Over at KF7LZE’s Blog a post about an upcoming integrated HF upconverter using tiny surface mount components has been posted. It is made by Marty KN0CK and will be for sale on KF7LZE’s site soon.
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.
A Hungarian hardware developer has been working on what appears to be a 2-in-1 software defined radio, combining the rtl2832u and E4000 tuner chips together with a HF upconverter all on the same PCB. The device is able to tune from 1MHz to 1.7GHz, and has two antenna connectors, one for the HF antenna, and another for the VHF/UHF antenna. Using the Google translation is difficult, but it seems the board has a protection diode, 100MHz oscillator, low noise amplifier (LNA), isolation between the two antennas, and also retains the ability to receive DVB-T and DAB broadcasts.
The developers article in Hungarian on this combined tuner can be found here, and a Google English translation here. Another version of the page which looks to be a product ordering page can be found here, and Google English translation here. We aren’t sure if the developer is still shipping these devices as the eBay listings have all gone down, but it seems you can order one by contacting the developer from the website.
Update 27 May 2013: Version 3 of this combined rtl-sdr can be now found for sale at this link. http://janielectronics.com/index.php?route=product/product&product_id=94.
The RTL-SDR software defined radio can be told to run in a mode called "direct sampling mode", which with a small hardware mod allows the dongle to tune to the HF frequencies where ham radio and many other interesting signals are found. This means that no upconverter circuit is required.
However, the difficulty with direct sampling is that a hardware modification to the dongle is required. Also, the performance can not be expected to be as good as an upconverter without the addition of extra filtering circuits. RTL-SDR Blog V3 Note: Note that our RTL-SDR Blog V3 already has the direct samping mod done and built in, so no hardware modifications are required for those units! Just see the V3 users guide for information on activating direct sampling mode.
The direct sampling mode was originally discovered and discussed in this Google groups thread.
YouTube user Superphish was able to receive HF AM broadcast radio, and a decode a HF weather fax signal at 5.8MHz using the direct sampling mod.
Upconverters give the rtl-sdr the ability to receive frequencies below it’s minimum frequency. This allows reception of things like AM broadcasts, ham radio signals, weatherfax, international radio and much more.
There are dozens of upconverter designs and commercial products that work with the rtl-sdr. Luckily to help you choose one, blogger and amateur radio hobbyist KF7LZE has posted a rather extensive review of all the upconverter options available for the rtl-sdr.
The article can be found here.
