 25 bucks. I have plenty. When you select CW do you get IF noise? If it goes dead then all you need to do is strap the SSB filter in. I do enjoy a CW filter but have no problem using SSB filter on CW.
73
Dave

On Jun 3, 2024, at 2:29 PM, Robert Holsti via <kh2br.w6@...> wrote:

I dont know how to send a private message on here, so this is the only way.

Dave How much do you want for the 600HZ cw filter?? I discovered that the SSB filter will not cut it in CW mode. Or Do you know how to force the filter I have to increase its band pass ??

Bob KH2BR



--
Dave Bohlen
To Dave Bohlen CW filter.

 

I dont know how to send a private message on here, so this is the only way.

Dave How much do you want for the 600HZ cw filter?? I discovered that the SSB filter will not cut it in CW mode. Or Do you know how to force the filter I have to increase its band pass ??

Bob KH2BR
Re: Mode switching problem or normal operation ?

 

Ok, Here is the symptom. Even with the symptom and it is not a solid fail. The radio works ok even with the symptom.
with no key plugged into the key jack, rotating the mode switch thru all of its positions,
no relays click which is good.

Plug the key into the key jack, starting from the cw position, rotate the mode switch left to the USB position. Result is that the t/r relay clicks. You can hear it and see it.?

I have 2 radios that I swapped the boards out with and the relay still clicks with the cw key plugged into the key jack. That mode switch sure has a lot of wires on it. I am not in a desperate
position with the need to swap it out with my parts rig since the radio works. I dont want to give to much information right now but that may come later. (information over load )

Bob KH2BR

?
Re: Mode switching problem or normal operation ?

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That sounds like a fun problem. I need to hear the symptoms again. I ran into something similar once and it was a problem with the VOX stuff I haven’t worked on one of those in years and the memory isn’t what it used to ?be. Hi I could put a mule on the bench and compare voltage reading with you.
Dave

On Jun 2, 2024, at 7:40 AM, Robert Holsti via <kh2br.w6@...> wrote:

[Edited Message Follows]

Turning the anti trip did not work, swapping out the vox unit board did not help so today I will spend my time tracing wires.
Robert KH2BR

Re: Mode switching problem or normal operation ?

[email protected]
 

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The manual is just better than nothing barely. Hi

On Jun 2, 2024, at 7:40 AM, Robert Holsti via <kh2br.w6@...> wrote:

[Edited Message Follows]

Turning the anti trip did not work, swapping out the vox unit board did not help so today I will spend my time tracing wires.
Robert KH2BR

Re: Mode switching problem or normal operation ?

 

600 is to wide.. I have a sotabeams DSP filter here that I will try. It may be better then any mechanical filter. They have trace comparisons between a collins filter and sotabeams. Very impressive difference.. take a look. ? ?
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