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100 watt carrier 40 meter TX




 
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Author Topic: 100 watt carrier 40 meter TX  (Read 2279 times)
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ka1tdq
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« on: November 12, 2016, 07:11:01 PM »

I almost have all the parts for another class E rig.  This one will be two FETs in push-pull and be 100 watts carrier for 40 meters.  The radio faceplate is from an RCA Radiola 17, vintage late 1920's.  I was thinking that it'd be a nice touch to add an old-meets-new element to the transmitter.  The bottom hole will be the series tuning capacitor, the dial hole will be an elongated LED bar graph showing power output, and the top hole will be a bright LED indicating IXDD driver bus power.  

I can't seem to get away from this style of transmitter layout.  It works, so what the heck.  

Jon
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Mike/W8BAC
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« Reply #1 on: November 14, 2016, 09:27:21 AM »

If you are going vintage, how about a window so you can view the finals?  Grin
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ka1tdq
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« Reply #2 on: November 14, 2016, 10:30:56 AM »

If these finals glow, I've definitely got a problem!

I tried to google images of solid state devices flaming, and found this.  Apparently it is a transistor with a filament.  I'm not trying to bring religion into this, but when someone drew this, well, wtf... ?

Jon


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ka1tdq
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« Reply #3 on: November 16, 2016, 11:26:36 PM »

I've started bolting things to the chassis. 

Black Friday is next week and I plan to get the modulation components then (Heising parts, audio amp and microphone preamp).

Jon


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steve_qix
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« Reply #4 on: November 18, 2016, 04:32:39 PM »

Single-Ended push pull might be a good way to do it.  I use single-ended push pull in my 40 meter class E rigs.  With type 61 core material, which is much better at these frequencies than 43, at least in terms of core heating.

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ka1tdq
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« Reply #5 on: November 18, 2016, 06:51:14 PM »

Ah, thanks.  Good to know.  I'll order different cores and use these ones for a different 75 meter project.

I figured going single ended, push pull would be easier at 40 meters than paralleling FETs.  It didn't work out too well for me the last time.  But, it sure made a really good 75 meter rig.  I talked with Louisiana last night on 75 with it.  I was happy about that since my dipole is pretty low. 

Jon
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ka1tdq
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« Reply #6 on: November 20, 2016, 11:40:34 PM »

A little more progress.  Mounted the front faceplate and the fiberglass rod going to the tuning capacitor.

Jon


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ka1tdq
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« Reply #7 on: December 30, 2016, 07:21:58 PM »

I'm almost finished with the heat sink assembly.  I just need to add an electrolytic to the IXDD supply buss. 

After that, I'll mount the output transformer and it'll be good for testing!  I'll do the LED power output bar graph after I get everything working. 

Jon


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ka1tdq
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« Reply #8 on: December 31, 2016, 01:44:04 AM »

Ready for testing!

https://www.youtube.com/watch?v=raWZraPHLqM


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steve_qix
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« Reply #9 on: December 31, 2016, 05:43:32 PM »

Looks real good - let us know how the testing goes!

Regards,  Steve
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ka1tdq
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« Reply #10 on: December 31, 2016, 09:16:16 PM »

It doesn't behave too well at 40 meters.  It gets really touchy on the tuning capacitor.  Just a slight nudge either way and it goes berserk.  From the picture you can see my test setup.  It's just a bunch of clip leads and different values of doorknob capacitors.

It does seem to play very nicely on 75 meters though.  You can see the 75 meter waveform on the scope in the picture.  It's not perfect, but I'm just playing around with values (and I've given up for the night since I have to get ready for a new year's party). 

On 75 meters, I'm getting 42 watts out at 24 volts on the drains.  I'm sure with 48 volts, 100 watts will be achievable.  I haven't calculated efficiency yet, but things look promising from the waveforms. 

I'm thinking this is going to be another 75 meter rig.  My goal was 100 watts on 40 meters, but it's just too touchy. 

Jon


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ka1tdq
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« Reply #11 on: January 02, 2017, 05:53:24 PM »

I tried a bunch of configurations, but efficiency for every one was around 70 to 80%.  I did manage to get it to play on 40 meters as well.  Here's the best I could do with this:

40 meters:  25 watts carrier (at 24 volts drain)

75 meters:  100 watts carrier (at 48 volts drain)

160 meters:  11 watts carrier (at 24 volts drain)

I like the 75 meter result, but efficiency was at 70% on that one.  I couldn't package it up and call it good.

I'm going to shelve this one for a while.

Jon
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steve_qix
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« Reply #12 on: January 02, 2017, 10:32:30 PM »

Hmm... something is amiss because particularly on 75 meters, you should be able to get close to, if not a little over, 90% efficiency.

If you post some close ups of the waveforms, it may help.

It's probably something simple.  Usually is  Smiley
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ka1tdq
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« Reply #13 on: January 02, 2017, 11:47:02 PM »

I'm sure it is something simple.  Usually what works for me with electronic problems is to take a nap.  Nine times out of 10, when I wake up the solution will hit me.  I'm going to put this away for some days, and when I pull it back out I'm sure I'll get it working right.  If not, I'll post some waveforms and hash it out the hard way. 

https://www.youtube.com/watch?v=O0wOD9TWynM 

Jon
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KB2WIG
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« Reply #14 on: January 06, 2017, 11:47:16 AM »



J,

Have you considered a pot of water, a blankie and a thermometer Huh? ??

klc
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ka1tdq
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« Reply #15 on: January 07, 2017, 12:14:17 AM »

I measured output power more accurately using a digital scope and things look much better. 

Input Power:  24.3 vdc @ 2.1 amps = 51.03 watts

Output Power:  Into a 50 ohm dummy load, the scope is reading 144 volts pp at the antenna jack. 

144 volts * .3535 = 50.9^2/50 = 51.8 watts

Efficiency =  output/input = 51.8/51.03 = 101.5%

That's obviously not possible and there's variances in readings, but it looks good nonetheless.

Jon
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ka1tdq
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« Reply #16 on: January 14, 2017, 08:29:20 PM »

The bright LED and bar graph LED display with RF pickup are all done and ready for testing.  I also got my regulated 48 volt power supply in. 

Hopefully, my next report will show pretty blue LED's. 

Jon


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ka1tdq
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« Reply #17 on: January 14, 2017, 11:27:50 PM »

I got a super-bright LED for the top hole, and boy is it bright!

The 10 segment LED strip is acting like a dot display rather than a bar graph.  I'm not sure why either.  I shorted pins 3 and 9 of the LM3914 to the 12 volt supply.  Anyway, it works.  The level on the bar graph in the picture corresponds to 100 watts carrier.  The LED display will shoot upwards on modulation.

Jon


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KD6VXI
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« Reply #18 on: January 14, 2017, 11:50:38 PM »

Mas clip leads,  por favor!

--Shane
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« Reply #19 on: January 15, 2017, 10:44:44 AM »

I got a super-bright LED for the top hole, and boy is it bright!

The 10 segment LED strip is acting like a dot display rather than a bar graph. 

Jon

It's very close to a bunch of RF?
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ka1tdq
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« Reply #20 on: January 15, 2017, 11:03:29 AM »

That's true, but I tried AA batteries using different voltages on the input pin (and the transmitter off). Same result.
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