I order a 50 volt LDMOS 24 hours ago and then I find this ....

[WINKDOGG]

VIDEO IN LINK , WELL WORTH THE 8 MINUTES IF LDMOS IS NEW TO YOU !

Let me start off by saying I have very little useful knowledge about LDMOS amplifiers so far .

But I'm also a pretty impulsive guy that loves new toys and technology , its kinda a problem HAHA

I finally got up the balls to buy a 50 volt power supply and a single LDMOS board /kit as my first "budget" 1kw+ Watt amplifier build (well at least assembly if we are getting technical ). Then I run across a reply to a post from my buddy kopcicle tonight .

Apparently now just 24 hours after I hit the order now buttons I learn that at 65 volts , that very same board with a 65 volt supply and a 65v LDMOS device will almost double the output power to over 1800 true watts !

I cant stop the order now and I'm sure the 65v setup would cost a whole lot more but I wanted to throw this out there for other LDMOS beginners like myself. I'm trying to keep my 1kw build under a $500 budget fully completed . I believe the cheapest you could complete the 65v box would be more like $1000 PLUS from the 22 minutes of research I just completed . Which is still amazingly great as fat as watts per dollar is concerned , I just think In a year or two we will be able to get our hands on all this stuff much cheaper !

Check out this 50 volt VS 65 volt video , the LDMOS devices are just incredible in my opinion .
https://www.nxp.com/video/nxp-65-v-ldmos-design-reuse:NXP-65-V-LDMOS-DESIGN-REUSE

73's Ill talk at you guys in the 1+KW club lol (well that's the plan anywhoo)

WINKDOGG 4-2-ZERO in NJ

And here is a bit of LDMOS eye candy for you boys and girls !!

The efficiency of the devices is just incredible I wish I had $5-10K to spend on some crazy stuff like a pickup truck bed filled with car batteries and an LDMOS 16 device box behind the seat with water cooling system

 

[Shadetree Mechanic]

I was looking at these too. I didn't want to spend a lot of money only to burn the thing up because I didn't know what to look for. The first thing I think would be to put a power switch for it somewhere you can hit it really fast in case it starts to oscillate. Other than that, and checking input and output SWR I would not know what to look for. Maybe someone else can shed some light on this.

 

[WINKDOGG]

I was looking at these too. I didn't want to spend a lot of money only to burn the thing up because I didn't know what to look for. The first thing I think would be to put a power switch for it somewhere you can hit it really fast in case it starts to oscillate. Other than that, and checking input and output SWR I would not know what to look for. Maybe someone else can shed some light on this.

Paging Kopcicle , paging Mr kopcicle haha

kopcicle , your the man with this info in spades ! kopcicle is currently building LDMOS gear and he really knows his shit , I just heard of them about 4-5 months ago and I know I have a lot to learn that's why Im taking the "budget" approach! One of the greatest things about these "tubes" , "devices" or "pills" is the durability ! A safe zone of 65/1 swr makes even me pretty confident lol and if you read my stuff you KNOW I have done my share of distruction lol ..Not to mention the efficiency of these handsome gold tabbed little beauties

Im sure when Kopcicle finds this he will link up some of his super knowledge packed posts and his own bench experience ! He also know how to explain things in such a way that even a lowly skip shooter cb dude like myself can understand . Without his input I never would have even clicked that "order now " button lol

73's Ill post as I build , right now deciding on 1 blf188 new , or 2 used and tested to spec with a warranty for the same price ?? At the price these devices go for if I buy the set of 2 I could easily step up to a 2 device amp so that's my main reason for even thinking about trying the used ones !

Winkdogg 4-2-Zero NJ just got down …..

 

[Captain Kilowatt]

LDMOS is fairly rugged once the circuit it is in is perfected. Experimenting with them while perfecting that circuit can be rather expensive however. They can be destroyed in less than a heartbeat if something is not quite right.

 

[Shadetree Mechanic]

I think there is something about the input drive level. Can't overdrive it even a little bit or it will smoke. And they only take 4w max pep? Or something like that. Would need an input limiter of some sort.

 

[Captain Kilowatt]

I think there is something about the input drive level. Can't overdrive it even a little bit or it will smoke. And they only take 4w max pep? Or something like that. Would need an input limiter of some sort.

I have an amplifier that consists of four MRF151G MOSFET devices. 10 watts of drive makes for an easy kilowatt output. They can be destroyed very easily if overdriven, It is driven by a 100 watt transceiver on 6m. To avoid any possibility of overdrive I purchased a 10dB ceramic attenuator from Florida RF Labs on Ebay. It is installed directly on the amplifier input and is bolted to the same heatsink as the finals are mounted on. This allows the radio to be run at full output and the drive level to the amplifier is no more than the 10 watts required for full output. It also safeguards against power spikes if I was to run the radio at reduced output. Some radios will produce a 100 watt spike before settling back to the reduced power limit due to slow ALC action.

 

[Klondike Mike]

Are there any server power supplies with 120v input / 65v - 20A output?

 

[WINKDOGG]

Are there any server power supplies with 120v input / 65v - 20A output?[/QUOTE
]
Probably not a server supply that can be repurposed as cheap as the 50volt setup that is one of the big expenses not to mention the $300+ per 60volt devices I think Im going for the 2 "remanufactured" blf188xrs si IF I do pop one I wont cry !! If I don't pop one ill get another power supply and run both !! Who knows we shall see what the future has in store for me ???

73's Brian !

 

[BJ radionut]

https://www.g0kla.com/references/eb104.pdf

http://www.communication-concepts.com/amplifiers/