The BIG and SMALL ANTENNA topic part 2

Hi Remko,
Thanks for your feedback, unfortunately I only have one gateway so I cannot swap it out. I must say the behaviour is odd.

regards
Chris Dann

Hi LoRaTracker,
I am observing the reducing RSSI on the recieve side at my gateway. I have two known devices that have not moved so I am guessing that my problem is in the recieve transmission line or I guess it is possible that as Remko suggested there is an intermittent reciever issue with my gateway.

Regards
Chris Dann

Yes, but if there is a loss or other problem with the receiving of the antenna, you would expect it to affect the transmitter also.

Or are you saying your gateway has seperate recive and transmit paths, from the gateway electronics to the antenna(s) ?

Hi Chris,
The process you may have to follow is that of elimination so you can exclude possible causes.

Hi All Great forum. I have yet to find an antenna I really like for a gateway and have tried a number over the last few years. I was keen to see what the Chinese ones are like. Like many of their statement there are often over stated, but I though I give a 10dbi colinear one ago 900mm long and also wanted to see the “vibrator” construction. I ordered this one from AliExpress.

I have tested it and the antennas VSWR was 1.38-1.45 so not great but ok. I range tested the gain with both up and down tilt of 5° and 10° and horizontal using test signal and calibrated antenna and spectrum analyser. The max gain was around 5.6 dBi max.

As it was so much less than the spec, I then decided to remove the radiating element (Just unscrew the base after heat treatment) to expose the antenna. I enclose the pictures below, for those interested. Not a vibrator construction but a modified CoCo antenna. A matching feed element (like a shorted balun dipole and λ/4 matching section), 2 sections of λ/2 and a nominal shorted λ/4.

The antenna was not as expected and explains why lacking gain. Its sad that they don’t make antenna to spec, as all the construction was very good practically. The have a good fibre glass radome, well-sealed, Brass CoCo and feed section.

For those interested the λ/2 sections are 107.2mm and λ/4 39.7mm. It uses solid dielectric (Vf of 0.66) of 9mm diameter and a 10mm o/d and i/d of 9.1mm brass tube. This would give the designed resonate frequency of around 920-930 MHz, but with radome and the very short λ/4 sections give a frequency of 860- 915MHz for less than 2:1 VSWR. Useable but not 10dBi.

IMG_0829 IMG_0830 IMG_0831 IMG_0832 IMG_0834

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Hi Remko,
I think water must be getting in somewhere. It might be the gateway or it could be the antenna. I have replaced all of the cables and connectors again and the performace remained poor. We have had 2 days without rain and the weather has been sunny. All of a sudden I see a 20db gain.

Regards
Chris Dann

Today we started our long-term testing of the RAK 5,9 dBi beta-antenna on the newest gateway of our community (TTN-Apeldoorn)

afbeelding
First coverage measurement shows expected coverage!

afbeelding
There is a minor issue with TTNMapper not showing the gateway location.

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Hi All,
I think I have found the problem. SMA connectors need to be done up with a spanner not just firmly finger tight. I also relocated the antenna on the top of my mast to ensure there was zero overlap. It was overlapping by maybe 10mm previously. Given the intermittent nature of the problem I suspect that a slight amount of play in one of the SMA connectors caused by the wind was enough to change the charaterisitics of my tranmission line at 915Mhz. Anyhow it has now been stable for over a week an producing excellent RSSI figures. Thanks for the suggestions. Regards
Chris Dann

Hi all,

i’m currently using an Cisco ANT-4G-OMNI-OUT-N= antenna which I had lying around. Now, after I finish my gateway, I wonder if it would be better to use a different one. Unfortunately, I do not have an antenna meter, so I do not know how good or bad the cisco is. :thinking:

https://www.ebay.de/itm/333174354221

The antenna is currently mounted on the garage with a 1m coax cable with n-connectors and then via 30cm pigtail to the RAK2243 board. So only a antenna with 2dBi profit would be possible anyway, i’m living in germany. :de:

My other problem is that the Cisco antenna is currently attached only with ducktape, :rofl: because I dont have a mount for it.

Does it make sense to use another? Are there any recommendations?
I have already looked at one of Delock…

https://www.ebay.de/itm/Delock-LoRa-Antenne-868MHz-N-Buchse-3dBi-starr-outdoor-32cm/333269015108?epid=2246854500&hash=item4d98619a44:g:gEUAAOSw3r5dLhze

And also Aurel’s, but I would need other coaxadapters again.
It would be nice if the antenna had a female N-connector.

Well, this is a antenna for cellular networks. The other alternative you list is for LoRa. What are you trying to use it for, LTE connection to the RAK2243 or for LoRa?

Here are the specs and charts for this antenna: https://www.cisco.com/c/en/us/td/docs/routers/connectedgrid/antennas/installing/cg_antenna_install_guide/Outdoor_Omni_for_2G_3G_4G_Cellular.html

You should be able to make simple mount using a cheap saddle mount, the sort of thing used to attach pvc pipe to a wall.

I want to use it for LoRa.

OK so the Cisco antenna is not the right one to use.

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I know the question is if it makes such a big difference.

Nominal gain (dBi) * 698 to 960 MHz—1.5 dBi . So you can suppose gain is <= 1.5dBi.

If it’s working for you, just use it.

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Hi

Does anyone have experience with this antenna:
https://www.delock.de/produkte/G_89583/merkmale.html?setLanguage=en

wants to combine it with a rak7258. Antenne outside. height 9 meter and rak inside Coax cable 3 meter.

Hi,
I’m considering this new SCO-868-6 antenna from SIRIO, combined with RAK2245 concentrator board. Does anyone have any experience with this antenna or the little brother SCO-868-4?
Thanks

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I have not used this antenna but given the coice of materials, the way the mount is engineered and the fact that this company is actually delivering radiation patterns with their antennas suggests to me that the antenna is acually doing what it is planned to so.

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Sirio-antenna is indeed a well know name in the antenna world. They started in 1972 and started out with CB antenna’s (mobile and base) but scaled up to Hamradio, VHF and UHF. Later added Cellular base antenna’s and WIFI antenna’s to the catalog.

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Have you got some price point from them about this antenna?

The best price I found is around 70 euro from this italian shop, he also sell on eBay.

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