[NLRS] Getting onto 5760 MHz

[Zack Widup]

Hi John,

What I did was make my own power amp from scratch using a device I got
on eBay for not much money.  I think I got lucky and got a 2 watt
device internally matched for that band for about $25.  But if those
aren't easily available I'd buy the FMM5056VF from DEM and make an amp
out of it.  You could get away with 0.015 inch thick Duroid 5880 which
is thick enough but you'd need a 0.025 inch thick spacer between the
pc board and the heatsink.

Most of these power FET's have a spacing between the power/RF leads
and the bottom of the device that they require some sort of spacer for
the thickness of the pc board used. If that didn't come with the kit
you got, you don't have much choice but to make your own.

And yes, you'd probably need some attenuation for some of these
devices to drive them from a +20 dBm source.  With the FMM5056 you'd
need an 8 dB attenuator.

What devices does the DEM surplus kit use?  What is the thickness of
the pc board? I've built a lot of little power amps from scratch and
can probably help you with this.

73, Zack W9SZ

On 09 Aug 2008 14:27:18 -0500, tosca005 at umn.edu <tosca005 at umn.edu> wrote:
>
>
> Hi, gang. I'm looking for some information to help me get going on 5760 MHz.
>
> I bought Lenny's 5760 transverter system. He sold it to me with a Kenwood
> 751-A 2 meter IF radio which is unmodified, and said that there were a
> couple of highly recommended mods that should be made to the radio when
> using it for driving a transverter. I've been Googling around but haven't
> come up with much. If any of you are using this radio for IF, are there any
> specific mods you have found to be useful, and do you have pointers to where
> I can find out about them?
>
> Also, his transverter was one of Down East Microwave's older models with a
> power output of 200 mW. Since I could imagine myself lined up with a bunch
> of you guys all operating at 2 watts, and my turn coming up and not being
> heard at 10 dB lower than the rest, I checked into raising the output power.
> I looked at DB6NT's offerings, and while he has a fantastic array of PA's at
> quite a few different power levels, they are a bit too rich for my blood.
> Especially when I discovered that Down East had a few "cutoff" boards from
> their 2 watt transverters that contain the 2 watt PA and a low-noise preamp,
> for a very reasonable price on their "surplus" page. (They are probably sold
> out of the kits with components, but had a lot of the PC boards in stock
> when I bought mine.) Anyway, I'm looking for someone who has actually built
> one of the 2 watt Down East 5760 transverters, because I have a few
> questions about the assembly process. (I got the circuit board and a set of
> components, and copies of some of the transverter assembly manual, but it is
> not really a "complete kit" or a manual that is directed towards the
> specifics of this semi-kit. I believe that the real transverter kit has an
> aluminum "pallet" which is part enclosure, part heat sink, part stabilizer
> for the thin and flexible circuit board, and I am wondering about the
> configuration of that piece of aluminum, since I will need to make up
> something to mimic it.)
>
> I have a weatherproof aluminum box to use as an enclosure, and my idea is to
> put the T/R relay inside this box along with the built-up board. The box
> would be mounted very close to the dish feed with a short semi-rigid
> SMA-to-SMA jumper between the feedhorn and the box. Then, the actual
> transverter could be mounted a little bit further away, either on the back
> of the dish, or even further, since some attenuation will actually be NEEDED
> between this box and the transverter. The 2 watt PA probably needs only 10
> to 20 mW of drive, vs about 200 mW available, so I need to lose 10-13 dB.
> I'm not sure of how much gain the preamp has, but most of that gain can be
> offset with feedline loss to the transverter while keeping the low noise
> figure of the first gain stage close to the feedhorn and simultaneously
> avoiding overloading the transverter's internal first gain stage...
>
> Anyway, I always have more projects in the pipeline than time to work on
> them, so there's no urgent need to get back to me ASAP, but I do hope to get
> this system on the air, at which time I will have equipment for ALL tha
> bands between 50 MHz and 10368 MHz. (And of course, SOMEday I'll even have
> time to turn them on and talk with them! So where was I during Rovermania?
> Right here, at my desk at work, like I usually am on many Saturdays and
> Sundays and nights and holidays and...)
>
> 73 de WØJT
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