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1KW - PWM - CLASS - E - 75meter - TRANSMITTER BUILD




 
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Author Topic: 1KW - PWM - CLASS - E - 75meter - TRANSMITTER BUILD  (Read 4532 times)
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ka1wlz
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« on: November 12, 2021, 12:33:58 PM »

Hello all,
Started the gathering of parts for the 75meter 1KW class E transmitter Model "DJS-1000-75E" Smiley
I have been talking with Steve some and looking at schematics and for the first one I think much of what I will use are predesigned boards.
Therefor much of this discussion in the beginning will be about gathering of parts, fabrication, layout, etc.....
I know there are many of you that have already build these types of units so any helpful techniques to avoid issues down the road are welcome
As I build the transmitter and post pictures and comments, I am sure conversations will go in many directions, but the plan is to take the entire journey on this thread of AMFONE.

tks
KK6IRZ/KA1WLZ
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ka1wlz
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« Reply #1 on: November 13, 2021, 10:06:03 PM »

Started figuring out the VFO. Somewhat the VFO shown on classicradio.com but already know I will make some changes for keying and spot but generally speaking it will be close.
Have the Supply A and Supply B done.
Found four 27000uf 160V caps in my junk drawer and a Hammond HPS 2000VA Transformer, FET one the way, bla bla etc... so the gathering is one the way.


* transformer.jpg (326.98 KB, 1600x1200 - viewed 143 times.)
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ka1wlz
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« Reply #2 on: November 18, 2021, 11:57:10 PM »

Hi All
I am building the phase splitter driver this weekend so if anyone has and rules of thumb or point of addressment I would love to hear it. I have attached my board design although just showing the top side. does not seem like anything to magical but I am sure I will get a surprise when I run it. Smiley
Look forward to hearing any helpful hints.

Thanks
Jeff
KK6IRZ/KA1WLZ

* FREQ-PHASE-SPLIT-DRIVER-BOARD.pdf (82.38 KB - downloaded 64 times.)
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vk3alk
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« Reply #3 on: November 19, 2021, 06:18:19 PM »

Hi Jeff...

This is going to be an interesting and very big build...
Many FETs and drivers etc: and testing along the way  Grin

I do listen at times to you guys on N1NTE and from memory where is only 2 stations running these TXs at that power level .... Steve and Brent ( who only operates during the winter months ) ...
Bob K1KBW runs 400 Watts and his signals are very strong most of the time....
He also has a WEB site with photos that maybe worth while looking at for ideas etc:

Have you build these circuits before ?
What is the VFO ?
There is also a duty cycle circuit ( on Steves WEB site ) that probably would be best to makeup...
If it was my TX would prefer both those circuits on the one board...instead of them all joined with jumper wires etc....

That will do for the moment...


Wayne
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ka1wlz
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« Reply #4 on: November 19, 2021, 08:21:44 PM »

Hi Wayne
Yes it is going to be a fun build but I have many of the parts already in boxes and bins. I am of course getting much information from classeradio website but I remembe4r the days back in the late 90s early 2000 when this was the main building conversations on the East coast. I have always been dominantly a Tube guy and when I say dominantly I mean I have one solid state rig and a Garage full of tube gear.

I have seen Bob's stuff and looks like some nice builds although I think recently I saw him playing with a 24 FET version. I think in that version he used some Doug's output boards which I also plan on using for this build.

I have build many transmitters over the years from 10 watts to 100,000 watts. Mainly between 1992 and 2005. Have not build one of these rigs so it does provide a little new for me but have had many other products over the years with similar technologies just not always RF.

I have not decided yet on the VFO specifically, have though about a DDS but being this will only be for 80 meters I was thinking I may just build a Colpitts oscillator to operate 17 to 20Mhz and then slice it down to 3.5 to 4Mhz for operation. Or I could just stick a china generator into it HIHI.

The photo on my last reply actually is based on Steve's VFO schematic on the website. on that prototype board I will be using junk drawer parts so the pots are actually not shown on the board but there is a trace that a panel mount pot will tie to. Smiley. This first board is just a prototype to get things started which would be the standard frequency cut in 1/2. I am just doing it to get some visuals on the waveforms. Later I will design and build a board with protection and whatever PTT controls I may decide to use.

I do appreciate your comments and advice on keeping things tight and complete on the board. I am looking forward to a fun weekend of playing. I may even build the power supply this weekend if I get motivated. I was lucky to find all I needed already in my horder stockroom hihi.

See Ya 73

Jeff
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KK6IRZ
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« Reply #5 on: November 19, 2021, 08:57:11 PM »

OK EVERYONE I JUST REALIZED I WAS SIGNED IN AS KA1WLZ WHICH IS MY OLD CALLSIGN

Dummy me.
Hi this is still Jeff but with my current call.

Smiley Smiley
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KK6IRZ
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« Reply #6 on: December 07, 2021, 09:56:21 PM »

Hi all

Thanks to Doug for sending me a set of his PA FET Boards they look great but there are 2 parts that are currently not available anywhere that I have checked. Maybe one of you have some spares.

Need 4 BUT WOULD LIKE TO GET 8 of the 100C152KT500X and Need 4 of the 900C224MT200X
I have everything to build the 24 FET PA except those 12 parts

CQ CQ CQ who's got the stash?
Smiley
 
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K9MB
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« Reply #7 on: December 08, 2021, 07:59:33 PM »

Hi all

Thanks to Doug for sending me a set of his PA FET Boards they look great but there are 2 parts that are currently not available anywhere that I have checked. Maybe one of you have some spares.

Need 4 BUT WOULD LIKE TO GET 8 of the 100C152KT500X and Need 4 of the 900C224MT200X
I have everything to build the 24 FET PA except those 12 parts

CQ CQ CQ who's got the stash?
Smiley
 
The boards are beautiful snd compact. Downside is that they use some expensive, hard to get caps in a few places…

For the 1500pF caps, look at these MLC Micas made by CDE.
They are rated at about 10 Amps at 1.8mHz and higher at 80 meters, so their ratings are very similar to the ATC100C caps.

https://www.mouser.com/ProductDetail/Cornell-Dubilier-CDE/MC22FF152J-TF?qs=aUB389kaodB6G%2F9MgOGeXw%3D%3D

I am going to use 3-470pF ATC 100E chips in parallel I bought a few years ago.
The values are not exact as long as they are big enough to prevent a spike that would kill the 11C90s on each bus. Nominally, 250pF per device according to Steve

The 0.22uF chip capacitor looks tougher to find.
I wonder if a WIMA low ESR film cap might be bootstrapped in until you are able to order the 900C chips…

73, Mike K9MB
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KK6IRZ
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« Reply #8 on: December 08, 2021, 09:55:51 PM »

Hey Mike
Thanks for the info and yes there are choices for other parts that would do the job but being Doug made such a nice looking board I was hoping to stay with the designed parts. hihi we will see.
I am actually a fair part into the experimentation of lower lever items.
Built a FET Colpiitts oscillator with a range from 7 to 8 Meg very stable even spread-out on the bench so when it is finalized within an enclosure I expect it will be more than adequate divided down to 80 meters.
My phase driver is also on the bench and working and I have good smooth control of the duty cycle and have everything for the PA except this parts.

I am hoping to hear fromn Steve sometime with hopefully new on availability on the boards and parts he has but it is the holiday season so I would imagine he is busy with more important things that putting together board kits hihi LOL
Anyway thanks for the suggestions and I will check it out but for right now I will keep searching for the design originals Smiley

73s
Jeff
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KK6IRZ
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« Reply #9 on: December 09, 2021, 10:52:36 PM »

Ok Guys found a stock pile for $5 each on the 100C152KT500 AND $6.30 ON THE 900C224MT200

Thanks to those who looked and thanks for the comment
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w8khk
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« Reply #10 on: December 10, 2021, 09:19:05 AM »

Ok Guys found a stock pile for $5 each on the 100C152KT500 AND $6.30 ON THE 900C224MT200

Thanks to those who looked and thanks for the comment

It would be interesting to know the source you located for these capacitors.  Could you please provide a link or other information for those who are also building Class-E transmitters?  Thank you!
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Rick / W8KHK  ex WB2HKX, WB4GNR
"Both politicians and diapers need to be changed often and for the same reason.”   Ronald Reagan
KK6IRZ
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« Reply #11 on: December 10, 2021, 05:16:44 PM »

ah sorry
I use findchips.com
they monitor many different distributors but in this case I got them from Quest Components.
I think I got the last of what they had but maybe someone else will pop up.
When I first did the post there were none available so I just loaded the part numbers in the notification area of my account and when they came available I went and grabbed them.

With all that said, findchips 99% will get me what I need

thanks
Jeff
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KK6IRZ
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« Reply #12 on: December 23, 2021, 10:12:20 AM »

Little added information on parts used with the PA.
I will post the list as it gets bigger but for now here is what I got

Thanks
Jeff

* partslist.pdf (76.66 KB - downloaded 42 times.)
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KK6IRZ
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« Reply #13 on: December 24, 2021, 02:11:19 PM »

Hello All
I am using the Boards that Duog N9SHU provides
Anyone know why there are an X1 and X2 position for mounting SMA connectors.
I have not ohm everything out but they seem to be connected together and was just curious to why there is not only one location for the input to the board.
I asked Duog but have not heard back from him so thought I would see if anyone had some insight.

Thanks
Jeff
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K9MB
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« Reply #14 on: December 24, 2021, 08:36:57 PM »

I understand that the second sma jack footprint is unused for the 24 FET rig, because each 12 FET board is the same phase, but there is an option that I am taking- to make a one board 12FET rig. That requires some cut traces and jumpers and Doug can provide that mod, if anyone wants to do a 500-600 watt 12 FET rig.
If you are doing 24 FETs, ignore the second SMA footprint.
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KK6IRZ
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« Reply #15 on: December 24, 2021, 09:12:38 PM »

Thank you
I figured it was for a mod for a one board PA but could see that it would require cutting and jumpers so I thought maybe there was another reason.

No worries, I am doing the 24 FET using 2 boards so should be no changes needed.

Thanks for the verification.

I am 3d printing a Ferrite Bead holder for my transformer configuration and should have everything mounted to the Heatsink next week I hope.

I am debating on heatsink compound or pads, Pads would be easier but compound works better. With the expected high efficiency it probably does not matter much anyway. Smiley

Again Thanks

Jeff
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K9MB
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« Reply #16 on: December 25, 2021, 01:13:35 PM »

Would like to see your Ferrite bead holder.
You will need to be sure that the Ferrite has good air circulation so heat can be dissipated. It is not a lot of heat, but even a small amount can cause cores to get hot if they cannot dissipate the heat.
I just glued the cores together in stacks and put copper tubes through them and then wound the secondaries through. If you use circuit board to connect the copper tubes and cut gaps, you can use the fiberglass FR4 to provide support and terminals can be attached to standoffs to make it all rigid. Lots of ways to do it.
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KK6IRZ
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« Reply #17 on: December 28, 2021, 12:05:50 PM »

OKIEDOKIE
Little explanation

First this transmitter is being built in a 21.5"Widex14"Highx15"Deep cabinet. The idea being that this would be like a old boat anchor transmitter sitting on a desk but able to do 1kw.

The heat sink is mounted on the back of the cabinet at floor level with the 2 PA boards mounter horizontal with the transformer between the the 2 boards but actually mounted to the floor of the cabinet.

The ferrite bead support has a .75 hole on one side to keep the beads from sliding out, a support that aligns to the middle of each bead to hold things straight, and then a cap which gets put on the other end of the support to lock all the beads into place. (Cap Not Shown)

Here is what it looks like

Thanks
Jeff

* FerriteBeadHolder_PA_Transformer.pdf (81.34 KB - downloaded 45 times.)
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K9MB
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« Reply #18 on: December 28, 2021, 07:44:38 PM »

Thanks for the explanation. Nice design on the core holder. Plenty of airflow there, I am sure.
I would love to see it implemented when you get it going.
73, Mike
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KK6IRZ
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« Reply #19 on: December 28, 2021, 09:01:51 PM »

No Prob Mike

I will be starting the initial physical layout in the cabinet in the next couple weeks.
I had several of the holders and end caps printed but waiting for them to show up.

I have most of the design worked out in my head and have been doing solidworks models of all the parts so I can work out mounting and final layout details in a virtual world before actually drilling and blasting.
Although I do have just about all my holes drilled and blasted on the heat sink at this point. Maybe by the end of the weekend I can at least post a picture of the heatsink and PA boards all mounted in the cabinet.

Hihi we will see

thanks
Jeff
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KK6IRZ
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« Reply #20 on: December 30, 2021, 12:12:46 PM »

Just to provide a little closer representation of the Ferrite Bead holder.
Here is a image with beads and wires
Just to make it easier to see how it will look

Thanks
Jeff


* FerriteBeadHolder_PA_Transformer.jpg (614.3 KB, 3180x2440 - viewed 53 times.)
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steve_qix
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« Reply #21 on: December 30, 2021, 03:02:12 PM »

This is going to be a great build !!!

There are 6 of the 24 MOSFET transmitters on the air that I am definitely sure of.   I think there is one other out there, but I can't remember who has it off hand.

The bypass capacitors at the DC side of the RF output transformers have been an issue with the boards in some builds.  This is a high current point, and we have seen some capacitor failures in the field.  Whatever capacitor is used as the DC bypass capacitor *MUST* be a high current capacitor, at least 7 amps and preferably 10 amps ( at the real operating frequency).  The problem gets worse the lower in frequency you go.  So, it's worse on 160 meters than on 75 meters.

The other thing if note is that the ideal value for the bypass capacitor is .15uF and not .22uF.  This was a change made in the field due to the fact that, at the time, the .15uF multilayer ceramic caps were not available.

This is a solvable problem!!!

Looking forward to following the progress of this build.

Regards,  Steve
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KK6IRZ
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« Reply #22 on: December 30, 2021, 07:41:17 PM »

Hi Steve
Thank you for the info
I am only doing 80 meters for this build

When I received the board from Doug he had a list of part numbers that he said were already qualified as being right for matching up with board design. The part number he gave me was the .22uf 900C224MT200X and I did notice that it was different than the schematic on the site.
However, I figured it was possibly due to board design adjustments.
I still do not see the .15uf caps available so I assume on 80meter I will do ok with the .22uf caps I have available.

Also Steve, maybe my emails are going to your junk folder.
I sent a couple request on getting your 3 board set with parts

Anyway, I expect to be running the board through the reflow oven next week for all the surface mount parts and then will install the through hole parts. Still drilling and tapping the 5 billion holes in the heatsink. hihi LOL

Again thank for the info and let me know when you can about the board sets and parts

Thanks
Jeff
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K9MB
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« Reply #23 on: December 30, 2021, 07:50:41 PM »

Hi Jeff,
Thanks for posting the representative image of your core holder. It is exactly as I visualized it. Very nice design. 73, Mike

PS: If you decide to make some extras to sell, let me know. MB
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« Reply #24 on: January 02, 2022, 01:05:57 PM »

One of the things we're looking at is to stack several MLC capacitors in parallel.  Possible 3 .047uF devices, or maybe a .068, a .047 and a .033 in parallel.  Still researching parts.

This is to increase the current handling capability of the RF bypass capacitors at the DC side of the RF output transformers.
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