Category: News

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.

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.

PantronX Titus II Ready for Production

Since September 2016 we’ve been slowly hearing news about the PantronX Titus II portable SDR system, but as of yet nothing seems to have eventuated. The Titus II is essentially an Android touch screen tablet running their custom software, a set of speakers, an antenna and an SDR chip with 100 kHz to 2 GHz tuning range all in one portable system that has been estimated by them to retail for less than $100 USD. The main goal with the system is to provide low cost receivers for digital broadcast standards like DRM, DAB and DAB+ to try and boost their popularity.

Titus II receiver features include:

  • DRM in the AM bands (MW, SW, LW) and VHF bands (FM-band, VHF band-I, VHF band-III) with latest xHE-AAC audio codec.
  • DAB Classic/DAB+ (VHF band-III).
  • FM stereo with RDS (Service Signaling).
  • AM with AMSS (AM Signaling Service).
  • Integrated service list management and service selection.
  • DRM/DAB Data Apps: Text Messages, Dynamic Label/DL+, Journaline, (Categorized) Slideshow, EPG, Transparent File Transmission (e.g., for educational services), etc.
  • Remote Radio Hotspot: Built-in WiFi hotspot feature, which allows any mobile device with an HTML5 web browser to connect to the Titus II via Wi-Fi, select radio services, listening to aud (HTML5 audio streaming) and accessing all the DRM/DAB data apps.
  • Recording feature and Archiving interface to select existing recordings for playback.

Recently there has been some new news over on the Radioworld.com magazine about radio broadcasting stating that the Titus II is now ready for production. They write:

Titus SDR, a division of PantronX, says the Titus II multi-standard digital radio receiver is ready for production.

The consumer software-defined radio digital receiver platform, which is the result of collaboration between Titus SDR/Patron X, Jasmin-Infotech, TWR, and Fraunhofer IIS, supports multi-standard radio reception, including DRM, DAB and DAB+ and core data applications. The system is based on a custom Android tablet platform, featuring multipoint touch, WiFi/Bluetooth and stereo sound.

Titus II units will be available as a stand-alone product from Titus SDR as well as from selected OEMs. Titus SDR explains that as a module, Titus II can serve as a full-featured basis for third-party product development, adding that PantronX provided the platform and RF expertise, while Fraunhofer IIS enabled the digital and analog radio features.

With latest xHE-AAC audio codec, Titus II supports DRM in the AM and VHF bands; DAB/DAB+; FM stereo with RDS; AM with AMSS; integrated service list management and service selection; DRM/DAB data apps; text messages and Journaline.

No news yet on exact release dates, but if you are interested you can sign up to their pre-order notification list at titusradio.com.

The Titus II
The Titus II

From YouTube we’ve also found a short video of them demonstrating the Titus II from DBS2017 back in March. Another video showing the interface up close can be seen here.

 

GNURadioCon17 CyberSpectrum Special Meetup Now Live

Live right now is CyberSpectrum #22, currently being held at the GNU Radio Convention in San Diego. Cyberspectrum is an often monthly meetup where SDR enthusiasts come from around the world to share their work. The video will be available offline once the stream is over too. But if watched live you can use the #cyberspectrum hashtag on Twitter, or join the #cyberspectrum on Freenode IRC to discuss the presentations live.

Speakers include:

• The Phil Karn (@ka9q

Low-cost general coverage/HAM receiver for Raspberry Pi & FUNcube dongle, or other cheap SDR.

• Clayton Smith (@argilo

By day, Clayton is a security researcher at ecommerce company Shopify, and by night a GNU Radio enthusiast and amateur radio operator (VE3IRR). He’s worked on projects such as gr-dsd (digital voice), gr-qam (digital television), gr-elster (utility metering), gr-rds (radio data) and sdr-examples. Tonight he’ll tell you about his recent work on HD Radio. 

• Josh Blum (@pothosware

Interesting features in Pothos framework, how we pull in GNU Radio project, and proposed additions to the GNU Radio project. 

• Alexander Chemeris (@chemeris

The first public demo of XTRX – a tiny high-performance miniPCIe SDR for the real world. Up to 120MSPS for simultaneous 2×2 MIMO receive/transmit. 

LimeSDR Mini Crowdfunding: $99 Early Bird RX/TX, 12-Bit, 10 MHz – 3.5 GHz SDR

Back in June 2016 the first LimeSDR crowdfunding campaign completed raising over a million dollars in pre-orders at a cost of $249 – $299 per LimeSDR unit. THe LimeSDR is a RX and TX capable SDR with a frequency range of 100 kHz – 3.8 GHz, bandwidth of up to 61.44 MHz, 12-bit ADC and 2×2 RX/TX channels.

Recently LimeSDR have begun crowd funding for their latest product called the ‘LimeSDR Mini’. This is a smaller and cheaper unit with slightly reduced specifications. The main changes are the slightly restricted frequency range of 10 MHz – 3.5 GHz, and half the maximum bandwidth at 30.72 MHz. The mini also only has 1×1 TX/RX channels.

LimeSDR Comparison

Currently the LimeSDR Mini is being sold on the crowdfunding site CrowdSupply for $139, but the first 500 early bird backer can get the lower price of $99. Accessories such as an acrylic enclosure and set of whip antennas are also available for $40. Crowdfunding is due to end on October 30 and the units are expected to ship on Dec 31, 2017. Note that in the last few minutes that it took to write this article the number of pledges went up by 5 (started at 41), so we’d suggest being quick to claim the early bird if you are interested.

The LimeSDR Mini looks like it could compete favorably with the PlutoSDR, which is another recently released $99 SDR with TX capabilities. Both the PlutoSDR and LimeSDR Mini are 12-bit devices, but the LimeSDR Mini has the larger 30 MHz bandwidth available, and can tune lower. In contrast the PlutoSDR only has a stable bandwidth of about 4 MHz, although it can be pushed higher with dropped samples. The PlutoSDR also has a tuning range (with hack) of 70 MHz – 6 GHz, vs the 10 MHz – 3.5 GHz of the LimeSDR Mini. Another plus of the LimeSDR products is that they are fully open source.

These are exciting times for SDR enthusiasts with cheap TX capable radios now starting to proliferate on the market!

LimeSDR Mini Renderings
LimeSDR Mini Renderings

Online 101 Course on RTL-SDR, DSP and MATLAB Starting Soon

Thanks to Juan Moreno for letting us know that his online MOOC (massive open online course) on RTL-SDR is starting on September 25. The course is presented by Juan and three of his colleagues from the Technical University of Madrid. It will focus on SDR 101 knowledge such as digital signal processing with the aide of an RTL-SDR to help with practical learning. In their video they also mention that MATLAB and Simulink will be required and used for most of the course, so it will probably be a fairly technical beginners course at a University level of learning. Their description of the course reads:

SDR is a reality around us. It is present in a lot of systems everywhere and is a versatile technology which can be used for many things (not only academics and industrial). The purpose of this course is to introduce students into general-purpose SDR tools. The SDR hardware platform chosen for this course is the RTL-SDR. It is worldwide available, it’s cheap ($15) and there is a lot of help in the Internet. But, as far as we know, there is no other MOOC focused on an introduction to SDR as this MOOC. Here we will not only learn about SDR but also a lot of related areas like antennas, digital signal processing, radio frequency and communication electronics.

The website and registration forms seem to all be in Spanish or Portuguese, but the course will be presented in entirely in English. Google Translate can easily be used to help with the signup process. The course is completely free and students that complete 75% of assignments will receive a free participation certificate. A more official accomplishment certificate can be obtained for a 50 Euros.

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)

Modded SUP-2400 Downconverters now Available at RXTXDX.com for $25

Last week we posted about KD0CQ’s interest check on his ready to go modded SUP-2400 downconverter. Interest was strong so the unit is now available for sale on a store he’s just set up at RXTXDX.com. The ready to go unit costs $25 USD including a 9V battery plug and F->SMA or MCX adapter.

Last year KD0CQ discovered that the SUP-2400 is a cheap $5 – $10 DirecTV (US satellite TV) module which can be hand modded into a downconverter for the RTL-SDR. A downconverter allows you to listen to frequencies above the maximum frequency range of the RTL-SDR by converting frequencies down into a range receivable by the RTL-SDR (or of course any other SDR). The modified SUP-2400 allows to you listen up to just over 4 GHz.

The SUP-2400 modification is moderately involved and requires soldering and desoldering SMD pieces, so this product is great for anyone who just wants a cheap and low cost downconverter which is ready to go. And at $25 USD it’s still very good value. Shipping within the USA is $7.75, and internationally it is about $13.50.

The modified SUP-2400 Downconverter
The modified SUP-2400 Downconverter

New Nano 3 RTL-SDR Available from NooElec

NooElec have just released their new NESDR Nano 3 RTL-SDR dongle for $27.95 USD. This is a new iteration in their line of ‘nano’ sized dongles, which are very small and suitable for use on small devices like Raspberry Pi’s and mobile phones. These nano form factor RTL-SDR dongles are also commonly used with the Stratux project which aims to bring lost cost ADS-B and UAT capabilities to small airplane pilots.

The Nano 3 appears to have a standard nano sized RTL-SDR PCB with TCXO inside, but comes with a new fully enclosed metal case with internal thermal coupling pads for cooling. A small external heatsink is also provided for optional use with the dongle. The dongle also uses a standard MCX connector, but the kit comes with an MCX to SMA F adapter. We’re not sure if the cooling from the small metal case will be enough to solve the L-band PLL lock problem, but perhaps when combined with the modified L-band driver tweak it might be enough. Failing that the external heatsink combined with slight airflow from a fan should be enough.

The NESDR Nano 3 small form factor RTL-SDR
The NESDR Nano 3 small form factor RTL-SDR

The previous model called the Nano 2, was also redesigned from the generic nano models for better cooling and to be able to use a TCXO. However, some tests by Chris of the Stratux project seem to show that the Nano 2 is quite a bit noisier than the cheaper generic nano dongles, and actually runs about 40 degrees F hotter. Noise is a problem with these small dongles as the noisy digital and switch mode sections are much closer to the RF sensitive parts. Heat is also an issue due to the lack of PCB space for heat dissipation. Hopefully the Nano 3 resolves these issues with the metal case and improved cooling.

There are now several generations and models of these ‘nano’ RTL-SDRs available. All briefly described below:

  1. Generic Nano Dongles:
    1. $16.99 USD + shipping costs.
    2. First nano dongles designed originally for DVB-T TV use. Difficult to find now, no longer seems to be sold apart from one US seller on eBay.
    3. Still a good choice, but the lack of TCXO limits the usefulness for many applications.
  2. NooElec Nano 2:
    1.  $21.95 USD without TCXO, $23.95 with TCXO.
    2. Slight redesign of the generic dongles for better cooling and TCXO. Although cooling and noise benefits are debated.
    3. Good choice if you like the Nano form factor and want a dongle with accurate TCXO clock.
  3. Stratux Dongle (with ADS-B/UAT Antennas):
    1. Two dongles for $40 USD with antennas, or two for $35 USD without antennas. We also wholesaled a few from them and sell them on our store for intl. buyers @ 16.95 USD each incl. shipping.
    2. Redesigned for low power usage and less noise. Uses a switch mode power supply for less power wastage, but designed to be unaffected by any additional switch mode noise. Runs about 60 degrees F cooler than the Nano 2 and 16F cooler than the generic. Does not have an enclosure so is a bit more fragile. Also does not have a TCXO.
    3. Good choice for Stratux or similar projects might struggle with the power requirements of multiple dongles on a Pi3. Doesn’t have a TCXO so mainly useful for frequency insensitive applications like ADS-B.
  4. NooElec Nano 3:
    1. $27.95 USD
    2. Redesigned enclosure with thermal pad coupling and heatsinks. Comes with TCXO.
    3. Untested by us, but we think it’s probably better than the Nano 2. So a good choice if you like the Nano form factor and want a TCXO dongle.