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[KT0DD]

I have inherited a Yaesu FT101EE and an AL811H amplifier. I was thinking of hooking these together and trying AM on 75 Meters. Both the operating and service manuals do not show what the ratings are for voltage and current on the keying line coming off the Jones plug on the main 11 pin socket of the FT101EE. I know everybody thinks I need the Ameritron ARB-704 relay buffer box, but I would like to know the keying line specs of the 101 so I can decide for myself whether or not I need one. My FTDX10 and AL80B have gotten along fine without the ARB704.  Does anyone have this info? I'm a little rusty in chasing circuits on a schematic, but the only info the manuals give on this is in the schematic diagrams.

Todd - KT0DD
 

[K8AC]

Do you have a VOM?  Use it to measure the voltage on the amplifier keying line to ground.  Then switch to current measuring mode and ground the line through the probes.  Unless the voltage or current is unusually high, you don't need the buffer.  Chances are it's around 12V and a few milliamps.  The FT101EE was around long before anyone ever heard  an ARB-704.

[KB2WIG]

A quick google returned this,

https://manualmachine.com/ameritron/al811h/7621821-operation-manual/

Connectors

Relay: keys amplifier when grounded. Sources +12 VDC open circuit and supplies 100mA when grounded. A built-in pulse canceling diode protects the exciter.

RF input: SO-239, 50 ohm input.

RF output: SO-239, 50 ohms with full power, into any SWR below 3:1.

Power: NEMA 5-15P 120V grounded style.

ALC: Phono Jack. Supplies up to 12 volts of negative voltage for ALC control of exciters.

  "


I don't own one, so this is the best I can do.... ..

Hope this helps.

klc

[W1QJ]

You don’t need any keying interface with an AL811 and FT101.  The 101 has a relay for amplifier switching and the 811 only has 12v100ma switching.  The relay can handle that no problem at all.

[KT0DD]

Thanks everybody. I'll give it a shot. Problem with the old 101's is they're heavy and very few techs if any still work on them. I'm getting too shaky to solder smaller stuff than a coax PL259 and I don't want to ship the 101EE off for repair unless I have to {if I can find anyone}. Good thing is I have a spare FT101F for parts, so I can swap a few damaged boards out if I have to. 
73. Todd - KT0DD

[KA4WJA]

Todd,
Well, as others have pointed out you should be good-to-go in regards to keying the AL-811H with the ole' FT-101ee. 

I don't have an AL-811, and it's been many decades since I've used an old 101e....and, I'm not a big "AM" guy....but, if it's okay, I'd like to point out a few things that you should understand / remember, before putting this pair on 75m AM...now, if you are already aware and already have planned for these, then please forgive my sticking my nose in.  hi hi (but, at least someone else might find this useful)

I have inherited a Yaesu FT101EE and an AL811H amplifier. I was thinking of hooking these together and trying AM on 75 Meters.

Thanks everybody. I'll give it a shot. Problem with the old 101's is they're heavy and very few techs if any still work on them. I'm getting too shaky to solder smaller stuff than a coax PL259 and I don't want to ship the 101EE off for repair unless I have to {if I can find anyone}. Good thing is I have a spare FT101F for parts, so I can swap a few damaged boards out if I have to. 
73. Todd - KT0DD

1)  You mention wish to use this combo (101ee and AL-811H) on 75m AM....which should be good!   But, there are 3 things here to keep in mind:

a)  If my memory serves me.....if tuned-up properly (and the tubes are good), the 101ee should produce an output of ~ 20 watts carrier and ~ 80 watts PEP in AM mode....(but, some push them even harder and get more output, but worse linearity, as well as shortening tube life and stressing other components as well.)

But, the good news is that you'll likely actually be reducing the carrier and mic gain of the 101ee, to keep its AM output to a more moderate level (maybe ~ 50 - 60w PEP, with ~ 12 - 15 watts carrier?) in order to keep the AL-811H running well (and the AL-811H outputting ~ 125 - 150 watts carrier and 500 - 600 watts PEP MAX!)


b)  The AL-811H will not survive long (well at least the 811a tubes won't) if it is pushed too hard in AM mode....and, while if you had a compliment of 572b's in it, you may be able to drive it with the full 80 watts PEP from the 101ee, but linearity would be probably be poor, anyway...

But, if your AL-811H has in fact four 811a's in it, I don't think it will survive long if you drive it with the full ~ 80 watts PEP, in AM mode, from the 101ee, as well as linearity suffering!   
And, the good news is, it isn't hard to reduce the "CARRIER" and "MIC GAIN" levels of the 101ee to keep its AM mode output within the range that the AL-811H will survive with. 


c)  When Tuning and Loading the AL-811H for "AM" operation, remember you need to TUNE and LOAD the AL-811H for your maximum PEP output (not your AM carrier output).   This means you need to tune/load for max output of the AL-811H when driving it with what your maximum AM PEP drive power will be....this is just like you tune/load when planning on using SSB mode, you tune/load using your selected max drive power.

With the poor 811a's (unless you've got some NOS RCA's, these days they are all questionable Chinese-made 811a's) being pretty marginal, this means tuning fast and not subjecting your AL-811H to constant carrier of ~ 600 watts output for too long!

Again, not having an AL-811H, I cannot be sure of the "numbers", but reading about these amps over-the-years, to keep things working (and to keep your AM signal clean / linear) it seems you should plan on ~ 500 PEP out, with ~ 125 watts carrier.   Some hams do report ~ 600 watts PEP, with ~ 150 watts carrier....but, I'd always plan on the more cautious side.


2)  Sine you mention you've read the manuals of the 101ee and the AL-811H, I will just advise a careful reading, before putting them up on 75m AM.

I believe the AL-811H manual states that the amp is designed for 70 watts (PEP) drive max in one section (page 3) and then mentions never exceeding 80 watts (PEP) of drive in another section (page 6)....and, then states 85 watts as the maximum drive power (with 65 watts typ) in the specifications (page 2).....and, also mentions never exceeding 7 seconds of constant carrier when tuning the amp....so, who knows exactly what Ameritron/MFJ actually does spec this thing as? 

Just keep your drive power low (12-15 watts carrier / 50-60 watts PEP...at most), and watch the meters of the AL-811H when you're tuning at max PEP power and when operating AM....and, if you have a scope, use it to make sure you're not flat-topping / over-driving it....and, you should be good. 

Even to those that don't care about linearity, if they read them, these warnings in the AL-811H manual, kinda' makes 'em want to keep that drive power down low any way.



Again, Todd, you may be all set in this regard....so, forgive me if I'm making a false assumption...I just wanted to point this out....just in case.  hi hi

Have fun!

73,
John,  KA4WJA

[KD6VXI]

Thanks everybody. I'll give it a shot. Problem with the old 101's is they're heavy and very few techs if any still work on them. I'm getting too shaky to solder smaller stuff than a coax PL259 and I don't want to ship the 101EE off for repair unless I have to {if I can find anyone}. Good thing is I have a spare FT101F for parts, so I can swap a few damaged boards out if I have to. 
73. Todd - KT0DD

Yeah, the old school FT101's are heavy.  I'm getting ready to bring mine down to the island on an airplane in a month.  Wish my back luck...  I have to go from the main terminal to the international terminal in Miami (sucks)....  And have 2 layovers.  The price I pay for a 300 dollar ticket vs a 1800 dollar ticket.  Even with the 1800 dollar ticket I'd still have one layover in Miami.  Suckage.

As to nobody working on them....  There are still guys that work on them.  Mine was a repair for a good friend of mine.  He lost interest after a major auto accident, so it's a memento of our friendship.  And it's a damn fine radio

If you need one repaired I might be able to steer you to someone who can do it.  What amazes me is the CB crowd will ship one across the country to have a good tech repair it....  But hams "it's too heavy to ship".  HOW THE HELL DID IT GET TO YOU FROM JAPAN?  (not saying this is your case, but I get so tired of reading "too heavy to ship".  I've shipped amplifiers weighing a thousand pounds or more (BIG transformers)...  You can't ship a 25 lb radio??)

--Shane
WP2ASS / ex KD6VXI

[DL9BDM]

Hi Todd,

as W1QJ says above, you don't need an interface to connect the power amp. At the ACC socket of the FT-101 pin 8 and pin 9 are responsible for keying an amplifier. Pin 8 carries ground potential and pin 9 carries the relay make contact for the power amp (this contact switch to ground when transmit). You only have to connect the center pin of the chinch/phono jack ("relay") of the AL-811 to pin 9 on the FT-101, then connect the shield to pin 8. That's all   

Good DX!

Eilert, DL9BDM

PS: In AM mode no more than 20 watts carrier power from the FT-101. Better less.

[VE7RF]

AM  + 811A's don't belong in the same sentence...and here's why.

The 811H is a 4 x 811A linear amp, rated for 800 watts pep out.  Tune it up to 800 watts pep out, and then set the UN modulated CXR for 200 watts, your tank efficiency (with the 200 watt UN modulated CXR) is now just 25%.
200/.25 = 800 watts  DC input....to get a lousy 200 watts of CXR.  800-200 = a whopping 600 watts CCS of anode dissipation.... =  bye bye 811A's. 

Even with the amp tuned to say  600watts pep out, and UN modulated  CXR set to 150 watts, the tank eff is still 25% or less.  150/.25 = 600 watts  DC input.    600- 150 = 450 watts of CCS anode dissipation....= bye bye 811A's.

Set the CXR to say 100 watts, and CCS anode dissipation is now  300 watts. Each 811A is only rated for 65 watts intermittently, or ICAS.  With a 100 watt cxr, your pep out is only 400 watts pep. Linear amplifiers are also known as...'variable efficiency amplifiers'.  You only get max eff (60-68%) when tuned for max pep output.   Once tuned for max pep output, any output less than max pep output, and tank eff drops like a rock.

Notice when using any linear amplifier in AM mode, that the UN modulated CXR  CCS anode dissipation is  TRIPLE the UN-modulated CXR !  You just lost it right there.   

 Linear AM is a silly + inefficient mode  at the best of times.   Even with say 200 watts of UN modulated cxr (800 watts pep out), when modulated, an average reading wattmeter will only swing 50%, or swing up to 300 watts.  That 100 watts of swing is TOTAL sideband power, or  50 watts per sideband.  So what you end up with is... 200 watts of CXR, 600 watts  CCS anode dissipation, 100 watts of total sideband power, 50 watts into each sideband, and 800 watts pep out (meter switched to read PEP).

Now compare the lousy 50 watts per sideband on AM... vs the full 800 watts PEP out sideband power into LSB (75m band) if  SSB was used.   800 watts pep / 50 watts =  an  instant 12.04 db advantage to SSB.   On top of all that, you just cooked the poor 811A's.    This is why AM went the way of the do-do bird, back in the 50's.

IF you are still hell bent to try AM on 75M,  the only way it's even feasible is to replace the oem 811A's...with a quad matched set of 572B's.... and increase the CFM of the fan.... IE: replace it with a higher CFM fan.  Even then it will be hard on the plate xfmr, which is only designed for 400 watts  average DC input.

Other ways to blow that 811H amp up is running FM on 10M (where tank eff is the lowest, like 50-55%) and also FT-8 / RTTY on any band.  17M is another bad one (using the 15M bandswitch position). Tank Q increases, and circulating current  through the tank coils and bandswitch increases 17%. FT-8 and 17M is a bad combo.

Sri to burst your bubble, but that 811H isn't configured to do what you want..at least in it's stock form. With 4 x 572B's + higher CFM fan, it will work..... but you still have to be real careful with the plate xfmr. 

[KA4WJA]

Todd,
I hope you don't think this is one of those "don't do that!" posts....nope, not what I'm writing....rather just that you should be aware of the further info provided by Jim (and some additional info here in a couple links)....and, you may rethink the use of the AL-811 on AM.


I respect Jim, VE7RF's expertise here....(and, while I understood the poor eff with AM, at carrier power....it seems those poor 811a's just won't cut it)
While it appears that you could possibly use the AL-811H at ~ 100 watts carrier / 400 watts PEP, your 811a's would probably be looking at an early grave.

So, if you must use the AL-811H on AM, it looks like the only respectable way would be to upgrade to a quad of 572b's, so you could get some reliability at 100w carrier/400w PEP.....(and possibly even increase power a db or two? but, then you're still stressing the poor AL-811)

Just doesn't seem like "good amateur practice", nor "good engineering", to me! 

And, in my opinion, that's a whole lotta' $$$ to put into a fairly wimpy amp (AL-811H), for just AM.....if it were me, I wouldn't bother with it....some hams (like W8IXY, mentions in this link below), have done this (use four 572b's in an AL-811H) and have used them on AM, but seems like a waste to me.

http://amfone.net/Amforum/index.php?topic=27712.msg211339#msg211339

http://amfone.net/Amforum/index.php?topic=27712.msg211517#msg211517


And, fyi, here are a few other tidbits on the AL-811(H), from the guy that designed it, W8JI...take 'em for what they're worth. 
(fyi, in addition to what Jim, VE7RF wrote above, these pages further show why the AL-811 is not the amp for AM use!)

https://www.w8ji.com/al811h_schematic.htm
https://www.w8ji.com/al811h_and_811_tuning_supplement.htm
https://www.w8ji.com/al811h%20fan%20speed.htm


Anyway, Todd....good luck. 

73,
John,  KA4WJA

[W1VT]

The ARRL web site has a classic article on the topic of using a tube linear amplifier on AM.
Technical Topics - Linear Amplifiers for AM 
QST Feb 1956, pp. 39-41
There's more than one way to generate AM. Get the scoop on using a linear. 
http://www.arrl.org/files/file/Technology/tis/info/pdf/5602039.pdf
http://www.arrl.org/amplitude-modulation

[KD6VXI]

The Al811H can be used on AM.  It has been discussed on AM related boards, and people have found out that it will work.  But, it's basically a sweep tube amp.

On SSB, it's an 800 watt ICAS amplifier.  Figure half that on AM, which means 1/8th that for carrier.  So, one hundred watts of carrier.

The 811 is a time averaged tube for plate dissipation.  If you want to be long winded and run in the roundtables where you lock the key and blather on for 5 or more minutes, this is not the amp for you.  If you want to talk for 30 seconds to a minute, then unkey for 5 to 20 minutes while the other people talk, then it will work just fine.

It also depends on the tubes you use.  CETRON / RCA / Westinghouse and other American tubes will take a lot more of a beating than the communist crap on the market today.

The AL811 and the H are hugely popular with the CB crowd.  If they weren't capable of AM operation they would be dying left and right.

I've repaired quantity one for a CBer.  It came DOA from a ham operator.  YMMV.

--Shane
WP2ASS / ex KD6VXI

[VE7RF]

I think the FT-101 used CXR + one sideband to generate an AM signal.

My old drake T4Xb/C's used.. 'controlled cxr modulation'...as did the heath DX-60 and a few others.   At least with controlled cxr AM, it was compatible with my drake L4B amp, and would do an easy 1290 watts pep out on AM.  Keyed, but without modulation, the UN modulated cxr was WAY down, down low enough, that the tubes are not cooked.  With modulation applied, the CXR would increase proportionately to the pep output.  I don't see any modern xcvr's that use CCAM these days...so it's a moot point.

What else that works, is to reduce the idle current on the linear amplifier, (increased bias V).... only when using AM.  Then when keyed, but no modulation, the reduced plate current now becomes the normal idle current.  The concept works per the AM phone forum folks.  Then you don't cook the poor tubes.  The extra required bias can be from an extra zener, wired in series with the existing oem zener, or a simple string of series diodes to obtain the required extra bias. For SSB use, a simple spst toggle switch shunts out the extra bias.

On a similar note, on CW mode, the idle current can be reduced to just above zero. You can't bias it completely off, or you will get key clix on any GG triode amplifier. 10-20 ma is ample for CW use.  On the Ameritron 'big-3' amplifiers, they use 2 x 7.5 vdc zeners in series for CW.   On SSB, one of them is shunted out with a spst toggle switch.

On my modified L4B amps, I installed a SPDT- center OFF  miniature toggle switch on the rear apron...requires a single 1/4" hole.  Then used 10 x 1N5408's in series for bias.  In the center OFF postion, all 10 x diodes are used.  The other 2 x positions tap the string at 3 x diodes..and also 7 x diodes.  On my hb amplifiers, I use a rotary switch. 

It's a simple concept to implement, then the poor tubes don't get cooked as much on AM.

[KD6VXI]

The FT101 uses 'high level' low level modulation.

It applies a modulated DC voltage to one of the driver transistors for the final amplifier.

The receiver uses the AM filter.  On TX it doesn't.

On PB1184 Q2 is modulated and then fed to the carrier control pot.  That, in turn feeds the RF amplifier strip on AM / CW.

--Shane
WP2ASS / ex KD6VXI

[KD6VXI]

What else that works, is to reduce the idle current on the linear amplifier, (increased bias V).... only when using AM.  Then when keyed, but no modulation, the reduced plate current now becomes the normal idle current.  The concept works per the AM phone forum folks.  Then you don't cook the poor tubes.  The extra required bias can be from an extra zener, wired in series with the existing oem zener, or a simple string of series diodes to obtain the required extra bias. For SSB use, a simple spst toggle switch shunts out the extra bias.

Yup, this does work.  K1JJ reported this and I had also tried this before and verified his findings.

HOWEVER, you must use a scope to set your mic gain control.  If not, and you set it for 100 pct neg modulation, and then use an amplifier that has a reduced bias setting on AM the final will baseline the negative mod quicker.  This will cause splatter (IMD).  If you use real QRO you will find out quickly.

You CAN run a class C amplifier on AM.  You HAVE to have a scope.  If not, the negative audio peaks will be wildly exaggerated and splatter all up and down the band.  Typically when someone wants to operate this way we tended to call it Class BC.

It's a real hoot when some smart ass with a degree comes along and jumps up and down that you HAVE to use an AB amplifier to amplify AM.  No, you really don't.  If you know how to set your audio gain and have a scope.

It was once stated by a prominent AM op that "Operating AM without a scope to monitor your signal is like driving at night with the headlights off".  Yup.

--Shane
WP2ASS / ex KD6VXI