This is a placeholder topic for “915MHz uFL antenna” comments.
Keep your LoRa devices small using this FPCB antenna.
Read moreThis title is 915mhz antenna but the desctiption has a very large range. Can someone confirm what is correct?
Thanks
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Hi Andrew,
Typically Antennas have a large band that they are usable at, the highest gain will often be listed in the title of the product.
This antenna will definitely work for LoRa/LoRaWAN (915MHz)
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Thanks
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Hi Andrew
Antennas are really a black art. If you are not prepared to do a lot of research and have some sleepless nights don’t worry about it. About all you can do is believe what is published and even take that with several grains of salt.
Liam is probably correct when he says
but the length dictates the resonant frequency and will be best at possibly several frequencies which will be mathematically related and depend largely on the number of quarter wavelengths involved. Anything in between will be some sort of compromise which in turn will depend on the actual construction .The actual “bandwidth” is dependent on the diameter of the active element.
I have no doubt this antenna will “work” over the quoted range (4:1) but I would like to see a performance graph but won’t hold my breath on that one. The actual construction would be interesting also. The device is 65mm long but a quarter wavelength at 700MHz is about 100mm so it is probably some sort of folded arrangement or a PC board
As Liam says this should work. I would not expect those performance figures to hold over the entire quoted operation range. You will have no way of measuring this anyway so if it works in your situation you are all good.
Cheers Bob
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Hi Andrew,
Liam and Bob are on the money here. The only thing I can offer is that this antenna was used when we tested early PiicoDev Transceiver modules, and LoRa E5 modules, and worked well at 915MHz.
Hi Andrew et al,
As an Amateur Radio operator all of the above is true … Robert is correct when he said that
There are many, many, many texts by many many many experts and “experts” on how to make the ‘best antenna’. I have used commercially manufactured antennas, and also have made several from scratch. All worked acceptably.
For the frequency band here - without disassembling the antenna - Roberts guesstimate re the construction is probably close to the mark. It may be a folded layout OR it may have some ‘loading’ on the end to effectively extend the length to the mathematical 1/4 wavelength … or … it may use the board substrate to allow resonance at frequency …
For the record, an antenna is whatever works for the frequency in use. I have talked to USA on a dipole antenna made from about 20m of very lightweight hookup wire, with a homebrew matching ‘balun’ in the centre, strung up between two trees with a 5 watt transceiver … The operator at the other end was using a 1000 watt transmitter into a 5 element high gain yagi beam antenna mounted on a 20m tower … he was somewhat amazed with my setup !
The overall goal is, for a transmitter - getting the best match between the transmitter and the antenna to give the strongest possible output signal, and for a receiver - you try to create the most sensitive directional antenna to ‘hear’ the faintest signal… not always compatible goals, so a lot of antennas are a compromise deal.
Murray
Edit – And as an Amateur Radio operator I am encouraged / expected to experiment … there are thousands of us out there, and ‘new’ / re-engineered / old designs for the ‘best’ antenna appear all the time - and as an Amateur I should also say that due to many of these experiments in the past, we now use a lot of our works (theoretical and practical engineering) in many existing public communications systems worldwide. Not just antennas either.
M
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Hi Murray
Yes there are a lot of publications out there and quite a bit of it is somewhat misleading too. Your remarks re success with a 5W transceiver are interesting. An antenna characteristics are the same for both TX and RX so the set up used by your compatriot in USA would be assisting the signal from you as well as his TX to you. I am assuming HF so any sort of Yagi would be pretty huge and at 5 element would not be a lot of gain. I have seen a station that had several rotatable log periodic and they are HUGE. Vertical fixed log periodic are used for fixed point to point circuits but they are large also.
When working I had a fair bit to do with TV transmitting antennas. And assisting the engineer (officially employed as a Scientist) which designed them on other antenna like projects. Where most HF antennas are fairly happy with a VSWR of 1.5 to 2:1 video is another ball game. The bogey man here is the very long feeder cable which can be in excess of 300M. The problem is the time for the signal to travel twice the length of the cable, any mismatch will produce a viewable ghost which is transmitted and nothing can be done about this at the receiver end. We used to measure the match in terms of return loss and could achieve numbers close to or at 40db or 1% which equates to 1.02:1 VSWR (anything better is arbitrary as the reference load is 50Ω 1%), not bad when you consider say TCN 9 Sydney had 192 half wave dipoles on it. I don’t know what the current state of the art is with Digital TV as I haven’t kept up. It may be more forgiving re ghosts, I just don’t know.
The bit that has me puzzled though is how can they get 6dbi gain out of an antenna that size physically. I would have thought unity gain at 700MHz would have been closer.
But like I said, a black art.
Cheers Bob
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Hi Robert
You are correct in that his very directional antenna system would have been the item that helped the contact - very powerful towards me on transmit, and very directionally sensitive for hearing my transmissions. (This was long path over the Pacific and all of continental USA to Long Island)
But I also briefly communicated with a station in Yugoslavia - where he was using a similar dipole style antenna. Both contacts were in the 40m Amateur band ( 7.1 MHz).
Raw power is not as necessary as some might think. Amateurs are experimenting with systems like FT-8 which is a signal processing device that can pull out signals that are very low down in the noise floor and to the ear are undetectable (also used for deep space signal processing now) and WSPR which is a system that sends a low power signal - typically < 1 watt - and which is monitored world wide for determining propagation around the globe. (yes it is pronounced ‘whisper’ and stands for Weak Signal Propagation Reporter). We demonstrated this at the scout camp I mentioned in my Borg Cube project.
Re your TV antenna VSWR value - I wish! that is scary good, and from your note essential to stop transmitting ghosts.
Murray
Hi Murray
Very true. I spent 4 years in Papua Nw Guinea and our VHF base stations (mobile networks) had a very useful quirk. If you had a defunct 50W Base station transmitter it could be replaced with a 25W unit out of a mobile and become a 25 W base until the original board could be repaired. The received signal only reduced to 0.7 of the original and in practise only noticeable at the fringe of reception area. The receiver was the same. The only part not interchangeable was the audio amplifier. Very useful trick out in the boondocks of PNG.
Cheers Bob
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WSPR web pages - fun to change selection params to see who can hear what frequency … transmit power levels from 5 watts to 0.2 watts
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