How much of an effect does the cable choice have on the signal strength

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JimHelms
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Re: How much of an effect does the cable choice have on the signal strength

Post by JimHelms » Mon Feb 11, 2019 4:50 pm

You might also try some coax cables like the LMR200 or LMR400 that are designed for this type of application.

tonydobbs
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Re: How much of an effect does the cable choice have on the signal strength

Post by tonydobbs » Mon Feb 11, 2019 6:14 pm

JimHelms wrote:
Mon Feb 11, 2019 4:50 pm
You might also try some coax cables like the LMR200 or LMR400 that are designed for this type of application.
I was thinking that originally, but you're out of the LMR400 and the 5ft LMR200 :(

swwifty
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Re: How much of an effect does the cable choice have on the signal strength

Post by swwifty » Mon Feb 11, 2019 8:36 pm

Based on the signal stats you shared (granted this was only a moment in time when the AT command was run, and not an average) with the antenna outside, I have a few observations, and ideas.

Observations.

1. The panel antenna is better. You can see this under the SNR (Actually, SINR in LTE, which is signal to noise plus interference) value. The little omnis have an SNR value of -10 (how they work like this is always amazing to me), and the panel has a SNR of 1. I suspect that the SINR is fluctuating a lot, if you run the at!lteinfo command a few times, or even at!gstatus.

2. Why is SINR so important in LTE? (Well really in any wireless system) It's because LTE has adaptive modulation rates, so the higher your SINR is, the higher modulation rate you can get, and hence more data throughput given the time frame.

3. SINR in LTE is: Signal (Desired Signal) divided by Background Noise + Interference (Interference in this case, is other cells broadcasting on the same frequency. LTE is as spectrally efficient as possible, and re-uses the same frequency as much as possible without causing too much of an impact to SINR, if possible.). Like I said earlier, LTE is a interference limited system, meaning that other cells will interfere with your desired cell signal, and cause your mobile/modem to have a poorer SINR ratio.

4. I explained all of this, because based on your signal stats from at!lteinfo command, it's clear that there is two cells that your antenna detects. The one your connected to which has a PCI (Physical Cell Identifier) of 56 and there's another that has a PCI of 421. You can see that RSRP is very close (This and SINR is the value you should care about most) and RSSI is also pretty close. This means basically that you are in the middle of two cells. It's possible, both of these cells are on the same tower, and you're just on the edge of two sectors, but it's tough to say. Based on your omni stats, and the PCIs though I suspect that one is physically closer than the other.

Ideas

You could try some high directional antennas specific to band two. This might help as the beamwidth of high gain antennas is much more narrow, so it will bring the desired signal in stronger, and weaken the signal that is coming from another direction. But then again, it's possible both of these cells are on the same physical tower, and by getting a higher gain antenna, it only gets worse. There's only one way to know for sure, and that's to try it, unfortunately.
Screen Shot 2019-02-11 at 9.37.31 AM.png
Screen Shot 2019-02-11 at 9.37.31 AM.png (53.53 KiB) Viewed 1717 times
Above is a screenshot of my signal stats this AM. You can see there's a secondary cell (when I say secondary I mean, one I'm not connected to) on band 2 (PCI of 113) and a secondary cell on band 12 (also with a PCI of 113). You can see i'm connected to a serving cell of 213, and have a CA cell of 213 on band 12 (even though its only listed under InterFreq) Also notice that my SNR of 14 is the difference in RSRP between the two band 2 cells I detect. This means that interference from another cell is my limiting factor (this is a limited interference) as opposed to just background noise limits.

swwifty
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Re: How much of an effect does the cable choice have on the signal strength

Post by swwifty » Mon Feb 11, 2019 8:36 pm

tonydobbs wrote:
Mon Feb 11, 2019 6:14 pm
I was thinking that originally, but you're out of the LMR400 and the 5ft LMR200 :(
I don't think the cable here is an issue, 5ft of what you have already should cause minimal signal loss.

tonydobbs
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Re: How much of an effect does the cable choice have on the signal strength

Post by tonydobbs » Sun Feb 24, 2019 4:09 pm

Thanks for the info Swwifty! It seems that there was an aiming issue... I went out to the field with all the gear and tested different positions, only to discover that the signal became much stronger if I aimed the antenna in the opposite direction. I don't believe this tower showed up on my maps, but who am I to argue with signal strength values. Once I remount the antenna for this aiming I will consider switching the antenna out for the yagis or the 15dBi panels that are still out of stock :(

swwifty
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Re: How much of an effect does the cable choice have on the signal strength

Post by swwifty » Tue Feb 26, 2019 9:18 am

tonydobbs wrote:
Sun Feb 24, 2019 4:09 pm
Thanks for the info Swwifty! It seems that there was an aiming issue... I went out to the field with all the gear and tested different positions, only to discover that the signal became much stronger if I aimed the antenna in the opposite direction. I don't believe this tower showed up on my maps, but who am I to argue with signal strength values. Once I remount the antenna for this aiming I will consider switching the antenna out for the yagis or the 15dBi panels that are still out of stock :(
Did that translate to better performance with these antennas at your house? Once you knew the true location of the signal?

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