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Author Topic: U-LULU (Updated LULU) for 48 meters, 20 Watt Class-E AM Transmitter  (Read 3963 times)

Offline Charlie_Dont_Surf

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My first build attempt at the U-LULU, with a board made by JLCPCB using CDS's gerber files.



Learning how to solder all over again with a hot-air rework pencil, great for the chip but how do I stop the tiny caps flying away  :)

On a test-jig I'm getting about 15w carrier, still more work to getting the output coil right and finding a suitable modulator.  Any ideas on something still available from China in 2023?

Very nice! I feel like a proud papa. :D I saw your DM too and you've obviously figured out posting photos on HFU and you have an additional 5 Watts since that DM so all is good. 

As for the power output, it would be good to know if you are trying to do this at 6250 KHz (as I did) or another frequency.

Using a different batch of PCBs (which is inevitable) and using a slightly different winding technique than mine (also inevitable) will introduce possibilities for variation. Your PCB manufacturer will likely have a slightly different material property (called Er, "E sub R" in the spoken lingo) than mine, meaning that you may want to adjust L2, C5 and C6 slightly to compensate. To tune L2, you can push and squeeze the wire of L2 a bit. 

One of the decisions I made during the design tuning was to sacrifice bandwidth for maximum power output and this means that the if you are trying to use this transmitter at 50-100 KHz away from 6250 KHz (approximately), you might not get the full output I claim. I think that it may make sense to also offer folks a broader bandwidth output tuning (which I have simulated in the computer but not built in real life) to make it a little less sensitive to my narrowband tuning I specified in 2021. My initial computer simulations suggest that I can get similar power output and broader bandwidth with a completely different set of L and C values. It remains to be seen if this is true in real life but when I verify I will update. I may also add a 43 meter band tuning option too.

For the modulator, perhaps you missed in the text (page 8 ) but I am recommending the Wondom AA-AB31184.
In North America, they are available here: https://www.parts-express.com/WONDOM-AA-AB31184-100W-Mono-Amp-Board-320-3341?quantity=1
In other parts of the world they seem to be available from Farnell in the UK, Audiophonics in France, AliExpress,  Ebay, Opentip, etc.

« Last Edit: March 14, 2023, 2022 UTC by Charlie_Dont_Surf »
I don't STRETCH the truth.

"Every minute I spend in this room, my signal gets weaker.
Every minute Charlie squats in the bush, his signal gets stronger."

Offline europirate

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Hi

Yes, aiming for the 6.2 - 6.3 range.  With 21 turns for L2 it was a little high, peaking in the 6.4 region so I tried 23 turns which brought it down to 5.8, so I've settled on 22 turns for the moment which seems about right with the ability to squeeze or open the coil a little.

I did see that you had used the Wondom board, they seem to be pure unobtainium in the UK, I have accounts with Farnell and their sibling CPC and they don't have them.  I'll trawl AliExpress and Banggood to see what they have.

I have tried a clone 100w mono board from eBay also based on the TPA3116 but no joy at all.  I'll give it another go this weekend when I have some more time.
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Offline Stretchyman

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https://www.aliexpress.com/item/1005001350507780.html

Always best to buy directly from the country of origin.

Farnell even sell them so not sure where you're looking but unable to find?

Didn't realise you were in the UK..

Str.
'It's better to give than receive' so why RX when you can TX!

         15W, 60W and 100W models available.

                   Buy one from me, NOW!


                                              ;)

Offline Charlie_Dont_Surf

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Yes, aiming for the 6.2 - 6.3 range.  With 21 turns for L2 it was a little high, peaking in the 6.4 region so I tried 23 turns which brought it down to 5.8, so I've settled on 22 turns for the moment which seems about right with the ability to squeeze or open the coil a little.

OK.

I did see that you had used the Wondom board, they seem to be pure unobtainium in the UK, I have accounts with Farnell and their sibling CPC and they don't have them. 

Forgive me, I was wrong and it appears that Farnell does not carry them nor does AliExpress any longer ("no longer available"). Well that's a bummer. When I started this thing in 2021 they were quite available but of course 2 years is an eternity in this industry, especially with the disruption of COVID-19.

I'll trawl AliExpress and Banggood to see what they have.
I have tried a clone 100w mono board from eBay also based on the TPA3116 but no joy at all.  I'll give it another go this weekend when I have some more time.

I have a DROK (or Bangood?) module or two and they are problematic in this application. The audio cuts out intermittently, especially at high output and I assume it to be the over-current protection circuitry doing this. The protection appears to be a bit more over-zealous than a real TPA3116-based module. (The U-LULU is something like a 3-4 Ohm load according to simulation.)

Whatever you end up going with, it needs to drive at least 5 Amps peak at 4 Ohms (100 Watts into 4 Ohms differential = ~5.3 Amps). Of course, we are using the amplifier single-ended with the U-LULU. Four Ohms differential (such as a loudspeaker) is equivalent to 2 x (2 Ohms single-ended to ground). If it can handle a 4-Ohm speaker then it should be good to go. Of course the Bangood and DROK are supposed to drive 3 or 4 Ohms too, so.....

For this weakness and a few other reasons (that I am too lazy to describe right now) I suspect Banggood and DROK modules are built around counterfeit TPA3116 chips that can't drive a 2-Ohm load like the real thing from TI. Caveat emptor.
« Last Edit: March 17, 2023, 0633 UTC by Charlie_Dont_Surf »
I don't STRETCH the truth.

"Every minute I spend in this room, my signal gets weaker.
Every minute Charlie squats in the bush, his signal gets stronger."

Offline redhat

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The ones I have are DROK or a clone off amazon, and they work fine up to 15-17W carrier and don't cut out until you hit 29VDC input.  The PA's I run are around 10 ohms at the DC input.  The small boards seem better than the larger ones.  I bought one of the larger 100W amps, and upon closer inspection found it had a small IC in it from a LCD TV, which also didn't pass DC.  Caveat Emptor indeed.

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Offline Stretchyman

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Shame they keep changing product design or they're simple short lived.

When I started using the TPA3116D2 amps you could get one with heatsink, volume pot with power switch, 1/4" I/p skt and space under the PCB for a voltage reg. I think they redesigned it about 5 times changing the shape and position of the connections every time. Made it a real pita. Ended up buying 200 of the last ones they produced. Less than 10 ea.

Tinytronics in NL did have them a while ago.

SKU:
000250

They may still have some...

Str.
'It's better to give than receive' so why RX when you can TX!

         15W, 60W and 100W models available.

                   Buy one from me, NOW!


                                              ;)

Offline europirate

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It appears you can also buy direct from Sure but the shipping is probably from Taiwan: https://store.sure-electronics.com/product/AA-AB31184

Bought a couple direct from the sure-electronics web site - just a week from order to delivery ... good price too

They are definately a cut above the boards I had from eBay, looks like they have 12v o/p and mute/standby switching as well.

Good call!
JRC NRD-515 & NRD-545
SDRplay RSPdx
Various wire antennas ... Global AT-1000 ATU
Shazam is the DXer's friend!

 

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