Marty KN0CK developed a very interesting v1.0 HF converter based on surface mount technology that fits inside the casing of an RTLSDR tuner dongle. He’s recently sent me schematics for the revision, which should offer even better performance.
This new iteration has a few major upgrades from the previous – an ESD protection diode on the input, and an optional Mini-Circuits MAR 8+ RF preamplifier which should really draw out some weak signals. Nice weather is coming up soon and once I have some free time, I’ll string up my long antenna – this should really pick out the weak shortwave signals I love hunting for.
I’ll be offering KN0CK’s converters for sale soon, so if you’re interested, please click here and I’ll let you know when it’s available!
Marty KN0CK sent me some details to publish about his great looking miniature HF upconverter board for the RTLSDR, the HF Alchemy DVB-T Active HF Upconverter. It’s an incredibly miniature SMT board with an SA612 mixer and SMT oscillator, and with some very careful soldering the entire board fits inside the housing and draws its power from the tuner’s USB port. The design upconverts at 120MHz, which is well out of the FM band to reduce the possibility of interference from strong local stations. A 40 MHz low-pass filter on the input further reduces interference. Marty reports it works GREAT!
I also had the opportunity to test an identical dongle and it was very easy to use. It requires a PAL adapter, but most of these dongles need an adapter and this one wasn’t difficult to locate; the integrated form factor is excellent. It’s very sensitive, a bit more-so than my other tuner module even, and the integrated form factor is perfect. It would be very easy to purchase an active USB extension cable and locate this integrated SDR in a shielded enclosure at your antenna’s feed point for even lower losses and versatility.
Update 5/1/2013: KN0CK is releasing a Rev B! I have a teaser.
Thanks for sending this in, Marty!
Reader David Forsman, WA7JHZ, read the round-up of RTLSDR upconverter choices and sent me a photo and build schematic of one he designed which was featured in the January 2013 issue of QST, the ARRL‘s monthly magazine.
This circuit up-converts frequencies between 2.3 MHz and 43 MHz by 125 MHz (127.3 MHz to 168.0 MHz) for driving the Realtek RTL2832 quadrature decoder DVB-T device with Elonics E4000 tuner chip with USB 2.0 output. It also incorporates an input bandpass filter (BPF), diode limiter, RF attenuator, and amplifier.
The filter’s response curve:
David reported he’s built two of these up-converters with good sensitivity on 20 and 15 meters. I think I have all the parts except the crystal and coils to build this on hand, so this might be a good excuse to sting my antenna up again and try it out. Thanks David for sending this in!
I’m trying to catalog all the different HF upconverters on the market for the RTLSDR. The RTLSDR stack, a combination of radio software such as GNUradio or SDR# with a Realtek RTL2383 + Elonics E4000-based DVB-T tuner using a modified driver, is getting to be very popular among amateur radio enthusiasts because it’s cheap and highly versatile to allow you to receive on a very wide frequency range. Unfortunately, the chip has some limitations – that wide range only goes from about 50-2200MHz with most in the 64-1700MHz range. That’s well above the HF bands where many ham radio operators and shortwave or AM stations are found.
Fortunately, the marketplace has taken care of that limitation, and quite a few choices for an HF converter / up-converter are now available which use a mixer and crystal oscillator to add around 100MHz to the incoming signals, shifting them into the tuner’s frequency range. There are several choices out there, including pre-built boards, partially built kits, and plans depending on your skill level and interest. An assembled board or a partially assembled kit will probably set you back about $50-100; if you’re savvy you can probably make it for $10-20 in parts – if you don’t mind winding your own coils. Your mileage may vary.
So, getting to it, these are your choices arranged with built boards near the top, partially built boards and kits near the middle, and plans and project logs near the end.
If you have any others I’ve missed, send me an e-mail!
1. There’s a new Ham It Up v1.2 HF upconverter for software defined radio produced by Opendous which has a large amount of documentation including layouts, and can be purchased mostly-assembled for only about $50. v1.2 makes some small improvements, including a 125MHz crystal instead of a 100MHz crystal to ensure there’s no interference from the U.S. FM Broadcast Band. It also features an input switch and an optional hardware noise source is an interesting, if possibly seldom used, feature. Ham Radio Science has a rather extensive review of the original revision and were pretty happy with it.
2. CT1FFU v4 HF converter is fairly new and features an antenna switch, solving the problem of the low-pass filters keeping interesting high frequency signals out of your system even if you do want them. You can avoid manually switching the upconverter in and out of the circuit with this feature. It offers some other design improvements over the previous revisions, which were themselves some of the first upconverters widely available. 68 Euro shipped worldwide with tracking. Offers optional 106.250MHz or 65.520MHz crystals to help mitigate interference from local FM stations.
It looks like 9A4QV built a model, the HF Upconverter SDR UP-100, which is for sale for 35 Euro + Shipping. There’s not much information that I can find on the site about it, but I think that’s a very attractive board. I especially like the neatly wound coils. Gone, but now he has an interesting Low Noise Amplifier for sale.
4. I’ve been using CT1FFU’s v3.1 dongle. German retailer Wimo sells completed kits, which have been in stock even when CT1FFU’s own kits have sold out. A no frills HF up-converter, mine came assembled except for the SMA connectors. It’s one of the early generation upconverters but still offers solid performance. V3.1 uses a 106.250MHz IF.
Wimo also sells the FunCube dongle, if you don’t already have an SDR.
5. JaniLab has started selling a derivative of the CT1FFU v2.0 on eBay for a bit lower of a price than some of the others. The older revisions work well, although with some more leakage than subsequent designs, and don’t have quite as fancy filtering or switching features.
6. Janilab also sells another DBM mixer-based converter, with an antenna switch to bypass the conversion.
8. If you’re looking for a more rugged commercial solution, High Sierra Microwave has an upconverter (FCD-1-55-UC) with a 133MHz IF frequency and BNC terminals with an integral amplifier. I’m a fan of converters whose LO frequency shifts the entire HF range above the FM broadcast band in general and the shielded enclosure will definitely cut down on noise. Looks like it’s suitable for mounting outside at your antenna’s feed point, and it also looks like you’re going to pay for those features. If anyone owns one and wants to share their experience with it, or if High Sierra Microwave wants to send me one to evaluate (*wink wink*) I’d
If you’re more ambitious, you can roll your own up-converter from parts. FAR Circuits appears to have manufactured PCBs for sale for many QST projects, including one upconverter. I’ve only recently discovered this site and there seems to be a lot of good stuff.
9. W9RAN put together a “Cheap and Easy” RANverter SDR 2.0 Converter Kit with 2 MHz wide bandwidth and 125 MHz oscillator frequency. There aren’t very many parts in this kit and they’re all through-hole so this should be an easy HF converter to assemble. Somewhat less of a commitment than building any of the of the ones just from plans, but more than a commercial board above. The kit is available for $31.95 + S&H and it looks like Far Circuits sells a bare board for you to populate yourself for a few dollars based on these plans.
10. If you’re comfortable speaking Dutch, or just with Google Translate, you can buy the Kit RF Converter for RTL SDR Sticks DC – 65 MHz. Unlike most other models, this one HF up-converter takes a BNC 50 Ohm antenna input and has an SMA 50 Ohm output with a 100 MHz oscillator frequency and built-in protection. This one also looks like a great starter kit with through-hole components and large coils and looks easy to build. You can also purchase the completed assembled kit in an enclosure, which also includes a power cable and SMA-MCX adapter cable. Looks interesting.
11. Kalle over at DGK Electronics has a great looking compact 100MHz HF converter designed to fit inside of a pre-made RF shielding box. It uses the ADE-1 mixer and an ASEM oscillator. It has some of the most complex filters and great filtering on the incoming power line, it probably performs very well. He describes the filters on his page, and there’s also a full schematic available. There’s a photo of a pile of boards, and he says there’s still some available, one might be left! DGK Electronics
12. Marty KN0CK built this incredible SMD SA612-based HF upconverter which fits inside the dongle housing itself and steals power directly from the USB cable. This is an incredible piece of work with very few moving parts. Read here to see some more photos and the full schematic. He’s also developing a Rev B to improve performance – check out the teaser!
13. David Forsman, WA7JHZ, sent me a photo and plans of his 125MHz HF up-converter with a diode limiter, attenuator, and amplifier all in one from plans featured in Jan ’13 QST magazine. Click through there to the article for a schematic and explanation for more details and a full schematic. Thanks, David!
14. Matt Dawson GW0VNR has a very interesting HF converter using more discrete parts than some of the other ones I’ve seen. It uses hand-wound transformers, an actual discrete diode mixer, and a Saronix oscillator running at 106.25 MHz. It uses a total of 23 parts and looks like it would be pretty easy to build. He doesn’t have any photos of the completed board, but does have a full schematic, overlay, transfer mask and Gerber files for the PCB. I’m pretty sure I have all the parts to build this one in my box as well. It looks interesting and simple. Check it out.
15. Radio amateur Paulino Sato has posted schematics and specifications for using the TA7358AP FM Front-End as an HF up-converter you can build yourself, using small coils wound on your own forms. It’s a bit of a commitment, but only has about 40 parts. The instructions are in PDF format. Download from me directly or the original is available on DropBox. The PDF contains PCB masks and silk screen layouts and a full schematic.
16. Over in the UK at the George Smart Wiki, we see homebrew plans by M1GEO using hand-wound coils with an SBL-1 mixer and 100MHz crystal oscillator. It has around 20 parts to assemble. These coils look like they could be hand wound on a dowel coil form, and the crystal and mixer are very large parts, so you could probably build this on perfboard without any trouble.
17. Bryce Salmi KB1LQC built a very rugged-looking clone of George Smart’s above with some modfiications dead bug style.
18. Romanian amateur Alexandru YO2LDK built a simple HF upconverter circuit using an NE602. This has an amplifier, limiter, regulated supply and 100MHz frequency like several of the ones pictured, but the circuit itself looks quite different. The amplifier stage is ahead of the limiter, which looks like this one is offering a constant gain versus the adjustable gain some of the others have offered. It looks like this one has more tunable components, which means a little more work to dial it in. I didn’t see any photos of the completed product.
19. Nick G0CWA built an interesting switchable upconverter design, complete with instructions and board layout PDFs.
There are plenty of options to build or buy for getting HF signals into the VHF range for your RTLSDR. With these choices, there are plenty of options for getting HF signals into the VHF ranges for use with the RTLSDR. It’s not difficult to modify these plans for even higher fidelity and accuracy, such as by increasing filtering on the power lines, building a shielded enclosure, improved antenna systems, and more.
I’ve been using my v3.1 Converter from Wimo for a few months, and have been very happy with its performance so far – there’s little noise and leakage, and I use it to pull in shortwave broadcasts from all over the world including the BBC, China, Cuba, Japan, Russia and more from my home in Seattle with only an 80″ long wire and a string of adapters – I highly recommend that model, or any of the models in this family, for great performance. I’m looking forward to trying out some of these other ones.
If you have a design you’d like to see featured here, let me know!
Edit 10/29/2012: NooElec offers “Ham It Up v1.0″ upconverter which looks to be based on a different design, and seems very high quality. Check it out!
Edit 2/2/2013: Better info about the Opendous Upconverter, KB1LQC’s DIY Upconverter, and WA7JHZ’s upconverter.
Edit 2/3/2013:Added 9A4QV HF Upconverter SDR UP-100, G0CWA 2012 upconverter, YO2LDK upconverter.
Edit 2/13/2013: Added Vandijken Elektronica upconverter and W9RAN RANVerter 2.0.
Edit 2/19/2013: Added KN0CK SMD HF Upconverter
Edit 4/13/2013: Added JaniLab converters, High Sierra Microwave converter.
Edit 4/25/2013: Informed 9A4QV Out of Stock – Thanks Adam!
Edit 5/14/2013: Ham It Up v1.0 > v1.2, Now Ships with 125MHz Crystal
I bought and did a quick setup on my RTLSDR dongle using SDR# a few weeks ago, where I used it to listen to FM radio stations around my area and a few public safety frequencies. That’s all well and good, but I’m much more interested in shortwave listening – when the weather is good, I can pick up a fair number of stations on my Hallicrafters receiver and there’s even more out there that I can’t tune in with that old equipment.
The RTLSDR tunes from around 64MHz up through around 1800MHz, but shortwave frequencies are much lower – only up to around 30MHz. Using an RF mixer, it’s possible to shift the signal into the RTL’s tuning range. Portuguese designer CT1FFU developed a mixing upconverter which adds 106.25MHz to the incoming signals, shifting them up into the correct receiving range and filtering out signals about 50MHz to prevent interference. His version comes as a kit which requires surface-mount soldering, but German retailer Wimo offers mostly-assembled versions of the kit which only need the antenna terminals and power connector soldered.
Finding those adapters was a bit challenging – I have a helical antenna which terminates in that alligator clip, feeding into a coax break-out, with an SMA-Coax converter. On the other end is an SMA gender-changer and an SMA to MCX adapter. Ultimately I ordered them from eBay and they work as intended. The USB port provides the +5V power supply for the converter’s operation but otherwise isn’t connected.
Reception is acceptable. With the aid of the SDR software, I can see where signals are more readily, but issues with my antenna setup and local interference are keeping it from performing as well as the Hallicrafters. I can identify human voices on more stations, but it seems there are fewer I can actually listen to with this equipment. I’ll probably try building a tuned loop antenna similar to this one, and see what I can do with better noise rejection and directionality. I might also add a low noise amplifier after whichever better antenna I end up using.
If anyone has a favorite, easy-to-build loop antenna for 10-160M I’d love to hear about it.