New Modulator - 4kw peak output - hold it in one hand!

[steve_qix]

Hi!

The modulator shown in the picture is part of the "Class E-Z" transmitter I've been working on.  This
transmitter is a two band (80 and 160 meter) transmitter featuring a broadband, untuned driver
stage flat from 100kHz to 4mHz.  The driver also works on 40 meters, however this needs much more
experimentation before making any pronouncements in this area.  The only RF tuned circuit in the
unit is in the RF output stage.


Click here for full size image

The modulator is a Pulse Width design, and includes a 4 pole torroidal filter, keeping size and weight
down.  The switching frequency is 160kHz, and the output filter corner is set at around 15kHz.  The
modulator also includes a 6 pole anti-aliasing (input) filter.  Due the nature of pulse width modulators,
and the high efficiencies involved, the power supply requirements are significantly reduced as compared
to other designs.  The transmitter, as shown, uses a 135v 3.5 ampere power supply.
The picture below shows the entire, operational transmitter.


Click here for full size image

The transmitter runs 45 volts at around 9 amperes - about 400 watts of power.  The modulator
can deliver up to 135 volts at 30 amperes giving a positive modulation capability of 200% positive!!  The
modulator is ultra clean, and the frequency response is flat from dc to around 5500hz, at which point the input
filter starts attenuating the modulating signal.  A DC coupled negative peak limiter is
part of the design.  The builder can optionally choose any filter corner frequency within the
audio range. 

My goal is to publish the entire transmitter design in QST, and to this end, I have chosen
"conservative" filter corner frequencies.

This has certainly been an interesting project!!!

Talk later and Regards,

Steve

[W2PFY]

Great Steve!! Is the adjustable wrench a common tie point???

[John Holotko]

It looks quite nice and might I add quite colorful too.

[w3jn]

Steve, are you gonna post skizmatics (especially for the PS/mudulator) for those who wanna get going immediately and don't wanna wait for the boffins in Newington to decide whether to publish the article or not?

I would seriously appreciate even a hand=drawn schematic.

73 John

[K6IC]

Yep,  Count me in, too,  Steve.

Have abt all of the parts for your traditional  E RF deck.

Would love to see info on  Driver chips  and cores,  and schematics when you can.

Looks  Great !!             Thanks    Vic            KF6RIP

[steve_qix]

Steve, are you gonna post skizmatics (especially for the PS/mudulator) for those who wanna get going immediately and don't wanna wait for the boffins in Newington to decide whether to publish the article or not?

I would seriously appreciate even a hand=drawn schematic.

73 John

I'm in the process if completing the design and doing the documentation.  The power supply is very standard (transformer/rectifier/fiter).

The whole thing is, so far, very simple. I want to lay out a PC board with all of the low level circuitry (PWM generator, aliasing filter, overload shutdown,
etc.) and also a PC board for the sine/square/two phase converter for the RF section.

It would be nice to have a self-contained VFO.  There are a couple of chips that might work for this... I'm investigating.

Talk later and Regards,

Steve

a PC board for the sine to square

[Ian VK3KRI]

So whats the difference in the breakdown voltage of the Inetrnational Rectifier data book vs the RCA transmitting tube manual?
                                       
 Looks cool ..                            Ian VK3KRI
   

[w3jn]

Steve - I've built up a simple VFO already - uses a schmitt trigger with adjustable duty cycle.  Bill KE1GF built a copy for use in his rig.  Lemme know if you want the skizmatic, it's really just a standard FET VFO (*no* noise producing gate clipper diode), a 2N2222 buffer, and a 74LS14 schmitt trigger with a pull-up pot to adjust duty cycle.

I don't wanna wait for PC boards, although if they're forthcoming fairly soon I suppose it would make things a bit easier.

73 John

[W2INR]

Brent and I want to build the RF deck but can't seem to connect to you Steve. Are we going to have to wait for the article we have been hearing about for three years now?

[steve_qix]

Brent and I want to build the RF deck but can't seem to connect to you Steve. Are we going to have to wait for the article we have been hearing about for three years now?

Hi Gary,

Brent and I have talked about getting together this week.  Nothing special about the design... it's just so new... Hopefully,
Brent come over and check it out!

On the QST article, the main reason I postponed publication is I felt the previous design had too many variables for the average
builder to tackle.  In particular, the driver was critical.  This new design removes all but a very few variables    Makes things
VERY predictable and reproducable.

I suppose like all good projects, there comes a time when you have to shoot the engineers and go into production!!!

Regards,

Steve

[W2INR]

I understand.

Bang Bang!!

[W2INR]

I take it I can add this RF circuit to the exisiting modulator I have built up already?

I have all built but the RF and It looks like I did the right thing by waiting.

Check it out in the Photo Galleries under my call.

[steve_qix]

I take it I can add this RF circuit to the exisiting modulator I have built up already?

I have all built but the RF and It looks like I did the right thing by waiting.

Check it out in the Photo Galleries under my call.

Hi Gary,

Yes - the RF amp will work with any modulator up to 135 volts peak output.  Carrier DC voltage levels of between 35 and 45 VDC are recommended, although if you keep the peak voltage below 135 volts, in theory, any carrier DC voltage will work.  I've run this one
at 50 volts carrier for very long periods of time (hours, continuously) while testing.  That's 50 volts at 10 amperes. 
Peak modulator output was set not to exceed 130 volts, which gives plenty of positive peak headroom (more than 150%).

BTW, your transmitter looks VERY nice.  Quite a work of art!  I could never build anything that was so neat :-)  It wouldn't
work    It seems in my shack, the more clip leads involved, and the messier it is, the better it works!

Regards,

Steve

[Joe-N2YR]

Steve - I've built up a simple VFO already - uses a schmitt trigger with adjustable duty cycle.  Bill KE1GF built a copy for use in his rig.  Lemme know if you want the skizmatic, it's really just a standard FET VFO (*no* noise producing gate clipper diode), a 2N2222 buffer, and a 74LS14 schmitt trigger with a pull-up pot to adjust duty cycle.

I don't wanna wait for PC boards, although if they're forthcoming fairly soon I suppose it would make things a bit easier.

73 John

http://www.oselectronics.com/ose_p36.htm#80%20Meter%20VFO%20Kit

Amateur Radio Receiver Kits (CW, SSB) 20, 30, or 40 Meters
     Compact and easy to build. Receives the entire band, CW and SSB. Great for monitoring W1AW code practice, listening to your favorite nets, etc. Small enough to take with you on field day. Operates on a 9 volt battery, and has audio output enough to drive a speaker, or use the a headset.
     These circuits employ a unique three pot varator tuning system. you can set the ends of the band that you wish to receive, or receive all of the band. The advantage to receiving just a portion (say just CW or just SSB) is that the tuning becomes much more precise and can eliminate adding an expensive ten turn potentiometer in order to achieve find tuning. The PC board size is 3" x 3", which will fit nicely in a number of cases of your choice. You will need to add your own knobs (2), speaker, case, and antenna connector. You can use an SO-239, RCA connector, or BNC connector.
   
80-1420......20 Meter Receiver Kit.....$26.98

I built one of these in a mini box and used a 10 turn pot instead of the two fixed resistors and a remote standard pot. It is stable at a 50 ohm load from about 3.6 to 4.0 mc @ 200 hz drift /4hours. The output is about 12v p-p asymetrical sine wave. I at one time installed mods that would give a perfect sine wave @ 5v p-p but restored the circuit back to original condition.

The box has three rca jacks. Output , 12vdc and key.

I also have the power supply tranny and heat sinks ready

BRING IT ON STEVE

[steve_qix]

Steve - I've built up a simple VFO already - uses a schmitt trigger with adjustable duty cycle.  Bill KE1GF built a copy for use in his rig.  Lemme know if you want the skizmatic, it's really just a standard FET VFO (*no* noise producing gate clipper diode), a 2N2222 buffer, and a 74LS14 schmitt trigger with a pull-up pot to adjust duty cycle.

I don't wanna wait for PC boards, although if they're forthcoming fairly soon I suppose it would make things a bit easier.

73 John

Hi John,

I'd definitely be interested in checking out the schematic.  How's the "pull"?  I'm particularly concerned about generating incidental FM or PM
with any VFO.  If the pull is not too bad, it's definitely the circuit to use!

Can you email me the schematic?    Email:  cloutier at piesky dot com  (disguised email address ;-)

Regards,

Steve

[KM5TZ]

Steve,

What is the part number of the MOSFET driver you are using?

I am using 3 x Maxim 4420's in parallel to drive an 11N40 FET very nicely on 40m. One 4420 will drive this FET just fine on 80/160m.

David.

[steve_qix]

Steve,

What is the part number of the MOSFET driver you are using?

I am using 3 x Maxim 4420's in parallel to drive an 11N40 FET very nicely on 40m. One 4420 will drive this FET just fine on 80/160m.

David.

I'm using the IXDD414.  I'm driving a total of 10 FQA11N90 MOSFETs.  I have one driver per FET, all in parallel - all gates connected to the "driver bus".  This is two 5 MOSFET modules.  The drivers do drive the FETs quite well on 40 meters.  The IXYS driver is a 14 amp peak output device.  Strapping!!!

Regards,

Steve

[w3jn]

Steve, I haven't had it pull at all.  There's enough isolation between the oscillator and the output to prevent this - a one transistor buffer stage and a 74LS14 schmitt trigger (I sent the signal thru 3 of the triggers on the '14).

One thing about this is you'll have to experiment a bit with the frequency determining elements to get the bandspread right and tame any drift.  This all depends on what coil you use... I used a coil with a nice solid polystyrene core that was once the VCO coil out of a GE 2-way radio.  DO NOT use a toroid core, they are really funky with the drift.  Never been able to tame 'em.

This is one area where you can't cliplead something together.  You need a well-shielded box and a well-bypassed power supply (otherwise you'll get RF in the thing) and nice mechanically solid construction.

My whole VFO fit into a 2"X4" minibox.... but YMMV depending on the size of you variable cap, coil, etc.

Expect the VFO skizmatic shortly.

73 John

[WA1GFZ]

The best vfo I ever built was with a bc221 tuning cap with the stator sawed in half.
I used a U310 FET.
Another good one would be to solid state a T195 pto. Air inductor will be the most stable. No where is that jar of temp comp caps.

[steve_qix]

The best vfo I ever built was with a bc221 tuning cap with the stator sawed in half.
I used a U310 FET.
Another good one would be to solid state a T195 pto. Air inductor will be the most stable. No where is that jar of temp comp caps.

I'm considering using the LTC1799 resistor set precision oscillator as the VFO.  They claim the chip is a good crystal osc. replacement - stable.
Variable resistor to change frequency.  Also is used as a VCO.

Delving into the world of surface mount, I guess.  Never did any, but it's time.... I wonder how I'm going to get a
clip lead onto a chip less than 1/8 inch long :-)

Regards,

Steve

[w3jn]

Steve, I'd strongly advise you against using a VCO as a VFO on a high-power Class E rig.  The phase noise, FM hum, etc., will be a real problem, especially with an open-loop VCO.  L/C oscillators are still the best by far if you're running hi power.

I really notice the rise in noise floor on certain strong signals - even some SWBC stations have crappy synthesizers that smack out a S-9 noise level.

73 John

[steve_qix]

Steve, I'd strongly advise you against using a VCO as a VFO on a high-power Class E rig.  The phase noise, FM hum, etc., will be a real problem, especially with an open-loop VCO.  L/C oscillators are still the best by far if you're running hi power.

I really notice the rise in noise floor on certain strong signals - even some SWBC stations have crappy synthesizers that smack out a S-9 noise level.

73 John

Yes, that is a very important consideration!  Linear Tech *claims* low phase noise.  If this is a problem, I will abandon the idea and use an L/C Hartley
oscillator.  I guess phase noise is even a problem in some rice boxes....

Regards,

Steve

[WA1GFZ]

The first tool you will need for surface mount work is a good microscope.
The second is a good soldering station.

Most rice boxes are crap generators.