I have a need to box up the RTK SMA breakout (https://www.sparkfun.com/products/16481) with a GNSS antenna for RTK fixes. Ideally I’d like to stack the antenna on top of a ground plate on top of the breakout and make the assembly low profile.
Does the RTK accuracy change between single or multiband antennas?
Yes, a lot. Without a multi-band L1/L2 antenna you will not likely achieve RTK, and unlikely anywhere near sub meter accuracy. The ZED-F9x is really only worth using if you use a L1/L2 antenna with it.
Ideally, I’d like to use the embedded antenna for its lower profile, are there downsides to this vs, say, the multiband magnetic antenna?
Most L1/L2 antennas use a stacked element design. I’m not aware of a low profile design but certainly let me know if you come across something new/interesting. There’s always a lot of demand for antenna miniaturization.
What is the best way to shorten the cable? My enclosure won’t support a coiled 1m cable (much less a 3m or 5m cable).
Hmm. I have had bad experiences self-crimping RF cable. Any reduction in performance of the RF leads to greater inaccuracy by the GNSS receiver. If it where me, I might pull apart a TOP106 (https://www.sparkfun.com/products/17751) or possibly the u-blox L1/L2 (https://www.sparkfun.com/products/15192), desolder the SMA cable from the PCB, and solder on the RF cable that I needed. I am much more confident in stripping and solder RF cables (see: https://learn.sparkfun.com/tutorials/th … oject#wifi) then properly terminating them.
Does SparkFun sell the SMA connector to re-terminate the shorter cable? (I didn’t see one)
Ok, thanks for that. There’s a lot of conflicting info on just L1 vs L1/L2 and accuracy.
So, your suggestion is to shorten the RF cable from the unterminated end, keeping the exposed ground and signal as short as possible? That should be easy enough, assuming I can get the enclosure open without breaking everything :).
RE: Shortening GNSS antenna cables - exercise caution here. Most current antennae are active, meaning there is a preamplifier (hence the requirement for 3.3V) in the antenna enclosure. The RG-174 type coax cable is extremely lossy at
the frequencies in question. The output of the preamplifier is designed to overcome these losses and present a usable signal to the receiver at the ‘far end’ of the cable. Reducing the cable length by a significant amount, to inches or a foot or so from the original 5.3m can cause the receiver to be seriously overdriven or damaged. I suggest exercising caution before radically shortening the provided cable. Check the RF specifications of your receiver…
I pulled apart the u-blox antenna (https://www.sparkfun.com/products/15192) as suggested. It was fairly easy to get the case off. However, the coax is soldered so that the signal wire goes under an EMI can and despite my best efforts, that can just won’t come off. I even cranked my hot air up to 800 deg. Any suggestions?
Hmm, we hit the same issue with the TOP106 RF shield; it’s just an enormous heat sink. MOAR heat, 2nd hot air gun. Sorry, they are a huge pain to remove.
