Rodrigo's system consists of an IF tap amplifier+filter board that is connected to an internally mounted RTL-SDR. The RTL-SDR is internally connected to the FT-991A's USB hub which had to be upgraded from a 2-port hub to a 4-port hub as the 2-ports were already in use by the CAT and Audio features. This required the stock USB hub IC to be replaced with a hot air rework station.
Everything is mounted inside the radio chassis itself, and the end result is a neat solution with no external wires, hubs or dongles that has essentially turned the FT-991A into an SDR. Plugging in the single stock USB cable from the FT-991A results in the standard CAT and Audio interfaces showing up, as well as the RTL-SDR.
What's also interesting is that Rodrigo makes use of the GPIO pins on our RTL-SDR Blog V3 to enable the RX_EN, BPF and BYPASS switches on the IF tap board. This allows for a cleaner solution as no external switches need to be installed.
The entire project is open source with schematics and the BOM provided over on the GitHub, and excellent documentation is available on the project's Wiki.
FT991A Converted into an SDR.
Turning FT-991A to a REAL SDR: Embedding a SDR Panadapter INSIDE the radio, no extra wires!
This week on the SignalsEverywhere YouTube channel Harold shows us the mobile SDR and ham radio setup that he's installed on his car. On the roof of his car he's installed several antennas for various amateur radio bands including the 1.25m, 2m, 70cm, 33cm bands, a modified GPS puck antenna for Inmarsat and Iridium reception, and an antenna and GPS pick dedicated for APRS.
Inside the vehicle is a Windows tablet attached to the dashboard which is used for APRS, remotely controlling a scanner radio stored in the trunk and for running SDRSharp. There is also an Android unit installed in the center console which has an RTL-SDR connected. The Android unit runs RF Analyzer, and an ADS-B decoder. As well as SDRs, Harold also runs several standard ham radios within the vehicle.
Amateur Radio Mobile SDR Load Out | SDR Plus 33cm 70cm 2m 1.25m and more!
Over on GitHub user mcogoni (Marco/IS0KYB) has recently released a new program called Pepyscope. Pepyscope is a simple and fast panadapter application that is designed to be used with direct sampling capable RTL-SDR's such as our RTL-SDR Blog V3 units. Like other panadapters you simply connect the IF output from the hardware HF radio into the input of the RTL-SDR. Then Pepyscope gives you a waterfall display that helps users to easily visualize the spectrum.
Pepyscope is open source and runs on Linux PCs. So far Marco has tested Pepyscope with a KENWOOD TS-180S (single conversion with IF at 8.83 MHz) and an RTL-SDR v3. He has also uploaded a demonstration video on YouTube.
A vector network analyzer (VNA) is an instrument that can be used to measure antenna or coax parameters such as SWR, impedance and loss. It can also be used to characterize and tune filters. It is a very useful tool to have if you are building and tuning home made antennas, filters or other RF circuits. For example if you are building a QFH or ADS-B antenna to use with an RTL-SDR, a VNA can help ensure that your antenna is properly tuned to the correct frequency. Compared to a standard SWR or network analyzer a VNA supplies you with phase information as well.
Until just recently, VNA's have cost roughly US$500 for a decent USB PC based unit like the miniVNA or PocketVNA, and have set people back thousands to tens of thousands of dollars for bench top units.
However, the cost of owning a VNA has now been reduced to only US$50 thanks to the NanoVNA. The open source NanoVNA project by @edy555 and ttrftech has been around since 2016, but only recently have Chinese sellers begun mass producing the unit and selling them on sites like Aliexpress, eBay and now Amazon. We note that it seems that there are some sellers selling them without shielding, so it might be worth double checking the listing to see if they mention that. All the listings we've seen seem to come with simple calibration kits as well.
The NanoVNA: A $50 Vector Network Analyzer
The NanoVNA is a small credit card sized VNA. It has a built in LCD screen that can be used to display graphs directly, or it can also be connected to a PC and the graphs viewed via the NanoVNA Windows software. When purchasing you can opt to include a small battery for portable operation for a few dollars extra. The frequency range is from 50 kHz to 900 MHz, although you should note that above 300 MHz dynamic range performance is reduced.
Over on YouTube several hams and radio enthusiasts have recently uploaded videos demonstrating and reviewing the NanoVNA. The overall consensus is that the unit is accurate and works well. For additional support there is forum available at Groups.IO.
Below YouTube user IMSAI Guy reviews the NanoVNA. Check out IMSAI Guy's other videos too as he has several where he tests the NanoVNA on difference filters and antennas, and checks the accuracy.
#350 NanoVNA Vector Network analyzer 900MHz VNA for $50
Below is YouTube user joe smith's review. He also has two other NanoVNA videos on his channel where he shows how to use the NanoVNA to measure antenna impedance, and how to use the NanoVNA to create SPICE models for simulation.
The NanoVNA, a beginners guide to the Vector Network Analyzer
Finally YouTube user Oli gives another overview. Please note that the following video is in Polish, but YouTube captions can be set to English.
NanoVNA - omówienie, kalibracja, pomiar anteny i filtra [english subtitles]
We've also seen several recent text reviews:
NanoVNA - A short review. In this review nuclearrambo shows off the calibration kit, and shows a practical measurements of a directional coupler and 137 MHz QFH antenna.
The NanoVNA, a real VNA at less than 48 €!. A review written in French, but Google Translate can be used. In this review David Alloza compares the NanoVNA against an Agilent E5062A benchtop VNA, and results look comparable.
A few days ago we posted about [dj0abr / Radio Electronics'] WebSDR software for QO-100. Having looked through his GitHub we've seen that he also has an a similar browser based server tool called WebWSPR for WSPR decoding and visualization (click with WebWSPR link) which was released earlier this year.
WSPR is an amateur radio digital HF mode designed to be decodable even if the signal is transmitted with very low power and is very weak. It can be used to help determine HF radio propagation conditions as WSPR reception reports are typically automatically uploaded to wsprnet. In the past we have been able to receive WSPR and similar modes like FT8 with our RTL-SDR V3 running in direct sampling mode.
Like his QO-100 WebSDR software, WebWSPR is designed to run on a single board computer like a Raspberry Pi or any Linux machine. It serves a web page that shows the WSPR waterfall, decoded data and has various WSPR related control options. The web page can be accessed remotely from any machine on the same network as the server, or could be put on the internet with port forwarding and a hostname service like noip.
A ready to use Raspberry Pi image for WebWSPR is available here (does not seem to support the latest Pi4 or 3B+ however). Manual installation instructions can be found here. The code is all open source and available on GitHub.
The software appears to take input from the soundcard for standard hardware receivers, but it should be possible to pipe audio from an RTL-SDR into pulseaudio, which the software can then use. The instructions from our RTL-SDR V3 WSJT-X tutorial may help.
Over on his YouTube channel Adam 9A4QV has uploaded a short video that demonstrates his 2.4 GHz homemade helical feed designed to be used with a reflector (prime feed satellite dish) for QO-100/Es'Hail-2 satellite reception. The antenna is made from an old can, 2-turns of copper wire, and a plastic insulator to hold the turns in place. The two turns are wound in left hand circular polarization (LHCP), because when used with a satellite dish reflector it will result in right hand circular polarization (RHCP), which is the polarization QO-100 uses.
One of the most important parts of the video is when Adam shows how he matches the antenna to 50 Ohms. He notes that without matching the antenna won't work properly, and the return loss will be about 8 dB or even less, resulting in poor performance. With matching he obtains 30 dB return loss.
Over on YouTube user [Radio Electronics] has uploaded a useful video showing how to install your own personal SDRplay or RTL-SDR based WebSDR for QO-100 (aka Es'Hail-2) reception. Es'Hail-2 is the first geostationary satellite with amateur radio transponders on board, and is positioned at 25.5°E which covers Africa, Europe, the Middle East, India, eastern Brazil and the west half of Russia/Asia.
The idea behind a WebSDR is to run your RTL-SDR QO-100 receiver on a remote Raspberry Pi (perhaps mounted close to the antenna on your roof etc). The Pi runs custom WebSDR software that has been created from scratch by [Radio Electronics] specifically for monitoring Es'Hail-2. Then you can access your QO-100 receiver from any device on your network that has a web browser (computer/phone/tablet etc). The interface of his WebSDR appears to be quite slick, which multiple QO-100 specific options and labels.
Quite a lot of work must have gone into this software which looks to be of high quality, so it is definitely worth checking out if you are interested in QO-100/Es'Hail-2 monitoring.
Es'Hail-2 QO-100 WebSDR
In the first video he first talks about various methods for downconverting the 10489.550 MHz QO-100 CW signal into a range receivable by the RTL-SDR or SDRplay. He then goes on to show the exact steps to install and run his WebSDR software on a Raspberry Pi 3.
In the second video he goes on to demonstrate the web browser interface highlighting the QO-100 specific features that he has implemented such as being able to compensate for any LNB frequency drift via a feature that can lock to the QO-100 PSK beacon.
The LimeRFE is a power amplifier and filter bank solution designed for the low cost TX capable LimeSDR software defined radios. It has multiple bands from HF all the way up to 3.5 GHz, and is capable of putting out about 2W on the HF bands. Currently LimeRFE is crowdfunding over on CrowdSupply with a cost of US$599 or alternatively there is now a cheaper unit for US$449 without support for the cellular bands. The campaign is active for 4 more days from the time of this post, and after that the price is due to rise by another US$100.
The team at LimeMicro sent a unit to Daniel Estévez (EA4GPZ) for testing, and he has recently posted about his results and thoughts when using the LimeRFE for WSPR transmission with a 15m long wire antenna. Daniel connected his LimeRFE to his LimeSDR and used WSJT-X piped into SDRAngel via Pulseaudio to transmit WSPR on the 10m band. He notes that for lower bands, the LimeRFE will still need additional low pass filtering to attenuate harmonics. SDRAngel cannot yet control the LimeRFE so he also created a simple Python script for this purpose.
Unfortunately Daniel's unit only achieved 25dBm instead of the advertised 33dB, but in LimeMicro's post they note that they believe that this is due to shipping damage. However, even with only 0.3W power, Daniel's transmissions from Madrid were able to be picked up in the Canary Islands, Netherlands and Northern England.
![NanoVNA - omówienie, kalibracja, pomiar anteny i filtra [english subtitles]](https://www.rtl-sdr.com/wp-content/plugins/wp-youtube-lyte/lyteCache.php?origThumbUrl=https%3A%2F%2Fi.ytimg.com%2Fvi%2FLbQDIMavIDc%2F0.jpg)
