[Amps] LDMOS HF amps

[GEORGE WALLNER]

Don,
I doubt that you will reliably get 1500 W out of a single BLF189 device. I 
have built three amps with single 188 pallets. With 49 V VDD they had 
outputs of 860 to 1140 W from 160 to 10 meters. (I have tweaked the output 
filters for minimum loss -- around 0.4 dB). With a VDD of 50 V a 189 will 
may give you 1200 W.
But 1000 W is decent output from any amplifier. If you must have more, 
either use two pallets (I have built three of those using the Russian EB104 
pallets) or, once you have your first single device amplifier working, build 
a second one and combine the two. I have used such a configuration (via 
splitter/combiner) for a reliable 1500 W on the Baker Island DXpedition. 
Conservative, reliable and with redundancy.

GL and 73,
George,
AA7JV/C6AGU





On Sat, 8 Aug 2020 11:06:50 -0400
  Don AD7LL <drfrasher at gmail.com> wrote:
>    As my first retirement project I am hoping to build an LDMOS amp.
> I have made the decision to go with a single device, a BLF189XRBU.  This is
> the
> same package as the more common BLF188, but rated at 1900 watts,   The hope
> is
> to achieve legal limit, or very close, output of 1500 and with using a
> single device use a single
> pallet with a simpler design.
>    I am hoping to keep it simple with manually switched band changes and
> such, and to build the LP filter and other sub-components myself.
>  I am however looking at purchasing the pallet itself instead of designing
> and building it from scratch.  I think that I am liking the designs by
> 4z4rb, although currently he doesn't have anything for sale, I had
> contacted him and he said he had been sick.  That has been 2 or 3 weeks
> back and  I haven't seen anything from him.  I am hoping he is ok and
> recovering well!
>  The W6PQL site has a lot of info and stuff available, but I'm not sure I
> care for his output combiner design and the way they just sort of
> flop around.
>
>    SO down to my actual questions.  Who would be the best pallet design /
> builder / supplier
> currently available?  And why?  with the slight higher current draw and
> such does anyone foresee any real issues with my using the 189 instead of
> the 188?   Or should I bite the bullet and just design my own pallet from
> scratch?
>
>      As it is, I am just now trying to learn Kicad so that I can put
> together my filters and such, but I really don't feel that I have the
> ability to design the pallet itself.  As it is I am looking at this as a
> long term project, but I would like to complete it before I die of old age !
>
>      Thanks in advance for advice!
>       73
>        Don Frasher  AD7LL
>
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