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Analog modulating a 1000 watt carrier class E rig




 
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Author Topic: Analog modulating a 1000 watt carrier class E rig  (Read 12231 times)
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Patrick J. / KD5OEI
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« Reply #75 on: September 11, 2019, 11:15:31 AM »

How did that happen? Hope it heals up well.
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« Reply #76 on: September 11, 2019, 12:46:32 PM »

Ouchy.

Drill bit broke and went into the palm of my hand. Iím ok though. Itís the simple power supplies that get you.

Jon

Jon,

The same thing hapened to me in 1972.  I drilled a broken bit right into my left hand at the base of the thumb using a hand drill. Nasty ripped up flesh and required a lot of stitches in emergency. Still have scars.  It complements my deep scars on the other hand when I got belted with 800VDC the same year.

I've not made that mistake again since...  using a dull bit that required pushing so hard that the bit snapped. I didn't know drill bits could be sharpened back then. Since then I bought a drill bit sharpener called "Dr. Drill" and keep 'em sharp.

Are you left-handed?  

T
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Frank / WA1GFZ says when he's working near high voltage, as a warning he sings this song by Jay and the Americans: "Come a little bit closer, you're my kind of man, so big and so strong, come a little bit closer, I'm all alone and the night is so long."
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« Reply #77 on: September 11, 2019, 03:34:32 PM »

Very similar situation here. I was pushing a dull drill bit hard with my hand 'out of the way.' It snapped, the broken bit still in the drill made a gash in my hand and the broken bit lodged itself inside my palm about 3/4" in a separate hole. There's the brief second after it's over and you look down at the damage with a drill bit sticking out of your hand and you wonder, "Did I just do that?"

It is healing up nicely with no stitches required. X-rays show no material still inside. And yes, I am left handed.

I got the transformer in for the power supply and now have all the parts. Hopefully I'll finish it soon.

Jon
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« Reply #78 on: September 11, 2019, 06:58:33 PM »

Wow, Jon, you are really lucky.

The broken sides of the bit are like a meat grinder. Could have torn up muscle, tendons, nerve pathways, veins, etc. Amazing you didn't need any stitches.

After all the many, many dangerous things I've done and risks I've taken, I am convinced we all have a guardian angel looking out for us. In your case he (she) wanted to teach you a good lesson and let you off hook easily.... :-)

These days I use a drill press, usually lock work down that can potentially spin, and use heavy leather welding gloves. I also have a bandsaw, lathe and other dangerous machines that can take fingers and hands clean off, so glad I learned early in life to think everything out carefully before jumping in.

I took a metal class in high school and noticed that the teacher was missing a finger from a router accident.  I think as hams we put much more emphasis on avoiding electric shock rather than machine accidents.  Young, new builders need to think about this more.

T
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Frank / WA1GFZ says when he's working near high voltage, as a warning he sings this song by Jay and the Americans: "Come a little bit closer, you're my kind of man, so big and so strong, come a little bit closer, I'm all alone and the night is so long."
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« Reply #79 on: September 18, 2019, 11:47:26 PM »

I have everything all mounted. Now, just wiring it up.

Jon


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« Reply #80 on: September 19, 2019, 10:29:33 PM »

What is in the top left corner in the image? Pressure sensor?
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« Reply #81 on: September 20, 2019, 01:07:31 PM »

It is a pressure sensor. The chassis used to be a helium compressor that I gutted.

I probably should've removed it, but I just painted over the front of the meter.

Jon
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« Reply #82 on: September 22, 2019, 12:49:06 PM »

Well, here it is.  It's definitely beefier than my old one. Now just to hook it up and retest.

Jon


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« Reply #83 on: September 22, 2019, 06:42:30 PM »

There's 400 watts on the dipole. I haven't finished fine tuning yet. Getting this far was frustrating enough because my hand would sometimes rotate the 'Wave Select' knob by accident and I'd switch between a sine wave and square wave. Everything would get thrown off and I'd go through a bunch of changes to figure out why, only to keep coming back to that waveform selection.

Anyway, enough for today. I'm going out for pizza.

Jon


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« Reply #84 on: September 23, 2019, 03:54:34 PM »


John,

  I always look forward to your updates.

Will be interesting on what the efficiency turns out to be.

You know, 400 watts (or 500 watts DC input) is a lot of CO2 from the power plant!  Kiss

Jim
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« Reply #85 on: September 23, 2019, 04:00:25 PM »

In the metro Phoenix area, we have the largest nuclear power plant in the country. Zero green house emissions sir...  Wink

That scope picture was taken with a lower drain voltage. I need to ease it up and tweak the controls to get it to where it should be. I just stopped by Harbor Freight too to pick up a few extra multimeters. It'll be easier for me to calculate efficiency with 5 digital meters all reading something at once.

Jon
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« Reply #86 on: September 23, 2019, 10:19:09 PM »

Not bad !! Looking forward to further updates.
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« Reply #87 on: September 24, 2019, 04:16:28 AM »

Iím waiting on a couple doorknob capacitors to arrive from Ukraine. Right now Iím fully meshed on the loading capacitor and this will give me some options upward. Iím sitting right around 3400pf.

Seems like a lot. But, to continue testing I want the options if things go that way. I can move lower too with the current mix of doorknobs I have.

Jon
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« Reply #88 on: September 24, 2019, 10:39:32 PM »

Hmm... That seems like a lot of capacitance for loading on 75 meters.  Do you have 4 modules of 6 FETs each, all in series with 1:1 output transformers (and combined out of phase of course)? 

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« Reply #89 on: September 25, 2019, 08:23:07 AM »

Yes to all that.

I have a 1500pf cap, a 1000pf cap and a 900pf variable cap fully meshed all in parallel on the output. Drain voltage is low right now too, so maybe that's playing a part. Another possibility is that I could have something squirrely going on with the antenna. Long story short, I think I have an intermittent PL-259 splice outside.

I'll put the rig on a dummy load in the shack to see how it behaves. The only problem is that the cantenna gets warm pretty quick.

Jon
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« Reply #90 on: September 26, 2019, 07:06:37 AM »



Put the cantenna in the fridge.


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« Reply #91 on: September 26, 2019, 09:53:49 AM »

Just make sure the oil residue doesn't get on the leftovers.

Jon
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« Reply #92 on: September 26, 2019, 11:18:21 PM »

Here's my test setup and the current waveforms. I'm limited in the amount of testing time I have due to dummy load heating. I need to wait overnight for the oil to cool.

Right now I'm at around 1350pf on the loading capacitor. I probably do have something wrong with my antenna. I'll do the rest of the testing using the cantenna.

This is at 325 watts carrier and about 80% efficiency. The waveform starts to get distorted as I raise drain voltage above 30 volts. I tried to tweak everything to compensate but my dummy load was at its limit. I'll try again tomorrow.

Jon


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« Reply #93 on: September 27, 2019, 12:50:41 PM »

Here are the waveforms for 400 watts carrier with 33 vdc on the drains. I still keep coming back to 80% efficiency though, unless there's some error in the way I'm measuring it. The good thing though is that current draw from each of the 4 buses is consistent.

The waveforms look pretty good though. I'm not sure how to improve on them.

Now I need to fix my antenna and maybe belch out some modulated RF!

Jon


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« Reply #94 on: September 27, 2019, 05:16:50 PM »

I still keep coming back to 80% efficiency though, unless there's some error in the way I'm measuring it. The good thing though is that current draw from each of the 4 buses is consistent.
/quote]

Jon,

  The peak Drain voltage should be about  ~ 4X the Drain supply. Also, try DC coupling the scope so you can see if the FET's are saturating close to ground when turned on. If the Gate drive has slow rise and fall times, then that will degrade efficiency as well. Does anything other than the Cantenna get hot?

Good Stuff!
Jim
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« Reply #95 on: September 27, 2019, 06:56:36 PM »

The heat sink does get a little warm, but not too bad.

I fixed what I thought was the problem with my antenna but SWR swings wildly.  When it's there, it's there... and the waveforms look beautiful. But then things start going haywire with SWR and power jumping all around. I noticed it too with my rice box on 20 meters. I use the same feedline for it and SWR has jumping way high there too.

I need to buy new coax for this setup. When I opened up the trouble spot in the coax, I noticed that water had seeped in along the shield for a long way.

Jon
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« Reply #96 on: September 27, 2019, 07:14:40 PM »

Hi Jon....

Its best to test into a Dummy Load.....
Ebay has some high powered 50 ohm non inductive resistors....will have a look later on and see whats around...

Can you post some pictures of your gate waveforms ....
One when there is no voltage applied to the Drains and one with voltage...
Could you overlap them a little too ... makes it easier to see what the timing is etc:

Just looking for things like Duty Cycle .... voltage levels etc:


Wayne
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« Reply #97 on: September 27, 2019, 09:50:26 PM »

Maybe for a quick 50R Dummy Load something like this:

https://www.ebay.com/itm/10-OHM-100W-Non-Inductive-High-Power-Resistor-100-Watts-x1/202394779668?hash=item2f1fab4014:g:LtIAAOSwhkRWg5eo

Order 5 of them .....put in a box with a couple of fans.....
The only thing its from China so maybe order one first and check the inductance and order more from the same supplier....


Wayne

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« Reply #98 on: September 28, 2019, 12:35:03 AM »

Hey Wayne,

My little cantenna actually does a pretty good job. It heats up and slows me down, but that could be a good thing.

I'll do a little more scope stuff in a little bit, but I really want to get my antenna problem nailed down first. I know I can get pretty waveforms with the rig right now, so I just want to do more testing with the dipole. Heating up dummy loads gets pretty boring after a while.

I'm drawn to this too because in between SWR excursions, the waveforms looked superb!  Even better than with the dummy load. Trust me on this one.

https://www.youtube.com/watch?v=yM25-lz1Yms

Jon
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« Reply #99 on: September 28, 2019, 07:52:02 AM »

Yes, "Something Wonderful" Love that video.  Grin


Jon,

   You could take this idea to a higher level. Add salt to lower impedance, and add water to raise the impedance.
 
https://www.flickr.com/photos/g6sfp/2781053531/in/photostream/

Need more key down 400 watt time, use a bigger bucket!

Jim
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