FT-101E Output Debate

[Champo]

This is a general question about AM output on an FT-101E. I had a discussion with a local yokel that claimed that he can get his FT-101E to key 20 watts while keeping it at the recommended 150mA i.c. and that it'll swing to 100 watts PEP using an amplified D104. I called BS. He's doing it on 11m (which I can't duplicate because mine isn't snipped) but on 10m and 15m the best I can get is an 18 watt key swinging to about 45 watts PEP in AM into a dummy. My FT-101E has full output on SSB. Was I wrong to call him a liar lol?

160m 90 watts
80m 140 watts
40m 140 watts
20m 140 watts
15m 135 watts
10m 120 watts

Thanks!

 

[nomadradio]

Ah, true "active meter" PEP? Or passive-meter PEP?

A FT-101 will typically deliver a higher PEP in AM mode than in SSB mode.

The SSB peak output is limited by the ALC, a circuit that monitors for grid current in the final tubes. At the first hint of grid current, the transmit gain is reduced. IMHO an incredibly clever way of doing this.

But in AM mode, no such limit is in place. Turn it up and you get burned rubber in this mode. And a few other parts we came to nickname collectively "11-meter burn". Parts in both the driver and final stages bear the stress of excess drive.

But apparently the sound of the waveform you get is found pleasing by those who cherish overdriven AM transmit. There is a trimmer capacitor in the dedicated AM modulator circuit. It will influence the ratio of peak modulated power to carrier power. Normally it's set for max forward swing short of where it distorts the peaks.

This ratio, of the minimum carrier power needed to maintain full modulated peak power is all over the map. Wasn't a controlled parameter spelled out in the specs, so what any one radio will do is kinda random. Anyone who sees more than a dozen of the same radio model will know that the max performance each one can deliver will not be exactly the same from one specimen to the next. You might have to turn the carrier up to 75 Watts before the modulated peaks stop increasing alongside the carrier level. Or the peaks may increase no further past the 15-Watt carrier level.

The average we have found for most of the E radios was between 20 and 45 Watts. There will always be a threshold carrier level where the modulation peaks won't increase any further with increased carrier.

And there is a way to fudge this and improve the 'swing ratio' of this model, but that will have to wait for another day.

73

 

[Champo]

Ah, true "active meter" PEP? Or passive-meter PEP?

A FT-101 will typically deliver a higher PEP in AM mode than in SSB mode.

The SSB peak output is limited by the ALC, a circuit that monitors for grid current in the final tubes. At the first hint of grid current, the transmit gain is reduced. IMHO an incredibly clever way of doing this.

But in AM mode, no such limit is in place. Turn it up and you get burned rubber in this mode. And a few other parts we came to nickname collectively "11-meter burn". Parts in both the driver and final stages bear the stress of excess drive.

But apparently the sound of the waveform you get is found pleasing by those who cherish overdriven AM transmit. There is a trimmer capacitor in the dedicated AM modulator circuit. It will influence the ratio of peak modulated power to carrier power. Normally it's set for max forward swing short of where it distorts the peaks.

This ratio, of the minimum carrier power needed to maintain full modulated peak power is all over the map. Wasn't a controlled parameter spelled out in the specs, so what any one radio will do is kinda random. Anyone who sees more than a dozen of the same radio model will know that the max performance each one can deliver will not be exactly the same from one specimen to the next. You might have to turn the carrier up to 75 Watts before the modulated peaks stop increasing alongside the carrier level. Or the peaks may increase no further past the 15-Watt carrier level.

The average we have found for most of the E radios was between 20 and 45 Watts. There will always be a threshold carrier level where the modulation peaks won't increase any further with increased carrier.

And there is a way to fudge this and improve the 'swing ratio' of this model, but that will have to wait for another day.

73

I appreciate your wisdom Nomad. So, without 11 meter burn, is it possible i.e. I owe him an apology lol...or is it not possible while maintaining the recommended 150mA i.c.? I'm skeptical that he isn't overdriving that radio to achieve that (if he's achieving that at all) but then again my experience is limited to one radio...mine lol! Thanks again!

 

[nomadradio]

The 150 mA IC only controls the carrier level. The mike gain controls the peak modulated power level, along with the random amount it gets you at this carrier level. A radio with a high ratio of peak to carrier built into it could get you 150 Watt peaks from a radio that only lets you have 130 on SSB. At the other extreme, a radio may only show 70 or 80 Watts PEP on AM with 150 mA cathode current on the finals. And if the resistor that goes from the driver tube's screen grid pin to ground has burned open, you could see more. But only until something gives from the excess stresses.

There is more than one way to make the FT101 show more power than is safe for it in AM mode, since the only "limiter" is your willingness to hold it down to a safe level.

73

 

[Wire Weasel]

Yeah you owe the apology. The 101's are rated for 25 watt max carrier on AM. Then they will swing to 100 p.e.p. You may also hit the 100 watts with a 20 watt carrier depending on the audio drive level. They should have built in some kind of limiting circuit on AM Carrier level power but they didn't. So you can turn the knob and go past 25 watts but it burn up the tubes in a short time.
And ..... you don't "snip" anything to get 11 meters on the 101. They are Crystal Controlled and have to replace one of more of the 10 meter crystal with 11 meter ones.

 

[Champo]

Yeah you owe the apology. The 101's are rated for 25 watt max carrier on AM. Then they will swing to 100 p.e.p. You may also hit the 100 watts with a 20 watt carrier depending on the audio drive level. They should have built in some kind of limiting circuit on AM Carrier level power but they didn't. So you can turn the knob and go past 25 watts but it burn up the tubes in a short time.
And ..... you don't "snip" anything to get 11 meters on the 101. They are Crystal Controlled and have to replace one of more of the 10 meter crystal with 11 meter ones.

Your 11 meter statement is incorrect. It includes an 11m crystal from the factory that covers 27-27.5 MHz with an 11 meter marking on the band selector switch. The mod to enable transmit on 11 meter is snipping the brown wire on the 11 meter band switch. You could go your alternative which is move the 11m crystal to the 10 (A-D) position but then you'd lose part of the 10 m band which is why most don't go that route.

On the PEP subject, with mic gain maxed the radio won't swing beyond 50 watts. What would be holding the radio back? I appreciate your feedback.

Jacob

 

[nomadradio]

After you see the first couple hundred radios of this model, it becomes apparent that they're not all the same. More to the point, not all the same as your FT101, no matter which one you may have. Was in production quite a while. The FCC crackdown that deleted 10 meters from ham amplifiers also caused Yaesu to lose the 11-meter receive-only band after some year. Maybe 1978?

Fox-Tango's web site should include that kind of historical context. Pretty sure you'll find it there. Won't find it in this post.

Easy to become an 'expert' after the first or third radio of a given type.

73

 

[Champo]

Understood. I never claimed to be an expert. Far from it. There wouldn't have been any reason to ask the question if that were the case.

 

[AudioShockwav]

My b model would only rx on 11 meters when I bought it many years ago.
And running it a @ 20 carrier on AM resulted in approx 90 watts peak output.
That was half a life time ago....
73
Jeff

 

[freecell]

Fox Tango International
Yaesu Users Group:
http://foxtango.org/foxtango001.htm

Fox Tango Library
http://www.foxtango.org/ft-library/FT-Library/index.htm

Fox Tango Manuals
http://www.foxtango.org/ft-library/FT-Library/FT101/FT101.htm

 

[Wire Weasel]

Your 11 meter statement is incorrect. It includes an 11m crystal from the factory that covers 27-27.5 MHz with an 11 meter marking on the band selector switch. The mod to enable transmit on 11 meter is snipping the brown wire on the 11 meter band switch. You could go your alternative which is move the 11m crystal to the 10 (A-D) position but then you'd lose part of the 10 m band which is why most don't go that route.

On the PEP subject, with mic gain maxed the radio won't swing beyond 50 watts. What would be holding the radio back? I appreciate your feedback.

Jacob

TNX for the correction on the 11M on the E Model.
On only seeing 50 watts out, provided you have properly tuned it up (Tune & Load) controls .... then if only 50 out then 1 or more of the 3 output tubes are weak.

 

[Champo]

TNX for the correction on the 11M on the E Model.
On only seeing 50 watts out, provided you have properly tuned it up (Tune & Load) controls .... then if only 50 out then 1 or more of the 3 output tubes are weak.

New Toshiba tubes (NOS). I also have a NOS set of NEC'S with the same output. Two different driver tubes as well. No difference with any of them. Radio has been recapped. All Nichicon caps. This is what I get in tune on them.

160m 1.9 90 watts
80m 3.7 140 watts
40m 7.150 140 watts
20m 14.175 140 watts
15m 21.25 135 watts
10m 29 120 watts

Perhaps re-peaking one of the bands is in order to see if I can net a change in modulation. Any other advice would be greatly appreciated! Thank you everyone.

P.S. I issued my apology during last nights net.

 

[Ed Cole]

This is a general question about AM output on an FT-101E. I had a discussion with a local yokel that claimed that he can get his FT-101E to key 20 watts while keeping it at the recommended 150mA i.c. and that it'll swing to 100 watts PEP using an amplified D104. I called BS. He's doing it on 11m (which I can't duplicate because mine isn't snipped) but on 10m and 15m the best I can get is an 18 watt key swinging to about 45 watts PEP in AM into a dummy. My FT-101E has full output on SSB. Was I wrong to call him a liar lol?

160m 90 watts
80m 140 watts
40m 140 watts
20m 140 watts
15m 135 watts
10m 120 watts

Thanks!

Wow. Here we go again.
The carrier should be set to only 30 watts on AM in tune mode. This gives you 120 PEAK watts of modulated signal, which is all the transformer can support. Any more will turn the rig into a toaster oven. All the information is available on the Fox Tango website, and in the downloadable service manual available online as well. Get a meter that reads true peak and rms, and you will be able to see it. But this is the design specifications from Yaesu. I promise. Go to the Fox Tango home page, and download the service manual. It's the best reference and assistance tool you could ever have in regards to a Yaesu FT-101-E radio.

 

[nomadradio]

The carrier should be set to only 30 watts on AM in tune mode

Even if the finals pull more than 150 mA? Some radios deliver no more than about 25 Watts' carrier at the indicated cathode current limit.

73

 

[Champo]

I know it has been several months but I figured I'd post an update. I've been chasing ghosts. It has a 19 watt carrier and just shy of 100 watts PEP. With the +/- 8% margin of error of the Bird meter it could be slightly higher or lower.

As Nomadradio stated I would exceed the 150mA threshold with a 25-30 watt carrier. It might need to be peaked again but that's where she stands.

I want to thank everyone for there help and insight. I greatly appreciate it.