How would you like to have a very good HF SDR receiver with a wide spectrum display covering 2MHz or more for about $75? Well, you can when you combine the Ham it Up HF Up-converter with a RTL2832U stick. NooElec is selling an HF Up-Converter board based on an open hardware design in conjunction with Opendous Inc. for about $50 plus shipping. The Up-converter board basically converts HF signals to the FM band (specifically 100.5 MHz to 150 MHz) allowing your RTL2832U to tune in the HF signals. When used in conduction with SDR Sharp or HDSDR you are able to receive HF signals in AM, USB, LSB, CW, and other modes. HDSDR gives you roughly the same functions found on most better HF receivers like noise blanking, automatic gain control, variable filters widths, etc. These inexpensive HF up-converters are nothing new. There have been many designs floating around in either DIY form or completed boards. However, the Ham It UP converter looks like the first product produced in quantity and is available directly from NooElec in the US. I purchased the Ham it Up HF converter for testing from NooElec and it arrived very quickly.
As mentioned earlier the converter is an open source design and all the information about the design and performance information can be found on the Opendous web site. There is pretty extensive testing information available about the converter if you are interested. Basically the Ham It Up converter is a very small board with a female SMA connector on either end. There is also a bypass switch, which is a nice edition which allows you to switch the converter out of the antenna path. You can go back to using your dongle in the FM/VHF/UHF modes without having to disconnect the converter. Power is provided by a +5V source such as a usb phone charger. You will need one with a Micro-B usb connector on the end that plugs into the converter. Fortunately these power adapters are easy to find. The Ham It Up HF Converter can be purchased at:
Ham It Up v1.0 – NooElec RF Upconverter For Software Defined Radio. Works With Most SDRs Like Funcube, RTLSDR (RTL2832U with E4000, FC0013 or R820T Tuners); MF/HF Converter With SMA Jacks
Setting It Up
The Ham It Converter is reasonably simple to get going with a RTL2832U dongle. You will need to buy or make an adapter cable to connect the Ham It Up converter to the antenna input of your Dongle. You will also need a SMA adapter to whatever connector you use for your external antenna. You can either make your own or buy prebuilt adapter cables (see list at bottom of the article). If you decide to make your own Radio Shack does sell male SMA plugs that you have to solder and crimp on. You will need to connect your RTL2832U antenna jack to the SMA connector labeled IF and your external antenna to the SMA connector labeled RF. You will also need to install the Oscillator package provided with the Ham It Up converter into the empty IC socket on the Ham It Up board. Be sure to line up the black dot on the Oscillator package with the white Dot on the circuit board. You will also need to have SDR Sharp or HDSDR already and set up running with your RTL2832U stick. Power up the Ham It Up converter. Make sure the switch is not in bypass mode. Tune SDR Sharp or HDSDR to around 100.00 MHz and switch the receiving mode to AM and you should be seeing / hearing local and distant AM broadcast stations. If this works, you should be basically good to go and now ready to do a little tweaking.
Tweaking the Software for Best Performance
The first thing you will want to do is to adjust the gain of the RTL2832U stick. Too much gain and you will overload the front end of the RTL2832U stick and you will begin to hear stronger stations all over the band. Too little gain will result in noisy weak signals. There is no standard for setting the gain since everyones RTL2832U, antenna system, and RF environment is different. I highly recommend not using the automatic gain settings provided in the ExtIO settings, but rather adjust the gain manually to get the best balance of a low noise floor and best signal. If you are using HDSDR click on the button labeled ExtIO to access these settings. If your using SDR Sharp click the Configure button near the top of the SDR Sharp window to access these settings.
You might want to also adjust the frequency offset which will allow SDR Sharp or HDSDR display the HF frequency you are tuned too. The Opendous web page has a section on how to calculate the offset frequency exactly. My suggestion when using SDR Sharp is to use the Frequency Manager to create a shortcut to a known standard frequency like WWV at 10 or 15MHz. In the offset box enter you calculated offset it should be something like -106,000,000. Save the shortcut. With SDR Sharp running double click on the shortcut in the frequency manager and you should land near your target frequency. If you are a little off, adjust the offset and try again. You can set a shortcut up for the center frequency of every HF band if you want and the offset will automatically be applied. In HDSDR the process is similar, but you will need to go in to the RF Calibration menu and select the Upconverter box. Enter your calculated offset number as a positive number something like 106000000. Again, some trial and error may be required. Check the Video in this post on how to setup the Ham It Up converter, software tweaks for SDR Sharp and HDSDR, and a demo of how well these setups receives.
How well does it work?
In my real world testing with the Ham It UP converter connected to a RTL2832U / E4000 stick, to say I was pleasantly surprised would be a understatement. It was amazing how well this $75 HF SDR setup worked. Ok, it probably doesn’t work as well as a $700 – $800 HF SDR, but it is 1/10th of the price for what I would bet about 90% of the performance. I have had at least one well rated $700 SDR receiver that I can say that the RTL2832U / Ham It Up combination was just as good or better in everyday use. I would definitely say this setup blows most of the sound card based SDRs away. Even compared against my commercial HF receiver with Digital Signal Processing, the Ham It Up / RTL2832U combination did a better job. The Ham It Up converter provided a very low noise floor allowing me to hear much weaker signals. When combined with HDSDR with its adjustable filtering and AGC, the received signal was excellent. When using good quality computer speakers, even SSB audio was superb not to mention AM broadcasts even better quality. Plus you get a nice 2MHz or more of waterfall display so you can easily watch the activity on an entire amateur band (this is something that even the more expensive SDRs don’t often have). Now to be clear, I am sure this is a situation where your “mileage will vary”. Performance will depend highly on how well you tweak the setup, your antenna, the individual RTL2832U stick and you RF environment. I can say that I have a less than optimal antenna (20 Meter Attic Dipole) and a less than ideal RF environment and still got very good results. For you DIYers, you could probably put the Ham It Up converter and RTL2832U stick in an enclosure and have a nice looking little VHF/UHF/HF radio. If you do, post a picture of your work in the RTL2832U Forum.
Video of Ham it Up Setup and Demo
For you that are not interested in making your own adapter cables, here are some links to some pre-made cables and adapters that should cover most DVB-T Stick antenna combinations:
“SMA” to “PL-259” Adapter Cable