Rough description of the original hardwareThere is two different kinds of outdoor units and each have many iterations over the years. According to stickers and date codes they range between 1999 and 2006. The newer Models have a slender unpainted housing at roughly half the width of the older units and have 2W TX @ 14,5GHz. These units are less complicated on the inside but turned out to have some difficulties regarding conversion to lower frequencies as they have a final PA that according to the datasheet has no gain at frequencies below12GHz which is really sad as they would be much nicer to be carried around. Maybe at some point i will still try to get one transmitting but my hopes are low.
The older Units consist of a water tight die cast aluminium housing with a waveguide output (WR75 with different hole pattern) on one end and an N connector on the other. On the Bottom there is two F connectors one of which is connected to the LNB.
The attached wave guide system differs between the versions but they all seem to be built similarly just with alterations in flanges and some times different LNBs.
New unit complete:
Old unit without horn:
The accessories can be unbolted and the lid removed, depending on the state the devices are in screws may snap as the stainless tends to gall and rot into the aluminium parts. Inside the following boards may be found:
Newest Version:
Oldest Version (even with factory bodgewire
) :
And the Version i will pay attention to from now on:
As you may have already observed they roughly consist of a few diplexer stages taking apart the input signal into the device next to the DC filtering, protection and regulation. The Signal coming from the indoor unit will consist of multiple frequencies for control, signal and LNB.
The entire upper, unshielded half of the board is essentially just power management and bias regulation for the rf ICs. There is no intelligence or logic whatsoever, just apply the right frequencies and this thing will transmit wich makes the modification pretty simple.
The RF path is also pretty straight forward. The large VCO box in the middle is a very ancient design and also has no intelligence built into it, just two active components and a buns of passives. You may find more detail in the thread linked in the first post here.
The VCOs output is amplified, filtered and then split. One signal will travel to the left, is amplified (this transistor has a variable supply current controlled by PWM supplied by the indoor unit), attenuated, frequency doubled, filtered again to get rid of the 6.XGHz signal, amplified twice and then reaches the Teledyne TBQ3018 30dbm Amplifier after wich the signal is fed into the coax to wave guide transition mounted in the die cast housing.
The signal traveling to the right after the split is fed into a PLL chip of which i could find absolutely no information. However it is operating at 128x prescaler. At 14GHz output that turns out to be a modest 109MHz of signal that the outdoor unit locks on to coming from the indoor unit.
The LM2941 i the upper left corner is the regulator of the final power stage and its current can be changed by the nearby potentiometer. Default bias is 600mA but im pretty sure it can be upped a bit without causing damage.
A little to the right there is a MMPQ2907A multi PNP used to control the bias current of the rf stages. The OPs next to it can be used to set the currents but so far i did not bother looking at this part as a constant bias and some bridges at the PNP did the job sufficiently and i dont eed remote power control. It shouldn't be difficult though if you prefer to do it the clean way.