The AM Forum

I would like to build a 2 FET, push-pull RF deck for 40 meters.  My plan is to use the frequency generator in the picture at 2x the frequency.  Use a 74F74 after that to get two phases 180 degrees out (it works with my current CW transmitter).  Then copy Steve's duty cycle adjuster, and run that into the IXDD614's. 

That's the easy cookie-cutter part...

I'm trying to fit this onto a 14" x 14" aluminum sheet and I don't want to re-engineer halfway through the project.  My question is what do I use for an output transformer for the FETs?  My current CW transmitter uses 8 FB-43-1020 cores to make a 1:1 transformer (4 stacks of 2).  I know that'll work, but is it best?  If something smaller will work, that'd be great because I want to fit it onto a smaller footprint. 

The series capacitor in the picture goes from 33 to 275pf (should be plenty for 40 meters).  I'll pick up a broadcast style air variable at this coming hamfest for the parallel cap. 

Jon
KA1TDQ

Research a TLT.   Mini coax and twisted pair on a torroid.  Commonly known as a Transmission Line Transformer.

WA1GFZ,  Frank,  has done extensive work on these I believe.

Work MUCH better than a binocular core.

--Shane
KD6VXI

Thanks Shane.  Good talking to you on 40 by the way a little while ago. 

I also got a response from a guy in Australia, and he used brass tubing in the cores for excellent primary to secondary coupling.  The secondary wire goes through the tubing.  It looks very neat!

I'm focusing on the driver right now.  I've ordered the parts to build Steve's VFO from the /2 flip flop to the output IXDD's.  The only difference is that my flip flop will be a 74F74.  I figured I'd build the driver separately.  That way if I get a small RF deck to work and want to go bigger, I can just unplug the driver and have that part all done.

I'm going all fancy too... SMA chassis connectors for the output.

Jon

Ok, I finally got around to building the duty cycle adjuster.  I'm getting 13.8 volt peaks (supply voltage to the IXDD's), but the duty cycle doesn't adjust at all when I move the 2k pots from one extreme to another.  It's the same with the signal driving the IXDD's, only it's a 5 volt peak signal.  And, from the picture, it looks to be >50% duty cycle, which is not good.

I'm pretty darn sure I cook-booked it correctly from the class E website.  I'm using a 5 volt pp signal from a DDS VFO for 20 meters.  That then goes to a 74F74 flip flop to divide the frequency by 2 and get a 40 meter, dual phase square wave.  The rest is from the class E website VFO schematic (from the 33pf capacitor on to the IXDD's).

Jon

Hi Jon,

Do you have a Link to the Duty-Cycle Adjuster diagram?

Have searched the E Forum,  and Class E Ratio sites,  but have only found the 2-Band VFO schematic,  and believe that that may not be it,   as it dates from about Feb '09 ...

Thanks,  Vic

the 2 band vfo schematic has duty cycle adjustment.

http://www.classeradio.com/vfo_2_band.pdf

Hi Bruce,

Did look at that schematic again yesterday,  and it DOES have 2 K Duty Cycle pots,  but had felt that there was another diagram floating around that used Comparators,   so was not certain just which diagram that Jon was referring to ... probably just defective memory cells.

Thanks,   Vic

I'm switching gears on this project.  I previously built a 2-FET push-pull CW rig for 40 that puts out 140 watts, and now I'm going to build a 4-FET push-pull.  I'll use an IXDD on each FET since it's harder to drive on 40 meters.  I found a nice chassis at a thrift shop and the whole thing should look pretty cool. 

Jon

I've gathered all the parts to build this schematic. I've verified with a scope that my DDS VFO will do single phase square waves with variable duty cycle at 5 volts + peaks.

I'm going to build it. Does it look right (for 40 meters)?

Jon

Everything looks quite reasonable !

Regards,  Steve

Cool, thanks! I'll start putting pieces together on the chassis.

This will be a relatively low power rig, but I can just use it for local talking. It'll be nice just to be able to turn the rig on and talk. I'll fire up the three 3-500's for nighttime battle conditions and use my other transmitter.

Jon

This will be the general layout.  A 1/2" block of teflon will go beneath the series capacitor to isolate it from ground.  And the coil will be cut down to proper size.

Jon

90% of the drilling is done.  I'm just waiting on a vernier dial to come in for the loading cap, and then I'll break out the soldering iron. 

Jon

With those components you could certainly run more than one lonely FET!

Joe-GMS

Yeah, it's a learning curve.  I need to get the concept with one FET, and then I can expand out.  I've never built one before, so I'm still thinking, "How in the hell is this thing going to work?" 

But true... it's a lot of big stuff for <100 watts carrier output, but I do want to get a working class E RF deck.  I'll worry about the modulator later.

Jon

It's all done except for adding the vernier dial on the loading cap.  Gravity pulls it out of position, so I need to add some resistance to movement.  Plus, this'll give me some fine adjustment capability.

The shunt cap turned out to be 150pf.  It's all I had. 

I'll use 13.8 vdc for the drain for testing before I put 48 volts to it.

Jon

   Jon,

   I marvel at the incremental improvements in your construction. Your latest invention is really beautiful. I do have a comment though. Look up that 540v transient zener diode, and look for capacitance versus voltage across the diode. You might be surprised at how much capacitance these devices have.

   With class E, the peak drain voltage at maximum output is ~ 3.8x the DC drain voltage. You could round that off to 4, and the Vdd to 50v, and get 200v peak drain voltage. Then from there how much headroom do you want to provide, 1.5x, 2x? I don't know, but you are over 2x now. Also zener diodes used like this have a delay time before they clamp; perhaps the lead inductance along with the device capacitance are the primary cause?

   One possibility is to use 2 or 3 lower voltage surface mount zeners in series. Using them in series will lower the capacitance by the number of devices in series, and increase the zener power available by the number of zeners. The copper in the ground plane under the PA FET could be carved out to make pads to install the zeners in a leadless (no inductance) arrangement.

   I just wrote this before my morning coffee, so consider that too as my points made might be off base.

Jim
Wd5JKO

Thanks Jim for the compliment.  I'm beginning to like this open frame construction.  The only thing with this one is that no one can touch the variable capacitor while transmitting, or should touch the variable capacitor.

I used the 540 volt zener that was in Steve's schematic.  I'm only guessing, but I'm imagining that the zener will clamp before the voltage gets to the maximum drain voltage of the FET, being 900 volts. 

If the capacitance turns out to be a problem, I will go ahead and replace it with surface mount ones.  I just need to look at the gate waveforms to make sure everything is kosher. 

...and I can't turn it on until the guy ships my vernier dial.  I ordered it on Saturday and the guys hasn't shipped it yet.  Too bad I didn't order it from Amazon, and then their drones could quickly deliver it to my door.

Jon

Can't wait to hear the new rig Jon.

We have a pipeline usually,  so should be FB hearing this one.

--Shane
KD6VXI

Ok, it has a pulse but it's not there yet.  

I rigged up a 3-gang electrical box which makes testing easier.  I can turn on the drive, drain, and choose 12 or 48 volts for the drain with the flick of a switch.  Attached is a picture.

I'm getting about 54% efficiency no matter what I do.  I've been varying both capacitors and I get different power levels, but they all end up being about 54%-ish.  At the current setting, I'm getting 6.3 watts output with 11.7 watts input (Id = .85 amps and Vdrain = 13.8 volts).  

Also, it looks like there is more than one waveform going into this thing.  I'm using a dirty Chinese DDS VFO and I'm thinking that I might have to put a low pass filter on it, or something.  The waveforms are there, but they're blurry.  So much for my $17 scope from the thrift store.  

So, that's where things sit right now.  I'm still waiting for my vernier dial.  I'm just playing with the loading cap carefully.

Jon

**  Oh yeah, and DON'T accidentally touch the variable cap.  Youch!

Here's a little better waveform.  

Gate is on bottom, drain is on top.

I've played around with things, and I'm guessing that my loss could be coming from the drain transformer.  I've even removed the shunt capacitor, but efficiency actually went down when I did that.  I put it back. 

Jon

Jon,

  I attach the manual to that Chinese signal generator. I am using mine for 2 tone audio tests. The 2nd harmonic is 40 db down as long as you don't overdrive the output op amps.

  As to your scope traces, are you sure the scope probes are set to 10X and the compensation capacitor is set properly? Those scope probe ground clips are pretty long too for 40m class E. As to the efficiency issue, I think your at a wall until you can square up that drive signal which looks more like a sine wave than a square pulse.

Also review this link concerning the MHS-5200a (that is what you are using isn't it?):
https://hackaday.com/tag/mhs-5200a/
https://github.com/przemekklosowski/mhs52xx/raw/master/MHS5200.pdf

Jim
Wd5JKO

 

That is the VFO I'm using.  I'm running it at 7.0 volts peak to get it to drive the IXDD's, which is probably too high for the VFO.  My plan to square things up is to run a sine wave out of the VFO at about 3 volts peak.  I'll run that into a hex buffer and adjust the VFO amplitude until I get about 40% duty cycle.  I can mount that chip directly onto the copper.  

I experimented around with lots of stuff last night, including the drain transformer.  I went down to 1:1 and things got worse.  I then went to a single core with a 1:2, but the core got hot.  I'm going to use 4 cores instead now with a 1:2 turns ratio (2x2 cores stacked).  Bigger is better.  

I'm now seeing how these transmitters are tuned.  Basically you tune for maximum power output on the loading cap, and then back off a little bit.  The series cap is for determining drain current and power output, up to a point.  At a certain point you can't reduce that cap's value any more.  

Jon

I'm up to 89% efficiency, but I had to go to 75 meters to do it.  The waveforms going into the FET look much more square at the lower frequency.  I'm getting 9.4 watts output with 13.8vdc drain voltage with .77 amps being consumed (10.58 watts total). 

I'd be just as happy to turn this into a 75 meter rig, since I don't already have one.  I didn't size the components though for the band.  My loading capacitor is all the way fully un-meshed.  The series capacitor is about half way (about 125 pf) and the coil is about 2.5uH. 

Where should I go from here to hit >95%?

Jon 

...and here's another waveform at 48 volts on the drain.  Efficiency drops to 85% at this drain voltage and I'm getting 82 watts output.  Not bad with only 15.5 watts being wasted. 

Jon

   Jon,

   Things are looking better on 75m for sure.

That drain waveform is still quite high when the gate drive comes on. I believe the class E guys call this "back porching". The solution is to optimize the output tuning network and/or reduce the pulse width of the gate drive.

Your MHS-5200 is capable of variable PW with the square wave output at these frequencies (< 6 Mhz?). You can also apply a DC offset to make the pulse go from 0 to +5v with the DC offset, and amplitude controls. I also believe the rear terminals have a TTL output as well. If you are using sine wave output still, consider the reduced duty cycle DC offset square wave.

Is that a different scope your using? A 2235 is quite FB.

Off topic, with the MHS-5200A VFO, how do you key it such that it does not block your receiver when not transmitting?

73,
Jim
Wd5JKO 

Yes, I am using a 2235 for my scope.  I got it at a thrift store for $17.

I reduced the duty cycle down to 35% from 40%.  I also backed off on the loading cap to reduce the back porching.  When I do that, I get a cleaner class E waveform (shown in the picture at 48 volts drain), but my peaks go way up and the efficiency goes to pot (50% ballpark).  

I'm using a 150pf doorknob as a shunt capacitor.  Should I up that value?  Would that help efficiency?  

I've tried changing the value of the inductor (by spreading it out and mooshing it together), as well as the series variable cap, but everything seems to come back and work happier right where they are (inductor at 2.5uh and series capacitor 1/2 mesh).  

In summary, my problem is that I get maximum efficiency when I'm almost unmeshed on the loading capacitor (while back porching), and not where it's properly tuned for class E.

I should also mention that I'm using 50v/div for the drain waveform (on top).  It looks to be 200 volt peaks.

Jon

Jon,

AB2EZ has a spreadsheet for calculating class E amps components.   Maybe grab a copy of it and figure out what values you need and go from there.?

Of course,  there are other software,  etc.   But Stu is local to the forum if you have problems.

I found,  at least at ten meters,  component values got very critical.  Haven't built a low band amp yet.....

--Shane
KD6VXI

I forgot to answer the question from before...

I use this VFO for my CW rig at 2x the frequency, so I don't hear the oscillator. This rig operates on the same frequency though. I will have to hit the "output off" button after each transmission.  I will think of something else though...

And Stu! Are you monitoring this thread? I could use that spreadsheet. But just on gut, I probably have to double the tank values to make 75 meters.

Jon

Maybe this will help:

http://tonnesoftware.com/classe.html

Jim
Wd5JKO

Awesome program.

My fixed variables are a 150pf doorknob shunt, 48 vdc drain voltage, and maximum tuning range on the series capacitor is 250pf.  The attached picture shows one test example with those parameters giving me 19 watts carrier. 

I wasn't sure about Saturation, Q, and Falltime, so I left those as default.

Does this look about right?

Jon

Here's Stu's spreadsheet.   Turns out I had it on my phone :-)

Jim Tonne's software is great,  too.

--Shane
KD6VXI

Ah, very nice!  (in my best Burat voice)

When you plug a number in that doesn't work, it lets you know.  AND, you can play with the numbers until things turn out nicely.  It sure saves a lot of time experimenting.  I was messing around with stuff for 3 hours last night and couldn't get good efficiency.  Now I see where I have to go.

Thanks!

Jon

Not a problem,  Jon.

Having a smartphone has really made me lose a lot of papers,  files,  etc.

Used to be,  it all got dumped to a single repository / drive at home.   Now,  a tablet,  couple laptops,  home computer,  shop computer,  audio processor pc....   Add a cell phone and where is it all a?  Lol

Anyway,  glad it helped.  Maybe Steve can drag the file or the post to another area for future safekeeping?

--Shane
KD6VXI

I ran the following numbers using Stu's spreadsheet, and I'm getting in the ballpark with Idrain and power output.  The waveform looks pretty good too.

My efficiency is low though... the best I can get is 62% and power output is 38 watts with Idrain 1.3 amps.  What's nice though is that I've been puttering with this thing key down for a long time and the FET is still cool to the touch.  My drain choke though is definitely running hot, and I think that's where my loss is.  I"m using (4) FB-43-1020 cores stacked 2x2 to make a binocular core.  The transformer is a 1:1 turn ratio. 

My series coil too is pretty cheesy, but it's all I had on short notice.  Attached is the picture.  It's green.

Jon

...and like the Energizer bunny, this thing is still transmitting.

You obviously didn't see my original pdm filter coils.

Like a foot long,  THHN  #12 on a 1.5 inch form.

The short one was like a foot long!

--Shane
KD6VXI

Jon,

   It looks like you are getting there. The waveforms are looking much better. One suggestion on the scope setup. Don't AC couple, and set the DC zero point of the top trace to the middle of the screen, and set the DC zero point of the bottom trace to the bottom of the graticule. This way you can see with just a glance if the FET drain is saturating, and what the ON voltage is. At 50v per division, it is hard to see a FET drain voltage of 2 volts, but when the zero point isn't defined, it is impossible to see the FET on voltage.

   You posted an earlier schematic with a 1t/2t transformer. Is that still in there? Both the Tonne program and the AB2EZ spreadsheet don't use one. The spreadsheet says the drain choke needs to be around 87uh. This will be an RFC, and with only a few amps average drain current, there is no need for big thick wire; 16 awg would be fine, and lots of turns.

Jim
Wd5JKO

First of all, thanks everyone for the responses, emails and messages from this last go.  To reduce heating on the transformer, one person suggested to increase from 1 turn to 2 turns on both primary and secondary.  That helped with efficiency rising to 69%, but it wasn't the cure.

Someone else pointed out (as did you Jim) that Stu's numbers are for a capacitively coupled output as opposed to a transformer output.  That's my next try.

So can I get away with just using one FS-43-1020 core for a choke? 

Jon

Use a PVC pipe to preserve coil for integrity.  Here's a show of my PWM / PS deck also the inductor for the RF deck. This is for 75 meters

Al

I switched to capacitively coupled rather than the transformer coupling, and again, it works but efficiency is low.  51 watts output and 70% efficiency.  This is actually turning into an academic exercise rather than a practical transmitter.  I could modulate it as-is after I buttoned it up, but who's ever heard of a 70% efficient class E transmitter? 

Anyway, the choke I used was my 2x2 stack modified to just a choke with 4 or 5 #12 gauge loops through it. 

The series coil was tightly wound, but I found that by spreading the coils out efficiency went up.  The transmitter tuning was a little more forgiving as well. 

On a positive note, Hillary just won Kentucky. 

Jon

I found out that my tuning cap value was too low.  I added a couple caps in parallel with it to get me around 420pf.  I then made a new coil to resonate with that. 

I'm getting 40 watts out at 75% now.  It's not perfect, but it'll do.  I'm going to build a Heising modulator for it.  I can't operate 75 meters at my house because of the power line noise, but I can take this mobile.  40 watts is comparable to any rice box and my audio will be much better. 

There's Mt. Lemon down in Tucson that's a mile high and you can drive up it.  It'd be fun to throw up a dipole some evening and put this on the air. 

Jon

I threw a DDS VFO on the front and changed the output network back to 40 meters.  I'm running a sine wave output and adjusted the DC offset to get the proper duty cycle.  I'm mounting this transmitter permanently in the shack now, like I had originally intended before.  During receive, I now have convenient access to the VFO's output pot so that I can turn it all the way down and not hear the oscillator (I just have to remember to turn it back up for TX, otherwise no output).

Funny thing about efficiency... On the cantenna dummy load I'm getting 70% efficiency.  When I put the transmitter on my 40 meter delta loop, I get 88% efficiency.  The delta loop has an SWR of 1.7:1 in the AM window.  It's resonant and almost 1:1 in the CW portion. 

The waveform looks cleanest and proper at 50 watts carrier, so I'll leave it there.  The Heising modulator that I'm planning to build will drop (as I've calculated) 2 volts at carrier across the choke.  This'll bring drain voltage to a more comfortable level of 46 volts.

Jon

I wanted to post a picture of how I'm affixing this to my shack, so here it is. I'm clearly running out of desk space.  After this, I can't build anymore.   :)

Everything is all done except for the modulator.  That will sit on the floor under the desk.  The meter for measuring drain current is behind the iambic paddle.  Sequencing is simple, but it requires an extra step.  I need to turn the VFO output on before TX, and off after TX.  Otherwise, it's just a toggle switch TX/RX operation.  

An RF pickup/headphone audio driver is in the aluminum box on the back left corner of the desk.  The headphones are switched in as well during TX so that I can directly monitor my TX audio.

I also mounted the scope on the floor so I can just quickly glance to check out the gate and drain waveforms.  

I still need to buy the parts for the Heising modulator, and they are:

Antek 8KVA 115/50 VAC transformer
124 uF film capacitor
(2) Hammond .1H/5amp chokes

Jon
  

Dpdt switch for changeover.

DDS vfo to ground on stby.  Maybe through a xister.

When you lift the switch,  the vfo will come on,  while the switch is transitioning from one state to another....
Assuming the vfo could handle a shorted output (AC coupled).

No??

--Shane
KD6VXI

It probably could handle it fine, but I don't want to risk the FET with no drive with voltage applied to the drains. Worst case right now is that I get no RF output if I have the VFO output at zero. During which case, I won't hear myself in the headphones, realize my brain fart, turn the TX switch back to RX, turn the pot on the VFO back to max, then switch back to TX.

The only way I would risk destroying the FET is by turning the VFO off with drain voltage applied. I doubt I'll do that though.

Jon

It seems so much easier to just build a series modulator and don't bother with any kind of modulation that involves iron or parts you don't have....

Hey, on your T/R problem - how about a sequencer?  Here's one I use (pretty simple and all common, easy components).

(http://www.classeradio.com/sequencer_new.jpg)

I know, it would make more sense to build a PWM (and probably cheaper too), but I just want to get this on the air simple, quickly, and with what I know works.  Here's a picture of the Heising modulator progress.  I'm repurposing my old single tube transmitter chassis. 

If I get this to work ok, then I'll go full-bore on my next transmitter with sequencing, PWM and a push-pull RF stage.  After all, I've got a 6 foot rack with nothing in it.  I think this rig'll be fine though.  I just did a full 10 minute on-the-air carrier test, and the heat sink and FET got warm (but just barely).  I'm sure it'll handle the modulation just fine.

Keeping the scope permanently connected to the rig I think is a good idea.  I've discovered that the boy likes to come into the shack and rotate my bread slicer repeatedly.  He'll make a good ham!

Jon 

Not a pulse width modulator,  a series modulator.

Series modulator can be 3 transistors,  or 1 transistor and a quad op amp.   Quad op amp will give you a couple stages of audio pre amp gain as well.

A series mod can be built up in about 20 minutes,  on perf board.

There are even solid state series mods on this site,  3 mosfet,  that will withstand 1.4 kv.

MUCH easier than a piss weak mod. (pwm)

--Shane
KD6VXI

Right, I was thinking about a fairly straight-forward analog series modulator.  Can be accomplished with 2 power MOSFETs and an op-amp.

You have a source follower output stage (connected to the RF amplifier DC feed), preceded by a class A voltage amplifier which is fed by an op-amp.  A DC feedback loop runs from the output back to the op-amp (on the non-inverting side) input, with suitable adjustments.  Easy Peazy.

This was the first modulator I used when developing a practical class E transmitter.  Very good for experimentation as long as the power is fairly low (50 to 75 watts -  100 watts tops).  Above this power level, the power dissipation in the modulator becomes excessive, and that's where PWM really works very well because it is SO much more efficient.

Here's the modulator progress to date.  All that's left is to buy and install the series chokes.  Hopefully I'll be able to come back with some modulation data in the first week of July. 

In the meantime...

https://www.youtube.com/watch?v=arZdeg_fL-I (https://www.youtube.com/watch?v=arZdeg_fL-I)

Jon

It works!

I installed my Hammond transformers tonight and put it on the air.  It sounds great!  I directly monitor the output of the transmitter and it's pumped into my headphones.  I'm getting 50 watts carrier with 200 watts peak (more if I hit it hard). 

I watched my waveforms on the scope while I talked and there was variation in the drain amplitude.  I'm a guess'n that's supposed to happen. 

I'll attempt a QSO when I have someone other to talk to than a foreign broadcast station. 

Class E... yeah baby, yeah!

Jon

That's pretty cool. What is the TO-220 for?

That is a 5 volt regulator which supplies the 3 diode keep alive negative peak limiter.

Well, I was able to give it a little workout today.  I talked with W6TSJ, Tom in CA.  He's in between San Diego and Los Angeles.  He was running 40 watts on a Globe Scout and me on this rig with 50 watts.  We made it despite all the noise and static crashes. 

Anyway, he gave me a really great audio report.  I felt the FET and heat sink after some long transmissions and they do get a little warm, but nothing nearly to be concerned about. 

This is going to make a nice local rig.  If I need high power, I can turn on my other transmitter which is paired to 3-500 triplets. 

Jon

This rig is awesome and I'm very happy with it.  However, at some point I'm going to want more power and I'll build a larger transmitter.  

For 40 meters, I guess you need to drive each FET (go with an 11N90) with it's own IXDD chip?  Or can you still drive two FETs with a single IXDD, like on 75 meters?

If you do have to go 1 for 1, is it practical to build an 8 FET, push-pull RF deck for 40 meters?  What's the biggest class E transmitter out there for 40 meters that someone's built?  

I just ordered a UDB1308S DDS VFO.  I have a way of getting a variable square wave duty cycle using sine waves with this particular VFO.  Now though, I'll have two outputs and can make a push-pull rig.

Also, there's an industrial metal shop just down the road from me.  They sell copper sheets any size and thickness you want.  This new rig would look pretty cool with a shiny copper base.

Jon

Good work on the existing transmitter !!!!  Maybe we can work sometime when the conditions are favorable.

You definitely need an individual driver for each MOSFET.  I do not know if the IXDD614 will function at 7 mHz.  The IXDD414 definitely worked up there.

The biggest 40 meter class E rig I know of is 1kW (carrier, DC input).  This is with 16 MOSFETs.

Hope this helps!

Regards,  Steve

I was talking with a guy in CA last night with this rig, and he asked me what the benefit was with class E vs. a tx with a linear combo. I cranked up the microphone gain high so that you could hear a pin drop in the shack, and I said, "Listen, no fans or blowers!" Granted, this rig just does 50 watts, but I'm going to start gathering parts for an 8 FET rig. Now that I know how these things operate and tune, it seems less mysterious.

I'm using a 614 with this transmitter. It seems to do the job.

We've worked at the 300 watt level, but I'm guessing that at 50 watts you would need to get your ESP going to pull me out of the noise.

Anyway, onto bigger and better things!

Jon

If you have 3 minutes to kill, I made a YouTube video demonstrating this radio.  Here it is:

https://www.youtube.com/watch?v=_2QdiDejfzQ (https://www.youtube.com/watch?v=_2QdiDejfzQ)

Jon

Nice work - nice video! Thanks for sharing

Jon,
Very informative video thanks. Great effort to get your transmitter to it's present state congratulations!

Thanks! 

Here's a picture showing the current state of the new one.  The aluminum knob on the tuning capacitor is temporary.  I'm going to use a non-conductive shaft/knob for that.

I'm going to order all the semiconductors in a little bit, and that's basically the next step.

Jon

Some day when the band is open and I'm on 40, it would be great to hear the rig!

Here's the FET deck so far.  The drain bus is vertical, as you can see, and the gate bus will also be vertical.  I thought afterward about possible RF coupling between the two, but there's space in between to mount a larger 3/4" grounded brass strip vertically the whole length.

There are 10 IXDD chips.  The ones directly center in the two busses are the two driver chips.  The other 8 drive the FETs.  

Soldering now is getting a little tight to finish, so I'm taking a break.

Jon