the old fart
Senior Member
There is a hole, on the board, to fit a wire aerial.
if I knew what a 1/4 wave bit of wire to use I would try it.
if I knew what a 1/4 wave bit of wire to use I would try it.
Advice Required for Connecting multiple picaxe over radio link.
- Thread starter the old fart
- Start date
inglewoodpete
Senior Member
I haven't been following this thread so I can't give a direct answer. Since wavelength is inversely related to frequency, the question is "what frequency are you using?"
If you google antenna length formula or antenna length calculator you should be able to find an on-line calculator.
If you google antenna length formula or antenna length calculator you should be able to find an on-line calculator.
neiltechspec
Senior Member
Not my calcs, but google returned this.
Calculated (rounded to single decimal):
433 1/4 wave = 164.7mm
433 1/2 wave = 329.4mm
433 full wave = 692.7mm
868 1/4 wave = 82.2mm
868 1/2 wave = 164.3mm
868 full wave = 345.5mm
915 1/4 wave = 77.9mm
915 1/2 wave = 155.9mm
915 full wave = 327.8mm
Neil.
Calculated (rounded to single decimal):
433 1/4 wave = 164.7mm
433 1/2 wave = 329.4mm
433 full wave = 692.7mm
868 1/4 wave = 82.2mm
868 1/2 wave = 164.3mm
868 full wave = 345.5mm
915 1/4 wave = 77.9mm
915 1/2 wave = 155.9mm
915 full wave = 327.8mm
Neil.
the old fart
Senior Member
thanks guys,
82.2mm required.
I'll carry out some trials later today.
Dave
82.2mm required.
I'll carry out some trials later today.
Dave
the old fart
Senior Member
using 868Mhz.
tried 1/4 wave antenna, made from 1mm brass rod.
And tried 1/2 wave.
line of sight somewhat better, but things like bodies cut the signal down a lot.
tried 1/4 wave antenna, made from 1mm brass rod.
And tried 1/2 wave.
line of sight somewhat better, but things like bodies cut the signal down a lot.
A 1/4 wave is a good place to start, but an exact 1/4 wave is unlikely to be the best length, especially without an effective ground plane.
A 1/4 wave with radials (groundplane) should perform better and a 1/2 wave is about as bad a length as you can get, 3/4 wave length in the next resonant length. .
When comparing antennas like this you really do have to take variables such as 'bodies' out of the picture, a large open field is best, between hilltops etc.
Its also important to measure the distance at which comms fails with the various antenna changes, in that way you can calculate the dB difference in antenna efficiency and this is a very useful number indeed.
A 1/4 wave with radials (groundplane) should perform better and a 1/2 wave is about as bad a length as you can get, 3/4 wave length in the next resonant length. .
When comparing antennas like this you really do have to take variables such as 'bodies' out of the picture, a large open field is best, between hilltops etc.
Its also important to measure the distance at which comms fails with the various antenna changes, in that way you can calculate the dB difference in antenna efficiency and this is a very useful number indeed.
the old fart
Senior Member
thanks Ron,
I have removed the original aerial, I see two surface mount resistors. will double check before I remove them.
TOF
I have removed the original aerial, I see two surface mount resistors. will double check before I remove them.
TOF
the old fart
Senior Member
this might be interesting.
the 'product details' on the rev-ed state that the "Inbuilt chip antenna for neat robust finish, up to 500m range (LOS)".
Wireless things,ciesco,gives the 'Chip Ant' range as 150M max.
https://www.wirelessthings.net/radio-comparison-chart
bought these because I needed the 500M range.
the 'product details' on the rev-ed state that the "Inbuilt chip antenna for neat robust finish, up to 500m range (LOS)".
Wireless things,ciesco,gives the 'Chip Ant' range as 150M max.
https://www.wirelessthings.net/radio-comparison-chart
bought these because I needed the 500M range.
LOS (line of sight) is way to vague as an indication on its own, as even if the TX and RX can see each other what is close to the path, such as the ground, can have a significant effect.
500M LOS between two tall towers or buildings is for instance very easy to achieve indeed. At ground level that could reduce to 50M or less.
the old fart
Senior Member
My point is that the information, in the rev-ed datasheet, is incorrect as to los distance using standard erf ceramic aerial.
I would be very surprised if you could not find a situation where the range was 'up to 500m range (LOS)'.
I would also not have assumed that 'up to 500m range (LOS)' meant you would, in all circumstances get 500M of range if the TX and RX just had visual sit of each other.
If reliable long range with high noise immunity is important then consider using LoRa modules, 10 to 30 times further than FSK style modules.
I would also not have assumed that 'up to 500m range (LOS)' meant you would, in all circumstances get 500M of range if the TX and RX just had visual sit of each other.
If reliable long range with high noise immunity is important then consider using LoRa modules, 10 to 30 times further than FSK style modules.
The information in the datasheet looks correct to me. An ERF with a ceramic aerial can have a range of 500m LOS when that is to an XRF with whip aerial as shown in the Wireless Things data chart.
We would not simply make up datasheet figures so those would have been based on manufacturer supplied information. It may be that, at the time, we were only informed of the maximal range and not any qualifications which came with that figure.
None the less; it does appear to me that 500m LOS is the maximal range of an ERF with ceramic aerial.
neiltechspec
Senior Member
I still think elevating just the radio modules is worth considering, especially for the master.
With a 1/4 wave dipole, that, after all is all what the ARF is.
Or use an ARF for the master & ERF's for the slaves.
Neil.
With a 1/4 wave dipole, that, after all is all what the ARF is.
Or use an ARF for the master & ERF's for the slaves.
Neil.
neiltechspec
Senior Member
Looks like the ERF may have been dropped now, not listed on 'wirelessthings.net' any more, well not as a purchasable item anyaway.
So maybe it would have to XRF's and add a 1/4 wave whip.
Neil.
So maybe it would have to XRF's and add a 1/4 wave whip.
Neil.
the old fart
Senior Member
the ERFv2.0 are SRF moduals mounted to an ERF board.
I have some 5db aerials being delivered, on long leads, so can mount them on top of signals posts.
I'll give them a try and see what reliable distance I can get.
If the ERF's have been dropped, it'll be just my usual luck.
Still waiting for ciesco technical to reply.
TOF
the old fart
Senior Member
2 ERF's with ceramic chips will only work upto 150M. as I read from the datasheet.
yes possibly upto 500M to XRF chip. but I have 4 ERF units.
Will see what performace I can get with new whip antennas.
As @srnet indicated, achieving range is something of a black art. The nature of the surrounding area, the objects within it and the proximity of the ground has a massive impact on the range even if the receiving antenna is visible from the transmitting antenna. I have played around with ERFs, XRFs, SRFs and ARFs as well as XBees, Xbee-Pros and so forth and I am astonished at how difficult it is to design for and predict range. I have a drawerful of various (?)RF units, antennae and so forth from when I first ventured into this field and "learning experience". Even the relationship between the ERF and the associated circuit board together with the cables that connect them make for a substantial difference in range, as does ceramic chip antenna orientation. Also, the presence of other devices in the area transmitting on the same or near frequency matters greatly. When it rains and the trees are wet the range is very different to when the weather is dry. And I cannot account for the impact on transmission over a large outdoor miniature railway track - the rails are bound to have an effect. The LOS range quoted by manufacturers assumes optimum conditions and these are rarely found in practice. The manufacturer cannot really be expected to give a "typical usage" range because a typical usage is so difficult to define. As srnet indicates, a reduction down to 10% of the quoted LOS figure is often the case in practice when less-than-optimal boards, instrument cases, antennae and the environment take their toll. Conversely, there are guarded claims of much greater ranges - have a look at this representation of the XRF module; http://www.farnell.com/datasheets/1973754.pdf "We have had reports from customers sending data over more than 3 Km using the standard supplied whip antennas!" Well I am not one of those customers...
Looking at your original post, I would expect ARF modules to work well; they have quite a spectacular range in comparison but I would not hold my breath for ERF modules to be always reliable in the environment you describe but the quarter wave antennae should make a big difference. ARF modules with the supplied antennae are really impressive; effectively these are ERF/XRF type devices with a high gain amplifier on the receiver and a power amplifier on the output. The output power can be adjusted in the settings and I am unsure that the maximum selectable output is within the permissible limits for the 868 MHz transmission band. Nevertheless, they sure have range! One kilometre in an urban environment - easy. Beyond this, there are LoRa units - I have achieved several kilometres urban range with these toys but they are probably much more than you need.
Well said, Circuit.
I was testing the Morse transmissions from the $50SAT board, the TX was at shoulder height in my garden, the RX was my FT60R. I wanted to hear it at the limit of reception, so I went for a walk. I lost the signals in the noise 1km from my house, its a typical urban area.
The very same TX board, running the same power, went into orbit. I would often hear it at the 1000km mark fairly clearly, with the very same receiver.
Now when you tell people the range difference between good LOS and a typical Urban setup can be more than 1000:1 they tend not to believe it.
I was testing the Morse transmissions from the $50SAT board, the TX was at shoulder height in my garden, the RX was my FT60R. I wanted to hear it at the limit of reception, so I went for a walk. I lost the signals in the noise 1km from my house, its a typical urban area.
The very same TX board, running the same power, went into orbit. I would often hear it at the 1000km mark fairly clearly, with the very same receiver.
Now when you tell people the range difference between good LOS and a typical Urban setup can be more than 1000:1 they tend not to believe it.
the old fart
Senior Member
Thanks for that, Circuit.
I found a statement from ciesco site saying that the ERFv2.0 uses the SRF, and that the range is reduced due to the compact size of the SRF board.
So the range of ERFV2.0 is now 100M chip to chip, 300M chip to XRF.
I now also have a draw full of RF units that I can't use, that's £80 down the drain. Wait til pension day to source some ARF boards.
TOF
I found a statement from ciesco site saying that the ERFv2.0 uses the SRF, and that the range is reduced due to the compact size of the SRF board.
So the range of ERFV2.0 is now 100M chip to chip, 300M chip to XRF.
I now also have a draw full of RF units that I can't use, that's £80 down the drain. Wait til pension day to source some ARF boards.
TOF
neiltechspec
Senior Member
I they have dropped the ERF with the standard 0.1" header, that is really annoying.
That 2mm pin spacing (XRF) is no use to me, I know adapters are available but it increases costs.
I'll have to look at some thing else for my planned project then.
Neil.
That 2mm pin spacing (XRF) is no use to me, I know adapters are available but it increases costs.
I'll have to look at some thing else for my planned project then.
Neil.
the old fart
Senior Member
reply from Ciesco re aerial,
"We use a 1/4 wave whip and do not usually bother to remove the ceramic and the small capacitor and inductor. "
"We use a 1/4 wave whip and do not usually bother to remove the ceramic and the small capacitor and inductor. "
How very interesting...so much for impedance matching! @srnet - comment from the expert??
the old fart
Senior Member
I understand 1/4 1/2 3/4 and full wave antenna lengths.
Am I right in assuming that the longer the antenna, the better the reception?
TOF
Am I right in assuming that the longer the antenna, the better the reception?
TOF
I think that @srnet already provided this advice in post 46;
I think that you are better off looking at adding a ground-plane and looking at "antenna tuning" as he suggests. It is a little tedious trying out various antenna lengths (taking off only a mm. or so at a time) and wandering off to check and note the range that can be achieved, but it is probably the best approach. I find that the antenna supplied with the ARF unit is really effective and these can be obtained quite easily from the major suppliers if you would like to fit them to the ERF units. Note that, despite the apparent length, these are still quarter wave antennae internally. I doubt that you will get anything better without going to directional antennae.
In my experience the output matching of these low end RF modules tends not to be very accurate. They may well be designed for around 50ohm, in order to be a good match into co-ax cable etc. But the actual impedance can be different, so it should be no surprise that the whip antenna length for maximum transmitted signal can be different to what a calculator suggests.
Ciesco may well find that leaving the ceramic antenna in place and adding a whip improves matters, but by how much ? Did anyone actually measure what happened if the ‘redundant’ components were then removed, I suspect not.
No.
For maximum radiated power, the impedance of the antenna needs to match the impedance of the RF output stage of the radio module.
The output stages are most often designed around an impedance of 50ohm, which is a good match to a 1/4wave with ground plane or a dipole.
The impedance of an end fed 1/2 wave antenna is around 2000ohms, and thus a very bad match to the radio module, and very little power gets transferred to the antenna.
the old fart
Senior Member
thanks srnet,
that explains it perfectly.
the old fart
Senior Member
I've been trawling the internet, re ground plane.
read somewhere that ground plane should equal attenna length.
so 82.2mm 1/4 wave requires a minimum, 82.2 mm diameter mounting plate, copper, brass, metal.
also it should be grounded to the 0v part of the circuit.
Expect I've got it all wrong, again.
TOF
The general arrangement is for a 1/4 wave vertical (the fed part) and then 4 x 1/4 radials, 90 degrees apart, connected to ground/0v.
http://www.ccars.org/projects/2mgp/tech_2mgp.htm
Although for a simple installation guitar wire (Ernie Ball Custom Gauge 13) is fine, bend over the cut ends to avoid stabbing injuries.
http://www.ccars.org/projects/2mgp/tech_2mgp.htm
Although for a simple installation guitar wire (Ernie Ball Custom Gauge 13) is fine, bend over the cut ends to avoid stabbing injuries.
the old fart
Senior Member
Thanks for link srnet, will have a read.