[NLRS] Cheap 10GHz LNBF mods for sat downlink.

[Dr. Gerald N. Johnson]

The phase noise is probably OK for FM satellite TV, but probably even 
for that broad band signal effectively increases the NF, or the MDS.

I have seen a couple other ways to use the LNBF. One is to create a 
local carrier at a handy offset from 10368 and capture the beat note 
between the carrier going through the front end and the desired signal, 
then the phase noise of the LNB LO gets cancelled and the IF phase noise 
depends mostly on the quality of that local carrier.

Another is to disable the LO and the mixer in the LNB and add a coax 
connector to take RF from the last RF stage (often there are two or 
three GaAsFET stages) and use it as strictly a LNA with WR75 waveguide 
input and use a taper or but a wr90 relay against it using a waveguide 
feed for the 10 GHz dish. I have the parts to do that but no idea when 
I'll make it work. I saw one like that tested at MUD 2008 that tested 
with a decent NF. Some have converted the waveguide input to coaxial, 
others could have used a bit of dielectric loading of the WR75 to make 
it more like WR90, but WR75 isn't horrible at 10368.

On 8/29/2016 4:01 PM, Doug Reed wrote:
>
>
> I ran into an interesting blog post about building a cheap 10GHz
> receiver from a cheap LNBF. The idea was to use it for monitoring the
> upcoming geostationary ham satellite with a 10GHz beacon.
> <http://destevez.net/2016/04/outputting-the-crystal-oscillator-directly-in-the-si5351/>
>
> The blog link goes first to a comment about getting a stable 27MHz
> reference for the LNBF PLL oscillator. The internal link about the
> LNBF receiver gives a bit more info on intended use and mods, and
> links to similar projects by other hams. I don't   believe his numbers
> for the LNBF ref oscillator stability but it does open some
> interesting options.
>
> With the original LNBF ref at 9.750GHz, it makes sense to RX at 618MHz
> using a rtl-sdr dongle for the RX. I particularly likes his suggestion
> to move the 27.0MHz crystal reference to 27.5150MHz so that 10368
> comes out on 432MHz. Too bad there is no equally easy way to upconvert
> for TX..... Maybe one of the other articles....
>
> For reference, the first LNBF I found on Ebay was $6.10 with free
> shipping from California and listed as "FTA Universal" and .2dB noise
> figure. But the phase noise spec is horrible! Probably doesn't matter
> much for TV bandwidths.....
>
> 73, Doug Reed, N0NAS.
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