HFU HF Underground
Technical Topics => The RF Workbench => Topic started by: ChrisSmolinski on October 06, 2019, 1627 UTC
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You've probably seen those "2MHZ-700MHZ 3W HF VHF UHF FM Transmitter RF Power Amplifier" listings on eBay. Here's what they look like:
(https://i.imgur.com/ODG7Rnz.png)
I bought one to see how they work, and whether I could use it as the basis for a QRP beacon on 40m or perhaps even 10m if the band ever opens again. Well, the answer is they don't work very well.
They are biased in such a way that they draw a substantial current in idle mode. I didn't measure it, but the heatsink quickly gets hot, in a few minutes it got up to 130F. I aborted the test before it got any hotter.
They use a RD01MUS1 for the amp, here's the datasheet: https://www.modelithics.com/models/Vendor/Mitsubishi/RD01MUS1.pdf
There's also another, low power, RF amp on the front end, as well as a 7805.
The heatsink is just clamped to the back of the PCB. There is a tinned area, but I didn't see evidence of any heatsink compound.
I rigged up a fan aimed right at the heatsink, this keeps the temperature down to 90F which seems reasonable. I can get about 1-2 watts out on HF onto a dummy load, less on lower frequencies, more on higher frequencies. I suspect it may do better on VHF, I need to find my 2m power meter and see. Not sure if you'll ever get 3 watts, and if so for how long ;D
(https://i.imgur.com/ZfRPc0I.png)
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I'd recommend to always go with Greek gear for MW and HF. There's something about Greece that they seem to be obesesed with these frequencies. There is so much stuff available that's better than the Chinese. They even make custom Class D and E.
Here is a good amp from a vendor I've used for a while:
https://www.ebay.com/itm/RF-POWER-LINEAR-AMPLIFIER-AM-MW-HF-HAM-RADIO/323931112378 (https://www.ebay.com/itm/RF-POWER-LINEAR-AMPLIFIER-AM-MW-HF-HAM-RADIO/323931112378)
It might need a pre-amp because I don't know what you're driving with.
Even if you don't need it, I think others might find this guys wares interesting :)
https://www.ebay.com/sch/kleop313/m.html?_nkw=&_armrs=1&_ipg=&_from= (https://www.ebay.com/sch/kleop313/m.html?_nkw=&_armrs=1&_ipg=&_from=)
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You could, "Go English"!
Str.
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That too :)
I am really curious about Greece though. Do they not have any radio laws there? There are so many pirates.
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I bought one of these kits to play with. The docs and assembly instructions have to be sleuthed out because the sellers don't ship any. I have included the links I found below
Kit 45W SSB Linear Power Amplifier CW FM HF Radio Transceiver Shortwave DIY
https://www.ebay.com/itm/DIY-Kit-45W-SSB-AM-Linear-Power-Amplifier-CW-FM-HF-Radio-Transceiver-Shortwave/293341065384?hash=item444c7d70a8:g:5bUAAOSwkklZpp4j
(https://i.ebayimg.com/images/g/5bUAAOSwkklZpp4j/s-l1600.jpg)
document links
https://pa0fri.home.xs4all.nl/Lineairs/RF-AMP-2078/RF-AMP-2078.htm
https://pa0fri.home.xs4all.nl/Lineairs/RF-AMP-2078/4Z4TJ%20(1).pdf
https://pa0fri.home.xs4all.nl/Lineairs/RF-AMP-2078/4Z4TJ%20(2).pdf
https://www.banggood.com/DIY-45W-SSB-HF-Linear-Power-Amplifier-Amateur-Radio-Transceiver-Shortwave-Radio-Development-Board-Kit-p-1018834.html (look for document link to RAR file)
https://drive.google.com/file/d/0B9RT-Z00GQUAdW5Ma1dNeUxIVjg/view
English User Manual:
https://www.dropbox.com/s/k6a1zbv7ou9m5kj/E1585-English%20User%20Manual.pdf?dl=0
The Winding Method of Magnetic Coils:
https://www.dropbox.com/s/2d92imnguqsoo0g/E1585-the%20Winding%20method%20of%20Magnetic%20coils%20V306.pdf?dl=0
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How did it work? Any better than Chris's mini space heater?