Linrad with rtlsdr with and the e4000 tuner.

Hello, This mail is sent to all the E-mail addresses I have found in the source code of tuner_e4k.c and librtlsdr.c I have made a couple of modifications to the software and I now want to ask whether you can make changes to the standard package that you supply so Linrad users will not have to download modified files from my site to get proper operation of Linrad in the future. The most important modification is the gain setting. The tuner code requires knowledge of the gain table or searcing for legal gain values by use of the returned error code. I think that this is impractical and I changed it so the routine will now always set the nearest possible gain value and return it to the caller. The routine e4k_set_enh_gain(...) does not affect the gain of my hardware so I allow the gain setting function to use it with always the same value because I have no idea what this function is intended to do.... The default IF gain is too high. I reduced it by 6dB for a 6 dB better dynamic range. With the tuner_e4k.c currently incorporated in Linrad there is an AGC action that degrades the dynamic range by about 10 dB. I do not know anything about the e4000 internals but in case this remaining AGC can be disabled and the gain set 10 dB lower in the particular gain step controlled by the AGC, the dynamic range would improve from 66 dB to 76 dB with respect to the usual MDS (noise in 500 Hz bandwidth.) That means going from outside the scale in the QST "Key Measurements Summary" in their product testing to a mediocre result 6 dB above the limit of the range they have for SSB radios. The rtlsdr would be superior to hand held units like TH-D72A or VX-8GR in adjacent channel rejection (QST July 2011 and September 2011) if the AGC could be disabled. The details are here: http://www.sm5bsz.com/linuxdsp/hware/rtlsdr/rtlsdr.htm The Extio_RTLSDR.dll file provides 6 dB worse dynamic range because of the high IF gain setting. It also has a poor noise figure. -------------------------------------------------------------- To be able to use the callback in Linrad I have had to include various structures in the Linrad c code. I need to have this code in Linrad: i = libusb_handle_events_timeout(dev_rtlsdr->ctx, &tv1); Therefore I need the structure rtlsdr_dev which is not included in rtl-sdr.h. That structure requires other structures and it would be a good thing if those things as well as something like this: #define MAX_RTL2832_SAMP_RATE 3200000 #define MIN_RTL2832_SAMP_RATE 900001 were included in rtl-sdr.h I attach the Linrad interface routine to rtlsdr in case any of you are interested to see how I use the library. I realize the chip is far more clever and that I do not use it well. There is a substantial DC offset that seems to be possible to auto-remove. The AGC I want to get rid of might be something related to: /* disable auto mixer gain */ e4k_reg_set_mask(e4k, E4K_REG_AGC7, E4K_AGC7_MIX_GAIN_AUTO, 0); Hard to know without any documentation on the chip.... 73 Leif / SM5BSZ