Category: SDRplay

Running an RTL-SDR On up to 100 Meters of USB Ethernet Extension Cable

Over on Aliexpress and eBay there are now multiple USB2.0 extenders that work using Ethernet cable. These extenders advertise that is is possible to use up to 100m of Ethernet cable. Extending the USB connection rather than using coax cable is desirable as coax cable introduces signal losses the longer it is. Extending the digital side of the SDR (the USB cable) results in no signal being lost.

However, the USB2.0 specification notes that the maximum limit of the length of an extension cable is only 5 meters. We can go beyond 5 meters by using active repeater cables, but even this has limits of up to 30 meters maximum only.

So how can these USB2.0 Ethernet extenders advertise a length of up to 100m? These devices essentially convert the USB signal into an Ethernet network signal. Ethernet cable for network connections has a limit of 100 meters. Using this Ethernet extender is quite similar to using a Raspberry Pi and running the RTL_TCP software over an Ethernet cable, except that the network connection is handled entirely by the hardware.

We purchased a $45 USB2.0 extender from Aliexpress to test (there is also a cheaper $32 unit that we saw recently that should work too). The extender comes with a 1.5m USB Male to Male cable, a transmit box, a receive box and a 5V plug pack. The transmit side plugs into the PC via the USB Male to Male cable. The receiver end is placed up to 100m away, and this side must be powered by the 5V plug pack. In between you can run up to 100m of Ethernet CAT cabling.

USB2.0 Ethernet Extender from Aliexpress
USB2.0 Ethernet Extender from Aliexpress

In our testing we purchased a 50m CAT6 cable and tested to see if the extender would work with an RTL-SDR Blog V3, Airspy and SDRplay. Initially we had trouble getting SDR# to connect to the RTL-SDR. Eventually we found out that the provided USB Male to Male cable provided was of poor quality. After replacing it with a higher quality cable the extender began working properly. We also found that some USB ports on our PC wouldn't run the unit. The USB3.0 ports on the back of the PC connected directly to the motherboard worked best.

USB2.0 Ethernet Extender
USB2.0 Ethernet Extender Test

Using SDR# the RTL-SDR Blog V3 worked exactly like it was connected directly to the PC. There was no lag noticed at all, with tuning being instant. Sample rates up to 3.2 MSPS worked fine, although of course 2.56 MSPS was the limit without drops. As the receiver box is powered by a 5V plug pack, there was plenty of power available to power a 100 mA LNA via the V3's bias tee as well.

Reliability was a bit of an issue. Sometimes we'd need to replug the USB port several times before it would connect to the RTL-SDR. But once running everything appeared to be stable, and we left it running overnight at 2.56 MSPS without any problems.

Unfortunately the lower bit rate and sample rate of the RTL-SDR appears to be the limit of what the extender can handle. The Airspy with it's higher data transfer requirements due to it's 12-bit ADC didn't work properly, with audio stuttering from dropped packets (even at the lower 3 MSPS sample rate with packing enabled). The SDRplay also wouldn't work, with the SDRUno software being unable to detect the RSP1A. Even using a shorter 2M Ethernet cable did not help for these SDRs. In theory it should work since Ethernet can support a much higher data rate, but perhaps the converter chipset used in the cheap extender unit that we have isn't fast enough.

If you want to try this out, be very careful of what you purchase on Aliexpress/eBay/Amazon. There are some very very cheap USB to Ethernet extenders out there that are advertised as USB2.0, but not all of them are truly USB2.0. The very cheap ones under $5 won't work. Those cheap units actually degrade USB2.0 down to USB1.1 which will not work for an RTL-SDR or any other common SDR. The extender units that will probably work properly are all priced over $30.

It's also possible that some of the more expensive units available on Amazon (e.g. [1][2][3]) may be implemented better and might work with the Airspy and SDRplay. If you've tried one of the pricier units please let us know in the comments if it works. In particular this $156 KVM unit which claims a high data rate and also supports PoE may work (although PoE may cause switching noise). For extreme extensions of up to 250m, USB2.0 fiber optic extenders such as this $359 unit, or this $459 fiber optic unit which can go up to 5km (3.1 miles) might also work. If you've tried any of these please let us know in the comments.

SDRplay Release the RSPdx: Replaces the RSP2/pro, Filtering & Intermod Improvements, 1kHz to 2 MHz HDR Mode

The RSPdx
The RSPdx

SDRplay have just released their new SDR that they're calling the RSPdx. This is their new top end product which replaces the older RSP2/pro line. The RSPdx is designed for high performance DX reception and they write that it achieves this with additional filtering, improved intermodulation performance, a DAB notch filter, additional attenuation steps, and a new high dynamic range for frequencies under 2 MHz.

Pricing is £159 GBP or $199 USD (excluding taxes). It doesn't yet appear to be for purchase, but they note that it will be fully released within the next few weeks.

The RSPdx is a replacement for the highly successful RSP2 and RSP2pro SDR receivers, which have been extensively redesigned to provide enhanced performance with additional and improved pre-selection filters, improved intermodulation performance, the addition of a user selectable DAB notch filter and more software selectable attenuation steps .

The RSPdx , when used in conjunction with SDRplay’s own SDRuno software, introduces a special HDR (High Dynamic Range) mode for reception within selected bands below 2MHz. HDR mode delivers improved intermodulation performance and fewer spurious responses for those challenging bands.

The SDRplay RSPdx is a single-tuner wideband full featured 14-bit SDR which covers the entire RF spectrum from 1kHz to 2GHz giving up to 10MHz of spectrum visibility. It contains three antenna ports, two of which use SMA connectors and operate across the full 1 kHz to 2 GHz range and the third uses a BNC connector which operates up to 200MHz.

The RSPdx also features a 24 MHz ‘plug and play’ reference clock input which allows the unit to be synchronised to an external reference clock such as a GPS disciplined oscillator (GPSDO)

This is one of many video guides from SDRplay - makers of the RSP family of SDR radios. See the full list of SDRplay videos and applications documents on: https://www.sdrplay.com/apps-catalogue/

SDRplay is a UK company. The RSP SDR receivers are made in the UK and can be purchased for worldwide delivery directly from http://www.sdrplay.com/ (click on purchase and select your country to view shipping costs) or you can buy from any of our worldwide resellers listed here: http://www.sdrplay.com/distributors/ Many of the resellers offer local free shipping and/or local language technical support.

SDRplay Product Comparisons
SDRplay Product Comparisons

Mike Ladd (KD2KOG) who works for SDRplay Technical services has provided the following demonstration video.

Major Announcement... The RSPdx from SDRplay.

Independent reviewer TechMinds has also uploaded a new hardware and software overview and unboxing video as well.

NEW: SDRPlay RSPdx 1Khz - 2GHz HDR SDR Receiver

Mike Tests our RTL-SDR Blog L-Band Active Patch Antenna on an SDRplay RSP1a

Over on YouTube Mike Ladd (KD2KOG) from the SDRplay technical support team has uploaded a YouTube video showing him running our recently released RTL-SDR Blog L-Band Active Patch antenna on an SDRplay RSP1a. In the video he receives and decodes AERO signals from his car with his RSP1a powering the active patch antenna via the built in bias tee.

If you didn't already hear, we recently released an active (amplified + filtered) high performance patch antenna designed for receiving L-Band satellites such as Inmarsat, Iridium and GPS. The patch is designed to be easily mountable outside on a window, surface, stick, tree branch etc as it comes with easy to use mounting solutions and extension coax, and is enclosed in a fully weather proof plastic cover. If you're interested the product is available over on our store for US$39.95 with free shipping.

You also might want to keep an eye on Mike's YouTube channel, as he notes that in the yet to be released part 2 video he will be giving away the antenna in a competition.

RTL-SDR Blog L-band patch antenna part 1

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

An Easy Windows GNU Radio Setup Guide and Video for the SDRplay

SDRplay have recently posted a new workflow document and video that shows how to easily set up GNU Radio on Windows with an SDRplay software defined radio. They write:

GNU radio is a popular environment for teachers and developers involved in Digital Signal Processing and exploring new radio architectures. For receiver applications, the low cost dongle is a popular hardware choice, but if you need reliable, clean, continuous radio signal reception from 1kHz to 2 GHz (without the need for block converters or external filters) then an SDRplay RSP is a useful alternative.

With help from the GNU radio foundation, SDRplay has now made available a workflow for windows for all its RSP radios: www.sdrplay.com/docs/gr-sdrplay-workflow.pdf

Special thanks goes to Frank Werner-Krippendorf (HB9FXQ) who did the original SDRplay source block development, and to Geof Nieboer who has developed the Powershell scripts which enable operation on Windows.

GNU Radio workflow for SDRplay and Windows

Leif Continues his Comparisons of the Airspy HF+ Discovery, RSP1, Perseus and more SDRs (Parts 3,4,5)

Leif (sm5bsz)'s series comparing the Airspy HF+ Discovery against various other SDRs such as the Perseus, SDRplay RSP1, Airpsy HF+ Dual, Airspy + SpyVerter and AFEDRI SDR-Net continues again, with parts 3, 4, and 5 now having been uploaded to YouTube. In previous posts we covered parts 1 and 2.

The comparisons are very technically inclined, so may be difficult to follow for those unfamiliar with radio theory. We have highlighted the time stamps where he discusses the results.

In conclusion, for all tests the Perseus always comes out on top, with the HF+ Discovery coming a close second. Generally third best is the HF+ Dual, then the AFEDRI, followed by the Airspy+SpyVerter and RSP1.

Part 3: Here performance with real antenna signals is compared. Attenuators are used to make the noise figure 26 dB of all radios at the output of the 7 port resistive splitter. This video is for dynamic range on 7.2 MHz.

Results @ 30:20

rx7compare-part3

Part 4: Here performance with real antenna signals is compared. Attenuators are used to make the noise figure 27 dB of all radios at the output of the 7 port resistive splitter. This video is for dynamic range on 14 MHz.

Results @ 16:04

rx7compare-part4

Part 5: Here here second order intermodulation is studied.

Results @ 13:07

rx7compare part5

Leif Continues his Comparisons of the Airspy HF+ Discovery, RSP1, Perseus and More SDRs

Leif (SM5BSZ) is fairly well known in the SDR community for doing very indepth technical tests of various SDR receivers over on his YouTube channel. Recently he's released part two of a series where he compares the new Airspy HF+ Discovery against various other SDRs such as the Perseus, SDRplay RSP1, Airpsy HF+ Dual, Airspy + SpyVerter and AFEDRI SDR-Net. In the first video he studied the blocking and second order intermodulation effects of each SDR using signal generators. We summarized those results in this previous post.

In the new video Leif compares the dynamic range of each SDR using real HF antenna signals at 7.2 MHz. In order to create a fair test of dynamic range, appropriate attenuation is added to each receiver in order to make their noise figures equivalent, so that the incoming signal strength is the same for each SDR.

The first set of dynamic range results is summarized at time 08:14, and these results show the dynamic range comparisons for strong night time signals. Again like in the other videos the Perseus is used as the reference SDR since it is always the best. The tests show that the HF+ Discovery trails behind the Perseus by only -3dB, followed by the HF+ Dual at -10dB, AFEDRI at -15dB, Airspy+SpyVerter at -18dB and finally the RSP1 at -23dB.

The second set of results is summarized at 17:47 and this includes a day time dynamic range test. The rankings are very similar to the night time test.

rx7compare-part2

Reviews of the Low Cost MLA-30 Wide Band HF Magnetic Loop Antenna

Recently Chinese manufacturers have begun producing a low cost wide band (100 kHz - 30 MHz) magnetic loop HF antenna known as the MLA-30. The loop can be found on eBay for under US$45 with free shipping. In the past wide band HF loop antennas have not been cheap, normally costing $300+ dollars from manufacturers like Wellbrook.

RF signals are electromagnetic waves that consist of an electric and magnetic component.  A magnetic loop antenna mostly receives the magnetic portion of the wave. This is useful as most unwanted interference from modern electronic devices is generated in the electric component only.  So, a magnetic loop antenna may be preferable in city and suburban environments over other antennas like wires and miniwhips. Magnetic loops are also directional, and can be rotated to avoid interference.

One of the biggest costs to a magnetic loop antenna is the shipping, because a large hula hoop sized piece of metal needs to be sent. The MLA-30 cuts costs on shipping by providing a folded up thin loop wire and no physical support for the loop. You are expected to provide your own support, or simply hang the loop wire on something. If you like you can also replace the included loop wire with a larger loop.

The MLA-30 comes with 10m of RG174 coax, is bias tee powered, and comes as a set with a bias tee injector that is powered over 5V USB. We tested our own unit with the RTL-SDR Blog V3, Airspy and SDRplay bias tee's and found that they all worked well instead of the included bias tee. So if you have one of those SDRs using the loop is as simple and neat as plugging it in and turning on the bias tee.

In terms of build quality, the unit is sturdy and the PCB is fully potted and protected against rain/weather. It is yet to be seen how the external screw terminals holding on the loop will age over a longer period of time however.

So how does the very cheap MLA-30 compare to higher end magnetic loop antennas? Below are some reviews by various hams and SWLs. The general consensus is that it works well for the price, but as you'd expect, falters on handling very strong signals and produces a higher noise floor compared to the more expensive loops, especially in the higher HF bands. But overall we'd say that it's probably still better than using a miniwhip, especially in suburban/city environments, and is probably the best compact HF antenna that you can get on a budget.

What's included in the MLA-30 set. Photo from David Day's Review.
What's included in the MLA-30 set. Photo from David Day's Review.

MLA-30 Magnetic Loop Antenna Review and Comparison by David Day (N1DAY)

In this review David compares the MLA-30 against a 30-ft ground loop and a Wellbrook ALA1530-LF. His results show that while the loop is capable of receiving the same signals that the two comparison loops can, the SNR is much lower. He also notes that the much thinner loop wire used on the MLA-30 seems to result in a much deeper null, and that IMD was a problem for him.

Inside the MLA-30 Active Loop Antenna by Matt (M0LMK)

This post is a complete teardown of the antenna. As the PCB is fully potted Matt had to boil down the epoxy in order to get to the actual PCB. He notes that the PCB is a simple single amplifier design with the exposed pot working as a gain control.

Cheap Chinese Magnetic Loop Antenna (MegaLoop aka MAGALoop) MLA-30 by John

In this review John compares the MLA-30 against a $345 W6LVP and Wellbrook ALA1530LN. His findings are very favorable concluding that it is an adequate performer, perfect for cash strapped SWLs.

First hour battle of the antennas W6LVP loop VS MLA 30 loop test by OfficialSWLchannel

This is a YouTube video where OfficialSWLchannel compares his MLA-30 against a W6LVP loop. He notes that his initial testing shows that the MLA-30 performs as well as the W6LVP loop.

First hour battle of the antennas W6LVP loop VS MLA 30 loop test

MLA-30 Loop vs 80M EFHW by Matthew Payne

In this YouTube video Matthew compares his MLA-30 against a 80M end fed halfwave antenna with an SDRplay RSP1a. 

MLA-30 Loop vs 80M EFHW

MLA-30 Magnetic Loop Modifications by Scanner and Sdr Radio

In this video the Scanner and Sdr Radio YouTube channel uses an RSPduo to compare the MLA-30 against a Wellbrook loop. His results show that the MLA-30 definitely has a higher noise floor compared to the Wellbrook, but still receives signals decently although chasing weak signals it's not good enough. He also shows how to improve the MLA-30 by replacing the cheap coax that it comes with, noting that the modification reduced his noise.

MLA-30 Magnetic Loop Modifications