Quick and dirty satfinder
I had a problem with my sat dish. It turned out I needed a LNB for Astra 3 instead of hotbird and so also a new mount for the others. So my dish and LNBs needed to be readjusted. Satfinders are cheap but ordering one was also a while without TV. But as HAM you build one yourself from junkbox parts.
I had no clue about the signal level so first I made a passive one first in an old CAI coupler thing.
The passive one
To bad, level was much to low. I used the 10uA currentrange from my Unigor multimeter as indicator.
Then I builded the little quick and dirty satfinder from the top picture, builded against all SHF rules but it supprised me. After some tweaking it turned out to detect from -55dBm (but then you only see a little movement) and very usable from -40dBm. Sensitive enough for satelite finding.
Schematic in Fred-cad
The schematic is based on that of this site: http://www.khazama.com/project/satfinder/default-en.aspx
The sat tuner gives a +13 or +18VDC voltage to energise the LO in the LNB. The LNB mixes the sat signal to around 1-2 GHz. The level should be between -50 and -35 dBm according to others, I have not checked with my SA. So the satfinder can be powered from that voltage and must detect that RF. In the schematic a LED is added to shows you if the LNB voltage is on. If you do more tuning it could be easy to add a 16V zener resistor and a diode before the regulator. If the LNB is on the led after the 7809 will burn and the led from the zener. But if the tuner switches to +13, only the led after the 7809 stays on.
It is also possible to use only one port and add a 18VDC by two 9V batteries so you do not need a tuner. You can mount a bnc instead and have a nice sensible RF detector for HAM use.
The inside, do not try this at home
Finally the problem was deeper. The tuner switches between 3 LNBs using a so called Diseqc switch. It is controlled by 22KHz tone bursts. My 10 year old switch had a factory fitted intermitting short and a resistor that was mounted only on one side and 90 degrees the wrong direction. So the port Astra 3 was on had never worked. After fixing this the satfinder helped to set all right within 10 minutes.