I need help to choose the correct cable for reach, what size is? In awg.
The options are in this site
http://www.digikey.com/products/en/cables-wires/coaxial-cables-rf/475?FV=fff40019%2Cfff8017b&mnonly=0&newproducts=0&ColumnSort=77&page=1&stock=0&pbfree=0&rohs=0&k=Rg-58&quantity=&ptm=0&fid=0&pageSize=500
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Hi,
To expand a little on selecting the right cable… First, I think there have been discussions on the forums about this. You my want to see if a search gives you the information you need.
The cable size as discussed previously depends on a few key points. (1) A longer cable usually means a bigger cable.
Look at the LNA (low noise amplifier) in the antenna. Say it is 40 DB gain. This gives you a loss limit for your cable. It should be less than 40DB at GPS frequencies (approx. 1550MHz). If it is over 40DB then you will loose SNR of your GPS signals.
You can search the internet for cable type loss in db per meter or foot. As long as the total cable loss is less than 40db, you should be good.
This means that you should only use an antenna with built in amplifier.
Next, what if my cable length from antenna to receiver is so long that I have more than 40 db loss with readily available cables. In this case, you would have to insert a booster amplifier to maintain your SNR at the receiver.
From pasternack.com, we see that RG174 has a loss of 31 db per 100ft.
RG58 has a loss of 13.4 db per 100 ft at 1500MHz. If our antenna LNA gain is 20db, then the RG174 would degrade SNR by about 11db. This may still be sufficient for good data, but you see that the GPS may perform more poorly. In this case, you would want the RG58 to avoid an inline amplifier.
freqelec.com has a pdf that gives some examples of different setups.
A search of GPS inline amplifiers will yield several sources if you find you need to go that route.
Hope this helps.
It’s help i think. And after re-read all about cable for rooftop base station, there are many choices, and I haven’t knowledge about cable, specific use of frequency, I just a surveyor (user). The point is I could choose rg-58 with 26 awg for rooftop base.
I have a run of 75 ft of RG58 for my rooftop base station. I use the Tallysman 3710 dome antenna with TNC bulkhead. I consistently get 4-7 satellite signals (GPS or GLONASS) with green dB levels on the Reach status page. I see 22 or 23 satellites consistently, including 3 SBAS. I had hoped for higher dB levels. I’m considering purchasing LMR 400. But with my current setup, I get fixed solutions on my rover via NTRIP or TCP in a matter of roughly 20-60 seconds.
That’s so fast fix. Do you use tw3710 for the rover, too?
Can we use TNC to mcx 2 meter from emlid for tw3710?
My plan is use rg58 (45-50ft) with tnc socket, then use tnc to mcx connector from emlid.
I should qualify this by saying I’ve only tested very short baselines thus far. 20-30 meters. I’ll report on much longer baselines in the future.
The 3710 is my base antenna only. I use the 4721 (https://emlid.com/shop/tallysman-multi-gnss-antenna/) for the rover unit.
I can’t speak to the adapter you mentioned. It sounds like it should work OK. My coax cable is terminated on both ends with BNC so I purchased the appropriate adapters.
Base antenna adapter: DHT Electronics RF coaxial coax adapter TNC male to BNC female https://www.amazon.com/dp/B00CXN4EX6/ref=cm_sw_r_cp_apa_2g5Eyb2QNK0MY
Base Reach Receiver adapter: 1Pc Adapter BNC Female Jack To MCX Male Plug Connector M/F DVB-T TV Antenna https://www.amazon.com/dp/B01CL296IG/ref=cm_sw_r_cp_apa_si5Eyb79ZDNA5
The 3710 TNC bulkhead is female with threads on the outside.
Are you sure the cable with BNC is 50 ohm? I have read that cable with BNC termination can be 70 ohm impedance. Just curious.
I am also curious if it would make more sense to run a USB to Ethernet adapter on the Reach and use Ethernet with passive POE. Then split the POE power to a DC buck on the reach end to power reach at 5V. More components and complexity I guess but would cause less loss. One could inject 5V and eliminate need for a buck. But not sure about cable loss. Might need 5.5 or 6v to account for loss over long cat5 run. Anyway just a thought. A weatherproof enclosure also required. We use pvc junction boxes.
As a bonus if you can find a wifi router that will support serial connects you can connect reach to it and stuff them both in enclosure.
Something like this if you are into hacking a bit. Never tried it myself. We use mikrotik gear.
GL-AR150 Mini router, Openwrt pre-installed, Repeater, 3G, Tethering, OpenVpn, DDWrt https://www.amazon.com/dp/B015CYDVG8/ref=cm_sw_r_cp_tai_l6nFybN66AK5P