Hi, I'm using that 433 super heterodyne receiver but...
When I builded my yagi antenna I was unable to find the + for antenna because the pin to solder on receiver is connected to the ground...
Somebody knows where can I find the + pin for antenna?
Thanks.
Is it not the other side of the coil, as shown in the attached photograph?
I was unable to find the + for antenna because the pin to solder on receiver is connected to the ground
How do you know this? What might look like a short circuit to DC can be high impedance to 433MHz.
That is not a superheterodyne receiver, but no matter. The antenna connection is the solder blob on the lower left corner of the board, looking at the component side (next to a small coil).
The antenna input circuitry is probably designed for a 1/4 wave dipole (17 cm straight wire) and probably not for a yagi antenna.
jremington:
That is not a superheterodyne receiver, but no matter.
Of course it isn't - it is a superregenerative. It has two transistors, apparently a simple (and I do mean simple) RF stage somewhat ameliorates the potential for co-interference.
jremington:
The antenna input circuitry is probably designed for a 1/4 wave dipole (17 cm straight wire) and probably not for a yagi antenna.
Trivial distinction - definitely "no matter". If used with a Yagi antenna, the two connection points would be the antenna terminal and a ground "thru" on the same end of the board.
Thanks for your answers. I'm a beginner in electronic that why I though that it was the ground.
To be sure I get that model
There is an antenna pin and a ground. Hope it works.
My aim is to make a tracker for Lost RC models.
My aim is to make a tracker for Lost RC models.
Well most RC models only have a receiver in them so how would that help you track them?
Probably by putting that transmitter in the model.
polymorph:
Probably by putting that transmitter in the model.
You're right, I want to put a transmitter inside. It's cheap and I can expect a good range with narrow band antenna.
With rc rx failsafe position I can active it only when needed so it doesn't disturb signal.
In the ham radio world this is know as a fox hunt. Someone hides and you have to find them. I have done this quite a few times. You do not need a yagi as there are too. Any side lobes. What works best is a dipole and you search for the sharp null not a maximum.
Grumpy_Mike:
In the ham radio world this is know as a fox hunt. Someone hides and you have to find them. I have done this quite a few times. You do not need a yagi as there are too. Any side lobes. What works best is a dipole and you search for the sharp null not a maximum.
I heard about fox hunting, I did a tape measure antenna from this "sport/game".
I just need to check if my antenna could work...
You might have to do a matching network to get the antenna to connect correctly. Look up the term balum.
Grumpy_Mike:
You might have to do a matching network to get the antenna to connect correctly. Look up the term balum.
I saw something about that, a piece of wire bend like a square that short circuit + and -. Is it what you talking about?
Well not quite it is a balanced to unbalanced coupler. You can make one with a coil and some capacitors.
Grumpy_Mike:
Well not quite it is a balanced to unbalanced coupler. You can make one with a coil and some capacitors.
I saw on wikipedia about balun, it talks about tuning and I think it's over my knowledges. Maybe I should buy to people whom know how to like that seller seems to. He says he can tune it to 433.92.
No it is not a matter of tuning the frequency, it is a matter of ruining the output impedance of the module to the impedance of the antenna.
You might very well be over your head.
jremington:
That is not a superheterodyne receiver, but no matter. The antenna connection is the solder blob on the lower left corner of the board, looking at the component side (next to a small coil).The antenna input circuitry is probably designed for a 1/4 wave dipole (17 cm straight wire) and probably not for a yagi antenna.
A Yagi is a dipole... Just has some extra passive elements too. The impedance mismatch
is less significant for a receiver, matters more for a transmitter. To a first approx dipoles are
75 ohms, and this happens to be the impedance of old analog TV downlead coax cable.
[Actually some Yagis are folded dipole, which are much higher impedance]
For tracking down a lost drone you don't need accurate directionality, but you
do need to know forwards from backwards, so a dipole and the nulling method
could send you precisely 180 degrees in the wrong direction for a while!
As MarkT says, a Yagi is just a dipole with extra elements. It is rather somewhat critical as to lengths of wire and distance between them. You can simply use the balun from a TV coax to twinlead adapter, it is built to cover a wide bandwidth and 433MHz is right in the middle of it.
A log-periodic antenna is by its nature wideband and much less critical.
Here is one made by etching a double-sided PCB, using hardline coax. The peak is in the direction of decreasing size. As pointed out, you can get a sharper indication by using the null off the back.
Where it attaches:
A schematic-like view of how it is connected:
Note the frequency range in this article, 400MHz to 1GHz:
A lot of TV antennas are log-periodic. This view gives a better idea of how they are constructed.
Here is an online calculator:
MarkT:
A Yagi is a dipole... Just has some extra passive elements too.
That is not the point and I am tempted to say and well you know it.
The passive elements on the Yagi add gain and lobes which ruin it's usefulness when tracking down a transmitter. Or have you never done that and are just book learned?
so a dipole and the nulling method
could send you precisely 180 degrees in the wrong direction for a while!
That is why triangulation is important.
A log-periodic antenna is by its nature wideband and much less critical.
No the impedance matching is just as critical, it is just it has a wider bandwidth at the expense of a lower gain.
I was unclear. I meant that a log-periodic antenna is less critical with respect to frequency versus size of elements.
The directional antenna is going on the receiver, and as has been said, impedance matching is a lot less important for reception. The balun is very important, but I pointed out how that can be done.
Grumpy_Mike:
You might have to do a matching network to get the antenna to connect correctly. Look up the term balum.
Balun.
You must be pulling our collective legs! The impedance matching on the module in question is absolutely nominal. At UHF it is common to completely ignore the balanced/ unbalanced matching on antennae (or use a simple stub balun).
Grumpy_Mike:
You do not need a Yagi as there are too. Any side lobes. What works best is a dipole and you search for the sharp null not a maximum.
Not for VHF/ UHF we do not use dipoles! Rubbish about side lobes! Yagis are standard, usually three element with good front-to-back ratio and minimum difficulty in the bush, though one of our “gun” hunters uses a slot dish for close-up 2m work.