Hi Keith, aye, tis! You have a very impressive setup and your coverage maps speak for themselves. Thanks for taking the time to write that up, it’s been very helpful. Sorry it’s taken me a while to catch up with this topic again. Here’s where I’m up to.
I have the setup you’ve seen running on a windowsill. RPi 3B, ProStick Plus, Uputronics SAW filtered preamp (LNA), then 1m of CLF200 coax to the FA antenna mounted on a high-gain kitchen-roll holder (okay, it was from ASDA).
I’ll be moving the antenna to the chimney. The LNA will be going up there too, and so I’m going to put the 1m coax up there to keep it close to the antenna. That also lets me feed it down and up into the underside of a weatherproof enclosure mounted just below the antenna (whereas a pigtail would be so short as for the LNA to need much more careful weatherproofing considerations I think).
That leaves me with the question of what coax to get from the other side of the LNA down to the ProStick Plus and bias tee. I’ll go with the same bias tee you used, it looks good and comes up on Amazon too. I can grab some GPIO single push pins to make up individual wires, or else hack a USB cable to get just the power, to power the bias tee. Sorted.
So what about the coax. This is confusing because there are so many options. I see CLF200, RG6, LMR400. There are 50 ohm coax runs with a dB/m attenuation. Then there are 75 ohm coax runs with different (lower?) attenuation with the cost of a small impedance mismatch at each end, not a big deal for receiving and especially with the LNA already on the roof maximising signal to noise. I’d prefer to find a source for coax which lets me order a desired length with prefitted SMA male connectors (one end for LNA up on roof, other end for bias tee indoors).
Do you have any general thoughts on 50 ohm vs 75 ohm? RG6 vs CLF200? LMR400? Other types? I don’t need anything special, just as long as it’s technically good quality with the minimal combination of losses (attenuation over length + attenuation from connection including any impedance mismatch losses). The Paoloni cable looks very nice but perhaps that rotor-friendly construction is overkill. I’d prefer to use Amazon UK (or Pi Hut) if what I want is there.
Now, my mate who’s been having the fun with dhcpcd resets… he has the same setup as me and he is also about to put his FA antenna on the roof. In his case his indoor parts are in the attic and so he just needs a 5-6m piece of coax to reach the antenna.
So in his case, although technically he can also move the 1m coax and LNA onto the roof, fit a weatherproof box and install a bias-tee inside, it would be much easier if he simply replaces the 1m CLF200 with a longer piece of coax. Perhaps the same but longer 5m prefitted coax available from Pi Hut.
Here’s a summary of his current setup and the two options.
Anthony from Uputronics very helpfully gave his thoughts on this. He feels that Option 1 isn’t going to present any problem since it’s only 5-6m of coax. The loss of LNA effectiveness from having 5-6m of coax between the antenna and LNA will be fairly low, and perhaps doesn’t justify the hassle of adding in a weatherproof enclosure and bias-tee.
My own feeling mirrors that, but then again since he’s going on the roof anyway to install the FA antenna, if moving the LNA and 1m cable up there too and then getting decent coax down to a bias-tee is able to eke out a bit more from the setup, perhaps it’s silly not to go for it. But how much more can it really eke out by moving to the antenna end of a 5-6m run of coax but with a bias tee now inserting loses into the equation?
It’s hard to make a decision since I have no idea what the realistic differences are between Option 1 and Option 2 in terms of the hassle involved vs the benefit gained from that hassle. The benefit is a combination of signal gains and noise reduction (from having antenna higher up and LNA closer) versus losses from bias tee insertion, or perhaps impedance mismatches and per-metre losses.
If it was 100m of coax then it’s a no-brainer, the LNA has to go next to the antenna. But 5-6m? Worth getting the LNA on the roof to avoid it?
I hope I explained it well enough, thanks and I welcome your thoughts and experience on the matter.