Band pass will will depend on your frequency of interest. I will say I had very good general-purpose success with this band-stop (eliminating the FM radio band before it hits the front-end): http://www.minicircuits.com/MCLStore/ModelInfoDisplay?14171027094400.9678991266784147
It is a now a permanent fixture on my HackRF, not cheap, but vastly improves the experience. Jay On Thu, Nov 27, 2014 at 10:10 AM, Larry DiGioia <[email protected]> wrote: > Thank you! That is the best explanation I have seen in months, and much > food for thought. I have slowly come to understand that this is not a > dongle, it is test equipment. Now - could you please give an example/source > of off-the-shelf "really good bandpass filters?" (For HF/VHF?) > > > On 11/27/2014 09:58 AM, McDonald, J Douglas wrote: > > I want to emphasize that the RF chain in mine is not defective. > > I tested it again last night. The three different gains all > > work exactly as expected. > > > > When connected not to an antenna but to a wired system > > the number of spurious signals is greatly reduced but is nowhere near > > zero and not as low as the dongles. > > > > I think that most people for over the air receiving purposes need > > to get really good bandpass filters to pick out only the signal of > interest. > > > > And remember that 8 bits is a very poor dynamic range for a system > > without a really good, designed to purpose, ANALOG AGC, so you have to, > > by hand, get the various gains exactly right. I do it by looking at the > > spectrum display. In general when working with weak signals > > you want to leave the amp off and slowly raise the two other > > gains in parallel from all the way down. At first if your is like mine > > you will see big jumps up and down in the level of weak signals, > > spurious signals, and noise. The spurious ones come and go > > as you raise gain. At some point the apparent noise level > > stabilizes and remains the same for a while as the real signal > > levels rise up out of the constant noise floor. Then the noise > > floor rises up. When it has risen about 5-9 dB you have reached the > > best sensitivity and more important dynamic range and > > lowest quantization distortion. I am fairly sure that this gizmo > > has no built-in dither at the 1-LSB level. If it does there is something > > bad going on, perhaps in the DC level area. > > > > One way to look at it is the HackRF is NOT a receiver: its effectively an > > IF strip with no AGC. > > > > Today I’ll try it as a transmitter feeding my old spectrum analyzer > > looking for spurious signals. Currently for most spectrum analysis > > I use either it (>2MHZ bandpass) or one of the dongles (better > > for narrow band). > > > > Doug McDonald > > > > > _______________________________________________ > HackRF-dev mailing > [email protected]https://pairlist9.pair.net/mailman/listinfo/hackrf-dev > > > > -- > "When people are free to do as they please, > they usually imitate each other." > > Eric Hoffer > > > _______________________________________________ > HackRF-dev mailing list > [email protected] > https://pairlist9.pair.net/mailman/listinfo/hackrf-dev > >
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