Increase range on 433 Mhz transmitter
 

Hello!

I just bought this: http://www.rustindustries.co.uk/remote.htm
The range is only 10-15 meters in free air, only 5-7 meters indoor.
Is it possible to connect a whip type antenna?
I have calculated a length ca 17 cm.
But i cannot see where to connect the antenna.
The transmitter has a loop style antenna, powered by one transistor and a
oscillator of some sort, i have drawn a schematic:
http://media.openbloc.com/1tpwr
I have tried to connect the antenna to the collector, but that gave me no
output at all.

Regards

Carsten Hjorth

Increase range on 433 Mhz transmitter
 

In article ,
Carsten Hjorth wrote:
Hello!

I just bought this: http://www.rustindustries.co.uk/remote.htm
The range is only 10-15 meters in free air, only 5-7 meters indoor.
Is it possible to connect a whip type antenna?
I have calculated a length ca 17 cm.
But i cannot see where to connect the antenna.
The transmitter has a loop style antenna, powered by one transistor and a
oscillator of some sort, i have drawn a schematic:
http://media.openbloc.com/1tpwr
I have tried to connect the antenna to the collector, but that gave me no
output at all.

I looked at the design of a similar 433 MHz nonlicensed transmitter a
couple of months ago (it was for an IR-remote-to-RF repeater system).

It looked to me as if it was using the loop both as part of a tuned LC
tank circuit, and as the radiating element. I suspect that the same
is true of the circuit in your transmitter.

Adding a length of wire to it would very probably de-tune the tank
circuit. At best, it'd oscillate and transmit on the wrong frequency.
At worst, the wire loading would de-Q the tank to the point that it
wouldn't oscillate at all.

To boost the transmitter power or the antenna gain (if doing so is
even legal under your RF-use rules) would probably require a
significant redesign of the circuit.

In your situation, would it be adequate to boost the _receiver_ gain
instead? You can probably do anything you want, legally, to the
receiver... add a collinear antenna, change to a Yagi, use a corner
reflector, etc.

--
Dave Platt AE6EO
Hosting the Jade Warrior home page: http://www.radagast.org/jade-warrior
I do _not_ wish to receive unsolicited commercial email, and I will
boycott any company which has the gall to send me such ads!

Increase range on 433 Mhz transmitter
 

What country are you in ?

The device is made in the UK and European EIRP limit should be 10mW.

We make low power transmitters at 433 and 915MHz and find we normally
get over 20m even with a resistor dummy load across the antenna terminal.

We made a transmitter in a plastic wris****ch that the oscillator
coupled directly into a loop antenna (you need to move the collector
connection along the loop till you get best match). This unit had
radiated power of around 100uW and still achieved 100m range.

Our 10mW units achieve over 1km line of sight outdoor range typically.
I cannot imagine a range of only 5-7m (unless the receiver is extremely
insensitive or the transmitter and receiver are not tuned to the same
frequency).

Dave Platt wrote:
In article ,
Carsten Hjorth wrote:
Hello!

I just bought this: http://www.rustindustries.co.uk/remote.htm
The range is only 10-15 meters in free air, only 5-7 meters indoor.
Is it possible to connect a whip type antenna?
I have calculated a length ca 17 cm.
But i cannot see where to connect the antenna.
The transmitter has a loop style antenna, powered by one transistor and a
oscillator of some sort, i have drawn a schematic:
http://media.openbloc.com/1tpwr
I have tried to connect the antenna to the collector, but that gave me no
output at all.

I looked at the design of a similar 433 MHz nonlicensed transmitter a
couple of months ago (it was for an IR-remote-to-RF repeater system).

It looked to me as if it was using the loop both as part of a tuned LC
tank circuit, and as the radiating element. I suspect that the same
is true of the circuit in your transmitter.

Adding a length of wire to it would very probably de-tune the tank
circuit. At best, it'd oscillate and transmit on the wrong frequency.
At worst, the wire loading would de-Q the tank to the point that it
wouldn't oscillate at all.

To boost the transmitter power or the antenna gain (if doing so is
even legal under your RF-use rules) would probably require a
significant redesign of the circuit.

In your situation, would it be adequate to boost the _receiver_ gain
instead? You can probably do anything you want, legally, to the
receiver... add a collinear antenna, change to a Yagi, use a corner
reflector, etc.

Increase range on 433 Mhz transmitter
 

We make low power transmitters at 433 and 915MHz and find we normally
get over 20m even with a resistor dummy load across the antenna terminal.


got a link?

Increase range on 433 Mhz transmitter
 

www.orbitcoms.com

We have a lot more in development that is not on the site yet so feel
free to email us if you are looking for something - we may have it but
not yet posted the details.

wrote:
We make low power transmitters at 433 and 915MHz and find we normally
get over 20m even with a resistor dummy load across the antenna terminal.


got a link?

Increase range on 433 Mhz transmitter
 

"Carsten Hjorth" wrote in message
...
Hello!

I just bought this: http://www.rustindustries.co.uk/remote.htm
The range is only 10-15 meters in free air, only 5-7 meters indoor.
Is it possible to connect a whip type antenna?
I have calculated a length ca 17 cm.
But i cannot see where to connect the antenna.
The transmitter has a loop style antenna, powered by one transistor and a
oscillator of some sort, i have drawn a schematic:
http://media.openbloc.com/1tpwr
I have tried to connect the antenna to the collector, but that gave me no
output at all.

Regards

Carsten Hjorth

You might want to do something with the receiving antenna. My 4xx MHz garage
door opener has about 30 meters range.

Tam/WB2TT

Increase range on 433 Mhz transmitter
 

"Tam/WB2TT" skrev i en meddelelse
. ..

"Carsten Hjorth" wrote in message
...
Hello!

I just bought this: http://www.rustindustries.co.uk/remote.htm
The range is only 10-15 meters in free air, only 5-7 meters indoor.
Is it possible to connect a whip type antenna?
I have calculated a length ca 17 cm.
But i cannot see where to connect the antenna.
The transmitter has a loop style antenna, powered by one transistor and a
oscillator of some sort, i have drawn a schematic:
http://media.openbloc.com/1tpwr
I have tried to connect the antenna to the collector, but that gave me no
output at all.

Regards

Carsten Hjorth

You might want to do something with the receiving antenna. My 4xx MHz
garage door opener has about 30 meters range.

Tam/WB2TT

I´m in Denmark and its frezing...
Should i extend the wip antenna on the receiver? Now it´s a 1/4 wave, should
i try full wave?

/Carsten

Increase range on 433 Mhz transmitter
 

Have you contacted the supplier to verify what the typical range should
be and get their recommendation for appropriate antenna ?


Carsten Hjorth wrote:
"Tam/WB2TT" skrev i en meddelelse
. ..
"Carsten Hjorth" wrote in message
...
Hello!

I just bought this: http://www.rustindustries.co.uk/remote.htm
The range is only 10-15 meters in free air, only 5-7 meters indoor.
Is it possible to connect a whip type antenna?
I have calculated a length ca 17 cm.
But i cannot see where to connect the antenna.
The transmitter has a loop style antenna, powered by one transistor and a
oscillator of some sort, i have drawn a schematic:
http://media.openbloc.com/1tpwr
I have tried to connect the antenna to the collector, but that gave me no
output at all.

Regards

Carsten Hjorth

You might want to do something with the receiving antenna. My 4xx MHz
garage door opener has about 30 meters range.

Tam/WB2TT

I´m in Denmark and its frezing...
Should i extend the wip antenna on the receiver? Now it´s a 1/4 wave, should
i try full wave?

/Carsten

Increase range on 433 Mhz transmitter
 

"Carsten Hjorth" wrote in message
...

"Tam/WB2TT" skrev i en meddelelse
. ..

"Carsten Hjorth" wrote in message
...
Hello!

I just bought this: http://www.rustindustries.co.uk/remote.htm
The range is only 10-15 meters in free air, only 5-7 meters indoor.
Is it possible to connect a whip type antenna?
I have calculated a length ca 17 cm.
But i cannot see where to connect the antenna.
The transmitter has a loop style antenna, powered by one transistor and
a oscillator of some sort, i have drawn a schematic:
http://media.openbloc.com/1tpwr
I have tried to connect the antenna to the collector, but that gave me
no output at all.

Regards

Carsten Hjorth

You might want to do something with the receiving antenna. My 4xx MHz
garage door opener has about 30 meters range.

Tam/WB2TT

I´m in Denmark and its frezing...
Should i extend the wip antenna on the receiver? Now it´s a 1/4 wave,
should i try full wave?

/Carsten

Full wave won't work, but 5/8 or 3/4 might work better than 1/4. If it does
not have to be non directional, you could use some kind of an antenna that
has some gain, like a 3 element Yagi. You are in the 70 cm ham band; so, any
of the common 430 - 440 Mhz antennas will work, provided you can connect it
to the receiver.

Tam

Increase range on 433 Mhz transmitter
 

Carsten wrote:
"Is it possible to connect a whip type?"

Probably, or perhaps a dipole.

The wavelength is short. You can get antenna gain without connections if
you use reflectors with your existing antennas. The reflecting surfaces
can be plane sheets or grids aligned with the polarization of the
antenna.

You did not give the size of your loop. If the loop has a perimeter of
one wavelength, propagation is broadside to the loop. If it is smaller,
propagation is in the plane of the loop.
Polarization depends on where the loop is fed.

Your wavelength is about 0.7 m.

If a perfect flat sheet is 1/4-wavelength behind your antenna, you may
get about 5 dB gain in the forward direction from the reflector.

Replace the flat sheet with a 90-degree corner reflector, and the gain
rises to 10 dB with 1/4-wave spacing between the antenna and the corner.

11 or 12 dB gain may be obtained by using a 60-degree corner.

For a 1/2-wave dipole spaced either 1/4-wave or 1/2-wave from a
90-degree corner, the gain is about the same (10 dB).

1/4-wave spacing of a 1/2-wave dipole from a 90-degree corner gives a
drivepoint impedance of about 85 ohms.

1/2-wave spacing of a 1/2-wave dipole from a 90-degree corner gives a
drivepoint impedance of about 125 ohms.

As the 1/2-wave dipole without a reflector has a drivepoint impedance of
73 ohms, impedance upset from coupling to the reflector is significant
but not excessive.

See Kraus "Antennas" under the topic: "Corner reflector" for details.

Best regards, Richard Harrison, KB5WZI