3G antenna selection

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SirHumphreyAppleby

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#284472 24-Apr-2021 10:56

I recently purchased a 3G VoIP gateway as it's easier for my parents than a mobile phone.

I was unable to reliably get the signal level on the device to show anything more than "No Signal", however, outbound calls did work. I ordered a cheap magnetic 7dBi antenna and when placed outside I attained 'two bars' of the three levels of signal the unit displays. I thought that was pretty decent, until I used SSH to access the unit and determined the signal quality was only 12 on a 0-31 scale.

I have since done some more investigation with my phone and determined my phone is connecting to a site 1.2km away, on the other side of the house from where the gateway needs to be installed. I am unable to find a larger omni-directional antenna at a reasonable price (and in stock), but there are a few options for LPDA antennas available. My concern is these have a relatively narrow beam width and there is no direct line of sight to the tower. Would either of these be suitable, or could anyone recommend something more appropriate?

https://www.snappernet.co.nz/product/30348/35-18683-blackhawk-lpda-antenna-698-4000-mhz-12-14-dbi-no-cable

https://www.gowifi.co.nz/antennas/ant-205.html

Cable length will need to be around 10m. Line of sight may be possible from the other side of the house, but the cable length would need to increase to 20m.

Thanks.

coffeebaron

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#2697540 24-Apr-2021 12:19

Either the one from SnapperNet or search for ANT-213 on Go Wireless.
I assume the gateway is on 900 or 850, not 2100.

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SirHumphreyAppleby

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#2697542 24-Apr-2021 12:43

coffeebaron: Either the one from SnapperNet or search for ANT-213 on Go Wireless.
I assume the gateway is on 900 or 850, not 2100.

I'm in an urban area, so it's most likely 2100MHz. I haven't been able to find the frequency the gateway is connecting to, but it supports both Band 1 and Band 8. My phone seems to favour Band 8 but does occasionally connect to somewhere on Band 1.

I guess ANT-162 would be the equivalent for 2100MHz? Conveniently out of stock.

coffeebaron

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#2697555 24-Apr-2021 14:27

850/900 bands are everywhere and I think you'll see 2100 disappearing from 3G in future as the spectrum gets refarmed for 4G or maybe even 5G.
What network us this on? And what device are you using?

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SirHumphreyAppleby

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#2697556 24-Apr-2021 14:31

coffeebaron: 850/900 bands are everywhere and I think you'll see 2100 disappearing from 3G in future as the spectrum gets refarmed for 4G or maybe even 5G.
What network us this on? And what device are you using?

I'm using the Vodafone network. The device is a Yeastar TG100.

SirHumphreyAppleby

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#2697558 24-Apr-2021 14:39

Phone connected on Band 1 again. Looks like it's the same location on cellmapper.net, so 900MHz should work fine.

Once I factor in the cost of the cable, both antenna options work out to about the same price.

hio77

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#2697563 24-Apr-2021 15:34

B1 will certainly go away. There is a large amount of refarming going on these days.

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SirHumphreyAppleby

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#2697568 24-Apr-2021 15:48

Sorry, I had my Bands around the wrong way. I'm connecting at 900MHz (B8) most of the time, 2100MHz (B1) occasionally.

I'll probably still go for the wide band antenna as the published gain at 900MHz is the same and it is available with the cable.

I'll order on Tuesday, so still happy to listen to any further advice. Thanks for your help.

SirHumphreyAppleby

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#2700417 1-May-2021 11:09

I thought this was going to be easy, but the antenna provides no sign of improvement. Am I perhaps overlooking something simple, or is there potentially a fault?

I ended up purchasing 6m of cable along with a ANT-55 as this was similar in dBi to the recommended antenna, covered the Band 8 frequency range and would fit my existing mast. It also appeared to be solidly built, but Go Wireless have replaced the Laird product with their own branded version. The Website wasn't updated to reflect this change, but the product has now been removed so this can be corrected.

One thing I noted is the active element, which is not a loop like on other antennas I've seen, instead constructed from rod and flat segments, is not perfectly parallel with the other elements. Could this be the cause of the issue?

The N-type connector is finger tight and the SMA slightly over finger tight, as seems to be the recommended for these connectors.

SirHumphreyAppleby

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#2700420 1-May-2021 11:14

Also, a quick note. Pointing the antenna in a random direction also showed no change.

It's possible the signal quality meter just doesn't work very well. I was using the output of Asterisk (gsm show span) to read the signal quality from the radio.

coffeebaron

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#2700505 1-May-2021 16:03

Is there a setting on the gateway to lock to external antenna? Can you also lock to band 8?

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SirHumphreyAppleby

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#2700513 1-May-2021 16:53

coffeebaron: Is there a setting on the gateway to lock to external antenna? Can you also lock to band 8?

Right, I think we're getting to the bottom of this. I have found a user manual for the radio. https://usermanual.wiki/Pdf/QuectelUC15ATCommandsManualV11.1891924351/html#pf31

I can't copy and paste from the file, but using AT commands I can see a value of 16, which indicates WCDMA 2100 is being used.

Last send AT: AT+QGBAND\r\n
Last receive AT: \r\n+QGBAND: 16\r\n

2100MHz clearly won't work with this antenna (or potentially at all in the future). The default band value is meant to be 147 (E variant), so 900MHz should enabled. I'm not sure why the unit isn't using it. I have been unsuccessful in assigning a value of 129 using AT commands, which would lock the unit to 2G/3G 900MHz. I tried two different SSH clients. PuTTY allows me to enter the command as per the docs (AT+QCFG="band",129), but I'm still getting an error. I might have to try different terminal emulation or contact support for this one.

TG100*CLI> gsm show span 2
D-channel: 2
Status: Power on, Provisioned, Up, Active,Standard
Type: CPE
Manufacturer:
Model Name: UC15
Model IMEI: -
Model CBAND:
Revision: 3A10E1G
Network Name: vodafone NZ
Network Status: Registered (Home network)
Signal Quality (0,31): 12
SIM IMSI: -
SIM SMS Center Number: +6421600600
Send SMS Center Number: Undefined
Last event: Unknown Event
State: READY
Last send AT: AT+QCFG=band,129\r\n
Last receive AT: \r\nERROR\r\n

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coffeebaron

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#2700572 1-May-2021 22:19

Try AT+QCFG="band",129,1

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SirHumphreyAppleby

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#2700587 2-May-2021 06:50

coffeebaron: Try AT+QCFG="band",129,1

The last setting was optional and unfortunately still results in an error.

I've opened a support ticket but due to a holiday in China, I won't receive a response until Thursday at the earliest.

SirHumphreyAppleby

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#2703010 6-May-2021 16:31

Thanks to those of you who assisted. We were 99% of the way there.

Turns out the only piece of the puzzle I was missing was escaping the quotes within Asterisk.

AT+QCFG=\"band\",128