Tagged: dipole

Akos Tests the RTL-SDR Blog Multipurpose Dipole Kit

Over on his blog 'Radio For Everyone' Akos has been testing out our multipurpose dipole kit for ADS-B reception. He goes over each of the components in the kit and does some tests with the kit set up outside. His results show that the dipole kit when used with the smaller antennas can compete favorably with the more expensive FlightAware antenna. We note that the dipole antenna is not designed to be used outdoors for extended periods of time as Akos did as they are not weather proofed for rain. The antennas are designed to be used temporarily outside in good weather conditions. Waterproofing could potentially be achieved by oiling the metal, or potting with hot glue etc.

Akos also does a comparison of the dipole used in two configurations. In one configuration the antenna is used in the recommended vertical orientation, and in the other position in a bunny ears configuration. Antenna theory says that the vertical orientation will work best as ADS-B signals are vertically polarized, and the results confirm that that is true.

FlightAware Antenna vs Dipole
Akos' Results: FlightAware Antenna vs Dipole

Using our new Dipole Antenna Kit

Over on our store we’ve recently released our new receive only dipole antenna kit which now replaces the older magnetic whip style antennas from the previous kit. This was done for a few reasons including 1) We believe that the dipole kit is much more versatile and will enable beginners to get better reception right of the bat, 2) magnets of any type are no longer welcome on most airmail parcel carriers (though they still get through for now). While the magnetic whip still works perfectly fine, the dipole kit should make it easier to get the antenna outside, and it also allows for a simple v-dipole configuration for satellite reception.

The units are currently in stock at our Chinese warehouse either bundled with an RTL-SDR or as an individual antenna set. The individual antenna set only has a small quantity at the moment, so get in quick if you want them as they’re only $9.95 USD shipped. We expect more stock to be ready in 1-2 months. Amazon USA should also be stocked with these units in about ~2 weeks from this post date. ALSO, please note that there is a large Chinese holiday between 1 – 7 October, and during this time parcels will not ship out.

www.rtl-sdr.com/store

This post is a guide on how to use the dipole antenna set in various configurations. First we’ll show and explain about what’s included in the set:

  • 1x dipole antenna base with 60cm RG174 cable and SMA Male connector. This is the dipole base where the telescopic antennas connect to. The short run of RG174 is decoupled from the base elements with a ferrite choke. This helps to prevent the feed line from interfering with the dipole radiation pattern. On the inside of the base the two dipole element sides are connected with a 100 kOhm resistor to help bleed off any static. The dipole has a 1/4 inch female screw on the bottom, which allows you to use standard camera mount products for mounting.
  • 1x 3 meter RG174 coax cable extension. This coax cable extension allows you to place the antennas in a place that gets better reception. E.g. outside on a window, or higher up.
  • 2x 23cm to 1 m telescopic antennas. The telescopic dipoles are detachable from the dipole base via a M5 thread which allows for greater portability and the ability to swap them out. These long telescopic antennas cover VHF and to UHF.
  • 2x 5cm to 13cm telescopic antennas. These smaller antennas cover UHF to 1090 MHz ADS-B, and even still work decently up to L-band 1.5 GHz frequencies.
  • 1x flexible Tripod mount with 1/4″ male screw. This mount allows you to mount the dipole on a variety of different locations. E.g. a pole, tree branch, desk, door, window sill. The legs of the tripod are bendy and rubberized so can wrap securely around many objects.
  • 1x suction cup mount with 1/4″ male screw. With this mount you can mount the dipole on the outside of a window, on a wall, car roof/window, or on any other smooth surface. To use first clean the surface with window cleaner or isopropyl alochol. Then place the suction cup on the cleaned surface and close the lever to activate the suction.
What's included in the new Dipole kit
What’s included in the new Dipole kit

Dipole Orientation

Signals are normally transmitted with either horizontal, vertical or right hand/left hand circular polarization (RHCP/LHCP). This is essentially the ‘orientation’ of a signal, and an antenna with the same polarization should be used too for best performance. A dipole can be used in either vertical or horizontal polarization, just by orienting it either vertically or horizontally.

If you mismatch vertical and horizontal polarization or RHCP and LHCP you’ll get an instant 20dB loss. If you mismatch vertical/RHCP, vertical/LHCP, horizontal/RHCP, horizontal/LHCP you’ll only get a 3dB loss.

There are also ways to optimize the radiation pattern with dipoles. For example for LEO VHF satellites you can use a V-dipole configuration. You can also make a somewhat directional antenna by using a bent dipole configuration. Some more examples of dipole configurations can be found on KK4OBI’s page on bent dipoles.

Terrestrial Signal Reception

Most signals broadcast terrestrially (on Earth) are vertically polarized.

To use the dipole for vertically polarized signals, all that you need to do is orient the elements vertically (up and down).

Satellite Reception

The dipole can be used in a V-Dipole configuration for polar orbiting satellite reception. See Adam 9A4QV’s post where he wrote about how he discovered that it was possible to use dipoles in this configuration for excellent satellite reception. The idea is to use the dipole in horizontal polarization. This gives 3dB loss on the RHCP satellite signals, but also nicely gives 20dB loss on terrestrial signals which could be overloading your RTL-SDR.

For 137 MHz satellites like NOAA and Meteor M2 extend the larger antenna elements out to about 53.4 cm each (about 2.5 sections). Angle the dipole so it is horizontal and in a ‘Vee’ shape, at about 120 degrees. Place the dipole in the North-Source direction.

With an appropriate L-band LNA like the Outernet LNA the dipole can also somewhat work to receive L-band satellites. Using the smallest antenna collapsed, use a V-dipole configuration and point it towards the L-band satellite. Ideally use a reflector too. In the image below we used a simple cookie tin as a reflector. A hole was drilled into the center and the mount used to clamp in the antenna. This together with the Outernet LNA was enough to receive AERO and STD-C.

L-band v-dipole with reflector tin

L-band v-dipole with reflector tin

Receiving Inmarsat signals with the Outernet LNA

Receiving Inmarsat signals with the Outernet LNA

Choosing the Antenna Element Length

Like with the whip you can use an online calculator to calculate the optimal length for your frequency of interest. We recommend this dipole calculator. The exact length does not matter too much, but try to get the lengths as close to what the calculator says as you can. With the dipole you want both elements to be the same length.

In reality extending the antenna to almost any random length will work just fine for most strong signals. But if you’re really trying to optimize those weak signals you’ll want to fine tune the lengths.

Basically the longer the antenna, the lower it’s resonant frequency. The shorter the antenna, the higher the resonant frequency. You want to be close to the resonant frequency. Remember that there is about 2cm of metal inside the antenna itself which needs to be added on. Below is a cheat sheet for various lengths and frequencies. Note that the length refers to the length of one side only.

  • Large Antenna, 5 Sections, 100cm + 2cm is resonant @ ~70 MHz
  • Large Antenna, 4 Sections, 80cm + 2cm is resonant @ ~87MHz
  • Large Antenna, 3 Sections, 60cm + 2cm is resonant @ ~115 MHz
  • Large Antenna, 2 Sections, 42cm + 2cm is resonant @ ~162 MHz
  • Large Antenna, 1 Section, 23cm + 2cm is resonant @ ~ 285 MHz
  • Small Antenna, 4 Sections, 14cm + 2cm is resonant @ ~445 MHz
  • Small Antenna, 3 Sections, 11cm + 2cm is resonant @ ~550 MHz
  • Small Antenna, 2 Sections, 8cm + 2cm is resonant @ ~720MHz
  • Small Antenna, 1 Section, 5cm + 2cm is resonant @ ~1030 MHz.

See the SWR plots at the end for a more accurate reading of the resonance points. But in most cases no matter what you extend the length to the SWR should be below 5 at most frequencies which results in 2.5 dB loss or less. More accurate info on VSWR loss graphs can be found in this document from the ARRL “Understanding SWR by Example” (pdf).

Using the Mounts

The mounts and RG174 extension allow you to more easily use the dipole antennas outside. But please note that like our older magnetic whip we do not recommend permanently mounting this antenna outdoors. This antenna is designed to be a portable antenna that you put up and take down at the end of the day – not for permanent outdoor mounting. It is not protected against water, not grounded so cannot handle a lightning strike and could be damaged with dirt and grime build up. For permanent mounting you could conceivably fill the inside and hinges of the dipole with silicon putty or maybe even hot glue and ground the antenna yourself, but we have not tested this. The stainless steel antennas won’t rust, but dirt and grime could gum up the collapsing mechanism.

The suction cup mount allows you to easily place the antenna on a window, or any smooth surface. To use it first clean the surface thoroughly with isopropyl alcohol or glass cleaner. Then apply the suction cup and close the lever to lock it in place. The lever requires some force to push down, and this ensures a strong grip. You can then angle the antenna in the orientation that you need using the ball socket. Once in place close the ring to lock the ball socket in place.

The flexible tripod mount is useful to mounting the dipole to almost everything else. Including tables, doors, poles, trees etc. The legs of the tripod have a flexible wire inside and rubber sheath so they can be bent into a position to grip almost anything.

Some examples of how to use the mounts.
Some examples of how to use the mounts.

Tightening the hinge

Once you’ve got the orientation of the dipoles the way you want, you might want to tighten the hinge so the elements don’t move so easily anymore. To do this simply take a small screwdriver and tighten the screw on the hinge.

Sample VSWR Plots

Small Antenna Collapsed

Small Antenna Collapsed

Small Antenna Extended

Small Antenna Extended

Large Antenna Collapsed

Large Antenna Collapsed

Large Antenna Extended

Large Antenna Extended

RG174 Cable Loss

RG174 Cable Loss

Other Notes

Note that this is NOT an antenna designed for TXing. It is an RX antenna only. So please do not TX with it unless you really know what you are doing as you could damage your TX radio. You’ll probably need to remove the 100kOhm static bleed resistor to TX anyway.

Akos Tests the RTL-SDR Blog Multipurpose Dipole Kit

Over on his blog 'Radio For Everyone' Akos has been testing out our multipurpose dipole kit for ADS-B reception. He goes over each of the components in the kit and does some tests with the kit set up outside. His results show that the dipole kit when used with the smaller antennas can compete favorably with the more expensive FlightAware antenna. We note that the dipole antenna is not designed to be used outdoors for extended periods of time as Akos did as they are not weather proofed for rain. The antennas are designed to be used temporarily outside in good weather conditions. Waterproofing could potentially be achieved by oiling the metal, or potting with hot glue etc.

Akos also does a comparison of the dipole used in two configurations. In one configuration the antenna is used in the recommended vertical orientation, and in the other position in a bunny ears configuration. Antenna theory says that the vertical orientation will work best as ADS-B signals are vertically polarized, and the results confirm that that is true.

FlightAware Antenna vs Dipole
Akos' Results: FlightAware Antenna vs Dipole

Using our new Dipole Antenna Kit

Over on our store we’ve recently released our new receive only dipole antenna kit which now replaces the older magnetic whip style antennas from the previous kit. This was done for a few reasons including 1) We believe that the dipole kit is much more versatile and will enable beginners to get better reception right of the bat, 2) magnets of any type are no longer welcome on most airmail parcel carriers (though they still get through for now). While the magnetic whip still works perfectly fine, the dipole kit should make it easier to get the antenna outside, and it also allows for a simple v-dipole configuration for satellite reception.

The units are currently in stock at our Chinese warehouse either bundled with an RTL-SDR or as an individual antenna set. The individual antenna set only has a small quantity at the moment, so get in quick if you want them as they’re only $9.95 USD shipped. We expect more stock to be ready in 1-2 months. Amazon USA should also be stocked with these units in about ~2 weeks from this post date. ALSO, please note that there is a large Chinese holiday between 1 – 7 October, and during this time parcels will not ship out.

www.rtl-sdr.com/store

This post is a guide on how to use the dipole antenna set in various configurations. First we’ll show and explain about what’s included in the set:

  • 1x dipole antenna base with 60cm RG174 cable and SMA Male connector. This is the dipole base where the telescopic antennas connect to. The short run of RG174 is decoupled from the base elements with a ferrite choke. This helps to prevent the feed line from interfering with the dipole radiation pattern. On the inside of the base the two dipole element sides are connected with a 100 kOhm resistor to help bleed off any static. The dipole has a 1/4 inch female screw on the bottom, which allows you to use standard camera mount products for mounting.
  • 1x 3 meter RG174 coax cable extension. This coax cable extension allows you to place the antennas in a place that gets better reception. E.g. outside on a window, or higher up.
  • 2x 23cm to 1 m telescopic antennas. The telescopic dipoles are detachable from the dipole base via a M5 thread which allows for greater portability and the ability to swap them out. These long telescopic antennas cover VHF and to UHF.
  • 2x 5cm to 13cm telescopic antennas. These smaller antennas cover UHF to 1090 MHz ADS-B, and even still work decently up to L-band 1.5 GHz frequencies.
  • 1x flexible Tripod mount with 1/4″ male screw. This mount allows you to mount the dipole on a variety of different locations. E.g. a pole, tree branch, desk, door, window sill. The legs of the tripod are bendy and rubberized so can wrap securely around many objects.
  • 1x suction cup mount with 1/4″ male screw. With this mount you can mount the dipole on the outside of a window, on a wall, car roof/window, or on any other smooth surface. To use first clean the surface with window cleaner or isopropyl alochol. Then place the suction cup on the cleaned surface and close the lever to activate the suction.
What's included in the new Dipole kit
What’s included in the new Dipole kit

Dipole Orientation

Signals are normally transmitted with either horizontal, vertical or right hand/left hand circular polarization (RHCP/LHCP). This is essentially the ‘orientation’ of a signal, and an antenna with the same polarization should be used too for best performance. A dipole can be used in either vertical or horizontal polarization, just by orienting it either vertically or horizontally.

If you mismatch vertical and horizontal polarization or RHCP and LHCP you’ll get an instant 20dB loss. If you mismatch vertical/RHCP, vertical/LHCP, horizontal/RHCP, horizontal/LHCP you’ll only get a 3dB loss.

There are also ways to optimize the radiation pattern with dipoles. For example for LEO VHF satellites you can use a V-dipole configuration. You can also make a somewhat directional antenna by using a bent dipole configuration. Some more examples of dipole configurations can be found on KK4OBI’s page on bent dipoles.

Terrestrial Signal Reception

Most signals broadcast terrestrially (on Earth) are vertically polarized.

To use the dipole for vertically polarized signals, all that you need to do is orient the elements vertically (up and down).

Satellite Reception

The dipole can be used in a V-Dipole configuration for polar orbiting satellite reception. See Adam 9A4QV’s post where he wrote about how he discovered that it was possible to use dipoles in this configuration for excellent satellite reception. The idea is to use the dipole in horizontal polarization. This gives 3dB loss on the RHCP satellite signals, but also nicely gives 20dB loss on terrestrial signals which could be overloading your RTL-SDR.

For 137 MHz satellites like NOAA and Meteor M2 extend the larger antenna elements out to about 53.4 cm each (about 2.5 sections). Angle the dipole so it is horizontal and in a ‘Vee’ shape, at about 120 degrees. Place the dipole in the North-Source direction.

With an appropriate L-band LNA like the Outernet LNA the dipole can also somewhat work to receive L-band satellites. Using the smallest antenna collapsed, use a V-dipole configuration and point it towards the L-band satellite. Ideally use a reflector too. In the image below we used a simple cookie tin as a reflector. A hole was drilled into the center and the mount used to clamp in the antenna. This together with the Outernet LNA was enough to receive AERO and STD-C.

L-band v-dipole with reflector tin

L-band v-dipole with reflector tin

Receiving Inmarsat signals with the Outernet LNA

Receiving Inmarsat signals with the Outernet LNA

Choosing the Antenna Element Length

Like with the whip you can use an online calculator to calculate the optimal length for your frequency of interest. We recommend this dipole calculator. The exact length does not matter too much, but try to get the lengths as close to what the calculator says as you can. With the dipole you want both elements to be the same length.

In reality extending the antenna to almost any random length will work just fine for most strong signals. But if you’re really trying to optimize those weak signals you’ll want to fine tune the lengths.

Basically the longer the antenna, the lower it’s resonant frequency. The shorter the antenna, the higher the resonant frequency. You want to be close to the resonant frequency. Remember that there is about 2cm of metal inside the antenna itself which needs to be added on. Below is a cheat sheet for various lengths and frequencies. Note that the length refers to the length of one side only.

  • Large Antenna, 5 Sections, 100cm + 2cm is resonant @ ~70 MHz
  • Large Antenna, 4 Sections, 80cm + 2cm is resonant @ ~87MHz
  • Large Antenna, 3 Sections, 60cm + 2cm is resonant @ ~115 MHz
  • Large Antenna, 2 Sections, 42cm + 2cm is resonant @ ~162 MHz
  • Large Antenna, 1 Section, 23cm + 2cm is resonant @ ~ 285 MHz
  • Small Antenna, 4 Sections, 14cm + 2cm is resonant @ ~445 MHz
  • Small Antenna, 3 Sections, 11cm + 2cm is resonant @ ~550 MHz
  • Small Antenna, 2 Sections, 8cm + 2cm is resonant @ ~720MHz
  • Small Antenna, 1 Section, 5cm + 2cm is resonant @ ~1030 MHz.

See the SWR plots at the end for a more accurate reading of the resonance points. But in most cases no matter what you extend the length to the SWR should be below 5 at most frequencies which results in 2.5 dB loss or less. More accurate info on VSWR loss graphs can be found in this document from the ARRL “Understanding SWR by Example” (pdf).

Using the Mounts

The mounts and RG174 extension allow you to more easily use the dipole antennas outside. But please note that like our older magnetic whip we do not recommend permanently mounting this antenna outdoors. This antenna is designed to be a portable antenna that you put up and take down at the end of the day – not for permanent outdoor mounting. It is not protected against water, not grounded so cannot handle a lightning strike and could be damaged with dirt and grime build up. For permanent mounting you could conceivably fill the inside and hinges of the dipole with silicon putty or maybe even hot glue and ground the antenna yourself, but we have not tested this. The stainless steel antennas won’t rust, but dirt and grime could gum up the collapsing mechanism.

The suction cup mount allows you to easily place the antenna on a window, or any smooth surface. To use it first clean the surface thoroughly with isopropyl alcohol or glass cleaner. Then apply the suction cup and close the lever to lock it in place. The lever requires some force to push down, and this ensures a strong grip. You can then angle the antenna in the orientation that you need using the ball socket. Once in place close the ring to lock the ball socket in place.

The flexible tripod mount is useful to mounting the dipole to almost everything else. Including tables, doors, poles, trees etc. The legs of the tripod have a flexible wire inside and rubber sheath so they can be bent into a position to grip almost anything.

Some examples of how to use the mounts.
Some examples of how to use the mounts.

Tightening the hinge

Once you’ve got the orientation of the dipoles the way you want, you might want to tighten the hinge so the elements don’t move so easily anymore. To do this simply take a small screwdriver and tighten the screw on the hinge.

Sample VSWR Plots

Small Antenna Collapsed

Small Antenna Collapsed

Small Antenna Extended

Small Antenna Extended

Large Antenna Collapsed

Large Antenna Collapsed

Large Antenna Extended

Large Antenna Extended

RG174 Cable Loss

RG174 Cable Loss

Other Notes

Note that this is NOT an antenna designed for TXing. It is an RX antenna only. So please do not TX with it unless you really know what you are doing as you could damage your TX radio. You’ll probably need to remove the 100kOhm static bleed resistor to TX anyway.

RTL-SDR V3 Amazon Back in Stock + A Preview of our Upcoming Multipurpose Antenna Set

The RTL-SDR Blog V3 is back in stock in Amazon USA (Dongle + Antenna) (Dongle Only). International buyers can continue to purchase units from our store at www.rtl-sdr.com/store.

Apologies for the long out of stock period, we sold out of our remaining Amazon US stock almost immediately a few weeks ago due to a large Reddit thread which popularized the Reddit /r/rtlsdr forums (a big welcome to any new RTL-SDR users!). Amazon is currently processing the new stock and it should be ready to ship out in a few days.

We also have a new antenna set in the works which should be ready for purchase in a few weeks. This antenna set is essentially a custom modified TV dipole with mounting kit. The kit will contain:

  • 1x Telescopic Dipole Antenna base with 20cm RG174 cable
  • 2x removable 22cm to 1M telescopic antennas
  • 2x removable 5cm to 13cm telescopic antennas
  • 1x 3M SMA RG174 extension cable
  • 1x suction cup window mount
  • 1x bendy tripod mount

Antenna Base

The telescopic antennas mount onto the antenna base via a screw, so they can easily be removed and interchanged between the large and small ones, or packed away for storage.

The dipole antenna base attaches to the suction cup or bendy tripod mounts using a 1/4″ camera screw. So any cheap camera mounting accessories like clamps, tripods etc can be used to mount the dipole as well.

The coax cable on the base also has a ferrite core choke on it to help decouple the feedline from the antenna, and there is a 100kOhm bleed resistor added to reduce static discharge.

Mounts

The included suction cup mount allows you to mount the dipole on a window (ideally outside) and orient it into a vertical, horizontal or V-Dipole position. The bendy tripod allows you to use the antenna on your desk, folded over a door, on a tree branch, pole, or anywhere that the tripod legs can be wrapped around.

Usage

The biggest problem that new RTL-SDR users face is the antenna. Most are starting off with a mag mount whip, and have no way to mount them outside where they should be for better reception. Keeping them inside can cause poor reception and increased pickup of local interference from electronics. Our dipole with the mounts aims to solve this problem.

Using a dipole generally results in better reception than with a mag mount whip, and also allows for easier outdoor mounting. The 3M coax extension cable allows you to get the antenna at least to a window in your room.

Note that although we recommend using the antenna outside, please remember to take the antenna back inside when not in use to avoid lightning/ESD/weathering problems. It is not designed for permanent outdoor mounting and please remember that any permanently mounted outdoor antenna should have good grounding to protect your radio against ESD and lightning.

For general use we recommend using the dipole in the vertical orientation as most signals are vertically polarized. The dipole can also be used in a V-Dipole configuration for excellent VHF satellite reception, such as for NOAA/Meteor weather satellites. Just extend the telescopic dipoles to be as close as possible to resonant at the frequency of interest using this calculator. Getting the length perfect is not critical, and actually using any length will still receive something.

Apart from NOAA we’ve also tested the dipole with L-band satellites. Together with an LNA and the smaller telescopic antennas it’s possible to receive Iridium and Inmarsat signals. Reception is not as good as a patch antenna, but you can still get the stronger AERO and Iridium signals quite easily. If you add a reflector made out of a small cookie tin the signals can be boosted further, and this is enough to receive the weaker STD-C and Outernet signals.

Eventually this dipole set will replace the mag mount antenna bundled with the dongles currently. Target price is between $9.95 – $14.95 for the antenna set by itself, and $25.95 for the dongle + antenna set. We expect the antenna set to be ready for shipping in 2-3 weeks, and about 3-4 weeks for the dongle + antenna set. More details and usage examples will be shown nearer to the release.

The Dipole Kit (Small antennas not shown)
The Dipole Kit (small antennas not shown)

Upgrading the Coax on a TV Dipole Antenna for Improved Reception

Over on his YouTube channel Corrosive has uploaded a useful video showing how to modify a standard TV dipole to make it better for general radio use. Many TV dipoles come standard with twin lead, or very poor quality coax cable. Corrosive shows in his video how simple it is to modify and improve one of these by adding high quality coax with a BNC connector.

These TV dipoles are great as general purpose antennas, and are especially useful for making V-dipole antennas for NOAA/Meteor M2 reception.

Using a TV Dipole Antenna for NOAA Satellite Reception

Over on YouTube icholakov has uploaded a video showing how effective a simple old TV bunny ears antenna can be at receiving NOAA satellite images. The old TV antenna is telescoping so it can be adjusted to be resonant for many frequencies, and for NOAA satellites about 20 inches makes it resonant. Using the antenna as a V-Dipole and placing it in a North to South direction optimizes the radiation pattern towards the sky, allowing for good reception of the NOAA satellite. Using it this way also helps to null out strong vertically polarized stations. More information on the V-Dipole can be found on our previous post where we posted about Adam 9A4QV’s idea to use the V-Dipole for satellite reception.

Also related to this post is a sneak preview on our new product: We’ve also caught onto the idea that TV antenna dipoles are extremely versatile, and are in the final stages of releasing a simple telescopic dipole product similar to the TV antenna used in this video. It will be released as an antenna set that comes with some portable mounting solutions like a suction cup and bendy tripod, and 3M of RG174 coax so that the antenna can be used anywhere. Target price is $10 -15 USD incl. shipping from China. This will probably also replace the stock telescopic whip antenna currently used in our dongle sets since the telescopic dipole is simply much more versatile.

ISS Packet Repeater Received with RTL-SDR

YouTube user ronpaulatemybaby has posted a video showing his reception of the International Space Station (ISS) amateur packet repeater on 145.825 MHz, using the rtl-sdr. He used a R820T dongle, two meter dipole, SDRSharp and decoding software MixW.

RTL-SDR Tutorial: Cheap ADS-B Aircraft RADAR

The RTL-SDR can be used as a super cheap real time air radar. Modern planes use something called an ADS-B (Automatic Dependent Surveillance-Broadcast) Mode-S transponder, which periodically broadcasts location and altitude information to air traffic controllers. The RTL-SDR can be used to listen to these ADS-B signals, which can then be used to create your very own home aircraft radar system. Compared to dedicated commercial ADS-B receivers which can go for between $200 – $1000, the $20 RTL-SDR is very attractive for the hobbyist in terms of price. However, note that the RTL-SDR probably shouldn’t be used for ADS-B navigation in a real aircraft for safety reasons. 

ADS-B broadcasts at a frequency of 1090 MHz. It has been discovered by the RTL-SDR community, that the RTL-SDR with R820T tuner has the best sensitivity at this frequency. The E4000 and other tuners perform poorly in comparison. So it is recommended that you obtain an R820T tuner if you want to set up ADS-B decoding with the RTL-SDR. Recently there has also been talk about the R820T2 tuner, which seems to have slightly better performance too. See the Buy RTL-SDR dongles page for more information on where to purchase.

We also now note that recently new higher end SDR’s like the $199 Airspy have developed very good ADS-B receivers that are several times more sensitive that the RTL-SDR.

Examples of RTL-SDR used as an ADS-B air radar

In this video, YouTube user Superphish shows a timelapse of air traffic over New Zealand using RTL-SDR, ADSB# and Virtual Radar Server.

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