This modification requires advanced soldering skills as well as a powerful soldering-iron.
The RF tuner in the 900MHz and 1.3GHz receivers are originally designed for satellite receivers and have a pretty wide bandwidth compared to what’s needed. So why is having a wide bandwidth bad? All bandwidth not used leads to RF noise that reduces the receiver sensitivity, which means shorter range.
Inside of the video receivers there is a SAW bandpass filter. This filter is located in the intermediate frequency (I.F) stage in the RF tuner and it determines the video bandwidth. The original SAW filter in one of these RF tuners are 27MHz wide. For transmitting video and audio about 14MHz of bandwidth is needed. By exchanging the SAW filter to one that has narrower bandwidth the signal to nose ratio can be greatly increased, which means longer range and better quality.
I will be using a ESC-D480A SAW filter which has a bandwidth of 17MHz. It’s easy to come by, cheap and well tested by others for this mod.
Start by unscrewing the 4 screws on the sides of the box. Desolder the RF tuner. A good tip is to mark the cables so you know where to reattach them later on.
Remove the top and bottom lids, they’re just clamped on.
The SAW filter is the big round one with lots of solder on it. The filter has three pins and the top is soldered to ground. You need a powerful soldering-iron for this as the whole bottom of the PCB is a ground plane which loves to suck up heat.
Suck out the holes and clean of any flux residue before you pop in the new filter.
Solder the new filter in place.
Make sure to clean the PCB after you’re done, you don’t want any flux or dirt left.
Done! It’s as simple as that.
This mod gives an increased sensitivity of about +3dBi! That’s the same as doubling your transmitter power!
(This modification does not work on 2.4/5.8GHz receivers, they are equipped with a 17MHz SAW filter stock)
I’ll report back when I’ve had the chance to try it out thoroughly.