How to modify an Hitachi or Sanyo WorldSpace antenna LNA for more gain on INMARSAT frequencies

On this site I want to summarize quickly how one can modify a Hitachi or Sanyo WorldSpace antenna LNA.
 
Here such antenna is shown as an example (conneted to a Funcube Dongle SDR Radio): 
 
The Hitachi and the Sanyo antenna both use absolutely identical patch antenna modules inside as well as identical low noise amplifiers.
Tha Patch element and preamplifier seem to be in fact produced by the company Mitsumi. They basically only differ in their housing :-)
(perhaps some of the other Japanese WorldSpace radio antennas also contain the same Mitsumi module?)
 
The preamp module has as a design feature a built-in band pass filter at its output. This is realised by means of a SAW filter centered around 1472 MHz.
The WorldSpace band is from approx. 1460 - 1490 MHz. This filter is there to prevent receiver overload from other ou-of-band signals such as GSM telephones, etc.
 
When using such antenna on purpose "out-of-band" this also means unfortunately that it will have a more or less significantly reduced gain....
 
By performing the below documented modification one can achieve more than 10dB additional Gain on the INMARSAT freuquency range.
 
Here as an example the Hitachi Antenna (see Sanyo modification further below):
 
Remove all screws and remove the back plate.
 
 
Remove carefully the rubber backplate
 
 
After removal of the rubber seal backplate you can see the preamp module
in the square aluminum box with a square shaped hole.
 
 
You need to heat each corner of the aluminum box with a soldering iron and when the solder melts you pull it slightly
upwards e.g. with a small screwdriver. By doing so step by step on every corner you will be able to remove the box.
(as seen in the photo above)
 
 
The SAW filter (that we want to remove) is the larger rectangular part in the upper centre of this PCB.
(marked with the centre frequency "1472" MHz)...
 
 
"POOR MANS" REMOVAL PROCEDURE:
 
We assume that the average electronics hacker does not have access to a hot air unsoldering station.
Thereofre we apply a brute force method, which works quite efficiently.
 
We take some small thin tipped pliers or wire cutter and destroy the ceramic structure
of the SAW filter. The SAW filter will break in many pieces.
Make sure you clean the PCB from all pieces afterwards.
 
Warning:
Make sure not to brake neighboring parts such as the capacitors (smd capacitors break easily)
Your pliers should allow sufficient clearance around it, before squeezig with it the SAW filter.
If your pliers are too large you better borrow smaller ones from a friend.
 
When the SAW filter is destroyed you can easily access its soldering pads for cleaning the
remaining solder or filter pieces connected with this solder.
 
Make sure everthing lokks relatively clean and tidy afterwards.
 
 
On this picture the SAW FIlter was removed and the solder pads roughly cleaned.
(still some ceramic filter leftovers are sticking on some of the ground pads)

You can see the ground pads (left pad + the four right most ones).
The filter input pad (bottom left pad) and output (upper left pad).
 
The last step is to insert a little solder bridge between the input and output pin.
You can see the wire in the photo above.
 
 
After closing the Antenna structure in reverse order, you will be able to enjoy > 10dB more gain in INMSARSAT frequency band....
(the antennas work actually up to GPS frequency band quite decently, but with directivity, which is not good for GPS)
 
 
Here as an additional example the Sanyo Antenna:
 
The case of the Sanyo antenna is mechanically a bit more difficult to open (and specially to close again) as compared to the Hitachi.
 
The electronics inside are identical for both antennas (Mitsumi made preamp module and patch antenna with identical parts numbers).
 
Lets get started as usual with opening the case:
 
After removing the back plate and foot plate it looks like this.
 
As one can see the patch reflector plane (with engraved letter A)
and preamp module case look absolutely identical to the Hitachi photo above...
 
Unsoldering the lid on all four corners and beding it up with a small screwdriver...
 
The same Mitsumi preamp shows up as in the Hitachi antenna above.
But this is an earlier revision A PCB (my Hitachi had Rev B PCB)
The only difference seems in the input matching circuit "solder pads"
The SAW FIlter is vsibel white box close to the centre.
 
Time to remove it...
 
 
Here the SAW filter is already half destroyed with the pliers. Still
too much of ceramic material is left over...we need to get rid of more...
(see SAW removal procedure description at Hitachi antenna above)
 
Here now half of the filter is gone and solder pads slightly cleaned with the soldering iron and solder wick...
 
SAW Filter fully removed and solder pads relatively clean...
(ceramic bits and pieces and contacts of SAW filter removed)
 
Tiny wire bridge and tweezers to hold it during soldering operation...
 
Bridge inserted between SAW filter input pin and output pin....
 
 
You may click on each photo to see the hires version of the picture.
(not great quality, since they were made with my mobile phone)
 
After closing the Antenna structure in reverse order, you will be able to enjoy > 10dB more gain in INMSARSAT frequency band....
Enjoy ! Happy INMARSAT exploring... :-)