Category: Antennas

SignalsEverywhere: Testing Wideband PCB Antennas from Hex and Flex

In the past we've posted twice about Hex and Flex who has been designing and selling various types of wideband PCB antennas. Previously we saw his wide band vivaldi antenna, and his wideband 400/800 MHz+ spiral antennas.

Now on the latest episode of SignalsEverywhere host Corrosive gives us a brief review of the Hex and Flex antennas, and goes on to demonstrate the spiral antenna in action. In his tests he was able to receive Inmarsat AERO, 433 MHz tire pressure monitors (TPMS), 300 MHz APRS signals, 300 MHz SATCOM, 800 MHz P25 and 1090 MHz ADS-B aircraft tracking signals with the spiral antenna and our RTL-SDR Blog Wideband LNA.

The video also comes with a 20% off promotion code for the Hex and Flex Tindie store. Simply enter the code "signalseverywhere" at checkout.

RTL-SDR Inmarsat, UHF Satcom, P25 and Portapack Hex and Flex Antenna Review

Creating a 21cm Galactic Sky Map with an Airspy and 1.8m Dish

Marcus Leech from ccera.ca is a pioneer in using low cost software defined radios for observing the sky with amateur radio telescopes.  In the past he's shown us how to receive things like the hydrogen line,  detect meteors and observe solar transits using an RTL-SDR. He's also given a good overview and introduction to amateur radio astronomy in this slide show.

His recent project has managed to create a full Hydrogen sky map of the northern Canadian sky. In his project memo PDF document Marcus explains what a sky map shows:

A [sky map] shows the brightness distribution over the sky for a given set of observing wavelengths. In the case of the 21cm hydrogen line wavelength, maps show the distribution of hydrogen over the sky. For amateur observers, such maps generally show the distribution within our own galaxy, since extra-galactic hydrogen is considerably more faint, and significantly red/blue shifted relative to the rest frequency of 1420.40575 MHz, due to relative motion between the observer and the target extra-galactic hydrogen.

He was able to make this observation using his radio telescope made from a 1.8m dish antenna, a NooElec 1420 MHz SAWBird LNA + Filter, a 15dB line amplifier, another filter and two Airspy R2 software defined radios locked to an external GPSDO. The system runs his custom odroid_ra software on an Odroid XU4 single board computer, which provides spectral data to an x86 host PC over an Ethernet connection. 

Over 5 months of observations have resulted in the Hydrogen sky map shown at the end of this post. Be sure to check out his project memo PDF file for more information on the project and how the image was produced. Marcus' blog post over on ccera.ca also notes that more data and different maps will be produced soon too.

Hydrogen Sky Map
Hydrogen Sky Map

A Motorized Backyard Radio Astronomy Telescope made with an RTL-SDR

A Geostationary Satellite Imaged with the RTL-SDR Based Mini Radio Telescope
A Geostationary Satellite Imaged with the RTL-SDR Based Mini Radio Telescope

Just a few days we posted an update on the PICTOR open source radio telescope project. That project makes use of an RTL-SDR and a small dish antenna to receive the Hydrogen line, and is able to measure properties of our galaxy such as determining the shape of our galaxy.

Now over on Hackaday another amateur radio telescope project has been posted, this one called the "Mini Radio Telescope" (MRT) which was made by Professor James Aguirre of the University of Pennsylvania. This project makes use of a spare Direct TV satellite dish and an RTL-SDR to make radio astronomy observations. What makes this project interesting in particular is the automatic pan and tilt rotor that is part of the design. Unlike other amateur radio telescopes, this motorized design can track the sky, and map it over time. This allows you to create actual radio images of the sky. The image on the right shows a geostationary satellite imaged with the dish.

In the past we saw a similar project by the Thought Emporium YouTube channel which used a tracking mount and a HackRF to generate images of the WiFi spectrum. This was to be a precursor to a motorized tracking mount for radio astronomy but it doesn't seem that they completed that project yet.

Professor James Aguirre 's project including designs for the rotor is fully open source and can be found over on GitHub.

The Miniature Radio Telescope Setup
The Miniature Radio Telescope Setup

An Active Low Cost HF Loop Antenna Made in the UK

Cross Country Wireless is a UK based company that has created an active HF loop antenna for only $70 USD including international shipping. The loop appears to have already been for sale for a while now, but recently they've created a new version that can be easily powered by a 5V bias tee with at least a 67 mA current capacity. This makes it very easy to use with radios that have built in bias tee's such as our RTL-SDR Blog V3 and SDRplay and Airspy units. The page reads:

The Loop Antenna Amplifier contains all the electronics needed for home DIY construction of an active loop (magnetic loop) low noise receiving antenna.

The amplifier consists of two units, a weatherproofed outdoor unit for connection to a suitable loop and a base unit to further amplify the signal and to provide DC power up the coaxial cable to the outdoor unit.

The outdoor unit is housed in a polycarbonate box with stainless steel antenna connections and a BNC socket. The indoor unit is a PCB with two BNC connectors and a USB socket to take 5V from a USB socket on a PC or phone charger.

Like our other active antenna products it has RF overload protection to allow it to be used very close to transmit antennas without damaging the amplifier or the attached receiver.

The loop depends on what the user has available. We have tested it with simple wire loops or deltas, coax loops and an alloy loop made from a bicycle wheel rim. We supply a 3m (10 ft) length of wire as a simple loop to make a first loop for testing.

The photograph on the right shows the prototype with a 1m diameter loop of LDF4-50 coax cable as a test loop.

With a simple wire loop or delta and a small USB powerbank it makes a very compact and portable receiving antenna for holiday listening or covert use.

The latest version can now have the head unit powered directly from receivers with a 5V bias-tee such as the SDRplay receivers or some RTL-SDR dongle receivers with a bias-tee option.

Specifications:

  • Frequency range: 10 kHz to 30 MHz
  • Loop amplifier input impedance: 0.3 ohms
  • Output impedance: 50 ohms
  • Supply voltage: 5 V from USB socket or charger
  • Supply current (head and base unit): 112 mA
  • Supply current (head unit fed with 5V bias-tee): 67 mA
  • Loop antenna outdoor unit connectors: Two M6 stainless steel threaded studs and BNC female (RF out 50 ohms)

There is no comparison yet that we've seen on how this loop compares against the cheaper US$45 Chinese made MLA-30 loop. In a previous post Martin (G8JNJ) reviewed the MLA-30 and noted several design flaws after reverse engineering the circuit. He has let us know that he will also be reviewing the Cross Country Wireless Active Loop and will let us know his thoughts in the future.

Cross Country Wireless Loop
Cross Country Wireless Loop

Cross Country Wireless Loop Antenna Amplifier VLF test with 1m diameter coax loop

Updates on the PICTOR Low Cost Open Source Radio Telescope Based on RTL-SDR

Back in July we posted about PICTOR, an open source and RTL-SDR based radio telescope project. The owner of the project recently wrote in and wanted to share some updates. His text is below:

A few months ago, PICTOR was launched. PICTOR is a free to use open source radio telescope that allows anyone to observe the sky in the 1300~1700 MHz range at any time via the easy-to-use online platform.

The goal of this effort is to introduce students, educators, astronomers and others to the majesty of the radio sky, promoting radio astronomy education, without the need of building a large and expensive radio telescope. 

Since the initial launch, PICTOR has gotten lots of updates and improvements, particularly in the software backend, providing more data to the users, using advanced techniques to increase the signal-to-noise ratio by calibrating spectra and mitigating radio frequency interference (RFI) (if present).

Here is an example observation with PICTOR, clearly showing the detection of 3 hydrogen-dense regions corresponding to 3 unique spiral arms in the Milky Way!

Graphs from the PICTOR RTL-SDR Radio Telescope showing the 3 unique spiral arms in the Milky Way.
Graphs from the PICTOR RTL-SDR Radio Telescope showing the 3 unique spiral arms in the Milky Way.

If you’re new to radio-astronomy, the developer of PICTOR has provided a PDF including some introductory radio astronomy information and instructions on how to observe the radio sky with PICTOR: https://www.pictortelescope.com/Observing_the_radio_sky_with_PICTOR.pdf

L-Band Patch Antenna Set Preorder Sale Ending Soon – Shipping Begins Next Week

Just a heads up that the preorder sale on our new L-Band Patch antenna set will be ending October 21 as we are almost ready to ship the units out. After the preorder sale ends the pricing will rise from $34.95 to $39.95 USD.

PREORDER PRICING: 34.95 USD incl. free shipping.
PREORDER ENDS OCTOBER 21!

Please see our store to preorder the unit.

Preorder has now ended and shipping will begin shortly. Thank you!

The product is a ready to use active patch antenna set that is designed to receive L-Band satellites such as Inmarsat, Iridium and GPS. It is enclosed in a waterproof plastic case, and can easily be mounted to a window using the provided suction cup and 2M coax extension cable. It can also be mounted to almost anything else using the included flexible tripod legs, or if you prefer, use the standard 1/4" camera screw hole to connect it to any mount that you like.

The antenna is powered via 3.3V - 5V bias tee power, so any bias tee capable SDR such as our RTL-SDR Blog V3 can be used to power it.

In terms of performance see our previous post that announced the product for sample screenshots and reception tips.

The RTL-SDR Blog L-Band Satellite Patch Antenna Set
The RTL-SDR Blog L-Band Satellite Patch Antenna Set
Inmarsat Reception
Iridium Reception

SignalsEverywhere: Testing out NooElecs PCB L-Band Patch Antenna

Over on his YouTube channel Corrosive from the SignalsEverywhere YouTube channel has uploaded a video where he tests out the new US$29.95 NooElec PCB patch antenna for receiving L-band satellite signals. In the video he shows how it can be combined with one of their SAWBird L-band low noise amplifiers in order to receive L-band satellite signals such as Inmarsat STD-C and AERO.

We note that our own RTL-SDR Blog Active L-band patch antenna will be ready to ship out before the end of this month, and while waiting for it we are currently having a preorder sale for US$34.95 including free shipping over on our store. For US$34.95 our patch antenna is fully contained in a waterproof enclosure, includes an LNA built in, and comes with several mounting options, so we believe that it is really a great deal. The patch design is based on the Outernet ceramic patch that was compared against the NooElec PCB patch shown in Corrosives video, so performance will be very similar.

Nooelec NEW Inmarsat Patch Antenna with Airspy SDR

New Product in Store: RTL-SDR Blog Magnetic Whip Antenna Set (Great for KerberosSDR Direction Finding)

We've recently released a new Magnetic Whip Antenna Set in our store. The set consists of a heavy duty magnetic mount antenna base with 2M RG59, a 9.5cm fixed whip antenna (usable from 400 MHz to 2 GHz+), and a 17cm to 1m telescopic whip (usable from 100 MHz - 400 MHz).

Click Here to Visit our Store

The antenna set costs US$14.95 each with free shipping. And if you buy four sets you will receive a 15% discount. Currently available to ship worldwide right now from our warehouse in China, and they will be on Amazon in 2-3 weeks.

One application of our KerberosSDR 4-Tuner Coherent RTL-SDR is radio direction finding. This requires four quality omni-directional antennas. We were disappointed to find that there were no high quality magnetic whip antennas available on the market for a low price that we could use with KerberosSDR so we made our own.

The magnetic base is designed carefully with conductive metal that is properly connected to the shield of the coax cable. Most cheap antenna bases just leave the shield connection floating and this causes insufficient coupling to the underlying ground plane resulting in poor performance and poor results when it comes to direction finding and reception.

We've tested this set with KerberosSDR and it is known to work well. The antenna can also of course be used for any other receiving purpose if you prefer to use a whip antenna over our multipurpose dipole antenna set.

In the first two images in the image slider below you can see a comparison between a black base that is not properly bonded to the coax shield, vs the RTL-SDR Blog silver base which is correctly bonded to the coax shield. Both tests used the 9.5cm whip antenna. You can see that the RTL-SDR Blog silver base provides a much lower noise floor and higher signal SNR due to the better ground plane. Also we note that when placing the antenna bases on a metallic surface to create a larger ground plane, the black base showed no further improvement, whereas the RTL-SDR Blog silver base did.

The final three images in the slider show the SWR plots of the two whips on the base. We can see that the 9.5cm whip provides an SWR of less than six below 412 MHz. The telescopic whip can be adjusted to provide better SWR for lower frequencies.

Magwhip SWR Plots

rtlblogconductive_whip
nonconductive_whip
VNA_191008_215346
VNA_191008_215722
VNA_191008_233654
rtlblogconductive_whip nonconductive_whip VNA_191008_215346 VNA_191008_215722 VNA_191008_233654

SignalsEverywhere: Testing Wideband PCB Antennas from Hex and Flex

In the past we've posted twice about Hex and Flex who has been designing and selling various types of wideband PCB antennas. Previously we saw his wide band vivaldi antenna, and his wideband 400/800 MHz+ spiral antennas.

Now on the latest episode of SignalsEverywhere host Corrosive gives us a brief review of the Hex and Flex antennas, and goes on to demonstrate the spiral antenna in action. In his tests he was able to receive Inmarsat AERO, 433 MHz tire pressure monitors (TPMS), 300 MHz APRS signals, 300 MHz SATCOM, 800 MHz P25 and 1090 MHz ADS-B aircraft tracking signals with the spiral antenna and our RTL-SDR Blog Wideband LNA.

The video also comes with a 20% off promotion code for the Hex and Flex Tindie store. Simply enter the code "signalseverywhere" at checkout.

RTL-SDR Inmarsat, UHF Satcom, P25 and Portapack Hex and Flex Antenna Review

Creating a 21cm Galactic Sky Map with an Airspy and 1.8m Dish

Marcus Leech from ccera.ca is a pioneer in using low cost software defined radios for observing the sky with amateur radio telescopes.  In the past he's shown us how to receive things like the hydrogen line,  detect meteors and observe solar transits using an RTL-SDR. He's also given a good overview and introduction to amateur radio astronomy in this slide show.

His recent project has managed to create a full Hydrogen sky map of the northern Canadian sky. In his project memo PDF document Marcus explains what a sky map shows:

A [sky map] shows the brightness distribution over the sky for a given set of observing wavelengths. In the case of the 21cm hydrogen line wavelength, maps show the distribution of hydrogen over the sky. For amateur observers, such maps generally show the distribution within our own galaxy, since extra-galactic hydrogen is considerably more faint, and significantly red/blue shifted relative to the rest frequency of 1420.40575 MHz, due to relative motion between the observer and the target extra-galactic hydrogen.

He was able to make this observation using his radio telescope made from a 1.8m dish antenna, a NooElec 1420 MHz SAWBird LNA + Filter, a 15dB line amplifier, another filter and two Airspy R2 software defined radios locked to an external GPSDO. The system runs his custom odroid_ra software on an Odroid XU4 single board computer, which provides spectral data to an x86 host PC over an Ethernet connection. 

Over 5 months of observations have resulted in the Hydrogen sky map shown at the end of this post. Be sure to check out his project memo PDF file for more information on the project and how the image was produced. Marcus' blog post over on ccera.ca also notes that more data and different maps will be produced soon too.

Hydrogen Sky Map
Hydrogen Sky Map

A Motorized Backyard Radio Astronomy Telescope made with an RTL-SDR

A Geostationary Satellite Imaged with the RTL-SDR Based Mini Radio Telescope
A Geostationary Satellite Imaged with the RTL-SDR Based Mini Radio Telescope

Just a few days we posted an update on the PICTOR open source radio telescope project. That project makes use of an RTL-SDR and a small dish antenna to receive the Hydrogen line, and is able to measure properties of our galaxy such as determining the shape of our galaxy.

Now over on Hackaday another amateur radio telescope project has been posted, this one called the "Mini Radio Telescope" (MRT) which was made by Professor James Aguirre of the University of Pennsylvania. This project makes use of a spare Direct TV satellite dish and an RTL-SDR to make radio astronomy observations. What makes this project interesting in particular is the automatic pan and tilt rotor that is part of the design. Unlike other amateur radio telescopes, this motorized design can track the sky, and map it over time. This allows you to create actual radio images of the sky. The image on the right shows a geostationary satellite imaged with the dish.

In the past we saw a similar project by the Thought Emporium YouTube channel which used a tracking mount and a HackRF to generate images of the WiFi spectrum. This was to be a precursor to a motorized tracking mount for radio astronomy but it doesn't seem that they completed that project yet.

Professor James Aguirre 's project including designs for the rotor is fully open source and can be found over on GitHub.

The Miniature Radio Telescope Setup
The Miniature Radio Telescope Setup

An Active Low Cost HF Loop Antenna Made in the UK

Cross Country Wireless is a UK based company that has created an active HF loop antenna for only $70 USD including international shipping. The loop appears to have already been for sale for a while now, but recently they've created a new version that can be easily powered by a 5V bias tee with at least a 67 mA current capacity. This makes it very easy to use with radios that have built in bias tee's such as our RTL-SDR Blog V3 and SDRplay and Airspy units. The page reads:

The Loop Antenna Amplifier contains all the electronics needed for home DIY construction of an active loop (magnetic loop) low noise receiving antenna.

The amplifier consists of two units, a weatherproofed outdoor unit for connection to a suitable loop and a base unit to further amplify the signal and to provide DC power up the coaxial cable to the outdoor unit.

The outdoor unit is housed in a polycarbonate box with stainless steel antenna connections and a BNC socket. The indoor unit is a PCB with two BNC connectors and a USB socket to take 5V from a USB socket on a PC or phone charger.

Like our other active antenna products it has RF overload protection to allow it to be used very close to transmit antennas without damaging the amplifier or the attached receiver.

The loop depends on what the user has available. We have tested it with simple wire loops or deltas, coax loops and an alloy loop made from a bicycle wheel rim. We supply a 3m (10 ft) length of wire as a simple loop to make a first loop for testing.

The photograph on the right shows the prototype with a 1m diameter loop of LDF4-50 coax cable as a test loop.

With a simple wire loop or delta and a small USB powerbank it makes a very compact and portable receiving antenna for holiday listening or covert use.

The latest version can now have the head unit powered directly from receivers with a 5V bias-tee such as the SDRplay receivers or some RTL-SDR dongle receivers with a bias-tee option.

Specifications:

  • Frequency range: 10 kHz to 30 MHz
  • Loop amplifier input impedance: 0.3 ohms
  • Output impedance: 50 ohms
  • Supply voltage: 5 V from USB socket or charger
  • Supply current (head and base unit): 112 mA
  • Supply current (head unit fed with 5V bias-tee): 67 mA
  • Loop antenna outdoor unit connectors: Two M6 stainless steel threaded studs and BNC female (RF out 50 ohms)

There is no comparison yet that we've seen on how this loop compares against the cheaper US$45 Chinese made MLA-30 loop. In a previous post Martin (G8JNJ) reviewed the MLA-30 and noted several design flaws after reverse engineering the circuit. He has let us know that he will also be reviewing the Cross Country Wireless Active Loop and will let us know his thoughts in the future.

Cross Country Wireless Loop
Cross Country Wireless Loop

Cross Country Wireless Loop Antenna Amplifier VLF test with 1m diameter coax loop

Updates on the PICTOR Low Cost Open Source Radio Telescope Based on RTL-SDR

Back in July we posted about PICTOR, an open source and RTL-SDR based radio telescope project. The owner of the project recently wrote in and wanted to share some updates. His text is below:

A few months ago, PICTOR was launched. PICTOR is a free to use open source radio telescope that allows anyone to observe the sky in the 1300~1700 MHz range at any time via the easy-to-use online platform.

The goal of this effort is to introduce students, educators, astronomers and others to the majesty of the radio sky, promoting radio astronomy education, without the need of building a large and expensive radio telescope. 

Since the initial launch, PICTOR has gotten lots of updates and improvements, particularly in the software backend, providing more data to the users, using advanced techniques to increase the signal-to-noise ratio by calibrating spectra and mitigating radio frequency interference (RFI) (if present).

Here is an example observation with PICTOR, clearly showing the detection of 3 hydrogen-dense regions corresponding to 3 unique spiral arms in the Milky Way!

Graphs from the PICTOR RTL-SDR Radio Telescope showing the 3 unique spiral arms in the Milky Way.
Graphs from the PICTOR RTL-SDR Radio Telescope showing the 3 unique spiral arms in the Milky Way.

If you’re new to radio-astronomy, the developer of PICTOR has provided a PDF including some introductory radio astronomy information and instructions on how to observe the radio sky with PICTOR: https://www.pictortelescope.com/Observing_the_radio_sky_with_PICTOR.pdf

L-Band Patch Antenna Set Preorder Sale Ending Soon – Shipping Begins Next Week

Just a heads up that the preorder sale on our new L-Band Patch antenna set will be ending October 21 as we are almost ready to ship the units out. After the preorder sale ends the pricing will rise from $34.95 to $39.95 USD.

PREORDER PRICING: 34.95 USD incl. free shipping.
PREORDER ENDS OCTOBER 21!

Please see our store to preorder the unit.

Preorder has now ended and shipping will begin shortly. Thank you!

The product is a ready to use active patch antenna set that is designed to receive L-Band satellites such as Inmarsat, Iridium and GPS. It is enclosed in a waterproof plastic case, and can easily be mounted to a window using the provided suction cup and 2M coax extension cable. It can also be mounted to almost anything else using the included flexible tripod legs, or if you prefer, use the standard 1/4" camera screw hole to connect it to any mount that you like.

The antenna is powered via 3.3V - 5V bias tee power, so any bias tee capable SDR such as our RTL-SDR Blog V3 can be used to power it.

In terms of performance see our previous post that announced the product for sample screenshots and reception tips.

The RTL-SDR Blog L-Band Satellite Patch Antenna Set
The RTL-SDR Blog L-Band Satellite Patch Antenna Set
Inmarsat Reception
Iridium Reception

SignalsEverywhere: Testing out NooElecs PCB L-Band Patch Antenna

Over on his YouTube channel Corrosive from the SignalsEverywhere YouTube channel has uploaded a video where he tests out the new US$29.95 NooElec PCB patch antenna for receiving L-band satellite signals. In the video he shows how it can be combined with one of their SAWBird L-band low noise amplifiers in order to receive L-band satellite signals such as Inmarsat STD-C and AERO.

We note that our own RTL-SDR Blog Active L-band patch antenna will be ready to ship out before the end of this month, and while waiting for it we are currently having a preorder sale for US$34.95 including free shipping over on our store. For US$34.95 our patch antenna is fully contained in a waterproof enclosure, includes an LNA built in, and comes with several mounting options, so we believe that it is really a great deal. The patch design is based on the Outernet ceramic patch that was compared against the NooElec PCB patch shown in Corrosives video, so performance will be very similar.

Nooelec NEW Inmarsat Patch Antenna with Airspy SDR

New Product in Store: RTL-SDR Blog Magnetic Whip Antenna Set (Great for KerberosSDR Direction Finding)

We've recently released a new Magnetic Whip Antenna Set in our store. The set consists of a heavy duty magnetic mount antenna base with 2M RG59, a 9.5cm fixed whip antenna (usable from 400 MHz to 2 GHz+), and a 17cm to 1m telescopic whip (usable from 100 MHz - 400 MHz).

Click Here to Visit our Store

The antenna set costs US$14.95 each with free shipping. And if you buy four sets you will receive a 15% discount. Currently available to ship worldwide right now from our warehouse in China, and they will be on Amazon in 2-3 weeks.

One application of our KerberosSDR 4-Tuner Coherent RTL-SDR is radio direction finding. This requires four quality omni-directional antennas. We were disappointed to find that there were no high quality magnetic whip antennas available on the market for a low price that we could use with KerberosSDR so we made our own.

The magnetic base is designed carefully with conductive metal that is properly connected to the shield of the coax cable. Most cheap antenna bases just leave the shield connection floating and this causes insufficient coupling to the underlying ground plane resulting in poor performance and poor results when it comes to direction finding and reception.

We've tested this set with KerberosSDR and it is known to work well. The antenna can also of course be used for any other receiving purpose if you prefer to use a whip antenna over our multipurpose dipole antenna set.

In the first two images in the image slider below you can see a comparison between a black base that is not properly bonded to the coax shield, vs the RTL-SDR Blog silver base which is correctly bonded to the coax shield. Both tests used the 9.5cm whip antenna. You can see that the RTL-SDR Blog silver base provides a much lower noise floor and higher signal SNR due to the better ground plane. Also we note that when placing the antenna bases on a metallic surface to create a larger ground plane, the black base showed no further improvement, whereas the RTL-SDR Blog silver base did.

The final three images in the slider show the SWR plots of the two whips on the base. We can see that the 9.5cm whip provides an SWR of less than six below 412 MHz. The telescopic whip can be adjusted to provide better SWR for lower frequencies.

Magwhip SWR Plots

rtlblogconductive_whip
nonconductive_whip
VNA_191008_215346
VNA_191008_215722
VNA_191008_233654
rtlblogconductive_whip nonconductive_whip VNA_191008_215346 VNA_191008_215722 VNA_191008_233654