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Author Topic: Tuning for reduced output power FT-101ZD.  (Read 406 times)

2E0LPL

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Tuning for reduced output power FT-101ZD.
« on: November 01, 2019, 08:53:18 AM »

Hi guys...still getting to grips with the 101ZD I bought a month or so ago.

The manual gives instruction on tuning but say that the tuning process is complete when the drive is at 100% with max power obtained on the meter.

Trouble is if I set the drive upto 100% in steps and tuning for max power plate and tune preselect the meter hits over 325ma maybe a tad higher....with an indicated 140w out on my watt meter.

Tuning is done through a 300w dummy load.

A pal suggested tune to the meter reads 250ma which I do...this gives an indicated 100w.

But I could do with setting the 101ZD for a power out of 50w on my output meter which I get at 200ma ic.

Of course tuning to this lower setting is not complying with the 101s manual which says tune all the way till the drive is maxed out.

Again my pal says this will give the tube a very hard time...which I am very concerned about.

Love to here your views guys.

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AC2EU

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Re: Tuning for reduced output power FT-101ZD.
« Reply #1 on: November 01, 2019, 10:23:44 AM »

I responded to your post in "Elmers". I forgot to add that once the tuning process is done,  you control the max output with the "carrier control" - not with the tuning!

2E0LPL

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Re: Tuning for reduced output power FT-101ZD.
« Reply #2 on: November 01, 2019, 11:05:03 AM »

Hi...my 101zd doesn't have a carrier control.

After the drive is at 100% and the final plate and tune adjustment all it says in the manual is return drive control to zero or fully anti-clockwise...mode to usb/lsb and adjust mic gain to suite.

The trouble and worry I have...if I tune with the drive at 100% the indicated ma reading on the meter is over 300 and I was told thats bad for the tubes.

Would it be incorrect to do as I was thinking...tune to max 200ma for the final tune and plate? if I wanted to tx at 50w.
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AC2EU

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Re: Tuning for reduced output power FT-101ZD.
« Reply #3 on: November 01, 2019, 12:35:42 PM »

Hi...my 101zd doesn't have a carrier control.

After the drive is at 100% and the final plate and tune adjustment all it says in the manual is return drive control to zero or fully anti-clockwise...mode to usb/lsb and adjust mic gain to suite.

The trouble and worry I have...if I tune with the drive at 100% the indicated ma reading on the meter is over 300 and I was told thats bad for the tubes.

Would it be incorrect to do as I was thinking...tune to max 200ma for the final tune and plate? if I wanted to tx at 50w.

Yes you do. It's called "drive" on your radio. it's on the upper left group of knobs!
You really should read the manual and go through the operating instructions. The description should be there.

HAMHOCK75

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Re: Tuning for reduced output power FT-101ZD.
« Reply #4 on: November 01, 2019, 03:47:45 PM »

Quote from: 2E0LPL
Of course tuning to this lower setting is not complying with the 101s manual which says tune all the way till the drive is maxed out.

Again my pal says this will give the tube a very hard time...which I am very concerned about.

Using your numbers let's do a little math. Assume CW mode. Suppose the plate voltage is +650 VDC. If you run 0.325A at +650 VDC then the input power is 211 watts key down. If your output power is 140 watts then the tubes are dissipating about 71 watts. Divided by two is about 35 watts per tube.

If you run 0.2A at +650 VDC then the input power is 130 watts. If your output power is 50 watts then the tubes are dissipating about 80 watts or about 40 watts per tube.
« Last Edit: November 01, 2019, 03:52:19 PM by HAMHOCK75 »
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2E0LPL

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Re: Tuning for reduced output power FT-101ZD.
« Reply #5 on: November 01, 2019, 04:06:00 PM »

Guys I need to say I am a comparative beginer...espesily with the hybrid radio.

AC2EU...I am not sure if your being rude but you confused me calling the drive control the carrier...I can assure you I have read the manual cover to cover.

Ok we have got that out of the way...so all I need is a little help guy so please lighten up....I'm sure you started like me once...but I am asking a question when I dont know the answer to the question.

Not quite sure why amateur radio brings out this superior attitude but I see it a lot.

But I do appreciate the help many amateurs have giver me over the last 18mts.
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VK6HP

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Re: Tuning for reduced output power FT-101ZD.
« Reply #6 on: November 01, 2019, 08:17:58 PM »

Nick,

I won't repeat my comments from the other forum, since you seemed to get the gist of my explanation and understand the full-power tuning process.  At that point it wasn't clear that you wanted to run reduced power, so let me tackle that now.  First of all, can you say why you want to run lower power?  For example, is it to satisfy a licence condition or are you trying to drive a linear amplifier and, if so, is the linear a valve (tube) type or a solid state type?  The reason I ask is because there are several ways of achieving the reduced output; the best one is a bit application dependent.  Also, what mode(s) do you wish to use - SSB alone or SSB and CW?

The most obvious way to lower the output is to tune for maximum output, then lower the drive to the power amplifier stage, in your case 2x6146B valves.  For CW you do that via the "drive" control, which controls carrier levels when there is a carrier.  For SSB without the processor, you use the mic gain to make the speech peaks reach the desired level, noting that average-reading power and current meters will read less than half (typically a third) the actual peak levels on uncompressed speech.  Your FT101Z also has a nice RF speech processor and, on quick scan of the manual, you set the input levels to that using the mic gain and the output levels with the "drive" control.  If you use the processor, make sure you read the manual and set up the ALC etc properly.

There is no escaping the reality of the valve dissipation calculated by Hamhock75 (above) but if you operate carefully with SSB, using uncompressed or very moderately compressed speech, you can keep the plate dissipation of each 6146B at the rated 35W for this class of service. Some radios intended for certain classes of Japanese operators often included a tapped HT transformer so the HT could be reduced for lower power operation within tube limits but I'm not sure if the 101Z has such an option.

Another way of controlling the power output is to use the ALC line on the "accessory" plug on the rear panel.  Normally, as an external linear amplifier like the FL2100Z approaches full output it generates negative control voltage which is fed back to the FT101Z exciter via the ALC line, limiting the drive to the amplifier.  You can use the ALC line in conjunction with a 9V battery and a pot to set the FT101Z power output.  Note that I have never used a 101Z but I did use this trick with my Kenwood TS-830S, which is a similar hybrid rig.

Finally, if you are doing something more critical, like driving a solid state linear amplifier, the most foolproof way of reducing the exciter output is to run the radio at full power, then reduce the output via a 3 dB power attenuator (50 or 100W), something you can build or get off eBay for $80 or so.  With an HF transceiver you can install the attenuator at the antenna connector since it has minimal effect on HF receive except for a small reduction in signal-to-noise ratio on bands above 14 MHz if you happen to live in a very RF-quiet location. (You can of course come up with a T/R switching scheme for the attenuator if you want).
 
I used an attenuator between my TS-590S and KPA1500 ampliifer but, since upgrading to a TS-890S with a very good and reliable power setting and limiting implementation, I've taken the attenuator out of service.

In trying to keep things simple I've glossed over a few deeper points in the explanations above but, in my judgement, it's close enough for what you're seeking.

Finally, if you have not yet found it, I'd have a look at the Fox Tango International web site (http://foxtango.org/ft101zd/FT-101ZD.htm, http://www.foxtango.org/ft-library/FT-Library/FT101ZD-901-902/FT-101ZDSG3.pdf, and associated pages) which has lots of good material on the FT-101Z.  In particular, you should check that a "death" capacitor coupling the RF drive to the PA grids has been replaced.  Apparently the original capacitors broke down, applying HT to the grids, destroying the final and, often, power transformers.  As I mentioned, I've never had a 101Z but that sounds to me like a "must do" modification.  In a somewhat amusing twist the notes outlining the 101Z idiosyncrasies also contain a nice section on how to seek help for faults (etc.) via internet forums.

73, Peter.
« Last Edit: November 01, 2019, 08:40:56 PM by VK6HP »
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2E0LPL

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Re: Tuning for reduced output power FT-101ZD.
« Reply #7 on: November 02, 2019, 02:46:48 AM »

Hello Peter.

And thank you for you comprehensive reply.

Ok were do I start....I noticed when tuning this radio into a dummy load as nearly everybody I ask says dont follow the Yaesu instructions in the manual as it gives the tubes/valves a very hard time...

So when I use the tuning method most recommend and this is for nothing more than SSB voice nothing else...

So hooked up to my dummy load I start with peaking the rx with the pre-select from the in mode check I have 50ma idle current...increase the drive to 150ma  and pre-select ajust for max power if above 150ma adjust down with drive to 150ma.

The dip the plate...from there increase the drive load control for max power or smoke as some like to say and the same with the plate control....keep on increasing the drive and peaking the controls till the drive is fully open.

Now the increasing the drive to 100% is the part I need clarification with...as I increase the drive it will indicate 350ma maybe more....no mention in the manual about observing this figure.

But A fellow operator in the UK with far far more knowledge than me says hitting 350ma during the tuning process is a sure-fire way to cause the tubes/vales to fail.

And suggests to me to tune to a max 250ma which is around 50% drive and coincides with an indicated 100w on the ATUs watt metter...which gives very accurate reading from the other 2 modern rigs I own.

So all I want to know...do I tune to a max 250ma or ignore my pal and continue advancing the drive as I tune in the process hitting 350ma with the power out reading 140+watts on my ATU meter.

The mention of a further reduction in power to 50w is to comply with my licence....but that a secondary question for another time...at the moment I need to ascertain if 250ma should be the limit I adjust the drive to during the tuning process.

And who do I believe....as A newcomer to tube type radios I,m sure you can understand my concern...its ok if you were brought up on this type of equipment...I was not.

Nick.







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W9IQ

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Re: Tuning for reduced output power FT-101ZD.
« Reply #8 on: November 02, 2019, 03:08:41 AM »

Nick,

The maximum continuous DC plate current for a pair of 6146Bs is 250 mA. Brief excursions above this may be tolerable but try to avoid it if at all possible. Each tube is capable of 220 mA on an intermittent basis so a pair could briefly tolerate 440 mA.

Since you are trying to limit your output power to 50 watts, you may find it easier to use a 9 volt battery and a variable resistor connected to the ALC input of the radio. The positive of the battery goes to ground since the ALC is expecting a negative voltage.

- Glenn W9IQ
« Last Edit: November 02, 2019, 03:13:00 AM by W9IQ »
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- Glenn W9IQ

God runs electromagnetics on Monday, Wednesday and Friday by the wave theory and the devil runs it on Tuesday, Thursday and Saturday by the Quantum theory.

VK6HP

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Re: Tuning for reduced output power FT-101ZD.
« Reply #9 on: November 02, 2019, 03:14:32 AM »

Nick,

OK, that's easier than I thought.  The simple answer is to tune (set drive, peak pre-selector, dip plate and load the radio) at whatever indicated current gives you about 100 W output.  That way you're getting a comfortable output without stressing the PA valves.  It's not worth chasing extra output over and above 100 W for the class of transceiver you're using, and by keeping the drive and output reasonable you'll have an exceptionally clean signal (better than almost all solid state PAs).

Bear in mid that metering shunts and multipliers often change over time (particularly the cathode resistors in valve PAs) and your front panel current meter may or may not be accurate.  If you have an external power meter you trust, I would regard that as my reference for 100 W, using the in-built current meter just to find the dip and as a sanity check as you're loading up.

I was listening to an FT101Z the other day and looking at the bandscope display on the TS-890S.  There's no doubt that most earlier and later Yaesu radios could learn a thing or two from the FT101Z in terms of signal quality.

By the way I think the earlier confusion may have been between the terms "drive" and "power output".  There is absolutely no need to have the drive control fully advanced once you hit 100 W or so; its position is immaterial in a practical sense.  It's a bigger deal to properly run the radio at much reduced power outputs (50 W or less), hence the pull of the discussion in that direction.

Glenn, I note your reply as I finished typing.  It now turns out he's not trying to run at 50% power and you may have noticed I suggested the battery and pot option earlier.

73, Peter.
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W9IQ

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Re: Tuning for reduced output power FT-101ZD.
« Reply #10 on: November 02, 2019, 03:18:46 AM »

Glenn, I note your reply as I finished typing.  It now turns out he's not trying to run at 50% power and you may have noticed I suggested the battery and pot option earlier.

Sorry, Peter I missed that you had already suggested that. Consider my post as an endorsement of your idea!

- Glenn W9IQ
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- Glenn W9IQ

God runs electromagnetics on Monday, Wednesday and Friday by the wave theory and the devil runs it on Tuesday, Thursday and Saturday by the Quantum theory.

VK6HP

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Re: Tuning for reduced output power FT-101ZD.
« Reply #11 on: November 02, 2019, 03:26:15 AM »

No worries Glenn.  Much as I love my classic radios, I have to admit to being completely won over by the TS-890S "Max-Po" feature, settable per band and per mode.  But the ALC pot is a good trick for the older radios.

73, Peter.
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HAMHOCK75

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Re: Tuning for reduced output power FT-101ZD.
« Reply #12 on: November 02, 2019, 04:22:37 AM »

The specification for the FT101ZD is 180 watts DC for CW/SSB. If the power supply voltage is +650 VDC, then the maximum plate current would be 270 mA.

I did have a look at the manual describing the final tuneup procedure for the ZD. I can see why you are confused. I suggest reading the final tuneup procedure for the FT101EE. The ZD procedure never mentions what the plate current should be, the EE version mentions not only that but that on 10M plate current should even be more limited to avoid excessive spurious. The EE uses different tubes though, 6JS6C's.

The EE version has mic gain/carrier instead of mic gain/drive. The ZD manual mentions the drive control at maximum. I never have carrier ( drive ) at the maximum, only what is necessary to achieve about 300 mA. plate current The manual allows 330 mA except on 10M where is is limited to 280 mA. The EE has a higher DC input power spec for SSB than the ZD due to the different tubes.

I agree with all those who suggest you keep  the plate current around 250 mA. The Yaesu description of tuning the finals in the ZD manual is shall we say lacking.
« Last Edit: November 02, 2019, 04:31:28 AM by HAMHOCK75 »
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2E0LPL

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Re: Tuning for reduced output power FT-101ZD.
« Reply #13 on: November 02, 2019, 04:28:18 AM »

Thank you so much guys and Gooday Peter....all very reassuring.

Just wish I knew an Elmer type of guy over here to take it to for some instruction...but they are few and far.

But I looks like I am headed in the right direction.

I would hate to think I was abusing this loverly old radio through ignorance.

And yes it does sound sweet an rx.

HAMHOCK75 I will have a read of the 101ee manual...glad to hear you say the 101ZDs manuals tune-up procedure is lacking...no wonder I was confused.

Many thanks.


Nick.
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HAMHOCK75

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Re: Tuning for reduced output power FT-101ZD.
« Reply #14 on: November 02, 2019, 04:30:27 AM »

I learned something too. Never recommend the ZD manual to a beginner learning how to tune a tube final!
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