A very easy 35dB gain amplifier, 600-1700MHz……..

Using the two MMIC post mixer Ics contained within one of the now obsolete "bullet" LNBs.

Interestingly, doing this uses only about 5% of the cicuit board assembly! (so you are still left with 5 11GHz thingy-fets and an 11GHz diode mixer.

Power supply can be taken either as originally intended, down the coax (ie, no mods needed), or it can be tacked onto on of a couple of points. Isolating the DC from the output coax is easy enough if required.

Supply required: 12-18v at 80mA (as long as the internal 7805 that feeds the rest of the cct is removed)

Modifications

  1. Drill ot the 4 rivets that hold the casting halfs together.
  2. Remove the 6 tap-tites that fasten the internal casting, and remove – revealing the pcb (be careful, the board is now only secured by by soldered joint on the F connector).
  3. Shorten a couple of the screws, and fit as shown, to clamp the board down once more.
  4. Remove the 7805 – this is the easiest way to avoid wasting a lot of current elsewhere.
  5. Drill out the plated through hole to the mixer output connection as shown above, where the output coax that has been added is terminated.
  6. One way of connectorising this coax is to pull the polyplex antenna off the casting and taping an N type as shown (see orange tape)
  7. Add supply lead if wanted – its easy enough to see where to connect close to the F connector.
  8. Put lid back with 4 M3 nuts and bolts (eventually)

 

 

Results

The following pic shows the response up to 1300MHz. The lf response falls away mainly because of the high-pass filter incorporated between the last MMIC and the F connector.