Receiving up to 4.5 GHz with an RTL-SDR and a $5 Directv Downconverter

KD0CQ has recently been experimenting with trying to receive signals at frequencies of up to 4.5 GHz with an RTL-SDR and downconverter. Since a typical R820T/2 RTL-SDR’s maximum frequency limit is about 1.7 GHz, an external downconverter circuit is required. A downconverter converts high frequencies down into the range receivable by the RTL-SDR. For example a downconverter with a 2.4 GHz local oscillator would convert a 3.5 GHz signal down to 1.1 GHz, which can be easily received by an RTL-SDR.

The secret to doing this cheaply is revealed by KD0CQ. He shows that a very cheap $5 Directv SUP-2400 upconverter can be converted into a 2.4 GHz downconverter simply by removing some filters. He writes that he hasn’t uploaded the full set of steps to modify the SUP-2400 yet, but he intends to do so in the near future.

There is also a discussion about this mod on Reddit. Several posters have been discussing what applications a cheap downconverter could open up. Some mentioned applications include receiving various satellites in the C/S bands, DECT cordless phones @ 1.9 GHz, SiriusXM satellite radio @ 2.3 GHz, ISM @ 2.4 GHz, RADARs, RC aircraft control/telemetry/video and ham beacons.

The SUP-2400 Directv upconverter that can be converted into a downconverter.
The SUP-2400 Directv upconverter that can be modified into a downconverter.

10 comments

  1. S.Chitra

    Sir, I have the product NooElec NESDR Mini 2 SDR & DVB-T USB Stick (RTL2832 + R820T2) w/ Antenna and Remote Control. The maximum received frequency is 1.7Ghz. I want to use this product for receiving 2.4 GHz (ISM band). Can I use SUP-2400 along with above RTL SDR for receiving 2.4GHz signal. How do I connect down converter with RTL-SDR? Will it properly receive 2.4GHz signals?. Kindly acknowledge Sir

  2. Don Fortner - W4DF

    Interested in using surplus ITFS downconverter fo 2.2 – 2.4 ghz DSN use and other services. Any info welcome Bob and others. I have 2 ft and 8 ft dishes with feeds for 2.5 – 2.7 ghz.

    • KD0CQ

      Yup, that’s the ATV mod. For this application though you need to take some additional steps. The signal won’t get through otherwise. Or at least not enough to bother with.

  3. AD5NL

    My understanding is that the sensitivity/NF on the stock RTL-SDR gets a bit bad as you get toward S-band.

    So, at the very least, a microwave downconverter ought to give you a way to improve sensitivity, since your RTL-SDR would be receiving at 100 MHz instead of, say 2.5 GHz.

    This application would be slightly more relevant of course if the IF of the downconverter were more like, say, 1.2 GHz instead of 2.4 GHz. C’est la vie.

    This downconverter *might* be useful for receiving the S-Band (2400 MHz) downlink from Phase 3E, if it ever actually gets launched.

    • Bob

      You could also use a “MMDS Downconverter” that cover by default about 2.2GHz to 2.7GHz with a LO @1998MHz [Most have a LO stability of around +/-30kHz (+/-15 ppm)] . Because they are waterproof sealed they might not be as easy to hack the filters out. Some come with filters from 2.2 to 2.5GHz and some with 2.4 to 2.7GHz, but that is clear stated when buying them.

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