Many thanks to SWLing Post contributor, LondonShortwave, who shared (via Twitter) this video with recordings made with his portable SDR in a London park:
Brilliant recordings, LS, and amazingly QRM-free!
You can follow LondonShortwave on his blog and via Twitter.
SWLing Post contributor, London Shortwave, has updated his portable SDR setup to achieve a lower noise floor by implementing a Wellbrook UMB130 balun.
My friend, @K7al_L3afta, posted to Twitter, the following fax he decoded from the Kyodo News Agency on 12,745 kHz today:
The Kyodo News Agency is possibly the last marine weather fax station which faxes daily news (full newspapers) and navigational warnings to ships at sea.
For those of you who might believe it takes a sophisticated setup to decode a FAX transmission, you would be incorrect. @K7al_L3afta uses only a Tecsun PL-660 portable hooked up to his PC running the MultiPSK application. He lives in Morocco–in an urban environment with lots of RFI as well, so those of you living in a similar situation should feel encouaged.
After posting the FAX image, our friend @LondonShortwave then sent a link to a Sony radio I have never seen before: the Sony CRF-V21.
The Sony CRF-V21 (Image source: Universal Radio)
The CRF-V21 is a full-featured shortwave radio receiver with built-in printer and decoding for FAX and RTTY. In fact, with an optional AN-P1200 satellite antenna, the CRF-V21 will even copy and print G.O.E.S. satellite weather transmissions.
Here is Universal Radio’s archived description of the CRF-V21:
The Sony CRF-V21 Visual World Band Radio is the first portable to offer integrated facsimile (FAX) and radioteletype (RTTY) shortwave reception. You can print RTTY and FAX transmissions directly with the built-in thermal printer. Supported RTTY modes include Baudot at 60, 66, 75 and 100 WPM and ASCII at 110, 200, 300 and 600 bps. FAX shortwave speeds include 60, 90 120 and 240 rpm. Even G.O.E.S. satellite weather transmissions may be copied and displayed with the optional AN-P1200 satellite antenna.
Frequency coverage is 9 kHz to 30 MHz for all longwave, medium wave and shortwave frequencies. Plus FM coverage from 76 to 88 MHz and NOAA satellite channels 137.62/141.21 MHz. The optional AN-P1200 antenna system adds 1.6910/1.6945 GHz G.O.E.S. satellite reception. Another highlight of this radio is built-in spectrum display showing a visual picture of 200 kHz or 5 MHz of the shortwave spectrum.
Other refinements include: Mini Earphone Jack, S Meter, 350 Alpha Memories, Carry Handle, Clock, 8 Event Timer, Scan, Sweep, FM AFC, Synchronous Detection, Attenuator, 6/3.5/2.7/14 kHz Selectivity, AF Filter, Record Jack, Dial Lamp, Keypad and LCD Contrast Adjustment.
The CRF-V21 is supplied with: AN-V21 telescopic antenna unit, ACP-88R AC power unit, NP-227 battery, BCA-70 charge tray, antenna cable, protective cover, UPP-21 thermal printer paper and manuals. Operates from 110/120/220/240 VAC. Requires two AA cells for memory retention. 16.25 x 11.25 x 6.75 inches (21 lbs.).
The CRF-V21 is basically an all-in-one Holy Grail portable for those at sea!
@LondonShortwave also shared the following video of the CRF-V12 in operation:
Simply amazing. I love the display–reminds me of the Eton E1. I would expect excellent audio out of this rig as well.
When I checked today, there wasn’t even one CRF-V21 listed on eBay–not even as a completed listing. I imagine they are rare indeed.
Out of curiosity, do any SWLing Post readers have a Sony CRF-V12 in their collection? I would certainly like to add one to mine someday.
Many thanks to my friends @K7al_L3afta and @LondonShortwave for this radio diversion today!
Many thanks to SWLing Post contributor, London Shortwave, who has posted an article on his blog regarding US/Cuba relations after Presidents Barack Obama and Raul Castro announced, last Tuesday, the re-establishment of relations. London Shortwave has included recordings from the VOA, Radio Marti and Radio Havana Cuba.
Click here to read the full article on London Shortwave’s blog.
London Shortwave, a regular contributor to the SWLing Post, lives in London, England and copes with serious amounts of radio noise (QRM) at his home. Unlike many urban radio listeners, the QRM didn’t chase him away from the hobby, rather he looked at it as a challenge. Besides taking his radio kit outdoors to escape the noise, he also has a noise mitigation set-up at his home which has been refined over the years.
London Shortwave shared this video demonstration earlier this year on his YouTube channel. Here’s his description:
In this video I demonstrate an improvement to indoor radio reception quality, which is possible to achieve in an urban environment.
I compare using a Tecsun PL-390 portable receiver to a radio set-up that combines Lowe HF-150’s sync detector, the Wellbrook active loop antenna and real-time noise reduction software.
I recently told London Shortwave that he’s a QRM-fighting Samurai; I believe he certainly deserves the title!
Any other QRM Samurai’s out there?
London Shortwave writes:
I’ve just discovered that there is an Amateur Radio equivalent of the StackOverflow website (a Q&A website for programmers where answers are upvoted/downvoted according to a number of strict guidelines, ensuring answer relevance and quality).
After a quick scan it seems that it contains many useful answers that are also relevant to SWLs, for example:
http://ham.stackexchange.com/questions/606/can-i-reduce-rfi-noise-at-the-antenna
Very cool! With over 630 questions ham radio questions so far, there are many answers that can help SWLs. Thanks for sharing this, LS!
One of the great things about the SWLing Post is that readers share their varied–and highly creative–methods of playing radio. A few weeks ago, SWLing Post reader, London Shortwave, shared his portable SDR set-up with us; he uses this outdoors to mitigate London’s heavy radio interference. Dennis Walter, president of Germany-based Bonito, commented, and later posted an alternative portable SDR solution using the Bonito RadioJet IF receiver.
Below, London Shortwave shares a guest post (also viewable on his blog) which describes in detail his design for his portable SDR around the FunCube Dongle Pro+ and an 8″ Windows tablet, and explains how effectively it works for him. This post includes recordings and a video; it’s an excellent tutorial:
This article is a follow up to the submission I made to the SWLing Post a little while ago. In short, the idea was to combine the FunCube Dongle Pro+ USB-based software defined radio (SDR) with an 8″ Windows tablet running SDR# to have a portable, on-the-go SDR solution.
The original inspiration
At the outset, I thought that all that was necessary was a tablet (I chose Toshiba Encore 8″), the FunCube dongle itself and just some antenna wire. This turned out to be a naive assumption because the tablet’s USB interface injected enormous amounts of radio frequency interference (RFI) into the SDR, making listening on some shortwave frequencies essentially impossible. Just to be sure that I wasn’t being plagued by a defect of my chosen tablet model, I tried out the same set-up on a Dell Venue 8, with identical results.
To deal with the issue of tablet-generated RFI, I bought a galvanic USB isolator, which, in essence, is a box that breaks the electrical connection between the USB dongle and the tablet’s USB interface while allowing USB data to pass through in both directions.
Heros Technology galvanic USB isolator
Connections
The isolator resolved the RFI issue completely, but created another problem altogether: the device specifications state that the isolator’s power output is restricted to 100mA at 5V. This is sufficient for USB devices that are self-powered but not for the FunCube dongle that draws all of its power from the USB port to which it is connected.
USB Y cable
One way to supply extra power to a USB device is to use a “Y-cable”. Such cables have one extra USB plug that can be attached to a source of additional power (for example, a USB power bank). This solution is commonly used to connect power-hungry items, such as large hard disks, to low-power, portable computing devices (laptops and tablets). Having bought this cable, my next step was to find/improvise a battery that meets the USB power specifications (5V, 500mA).
My first thought was to use the mobile USB power bank that I use to charge my iPhone while on the go. After all, it already has a USB port and supplies power with the right voltage. Once again, my expectations were confounded and RFI reared its ugly head! The power bank radiates significant interference into the circuit because it uses a switching regulator to maintain steady voltage. Luckily, I came across Gomadic’s portable AA battery pack with regulated 5V output that emits way less interference than any of the other USB batteries I tried (my intermediate solution used 4 rechargeable AA batteries and a makeshift USB connector, and although this resulted in zero additional interference I decided that it’s not safe to supply the SDR with unregulated voltage that doesn’t match the rest of the circuit). I used the handy passthrough USB voltmeter I bought in Maplin to check that Gomadic’s nice-looking gadget does indeed give out 5V as advertised.
So, what can one do with the remaining RFI from the additional power supply? It turns out that it can be mitigated quite effectively by inserting a balun (item 10 on Figure 2) between the SDR and the antenna wire (item 12). The balun is connected to the SDR with a coaxial cable (the “feed line”, item 11). Additionally, ferrite choke rings (item 9) attached to the feed line help reduce this RFI further: winding the feed line through the choke rings several times is sufficient. However, neither the balun nor the chokes are effective enough to replace the USB isolator! It appears they only help with the noise generated by the power supply, which is relatively minor anyway.
When SWLing Post published the details of my intermediate solution, Dennis Walter – one of the engineers behind Bonito RadioJet – popped up in the comments section and suggested that my setup is too tedious, as it involves lots of cables, and that his SDR is superior in terms of portability and the supplied software. While I haven’t had the chance to evaluate RadioJet, I pointed out that the cost of his radio is significantly higher than that of all of my components put together. I also mentioned that the free SDR# software I use is superb: it sounds excellent and offers a number of features that many software packages and conventional radios don’t have. So, having finalised my design, I thought that it might be time to tally up the cost and listen to the results.
Below is the full component list:
1) Toshiba Encore 8″ tablet $194
2) On The Go USB host cable for Toshiba’s micro USB connector: $7
3) Heros Technology USB Isolator: $125
4) USB Y cable with two males + 1 female plugs: $8
5) Gomadic Portable AA Battery Pack with regulated 5V output: $20
6) Gomadic female USB connector tip: $6
8) USB volt-meter (optional): $33
11) Feedline cables $7
12) 6 metres of thick copper antenna wire: $8
Adding up the prices of items 2 – 12 (and excluding the optional voltmeter) brings the total cost to $449 vs. Bonito RadioJet’s $689. For the price difference you can throw in the Toshiba tablet at $194 and still have some change, enough to buy a carrier bag and perhaps even a nice pair of headphones!
Figure 1. Radio components
Figure 2. Antenna components
In terms of portability, the entire setup fits nicely into an 11″ laptop carrier bag.
Figure 3. Packing the components into an 11″ carrier bag
Figure 4. Ready to go
Setting things up in the field is not particularly cumbersome, either:
Figure 5. Portable SDR setup in action in a local park
As for the results, listen to the below snippets and be the judge. The only thing I will say is that none of my other portable radios have ever given me this kind of performance, not even with the long wire antenna attached:
And while we’re at it, here’s a demo video:
Portable SDR on Toshiba Encore 8″ Tablet from London Shortwave on Vimeo.
At one point I wanted to build an enclosure to house the FunCube dongle, the power supply and the USB isolator in a single tidy unit, but I no longer see the need. It’s easy to pack all of those items into the carrier bag and also they are all useful individually: the USB isolator can be paired with other SDRs, and I recently discovered a neat additional use for the Gomadic battery pack.
Well, that brings me to the end of this post. I hope my design will inspire you to come up with your own portable SDR system, and that you will share your results with me in the comments section. Happy listening!
