Hi,
I bought the RTL-SDR from Amazon. I followed the instructions for installation (Windows 10) as shown
on the manufacturer's home page and it went without a hitch. I also bought "The hobbyist's guide
to the RTL-SDR" (Amazon/Kindle). With that I could easily handle the subset of the system's
comprehensive set of parameters, that I needed.
I have used the SDR-RTL on a system consisting of a central system with a Pixaxe 08M2
and a Picaxe 28X2 chips and 4 decentralised systems each containing 14M2 chips (in its final
configuration). The distance between a decentralised system and the central system is in the worst
case about 10 m with a house in between. The TX- and RX-transmissions are handled by Dorji DRA
887/886 modules at 433.92 MHz.
The first screen of the RTL-SDR is shown in the second picture below. The most important parameters
are:
- on the left side of the screen (the only thing I had to choose) is AM (radio) - the rest is
default
- on the right top side:
- at the top I have selected the frequency - 433.92 MHz
- the upper half of the screen shows:
- the frequency chosen marked by a red line
- the frequencies surrounding 433.92 MHz
- the noise level
- a spike shows up at the corresponding frequency and the height of the spike shows the
strength of the signal with the scale on the left
- a vertical green line shows up under the curser with the frequency indicated. If you move
the curser so the green linen covers the red one, the green line disappears and
you are shown the frequency, the strength of any spike on the frequency, the noise floor
and the SNR.
The second screen of the RTL-SDR is shown in the first picture below. It shows three
transmissions:
- at the bottom is shown the transmission from the Picaxe 08M2 - a short burst.
- a bit higher up ( a bit later) is shown the reply from the decentral system's Picaxe 14M2 to the
Picaxe 08M2's request for data - also a short burst, but sent from location about 1.5 m from
the RTL-SDR's antenna.
- at the top is shown the central system's Picace 28X2's confirmation of receipt. The transmission
is prolonged for testing purposes.
All three signatures will move down and out of the bottom of the screen as a set. Apparently the
three Picaxes dont quite agree on the frequency to transmit on.
Result:
The four antennas used are shown in the picture in the next subject. The monopole antenna showed good strength
and rather poor SNR compared to the dipoles, and when I used it in the system some time ago it gave
a lot of transmission errors. Its a bit of a mystery that the helical ones work at all:
Below are the figures for a distance of about 10 and 20 m and with a house with one outer and one
inner (light) wall plus a shed in between (strength/SNR):
Antenna 10 m:
dipole (173 mm): -6/44
dipole (168 mm): -8/40
helical (long): -21/32
helical (short): -20/32
Monopole of plastic covered copper wire/173 mm: -15/37
A commercially available monopole produced: -12/38
Antenna 20 m:
dipole (173 mm): -12/36
dipole (168 mm): -9/40
helical (long): -24/31
helical (short): -26/28
Monopole of plastic covered copper wire/173 mm: -17/35
A commercially available monopole produced -18/34
Feed line is 50 Ohm coax, about 10 cm. A small car and a metal mailbox at about 3 m distance.
Quite a bit of uncertainty is associated with the figures.
best regards
torben
I bought the RTL-SDR from Amazon. I followed the instructions for installation (Windows 10) as shown
on the manufacturer's home page and it went without a hitch. I also bought "The hobbyist's guide
to the RTL-SDR" (Amazon/Kindle). With that I could easily handle the subset of the system's
comprehensive set of parameters, that I needed.
I have used the SDR-RTL on a system consisting of a central system with a Pixaxe 08M2
and a Picaxe 28X2 chips and 4 decentralised systems each containing 14M2 chips (in its final
configuration). The distance between a decentralised system and the central system is in the worst
case about 10 m with a house in between. The TX- and RX-transmissions are handled by Dorji DRA
887/886 modules at 433.92 MHz.
The first screen of the RTL-SDR is shown in the second picture below. The most important parameters
are:
- on the left side of the screen (the only thing I had to choose) is AM (radio) - the rest is
default
- on the right top side:
- at the top I have selected the frequency - 433.92 MHz
- the upper half of the screen shows:
- the frequency chosen marked by a red line
- the frequencies surrounding 433.92 MHz
- the noise level
- a spike shows up at the corresponding frequency and the height of the spike shows the
strength of the signal with the scale on the left
- a vertical green line shows up under the curser with the frequency indicated. If you move
the curser so the green linen covers the red one, the green line disappears and
you are shown the frequency, the strength of any spike on the frequency, the noise floor
and the SNR.
The second screen of the RTL-SDR is shown in the first picture below. It shows three
transmissions:
- at the bottom is shown the transmission from the Picaxe 08M2 - a short burst.
- a bit higher up ( a bit later) is shown the reply from the decentral system's Picaxe 14M2 to the
Picaxe 08M2's request for data - also a short burst, but sent from location about 1.5 m from
the RTL-SDR's antenna.
- at the top is shown the central system's Picace 28X2's confirmation of receipt. The transmission
is prolonged for testing purposes.
All three signatures will move down and out of the bottom of the screen as a set. Apparently the
three Picaxes dont quite agree on the frequency to transmit on.
Result:
The four antennas used are shown in the picture in the next subject. The monopole antenna showed good strength
and rather poor SNR compared to the dipoles, and when I used it in the system some time ago it gave
a lot of transmission errors. Its a bit of a mystery that the helical ones work at all:
Below are the figures for a distance of about 10 and 20 m and with a house with one outer and one
inner (light) wall plus a shed in between (strength/SNR):
Antenna 10 m:
dipole (173 mm): -6/44
dipole (168 mm): -8/40
helical (long): -21/32
helical (short): -20/32
Monopole of plastic covered copper wire/173 mm: -15/37
A commercially available monopole produced: -12/38
Antenna 20 m:
dipole (173 mm): -12/36
dipole (168 mm): -9/40
helical (long): -24/31
helical (short): -26/28
Monopole of plastic covered copper wire/173 mm: -17/35
A commercially available monopole produced -18/34
Feed line is 50 Ohm coax, about 10 cm. A small car and a metal mailbox at about 3 m distance.
Quite a bit of uncertainty is associated with the figures.
best regards
torben
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