LoRa/LoRaWAN tutorial 43: Sleeve Dipole Antenna

[@K9-33]

Antenna B is called a sleeved dipole antenna with a decoupling choke. The extra sleeve (tube) is a choke which increases the bandwidth of the antenna so tuning is not so critical. This is a trick to sell one antenna for multiple bands.

[@dimerod5073]

I must be grateful for the clear and well-illustrated explanations for a subject that is difficult to understand in the academy. Thank you

[@bryanchoong5920]

Bruh your videos r so so professional and detail. I feel like I'm reading experiment/research report by watching your video!!! KZbin need more peoples like you. :)

[@TrystansWorkbench]

Very good, Sir. Excellent. A very thorough, and brilliantly well-done video on the sleeve dipole. Thank you.

[@TheHamdibaba]

Thank you for beautiful explanation you saved my day.

[@raymondbruns3291]

Nice clear video. I'm no antenna engeer either, but I think that antenna b is a valid design. When I look at the design I see 2 antenna's. Antenna 1 consists of tube 1 , the insulated piece inside tube 2 and tube 3. Antenna 2 consists of tube 3 and a part of tube 1 and 2. I think the second antanna is tuned to roughly 2 times the center frequency of antenna 1. At this frequency tube 1 and tube 2 are 3/4 wavelength witch is fed at 1/4 wavelength. So 1/2 wavelength is canceled out. This leaves 1/4 wavelength in tube 3 and 1/4wavelength in tube 1. The point of maximum power radiation is near the top of tube 1, so the shielding of tube 2 doesn't affect gain much.

[@raymondbruns3291]

Btw, I look forward to your reaction.

[@Mobilefish]

Hi Raymond, I do not understand your antenna 2 remark. But even if I was, I still do not know for CERTAIN if this antenna works correctly. I think you are right that this is a VALID antenna. BUT I NEED SOME PROOF AND I ALSO WANT TO KNOW THE GAIN. After your comment I have modelled the antenna in 4NEC2. I had hoped the antenna model could provide the answer if this a valid antenna. Unfortunately the VSWR is greater than 8. I tried to use the 4NEC2 optimise functionality but I got an error message. At this moment I have no idea how to solve this. Antenna model: www.mobilefish.com/download/lora/sleeve_dipole.nec.txt I updated my presentation, see last 3 pages. www.mobilefish.com/download/lora/lora_part43.pdf I am not a 4NEC2 specialist, so I presume I have not modelled the antenna correctly. I will revisit this again when I have gain more 4NEC2 knowledge.

[@HFLC]

Hello, I really liked your videos and I'm a new subscriber. Would you happen to have a pdf file of your tutorials so I can read them offline on my ebook reader?

[@weldyguruh2712]

Thanks for your explanation

[@ManuelPinner]

I like Making Antennas for both HF and Higher Ham Bands,

[@syarifspero]

can we reduce the VSWR value (to the value of 1.2 - 1.5 for example) from the sleeve dipole antenna by modifying the antenna such as adding LC components (without making antenna from the beginning)?

[@Mobilefish]

Syarif, I am not an antenna engineer, so I can not answer this question. I have read articles using LC components for impedance matching but to change the VSWR? I do not know...

[@Lexdrumz]

The correct way of adjusting the voltage standing wave ratio is by cutting the radiators (metal?) length. But.. I've had a few antenna's for my transmitters which were fixed length and needed to be tuned with metal rings on the bottom, which had some capacitive or reactance influence on the antenna. So yes its possible with LC network but best is tuning with adjusting length and if that doesn't work, then other ways.

[@kavindugilshan]

What is the difference between sleeve dipole and Hertzian dipole ?? Very common antenna for wifi exactly same as on your tutorial . But they are shorter than usual wavelength . For 2.4 ghz it is 25 mm . But normal quarter wave for 2.4ghz is around 31mm .

[@TrystansWorkbench]

Great question Kavindu! Antennas are usually shorter than the theoretical physical size, due to a thing called "Velocity Factor" (VF). So in a cable, even though you would expect radio waves to go at the speed of light, they can go considerably slower. Some coaxial cables can have velocity factors of 0.66 for example. Also, there is an "End Effect" which typically shortens an antenna by 5%.

[@hienthu211]

Can you please suggest which type of antenna (868 MHz) is better for end node when gateway kept with the altitude of above 50?

[@Mobilefish]

It depends on the environment your end node is used. But in general a sleeve dipole antenna is a good antenna, but this antenna is sticking out.

[@makestuffwork9205]

Where can I find the theory to calculate the element and sleeve length? I've already trawled through endless vids and documents but no-one seems to have the formulas to allow for the sleeve diamter and thickness. Thanks.

[@Mobilefish]

For whatever it may be worth here is my 2 cents: As far as I know there are no formulas for sleeve diameter and thickness. The sleeve material is important. It must not contain materials which can shield electromagnetic radiation. For example certain plastics can contain carbon fibres, which is not good. Another point to consider, some plastics degrade more easily when opposed to direct sunlight. With regard to the thickness / diameter: Preferably make the thickness / diameter as small as possible. Make sure it does not break easily! It must withstand harsh weather conditions: rain, hail, wind etc. And of course rough handling. A smaller antenna is good because it take less space and weigh less. The antenna does touch the sleeve but try to minimise it!

[@TrystansWorkbench]

The length of the sleeve is a quarterwave of the frequency that you want (or a tiny bit less), diameter (or thickness) is not critical as long as you can put it over the coax. Wider diameters will give you additional bandwidth, but it's not critical.

[@halukyilmaz9621]

i got stock ttgo antenna, when i try to communicate with arduino-lora code i got around -40 rssi, why is that?

[@Mobilefish]

RSSI values are negative. Near 0 means excellent signal (never happens). To give you an idea: I have a self build 1/2 wave dipole antenna. If the distance between end node and gateway was 6 meters, I got RSSI = -27. If the distance was 2 km, RSSI = -100

[@halukyilmaz9621]

@@Mobilefish i got some couple antennas 433 and 868 , and i use ttgo lora sx1276 module, if you can share email i can send antennas photos, how can i best coverage urban?

[@Mobilefish]

You can contact me, goto www.mobilefish.com on the bottom of each page you see the link: send an email to Mobilefish.com. Or goto twitter and send me a message: twitter.com/mobilefish Or goto linkedIn and send me a message: nl.linkedin.com/in/robertlie