Author Topic: Direct Base band sampling on hf frequency with rtl Dongle  (Read 29998 times)

Anton Janovsky (ZR6AIC)

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Direct Base band sampling on hf frequency with rtl Dongle
« on: February 12, 2014, 08:58:52 PM »
Direct Sampling with No Hardware Mod Discovery :)

There is also a discovery for the E4000 tuner found by Reddit user Anonofish. Anonofish found that when tuning to frequencies between 3686.6MHz 3730MHz, the rtl-sdr dongle acted as if it was in direct sampling mode, passing the radio signal directly past the tuner and into the RTL2832U chip. This allows the lower end of the HF spectrum to be received without any hardware modifications.

Balun Hardeware Mod :)

Since the RTL2832U uses two pins to create a differential input, a balun can be used to connect both pins one and two to an antenna. Essentially this mod involves finding or winding your own balun, and connecting the balun inputs to both pin one and two, and the other end of the balun to your antenna. Here is a pdf file with schematics for this modification.

The Direct conversion RTL dongles modified as above is available here

Read more about it at
« Last Edit: January 28, 2016, 07:40:57 PM by Anton Janovsky (ZR6AIC) »


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Direct Base band sampling on hf frequency with rtl D
« Reply #1 on: March 07, 2016, 03:16:41 PM »
I expect this has been asked before so please point me to the answer if you know where to find it.

I recently completed building a kit that mounts the guts of an RTL2832 based dongle into a mother board and allows it to be used for both HF and V/UHF reception.  I wired the HF input balun to pins 1 and 2 of the RTL chip.  Ive been using it with ADSB# which requires selection of "Direct sampling I branch" for HF, and selection of "Quadrature sampling" for V/UHF.  It seems to be working quite well.

My plan is to use the kit as a panadapter for my TS-590S.  This requires CAT control which ADSB# does not appear to support. 

I have installed HDSDR and an RTL support DLL.  This works for V/UHF but I cannot find any option to select "Direct sampling I branch" which I assume I have to do to make it work on HF.

Can someone please tell me what I need to do to make HDSDR work with my device for HF?

Otherwise, can someone point me to a different SDR application that will support both ""Direct sampling I branch"" and CAT control.

Thanks for any help.

Andy k3wyc