Home Brew Broadband Magnetic Loop
edited January 2018 in Installation, Antennas and Interference
This LNA was discussed in an earlier thread and I decided to see how it might work with a home brew loop. https://www.amazon.com/gp/product/B01N2NJSGV/ref=oh_aui_detailpage_o00_s01?ie=UTF8&psc=1
I spent a total of $25.88 for parts. I had the PVC pipe for support and coax cable in the junk box. This little LNA connected to a loop made from 14' of coax and powered with a 9vdc battery is providing signals from 5KHz to ???, well at least 30MHz for the KiwiSDR. It has been tested, but is not currently online as I'm working to "ruggedize" the LNA in a small pipe.
I think an inexpensive antenna such as this could improve some KiwiSDR installations. It isn't perfect and displays more repeating interference spikes than I would like, but it is still better than many other antennas I've listened to. Not quite as good as the W6LVP but it is better below 500KHz and probably equal up to 18MHz. It needs more comparison testing and the loop circumference might make a difference.
1.The amplifier at operating frequencies less than 500MHz, has a very good gain flatness, careful adjustment can be 1dB lower frequency, the higher the gain consistency
2.The lower limit of the operating frequency of the amplifier is subject to the input and output capacitors, the default is 0.1uF, can work to 0.1MHz; can be appropriate to increase the input and output capacitors to expand the lower frequency limit,Such as: 10uF, you can work to 5KHz. For detailed calculations, pay attention to the input and output impedance of 50 ohms, calculate the required capacitance value, while enhancing power supply decoupling and voltage regulation.
3.When the supply voltage varies from 5-8V, it can be used as a variable gain amplifier. The gain increases with the supply voltage. Ideal for RF receive front-end circuits, with DA control supply voltage, thereby controlling the amplifier gain, automatic gain control. When the supply voltage at 8-10V, the low-frequency gain of 30dB, this amplifier has a lower noise figure and better stability.