The BIG and SMALL ANTENNA topic part 1


#41

you probably speak chinese ? nice tool that pocketVNA :sunglasses:


(Phang Moh) #42

I can speak very little Chinese, like buying food and ask for direction. I used Google translate all the time and re-read the translation (the pin ying of course) so it makes sense before I hit the enter button!


(Phang Moh) #43

For the Smith abacus, you forgot to put the marker on the right frequency
I forgot about that but I did a trace along the path it is as what I have mentioned.

Any chance you can get the gain tested? Last time I did something like that, it required two identical antennas and an anechoic chamber, among other things...
Unfortunately I don't have access to an anechoic chamber.

The USB VNA really helps because I used to purchase lots of antenna and to test them I usually put them on top of the roof to get as much of LOS as possible. It also means climbing up and down the roof to test. Surprisingly majority of these antennas are craps and totally out of tune. So, the VNA really helps to filter out bad antenna before even testing them outside. :slight_smile:


#44

I did a search on that site .... but :fearful:


(Phang Moh) #45

You should always search using Chinese words instead of English. That way you get what you really want. Those results with English are usually used as a bait for people out of China I guess (just look at the price, it's high even for Taobao standard). Here's a modified search of yours in Chinese. I basically translate the phrase "antenna glass" into Chinese and add 868MHz at the back. Once you see something you like but want to see more of these, mouse over them, there's an option of "find similar". It's sort of like an art. Unless you are searching for rock band T-shirts, very less likely your English phrase search is useful!


(Jangeirnaert) #47

will this Aomway 915MHZ 933MHZ 3dBi 50ohm T Type Spring Spiral Antenna SMA RP-SMA For rxReceiver. I am testing simple dragino + arduino on 915+ mHz indoor. I am a total newby to all this. Here is the link. https://www.banggood.com/Aomway-915MHZ-933MHZ-3dBi-50ohm-T-Type-Spring-Spiral-Antenna-SMA-RP-SMA-For-rxReceiver-p-1126186.html


#48

only for receiving (possibly it is not 'matched) .. not the best choice


(Aanhanger) #49

Could you tell it where it's from? I bought a new replacement gateway and am in the market for a cheap antenna, this seems to fit the bill. A link would be nice, as I can't find it, though I tried multiple. The only one I found are these ones, might go for the black one (2nd link):


(Phang Moh) #50

Hi,

Here's the shop. If I post the product page directly, somehow the URL contains information related to my account and when you click it, it will be invalid. It's a tiny shop, so should be easy to find. And also, depending on your region, they might redirect you to the world subdomain of taobao,com. Certain product can only be seen on the China domestic market, so it will complain product doesn't exist.


(Aanhanger) #51

Thanks a lot. For the other people I think this is the 1.2m variant:

And this is the 58cm variant:

Ordered the 58cm variant, thanks!
(I bought the 58 + N > SMA connector for 17€ incl. shipping)


(Gig) #52

Wow, this is really dirt cheap. Keep us in touch when you try them out!


(Jens) #53

THIS one for 868 MHz!!! :wink:

A dream???

http://www.mpantenna.com/product/400mhz-uhf-base-station-antenna/


(Laurens Slats) #54

Pretty cool news, we've started the development of an open, freely available online course around LoRa and LoRaWAN.

Part of the course is about Antennas. Does anyone has or knows good resources explaining the fundamental basics about antennas? People following the course should be able to understand it without prior knowledge. The format doesn't matter, it could be a paper, blogpost, Youtube video...

Something like the link @dbrgn posted


(Rkluthe) #55

I have found an antenna in the DeLock portfolio.

Delock LTE / GSM / UMTS Antenna N jack 2 - 6,5 dBi omnidirectional fixed pole mount white outdoor

It is also not expensive. I paid about 23€.
In the specification a frequency range from 698 - 960 MHz listed. Thus the antenna should also be suitable for LoRa gateways.

Has anyone already experiences with this antenna?

I have ordered an antenna yesterday, but I did not have the equipment to test the transmisson quality.
Are tools or software available to perform simple comparison tests?


#56

Going by the specs it doesn't seem like a particularly useful antenna for 868MHz. Its gain at this frequency even seems lower than what should be theoretically feasible for a monopole. It's probably a very low-cost multi-band antenna prioritising coverage of the wide cellular frequency bands in stead of gain at a particular frequency. It will be usable, but it will be far from good.

Antenna VSWR can be tested easily, but testing antenna gain is quite difficult. You need a lot of specialised equipment, not to mention a RF anechoic test chamber. Poor mans gain test would be to measure the RSSI levels of a fixed node in LOS of an antenna with a known gain, and then swapping this antenna with the one to be tested and compare RSSI.


#57

Indeed that the way I found out that one of my homemade antenna's was a real horror.
My story on that : http://www.ph2lb.nl/blog/index.php?page=lora-measuring-antennas


#58

great antenna test !

The diy bolkensteijn GP performs very well !

and if you're not that handy its available here

  • question .. what's the influence of the radial angle


#59

The radial angle influence the take-off angle and the impedance of the antenna.

For more detailed explanation check out :
http://www.comportco.com/~w5alt/antennas/notes/ant-notes.php?pg=21


#60

It changes the impedance of the antenna. 45° yields around 50 ohms.

It should also influence the selectivity/bandwidth of the antenna a bit.


#61

tnx for the info .. nice site to !

@laurens antenne info --> http://www.comportco.com/~w5alt/antennas/notes/ant-notes.php?pg=1