If the loop remote preamp section is okay, you can buy an assembled bias tee for a few dollars via eBay, Aliexpress, etc. If you do not have a dedicated DC power supply, even a 9v battery worked fine when I initially tested a MLA-30 here.
Actually the included MLA-30 bias tee with its 5vDC->12vDC boost converter chip is somewhat over spec for the usual preamp chips being used anyway. The usual LM592, NE592, etc. VGA video amps repurposed as inexpensive basic RF preamps typically used are rated for more like ~8vDC. Some of these basic amp chips will work sometimes at even lower voltages with mild to moderate reductions in gain. You might even check if your RTL-SDR's own integrated 5v bias tee will power your MLA-30 remote preamp and provide have enough gain for your purposes. YMMV
You can build a YouLoop-style antenna for a few dollars. A piece of whatever coax, a mix 73 binocular ferrite, and a little wire.
https://swling.com/blog/2020/04/diy-how-to-build-a-noise-cancelling-passive-loop-ncpl-antenna/One concern is a passive loop tends to need a receiver with decent dynamic range, like an Airspy HF+D, SDRplay RSPdx, or similar. Otherwise plan on needing a preamp. which off-the-shelf can cost anywhere from a few dollars to ridiculous money depending upon the desired performance characteristics.
Of note there are YouLoop-style antenna kits with bundled preamps on eBay and elsewhere, though I suspect the preamp stage is probably yet another inexpensive video preamp repurposed as a basic RF preamp. The other downside is it is not a remote preamp bundled with the kits I have seen, though that tends to be less of an issue at lower HF and MW.
BTW, I have used a YouLoop with a basic antenna tuner instead of a preamp to improve matching with a receiver, for example with my Tecscun PL-330. That said, admittedly, a preamp tends to be the much easier and straightforward solution in such a situation.
https://www.hfunderground.com/board/index.php?topic=71326.0
Topic: Best cheap loop or compact antenna? (Read 900 times)
