[hvalentim]

It also seems antenna gain has a relation with directivity. The more "directive" the design the higher the gain, the drawback being you need to more accurately point the antenna to the source of the signal.

Performance wise, it seems then a Yagi should be the best option for signal reception.

A Yagi can actually be made to look "cool"/decorative:

source : Antenna for Superheterodyne pin???

The issue being Yagis tend to be quit large/occupy a lot of space. Since the signal will come from above/the roof I guess it would be placed vertically (???) which would help.

According to this calculator it is perhaps possible to have a 6dB gain with a design "as small" as 24 x 17 cm (results below).


**** Logarithmic Periodic Dipole Antenna ****
http://www.changpuak.ch/electronics/lpda.php
JavaScript Version 12.01.2014, based on ARRL ANTENNA BOOK, 17th ED.
------------------------------------------------------------------------------
Min. Frequency : 433 MHz
Max. Frequency : 434 MHz
Boomlength : 237 mm
Gain : 6.70 dB
Elements : 4
tau : 0.792
sigma : 0.142
------------------------------------------------------------------------------
Bandwidth (active region) : 2.01
Bandwidth (structural) : 2.01
Bandwidth (effective) : 1.00
------------------------------------------------------------------------------
Element 1, Rod : 173 mm, Position : 0 mm, Diameter : 3 mm
Element 2, Rod : 137 mm, Position : 98 mm, Diameter : 3 mm
Element 3, Rod : 109 mm, Position : 176 mm, Diameter : 2 mm
Element 4, Rod : 86 mm, Position : 237 mm, Diameter : 2 mm
------------------------------------------------------------------------------


More interesting stuff, often referenced:

---

Another "trick" on the transmitter part seems it could be to increase voltage to 12V.

Judging by the look of the RX board (below), seems this is already the case?

   

"433MHz Superheterodyne 3400 RF Transmitter and Receiver
Transmitter Specs:
Working voltage: 3V~12V"

[werk_ag]

Another "trick" on the transmitter part seems it could be to increase voltage to 12V.

Judging by the look of the RX board (below), seems this is already the case?

Both transmitter modules in TX units and RX units are powered by 9V. In fact the reason for this is to increase the transmitting power.
Powering the modules just with 9V was proven by tests, being enough to give a reasonable cover range.

For a reliable use of the RX data relay function, the unit must be powered from an external 12V power supply, and not only by the 5V from USB

[meteoestarreja]

In deed, yagi antennas do a pretty good job, however, that's one thing to consider:
They tend to be very directional what means that, if you don't adjust the direction accurately and depending on the RF pattern, you will get a worse result with the yagi than with an omni-directional antenna.

Something like this:


VS



Those images refer to different view/axis, but I think you'll get the ideia.

You could also test different yagi construction and materials, even if it's only for fun/educational

If you want to do that and need some help, just talk to me. I can help you and/or give you an emulator for analysis

[hvalentim]

I am testing the Superheterodyne 3400 RF Link kit (TX/RX couple) I received in a test board.

I am using a couple of Nanos powered by the PC USB ports and the Virtualwire receiver/sender demo examples (transmitter in PIN D12, receiver in PIN D11), which loop transmit a “hello”.

It is working. The TX part, even using an improvised non-optimal league of 18 cm fence wire as antenna, seems to be "heard" by a Wouxung portable radio at least 200 meters away, with a house and a few trees in between.

As for the RX part, it is receiving better without the improvised antenna than with it, so I am certainly missing something. I suspect this may be the way I am connecting the GND.

It turns out the RX unit has no less than 3 pins labelled “GND”, two of them side by side, next to the ANT (antenna) PIN. So I am figuring two hypothesis:

H.1 - perhaps I should connect the GND closer to the ANT pin to the central pin on an SMA PCB connector and the other (the one farther away, next to the 5V pin) to the Nano GND? (currently I have both of them in common with the Nano GND)?

H.2 - perhaps I should connect the GND closer to the ANT pin to the second GND Nano Pin, the one in the opposing row, where D11 is located?

Can anyone please help me enlighten this?I found plenty of examples on how to wire 433Mhz receivers for test purposes to an Arduino, but not this particular receiver model.

Also, does anyone know about a piece of software library/a procedure (preferably using the Nano itself and not involving additional hardware) allowing me to have an idea of the quality of the received signal? So I can subsequently test different antenna models.

Thanks a lot,
HDV

[meteoestarreja]

I don't have any of those right here with me, but if I'm not mistaken, it's the same connecting in any of those GND because electrically they are connected together (in the module itself and on the pcb).
Anyway, since you're testing just with a fence wire, you could forget about GND for now, since using just a simple wire, you must connect it, to the ANT pin and nothing else.
By the way, try with 16cm and not 18cm since it's near from 1/4 wave length for 433Mhz (if I was not mistaken in calculation, the best measure should be 16,5 cm). Being that "far" from the right value, will affect specially RX like you're experiencing.

About the second question and without using additional hardware, I'm not imagining an arduino measuring signal strength at least with accuracy.

You could try for example use a "special" TV dongle (you can find it very cheap on ebay) and use SDRSHARP with it.
Google it for more info or if you are interested on that, just ask about it and I could give you more info.

[uncle_bob]

If you want to do that and need some help, just talk to me. I can help you and/or give you an emulator for analysis

Hi meteoestarreja,
Interestingly on a new TX unit I've just built, if I attach a "rubber ducky" type antenna the signal stops being received (at a distance off less than a metre). Here's the actual ebay item http://www.ebay.com.au/itm/281126334076

Its like if there's a dead short across it, yet a test with a multimeter shows it's an open circuit between the antennas' nut and conductor.

It seems to work ok on a receiver though.
Any ideas?

[meteoestarreja]

Hello uncle_bob,

First of all, never trust a multimeter for test an antenna.
Not for looking for a short at least ... The thing is, even if you encounter a short-circuit between the inner conductor and the shield, that does not mean that the antenna is rubbish ... in some cases, it could mean the opposite.
I have several antennas that have that behaviour and electrically speaking, in fact they are in short using a coil (the coil is not in plain sight) ... RF speaking, that coil isn't a short and do his job perfectly. I'm remembering one example and the antenna could work with hundreds more power that those tx module that we use in our weather station.

Now, looking at your problem, it looks like the same problem that I spoke today in another topic.
It seems that you have an antenna for working somewhere else than 433Mhz ... Chinese people sometimes does not put the right description in the right article.

The receiver that we use, do have a good sensitivity with good noise rejection and even with a poor antenna, they do a pretty nice job. I was able to run several tests and the receiver performed very well - thanks for the previous research Werk_AG, you saved me a few bucks in orders for testing RX modules
For TX modules in another hand, the thing is completly diferent, you need a good antenna or at least, an antenna calculated well for the frequency you want. If you use no antenna or an antenna that is not resonant for the frequency that you will broadcast, the result is poor or no signal at all.
So, in this case I belive that's precisely the problem, I think that the description is wrong because that don't seem to be an 433 antenna, or at least, it's behaviour it's not suggesting that.

Did you tested to take the antenna apart? Sometimes in that kind of antennas, it's relatively simple to take the black plastic and watch inside without break anything.

I have plans for building an antenna analyser using an arduino (not a nano, but a more musculated "cousin"), maybe then I will accept all those antennas from ebay for testing and tell you for which frequency are they designed to

If you want to do that and need some help, just talk to me. I can help you and/or give you an emulator for analysis

Hi meteoestarreja,
Interestingly on a new TX unit I've just built, if I attach a "rubber ducky" type antenna the signal stops being received (at a distance off less than a metre). Here's the actual ebay item http://www.ebay.com.au/itm/281126334076

Its like if there's a dead short across it, yet a test with a multimeter shows it's an open circuit between the antennas' nut and conductor.

It seems to work ok on a receiver though.
Any ideas?

[werk_ag]

Hi meteoestarreja,
Interestingly on a new TX unit I've just built, if I attach a "rubber ducky" type antenna the signal stops being received (at a distance off less than a metre). Here's the actual ebay item http://www.ebay.com.au/itm/281126334076

Its like if there's a dead short across it, yet a test with a multimeter shows it's an open circuit between the antennas' nut and conductor.

It seems to work ok on a receiver though.
Any ideas?

Hi uncle_bob

Not disregarding the wise words of meteoestarreja, I believe that your antenna will work. This already happened to me.
Don't put your TX unit so close to the receiver, try it at 10, 15 ou 20 meters away.
I have some anttenas like your, and they are good performers.

Try it, and please report back the result.

[werk_ag]

I have plans for building an antenna analyser using an arduino (not a nano, but a more musculated "cousin"), maybe then I will accept all those antennas from ebay for testing and tell you for which frequency are they designed to

That would be a fantastic device! And I have no doubt that you have the knowledge to do so.
Do you need a beta tester?

[uncle_bob]

Do you need a beta tester?

+1
I also have a Arduino Mega and a spare DTV dongle like the one used for my Aircraft radar

Werk, I first noticed the problem with the antenna when it was actually outside (5-10 metres away through a couple of walls). Where my 16cm length of wire is usually used with good results.