Can someone please recommend a solution for an LNA/Pre-Amp+Bias Tee (i.e. products) that would largely be “Plug 'n Play” for me. I have a 50ft coax cable between my antenna and dongle (which includes a filter + amplified but no Bias tee).
I’ve seen there is a long thread about it but couldn’t really see a firm “Buy X + Y” recommendation.
I recently tested a Bias Tee that seems to be available from a lot of places. Bottom line is the feed through loss was perfectly acceptable, about .1 dB-ish.
Enclosed is picture of the Tee and a screen shot from the spectrum analyzer. The waviness is due to the 20" cable at one end. Need to make/find some 3" cables for this sort of testing… but look closely at the Y scale at the left. It’s .2 dB per division. And note that when I went from a 20" cable to a 36" cable (same cable type), you can see the cable loss.
Now the yellow and green used the same 20" cable, so the loss induced by the cable is the same. Cable was a RG58 type that has the foam insulation.
And then, just for grins, I tried a 40" higher loss (RG-174-ish but Teflon for all the insulation).
I did not test the power input to output to see if power supply noise would leak through, will do that when I have the LNA I’m home brewing done. I will be adding more filtering at the Tee and also add an 18 TVS (Transient Voltage Suppressor) diode as a safety measure (for ESD - Electro Static Discharges AKA “door knob sparks”). this will also protect the internal capacitor that has a 50V maximum rating.
If the tech talk is too much…
Bottom Line: I think this injector is fine, and compared to the cable losses you will have, the losses due to the Bias Tee are negligible. Of course the Tee would most likely be near your PI and Dongle, and as such either not exposed to or protected from the weather elements.
Thanks. Yes, I was planning on putting the LNA of a very short cable, then the outside to the long cable.
What cable size does that Triple Amplifier LNA take?? Just trying to work out what connectors/cable I need between the antenna and LNA, and then LNA to the coax I posted above.
My USB pigtail has a type A plug so I can just plug it into my Pi. I took an old plastic sauce bottle, cut off the neck with a hacksaw, painted it inside and out with acrylic spray paint (black on the inside for shade, white outside to reflect heat) and attached it to the mast upside-down with the LNA inside, connected via a couple of short RG316 jumpers leading to the antenna and my LMR240 coax. That keeps the rain off of the LNA. Or you could get a small waterproof electrical junction box, but being square or rectangular those are a bit harder to attach to a mast. The bias-T supply board has screw terminals for the DC power supply and two SMA connectors. You can get these things on Amazon or eBay. I put my bias-T board inside my old plastic Pi case as I had replaced it with a ventilated aluminum one with a fan. That keeps it from shorting out or anything. I’m using two more short RG316 jumpers to connect the board to the dongle and LMR240. This is just a temporary arrangement until I can get a dongle with its own bias-T supply but it works very well in the meantime. (FYI my LNA is an RTL-SDR Blog triple-filtered one for 1090MHz.)