Tagged: magnetic loop

SDRplay RSPDuo Diversity: Combing a Magnetic Loop and Miniwhip Antenna

The SDRplay team have posted some more videos that demonstrate the SDRplay Duo's diversity function. The SDRplay RSPDuo is a 14-bit dual tuner software defined radio capable of tuning between 1 kHz - 2 GHz. It's defining feature is that it has two receivers in one radio, which allows us to combine the signal from two antenna together.

In the video Jon uses a Wellbrook Magnetic Loop antenna and a Bonito Miniwhip antenna both connected to the RSP Duo. Individually each antenna receives the signal relatively poorly and fades in and out as conditions and signal reflections fluctuate. However, with diversity enabled the SNR is improved and fading is significantly reduced.

The method they use to combine signals is a relatively simple method called maximum-ratio combining (MRC). The idea is that the two signal channels are added together, with the currently stronger and less noisy channel having increased gain. So while the signal levels fluctuate, as long as one antenna can receive the signal you will see no fading.

SDRplay HF Diversity Demo

SDRplay note that the key to a good setup is to have the antennas spaced out at a quarter wavelength of the signal frequency that you are receiving. In a second video they show how to properly set up an antenna system for proper HF diversity receiving.

This video demonstrates how SDRuno diversity and the RSPduo can bring enhanced reception at HF using 2 antennas separated by approximately a quarter wavelength. It uses the the current version of SDRuno (V 1.32) and the dual tuner RSPduo SDR from SDRplay.

In this experiment we had a wire dipole with one leg approximately a quarter wavelength from a Boniwhip vertical - both were picking up similar strength signals before going into "diversity" (max ratio combination) mode.

The benefits of diversity tuning at HF are very dependent on many variables, most notably the changing nature of the reflected signal path and the degree to which noise and unwanted signals are not as coherent as the wanted signal.

Antenna and SDRplay set-up for HF diversity reception (rev1)

Testing an SDRplay RSPduo with Bonito Active Loop Antennas

Bonito is a company that sells various active dipole and loop antennas for ham radio and DX applications. Recently they decided to test their MegaLoop FX and MegaDipol MD3000DX antennas on an SDRplay RSPduo, and compare it against a higher end WinRadio. Bonito found that the RSPduo performed well on the weaker longwave stations, but the Winradio outperformed it on the stronger ones. The differences were due to the better dynamic range of the Winradio.

The article goes on to make some recommendations for using their antennas on the RSPduo. They write that if intermodulation due to very strong signals occurs, there are some fixes that can be applied on their antennas to desensitize them and prevent overload. With the loop, a smaller loop size should be used, and the gain selector should be set to medium or min. With the dipole, they note that shortening the elements, and using it in an L-configuration with the lower radiator pointing towards the interfering signals can be used to attenuate them out. This works because a dipole configured in a L shape provides a bit of directionality.

The article also notes how grounding, very good coax shielding, good quality USB cables and galvanic isolation are all very important for reducing noise.

Bonito RSPduo Antenna Test Setup
Bonito RSPduo Antenna Test Setup

Identifying Noise Sources in the Shack using an SDR and an Active Receive Loop

Over on YouTube user SignalSearch has uploaded a video showing how he uses an active magnetic loop antenna indoors to identify local noise sources. Magnetic loop antennas are directional, meaning that they receive best when pointing towards a signal. This means that they also receive noise better when pointed at a noise source.  In the video SignalSearch uses a W6LVP receive loop antenna and demonstrates noise being emitted from his lightbulb, and from a plug in Ethernet over powerline adapter, which are known to be huge sources of HF noise.

If you are interested in the noise produced by these Ethernet over powerline adapters then we did a previous post on this problem over here.

Using an Active Receive Loop Indoors & utilizing Software Defined Radio to identify noise sources

The K9AY Loop Antenna: A Directional E-H Antenna for HF

Thank you to Frank Sessink (PA0FSB) for submitting to us his document describing the K9AY loop antenna (pdf), which is the antenna that he successfully uses with his RTL-SDR for HF reception. The antenna combines magnetic (H) and electric (E) field reception in order to create a directive radiation pattern. Frank extends the idea by showing a method that can adjust the directivity electrically with some simple resistor switching.

The antenna that I use is for medium wave DX, specially to receive MW from USA here in Europe/The Netherlands. The antenna is a combination of a magnetic loop and a sense antenna for the E-field. The magnetic loop is directive, but has no front-rear ratio. The E-field antenna has omnidirectional sensitivity. The combination, in correct phase and amplitude, results in a front-rear ratio of more than 25 dB over the frequency range from 500 kHz to around 3 MHz. Higher frequency makes no sense, since skywave signals distort the ground wave directivity pattern.

A simple modification is used as directional antenna with remote control: two orthogonal loops that combine E and H-field in a simple way. I can make 8 selectable directions.

The full document is available here in PDF format.

The K9AY E-H HF Antenna
The K9AY E-H HF Antenna

A Homemade Magnetic Loop Antenna used with RTL-SDR Direct Sampling

Over on our forums user "SandB"  has submitted his designs for a homemade magnetic loop antenna with preamp that he uses together with his RTL-SDR in direct sampling mode. The antenna looks like an interesting build so we are resharing it here. He writes:

So, antenna itself represents as handmade on-PCB winding made of two-side-foiled fiberglass size of 30x40 cm. Both 'windings' connected in the middle and thus winded to 'continue' each other.

Preamp located in metal box attached to antenna and connected via 1.5m S/FTP cable to another box with RTL stick. Note that some transistors soldered on PCB in upside-down - dot on layout means base.

Electrically preamp made as 3-stages balanced signal amplifier with low-input impedance and low-pass filter before input with cut-off at 15MHz. Such complications were required to reduce interferences and intermodulations. Antenna itself is more effective on long-medium waves, so preamp has higher gain on short waves (gain varies from 45db at 200KHz to 68 db at 10MHz - see attached freq responce pic). Getting more flat responce at lower frequencies is possible by increasing C10/C11/C12 to 22nF.

My implementation has some additional elements to make possible to adjust preamp's gain in few db's. But seems its quite useless so that details not included in this post. Anyway, its possible to reduce gain by increasing R6 to 500K.

Box with RTL SDR: I put both signal wires as 3 windings via ferrite ring with high permeability just before RTL chip. This noticeable reduced stray interference, that induced in that cable but doesn't affect differential signal.

ant_preparing
rtl-box
on-the-wall
preamp_n_antenna
ant_preparing2
board-front
board-back
principal
freq_responce_modeled
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SDRplay RSPDuo Diversity: Combing a Magnetic Loop and Miniwhip Antenna

The SDRplay team have posted some more videos that demonstrate the SDRplay Duo's diversity function. The SDRplay RSPDuo is a 14-bit dual tuner software defined radio capable of tuning between 1 kHz - 2 GHz. It's defining feature is that it has two receivers in one radio, which allows us to combine the signal from two antenna together.

In the video Jon uses a Wellbrook Magnetic Loop antenna and a Bonito Miniwhip antenna both connected to the RSP Duo. Individually each antenna receives the signal relatively poorly and fades in and out as conditions and signal reflections fluctuate. However, with diversity enabled the SNR is improved and fading is significantly reduced.

The method they use to combine signals is a relatively simple method called maximum-ratio combining (MRC). The idea is that the two signal channels are added together, with the currently stronger and less noisy channel having increased gain. So while the signal levels fluctuate, as long as one antenna can receive the signal you will see no fading.

SDRplay HF Diversity Demo

SDRplay note that the key to a good setup is to have the antennas spaced out at a quarter wavelength of the signal frequency that you are receiving. In a second video they show how to properly set up an antenna system for proper HF diversity receiving.

This video demonstrates how SDRuno diversity and the RSPduo can bring enhanced reception at HF using 2 antennas separated by approximately a quarter wavelength. It uses the the current version of SDRuno (V 1.32) and the dual tuner RSPduo SDR from SDRplay.

In this experiment we had a wire dipole with one leg approximately a quarter wavelength from a Boniwhip vertical - both were picking up similar strength signals before going into "diversity" (max ratio combination) mode.

The benefits of diversity tuning at HF are very dependent on many variables, most notably the changing nature of the reflected signal path and the degree to which noise and unwanted signals are not as coherent as the wanted signal.

Antenna and SDRplay set-up for HF diversity reception (rev1)

Testing an SDRplay RSPduo with Bonito Active Loop Antennas

Bonito is a company that sells various active dipole and loop antennas for ham radio and DX applications. Recently they decided to test their MegaLoop FX and MegaDipol MD3000DX antennas on an SDRplay RSPduo, and compare it against a higher end WinRadio. Bonito found that the RSPduo performed well on the weaker longwave stations, but the Winradio outperformed it on the stronger ones. The differences were due to the better dynamic range of the Winradio.

The article goes on to make some recommendations for using their antennas on the RSPduo. They write that if intermodulation due to very strong signals occurs, there are some fixes that can be applied on their antennas to desensitize them and prevent overload. With the loop, a smaller loop size should be used, and the gain selector should be set to medium or min. With the dipole, they note that shortening the elements, and using it in an L-configuration with the lower radiator pointing towards the interfering signals can be used to attenuate them out. This works because a dipole configured in a L shape provides a bit of directionality.

The article also notes how grounding, very good coax shielding, good quality USB cables and galvanic isolation are all very important for reducing noise.

Bonito RSPduo Antenna Test Setup
Bonito RSPduo Antenna Test Setup

Identifying Noise Sources in the Shack using an SDR and an Active Receive Loop

Over on YouTube user SignalSearch has uploaded a video showing how he uses an active magnetic loop antenna indoors to identify local noise sources. Magnetic loop antennas are directional, meaning that they receive best when pointing towards a signal. This means that they also receive noise better when pointed at a noise source.  In the video SignalSearch uses a W6LVP receive loop antenna and demonstrates noise being emitted from his lightbulb, and from a plug in Ethernet over powerline adapter, which are known to be huge sources of HF noise.

If you are interested in the noise produced by these Ethernet over powerline adapters then we did a previous post on this problem over here.

Using an Active Receive Loop Indoors & utilizing Software Defined Radio to identify noise sources

The K9AY Loop Antenna: A Directional E-H Antenna for HF

Thank you to Frank Sessink (PA0FSB) for submitting to us his document describing the K9AY loop antenna (pdf), which is the antenna that he successfully uses with his RTL-SDR for HF reception. The antenna combines magnetic (H) and electric (E) field reception in order to create a directive radiation pattern. Frank extends the idea by showing a method that can adjust the directivity electrically with some simple resistor switching.

The antenna that I use is for medium wave DX, specially to receive MW from USA here in Europe/The Netherlands. The antenna is a combination of a magnetic loop and a sense antenna for the E-field. The magnetic loop is directive, but has no front-rear ratio. The E-field antenna has omnidirectional sensitivity. The combination, in correct phase and amplitude, results in a front-rear ratio of more than 25 dB over the frequency range from 500 kHz to around 3 MHz. Higher frequency makes no sense, since skywave signals distort the ground wave directivity pattern.

A simple modification is used as directional antenna with remote control: two orthogonal loops that combine E and H-field in a simple way. I can make 8 selectable directions.

The full document is available here in PDF format.

The K9AY E-H HF Antenna
The K9AY E-H HF Antenna

A Homemade Magnetic Loop Antenna used with RTL-SDR Direct Sampling

Over on our forums user "SandB"  has submitted his designs for a homemade magnetic loop antenna with preamp that he uses together with his RTL-SDR in direct sampling mode. The antenna looks like an interesting build so we are resharing it here. He writes:

So, antenna itself represents as handmade on-PCB winding made of two-side-foiled fiberglass size of 30x40 cm. Both 'windings' connected in the middle and thus winded to 'continue' each other.

Preamp located in metal box attached to antenna and connected via 1.5m S/FTP cable to another box with RTL stick. Note that some transistors soldered on PCB in upside-down - dot on layout means base.

Electrically preamp made as 3-stages balanced signal amplifier with low-input impedance and low-pass filter before input with cut-off at 15MHz. Such complications were required to reduce interferences and intermodulations. Antenna itself is more effective on long-medium waves, so preamp has higher gain on short waves (gain varies from 45db at 200KHz to 68 db at 10MHz - see attached freq responce pic). Getting more flat responce at lower frequencies is possible by increasing C10/C11/C12 to 22nF.

My implementation has some additional elements to make possible to adjust preamp's gain in few db's. But seems its quite useless so that details not included in this post. Anyway, its possible to reduce gain by increasing R6 to 500K.

Box with RTL SDR: I put both signal wires as 3 windings via ferrite ring with high permeability just before RTL chip. This noticeable reduced stray interference, that induced in that cable but doesn't affect differential signal.

ant_preparing
rtl-box
on-the-wall
preamp_n_antenna
ant_preparing2
board-front
board-back
principal
freq_responce_modeled
Loading image... Loading image... Loading image... Loading image... Loading image... Loading image... Loading image... Loading image... Loading image...

Using the SDRplay with a W4OP Loop

Over on YouTube user SignalSearch has uploaded a video showing and explaining the use of a W4OP magnetic loop antenna on a SDRplay SDR. On the video he explains what the W4OP loop is, and demonstrates it’s operation in SDR-Console with his SDRplay. The video description reads:

Experiment: Hookup the SDRPlay RSP 1 (SDR receiver) to the W4OP (Small Transmitting Loop). I’ve always wanted to try hooking up a loop to my SDRPlay. Though different from an active receive loop (one that has a Low Noise Amplifier), this loop can be used for transmitting @ QRP levels – but works great for shortwave listening too! For more info. please visit my website @ www.k5acl.net!

Using the SDRPlay with the W4OP Loop