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Please help. regards Rusty.
An easier start would be to set the DTX1 to a frequency which the Tandberg can tune to directly, for example 1249MHz in the 23cm band. The Tandberg will not go below 2ms/s according to the specification. Try this and see if it works.
I am guessing that you have one of these SUP2400 units that converts UHF up to satellite band. If so, 437 should come out at 1963MHz.
73 Shaun G8VPG.
Tandberg TT1200 is pretty old now, circa 2000, firstly does it actually work? They had a high failure rate in VK
Test it with a sat dish or as Shaun suggested, if it's junk, use the box for you next project, get something modern
Your Tandberg will like 75dbuV, Value in dBm + 107dB = Value in dBuV (in a 50ohm world, but rough enough)
Your DTX1 is rated around -5dbm flat out, try 20db attenuator or use a couple 1/4 wave antennas across the bench
Remember there may be volts on the Tanberg output (to power the LNB) that will burn regular attenuators
You may need to turn off the power or use a blocker capacitor
From memory you'll damage that tuner with lots of signal, so go gently if you connect direct
Use a little L shaped wire poked into both f connectors around 60mm at 23cm if you don't have attenuators
Settings as per Shaun's suggestions
LNC Freq.: 10.000
Sat. Freq: 11.963 (70cm) or 11.249 (23cm)
Symbol Rate: ?
Inner Code: ?
LNC Volt: On with SUP or Off for 23cm
LNC 22kHz: Off
Spectr inv.: Off
Cheers Roger VK5YYY