My homebrewed PA0FRI Active Antenna is working well from a very physically constrained location.
3D render:
Schematic:
Results:
The antenna is connected to a RSP1 Clone SDR which is running custom FT8-band-hopping software. I am using a SOLID 4-Way 5-2400 MHz RF splitter to connect multiple SDRs to the same active antenna. NB: Plug in 75-ohms dummy loads (terminators) on the unused ports of the RF splitter - MX-282 / MX-280 75-ohms dummy loads work fine.
Time to build: Less than 45 minutes for the PCB. The mechanical aspects (loop construction and boxing) can take a while.
My live reception results from this antenna can be viewed at the following URL(s):
Testing Update: A 10m EFHW antenna installed in the same 'surrounded balcony' location receives less than half-the-countries as compared to the PA0FRI active antenna.
Magic might not exist for grownups but the reception results of this Active Antenna from a very limited physical location are nothing short of magical!
The files for this project are published here for personal (non-commercial) usage.
Special shout-out goes to Ismo (OH2FTG) and Gajendra Kumar Sir for their guidance on these topics - thank you!
Notes:
The first two decodes in the following screenshot are from a "turned off" active antenna. The last two decodes are from the same active antenna when turned on.
Remember the Don't let the perfect be the enemy of the good saying? While theoretically better active-antenna designs exist, we are not keen in pursuing those designs because the results of this PA0FRI AA are good enough (TM).
References:
- Simple active receive loop antenna - for physical construction aspects
Update (14-August-2025): My Active Antenna was performing pretty well for weeks and then the performance dropped suddenly one day - this got me wondering. I went to the terrace and found that the DC power supply line had gotten disconnected (some guest seems to have tripped on this line during a recent pooja event at home).
As you can see the performance of the "AA" fell drastically without power - pretty obvious (to many).
As soon as I connected the power back, the performance improved pretty dramatically and visibly!