You can build your waveguide filter and amplifier
![](https://www.albfer.com/wp-content/uploads/2022/06/1-5-1024x768.jpg)
This is a Brass profile similar in dimension to an std waveguide WR90.
The cut-off frequency, the frequency at which the energy starts propagating inside the guide, depends on the guide dimension, in this case, 6.5 GHz.
![](https://www.albfer.com/wp-content/uploads/2022/06/2-2-1024x768.jpg)
As an exercise, in order not to do the same things, I added a ridge to lower the cut-off frequency and a fat coax transition in order to broadband the filter.
![](https://www.albfer.com/wp-content/uploads/2022/06/3-2-1024x767.jpg)
With the addition of an amplifier from surplus RF microwave
![](https://www.albfer.com/wp-content/uploads/2022/06/4-2-1024x766.jpg)
This is the result of a high pass filter with gain.
![](https://www.albfer.com/wp-content/uploads/2022/06/5-2-1024x768.jpg)
The same DR filter measurement
![](https://www.albfer.com/wp-content/uploads/2022/06/6-2-1024x768.jpg)
With a lot more dynamic range
![](https://www.albfer.com/wp-content/uploads/2022/06/7-2-1024x768.jpg)
If you add an extra amplifier at the RX port
With a reduction of the TX power, that is useful to reduce the part of RF that cross-talks inside Pluto,
To stay in linear mode.
![](https://www.albfer.com/wp-content/uploads/2022/06/8-2-1024x768.jpg)
This is the total dynamic range after a calibration plus the reflected image of myself; the phone is an easy way to take pictures, but no way to use the powerful tools that Alberto provides….
![](https://www.albfer.com/wp-content/uploads/2022/06/9-2-1024x768.jpg)
The same DR filter, the jump over the zero is due to the impedance mismatch.
A couple of small attenuators solve the problem.
Remember that a 3 dB attenuator adds 6 dB to the return loss; 6 dB adds 12dB, so up to you without
reducing too much the dynamic range.
![](https://www.albfer.com/wp-content/uploads/2022/06/10-2-1024x768.jpg)
The inside of the amplifier, again, the same surplus parts
The other design
![](https://www.albfer.com/wp-content/uploads/2022/06/11-2-1024x768.jpg)
If someone wants to produce a PCB.
![](https://www.albfer.com/wp-content/uploads/2022/06/12-2-1024x768.jpg)
The waveguide is a little larger than a WR90 to have a cut-off frequency of 6 GHz
![](https://www.albfer.com/wp-content/uploads/2022/06/13-2-1024x768.jpg)
Otherwise use the same surplus amplifier
![](https://www.albfer.com/wp-content/uploads/2022/06/14-1-1024x768.jpg)
All soldered together
![](https://www.albfer.com/wp-content/uploads/2022/06/15-1-1024x768.jpg)
The output of the amplifier
![](https://www.albfer.com/wp-content/uploads/2022/06/16-1-1024x768.jpg)
The amplified filter is quite similar to the previous one (the scale is different from 5 dB vs. 2 dB of the other picture)
![](https://www.albfer.com/wp-content/uploads/2022/06/17-1-1024x768.jpg)
Boards are as PIGS noting to throw, so why not reuse its power supply…..