[amsat-bb] LNB use on 10 Ghz?

[Daniel Estévez]

El 29/12/15 a las 20:02, jameshickox at sbcglobal.net escribió:

> Hello,Questions about the discussion on inexpensive downlink using the satellite TV LNB's.
> Do they require any conversion to get from 11 Ghz down to the 10ghz ham band?
> If they don't, is there any significant loss in signal from being used on a different frequency than they were intended for?
> Is there anything posted on a Web page showing a working setup?
> Lastly, (I promise) Are there any working sats in the 10ghz range to test a system on?

Hi James,

I have used an Avenger PLL321S-2 LNB. This has good gain in the in the
10GHz band (although probably a bit less than in the 11GHz). With it
I've been able to receive my local terrestrial beacon without using a
dish. The beacon is 200mW, about 40km away and not line of sight, so I
think that the receiving performance is OK for many ham applications.

The main problem is that the local oscillator in the LNB is not very
stable. If you're using it for a narrow-band application, it will drift
quite a bit.

I think that the situation (regarding gain in 10GHz and oscillator
stability) is similar with all the satellite TV LNB's. Some people have
done modifications to the LNB to improve the stability. The most popular
are:

* To use an external PLL driven by a TCXO or OCXO.
* To generate a strong carrier in the 10GHz band, to receive the carrier
and the signal of interest with the LNB, and to use the carrier to mix
the signal of interest down to, say 28MHz. Since the carrier and the
signal are both affected to the same extent by the LNB LO drift, this
cancels most of the drift.

Regarding sats in the 10GHz, I don't know of any which is working right
now. If I recall correctly, the two future geostationary sats will have
10GHz downlinks. However, if you just want to play a bit, there are many
geostationary which transmit narrowband data streams on the 11GHz band,
so you could use this to test your setup.