[NLRS] CSVHFS article by WA5TNY

[Zack Widup]

I think I have some IMFETs for the 5760 band in my junquebox. I think they
are good for a couple watts each. You could probably make an etched power
combiner for four of them to get 8 watts or so out. I forget the part
numbers or manufacturer except they had 5764 in the part number.

73, Zack W9SZ


On Mon, Oct 17, 2011 at 12:50 PM, <tosca005 at umn.edu> wrote:

>
>
> Thanks for the several kind offers, everyone. Paul Husby already beat all
> of you to it by sending me a PDF that he made from a scan of the article.
> MANY thanks to Paul!
>
> I reallized that some of you may be wondering what I'm up to.
>
> My 5760 transverter is an old DEMI low-power model. I think it's only 200
> mW out, but I haven't had a chance to test it. I did pick up the "cut-off
> board" (the part that Steve was cutting off the full-power board to make
> the low-power model) and, importantly, the parts needed to build it. The
> cut-off board from DEMI provides a lower-noise preamp and around 1-3 watts
> of power (I forget the details), but haven't had a chance to build that
> either. I am SO looking forward to my imminent retirement! One of the
> WA5TNY boards would still be a significant step up in power, if the IMFETs
> could be found.
>
> A newer article refers to the older article, but he tested a variety of
> IMFETs including the use of the 8 watt part to make 30 watts or so.
>
>  http://vk3nx.com/files/5760_MHz_SSPA.pdf
>
> I was under the impression that "only" 4 IMFETs were used, but the newer
> article does not show the circuit or board layout, but mainly the results
> with several different devices. I guess the 5th IMFET was included if you
> didn't have enough power to drive the four 3-watt devices fully. I think
> they have around 9 or 10 dB of gain, so each one probably needs 300 mW for
> full drive.
>
> Not knowing how easy it would be to get the IMFETs or at what cost, I asked
> for a price quote from a source on the Internet for a LOWER frequency part
> that is actually rated for 5760 MHz. They gave me no price figure, but
> simply said they have no stock. I guess I need to look harder if I want to
> pursue this. But if I can successfully build the DEMI cutoff board, I
> should be up to a more reasonable power level. And I actually have a couple
> of the Avantek amplifiers that should each provide 6-10 watts once I build
> a new switching power supply to provide the needed voltages from from +12v
> instead of -14v or -28v.
>
> I was actually thinking about K0MHC's request for a smaller amp than the
> Avantek, and then got interested in it for myself. If I could find the 8
> watt IMFETs for the WA5TNY board as mentioned by VK3NX, I'd probably have
> more power on the band than nearly anyone else in our area! Toshiba used to
> make 35, 45, and 60 watt versions of the IMFET chip. Probably rarer than
> hen's teeth and priced like pure gold, but a guy can dream, right. Besides,
> the chip dimensions on those big boys are bigger, so that would also mean a
> new board design.
>
> Anyway, LOTS of things to keep me busy once I retire!!!  :)
>
> 73 de W0JT
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