Thoughts on the BLF188XR

[LeapFrog]

I have no experience with high-voltage in relation to Radio, although if anyone has any thoughts or experience with the LDMOS Amplifiers using BLF188XR or similar devices please share them here.

The 50v power supply is my first challenge, these parts are much more efficient than the typically used (almost extinct) 2sc2879 although they require higher voltages. Newbie question: generally speaking a switchmode powersupply will not handle the current demands here?

Searching fleabay I find two post of interest I wish to bring into discussion:

LDMOS BLF188XR BOARD LINEAR AMPLIFIER
Source Country: Israel

1.2 KW LDMOS power amplifier 1.8-54MHz HF for BLF188XR
Source Country:
Russian Federation


I don't have the experience / confidence yet to save up some cash & buy one of these boards, just to pain-stakingly rip it apart piece-by-piece to reverse engineer it and measure / record every component

and document every trace, just to get a blue-print.

My concern form using the board as-is, the material used does not seem thick enough! I want to build this unit like a Tank, Rugged. The goal is to build an lmdos unit that will "loaf around" @ under 1 KW, use a board easily sourced (or improve upon one that's available currently). So this little pcb doesn't meet the demands, it looks way to thin. Hence reverse engineer it just to build it "stronger", more rugged. Also this project is for information/ experimentation/ research & will NOT be another 11 meter splatter box shooting harmonics to the moon, a proper filter and dummy load will be used.

 

[n8fgb]

http://www.ebay.com/itm/152093672588?_trksid=p2060353.m1438.l2649&ssPageName=STRK:MEBIDX:IT

As you can it is the copper plate that makes the difference.

http://www.ebay.com/itm/152093756267?_trksid=p2060353.m1438.l2649&ssPageName=STRK:MEBIDX:IT

The backside of the board is heatsink material. The LDMOS is sweated directly to the copper plate. The copper is then mountedto a large heatsink, with fans. YOu can buy just about all the components from the Russian dealers on Ebay, and just assemble it yourself. I think this cool technology.
Rich

 

[Captain Kilowatt]

The 50v power supply is my first challenge, these parts are much more efficient than the typically used (almost extinct) 2sc2879 although they require higher voltages. Newbie question: generally speaking a switchmode powersupply will not handle the current demands here?

Switch mode power supplies will certainly handle the load and are actually your best bet to power such a device. I have a Larcan television module modified for use on the 6m band and runs four MRF-151G's which are nearly antiques now but still very popular. Each device runs 300 watts out for a total of 1200 watts. They are 50 volt devices as well. I have a Hewlett-Packard server power supply I picked up on Ebay for $35 but it cost an extra $60 to ship it to Canada. It is a 3 Kw supply puts out 50 volts at up to 60 amps. They are not plug and play but almost. Plenty of documentation online and all you need to do is solder a few jumpers and make up AC and DC power leads.

 

[LeapFrog]

Hewlett-Packard server power supply I picked up on Ebay for $35 but it cost an extra $60 to ship it to Canada. It is a 3 Kw supply puts out 50 volts at up to 60 amps.

Captain Kilowatt That server supply looks promising, thank you! And the Larcan module looks like a real beauty (online pictures)!

You can buy just about all the components from the Russian dealers on Ebay, and just assemble it yourself. I think this is cool technology.
Rich

No doubt what I missed was the big copper heart of the device, It is neat that the Russians have all kinds of filters and other supporting hardware that goes along with the power amplifier board.
To buy it all though kinda defeats my homebrew-esque purposes!

Perhaps just the main pc board and copper dimensions will be "barrowed" from them.

 

[BBB]

Water cooling would be a plus. Plenty of Water Cooled CPU stuff around to convert.

http://www.aavid.com/product-group/liquidcoldplates

http://catalog.chtechnology.com/vie...-fin-heat-sinks/liquid-chill-plate?&plpver=10

 

[LeapFrog]

Water cooling would be a plus. Plenty of Water Cooled CPU stuff around to convert.

http://www.aavid.com/product-group/liquidcoldplates

http://catalog.chtechnology.com/vie...-fin-heat-sinks/liquid-chill-plate?&plpver=10

Very Good Input Here for Any Guys Who Want to Over-Volt Parts And push them towards the limitations of the device, any time you keep the temperature down, *generally speaking* the parts can take more abuse and be pushed to perform beyond the manufacturer's specifications provided in the data sheet.

CPU over-clocking is a great example.
For instance let's use bios manipulation, & overclocking software tools to
Make a 2.6 Ghz Intel P4 CPU
run @ 3.1 Ghz That is 500Mhz of extra processing power! (more cpu "speed" )

The trade off is that (Lots of) heat is generated and it can quickly destroy the part if extra measures are not gone through to ensure the heat is dissipated efficiently.

Some over-clockers use water or oil cooling some use huge fans, large heat sinks, and for a record breaking attempt it's not unheard of some to use liquid nitrogen or CO2!

I wouldn't mind seeing a video of a 2sc2879 pushed to it's real limits with voltage and high input drive, and then done again with a some extreme & over-the-top cooling method implemented.

Record the amount of watts produced relative to the temp, input drive, & voltage plot the stats on some graph paper and look at the sweet curves of data!

 

[Captain Kilowatt]

Whatever happened to sense and sensibility of running components within rated spec anyway? Give me a big old heatsink and a small fan to cool my RF devices being run within spec anyday over some over volted device being run beyond spec and cooled with a rediculous cooling system because.........well just because. If you need liquid or exotic refrigerant gas cooling then what you REALLY need is a bigger device or bigger sink.

 

[LeapFrog]

I agree with you 100%, this BLF188 Amplifier is gonna be just fine running as a legal limit amplifier heck it wont even be running at 100%!

 

[Crusher]

I've had good luck with blf188xr from one I built so far. Still needs filtering. With 3.5w drive I'm getting around 1100w pep. I used a broadband transformer instead of transmission line transformer with good results. Built from scratch. Tracking bias is important.

 

[Captain Kilowatt]

I agree with you 100%, this BLF188 Amplifier is gonna be just fine running as a legal limit amplifier heck it wont even be running at 100%!

That device is rated at 1400 watts so true legal limit of 1500 watts would be in fact pushing it slightly beyond it's rated output at 107%. You won't have as much headroom as you think.

 

[2RT307]

I've had good luck with blf188xr from one I built so far. Still needs filtering. With 3.5w drive I'm getting around 1100w pep. I used a broadband transformer instead of transmission line transformer with good results. Built from scratch. Tracking bias is important.

Sounds like it would pair up nicely with a Flex 1500 with that low level of input power.

73,
Brett

 

[Captain Kilowatt]

Sounds like it would pair up nicely with a Flex 1500 with that low level of input power.

73,
Brett

Or a Cobra 148GTL.

 

[2RT307]

Or a Cobra 148GTL.

Well, that's a given, after re-reading previous posts. But, I know some guys that were looking for amps to run with the Flex 1500 without breaking the bank. Some end up buying an RM Italy amp to drive a bigger legal limit amp because the Elecraft and Tokyo High Power ones are so expen$ive. This amp could be an option?

73,
Brett

 

[n8fgb]

If FCC drops the 15db rule, you should a few available from the big companies

 

[Crusher]

I use a 148gtl with a 6db pad. Works well. 52v DC supply. Just remember, the BLF188XR does not like to be overdriven. 2 keys is all I got the first time. Then pop. Proper drive level and understanding it is important. $200 lesson for me. Don't make the same mistake.