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RTL and the ham it up for short wave


mbb373
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hi all im wondering if anyone has had any luck with using the RTL and the ham it up converter to listen to shortwave or world band radio?

i think i have the offset wrong and not sure how to set it properly and as well as the frequency ranges that would work

i just got the ham it up 125 MHZ model / the 1.21 version. set to filter mode not pass thru

i am using SDR#

i have a 28 foot single conductor antenna and get random stations but very poorly

offset is currently set to -124,006,000

also i have it set to AM should it be set to USB or something different?

id love to get more info if there is any available.

thank you in advanced.

Matt B.

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I have the same board and mine is relatively deaf so I'm not surprised. My measurements show the conversion works at about 0.05mV@1.8MHz to make both 126.8MHz and the image at -77dBm which is about 3 dB up off the noise floor according to my HP8590E. The fix is this cool little preamp http://kitsandparts.com/rfamp1.1.php which will easily boost the low band sensitivity well into -97dBm range which will put this card on par with most common receivers. Additionally, the HackRF is also deaf as a door knob so an IF gain stage will also greatly help boost the performance of the whole setup well into the super receiver territory but you will want to place a high pass filter after the IF amp to hack off everything below 126MHz. Bare bones (no preamp or IF gain stage it takes a solid 0.5mV@1.8MHz (yes, a 450mV jump to make it work!) to just barely get the carrier up out of the noise floor on the HackRF display (yikes!). My SDR# spectrograph shows the noise floor at -65 (and I measured the signal of interest at -63dBm on the spectrum analyzer so that jives!) and the frequency readout indicates 127.42MHz (of the original 1.8MHz) which indicates 500kHz high which is consistent with all my other observations. REMEBER - BEFORE YOU TURN YOUR SDR INTO A SDT, YOU NEED TO BYPASS ALL OF THIS STUFF OR YOU WILL LET THE MAGIC SMOKE OUT. :ohmy: Fortunately, there is a very convenient RF bias output option which can be enabled on TX into the antenna connector to trigger the appropriate switching circuit.

KD6W

Edited by KD6W
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great information still new to all of this stuff but starting to get it.. thanks KD6W! how does that that affect your audio and experience listening? also what bands are you listening to in what area of the world are you in? and of course any other info is always welcome.. cheers!

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I have a full wave 80 meter loop antenna (500+ feet of wire) at 50 feet and I just worked a guy this evening in Flagstaff, Arizona from my house in Menlo Park, CA. using 50 watts (LSB) on 40 meters (7.268MHz to be specific) no sweat. I regularly work anywhere in the US, Italy, Germany, Israel, Egypt, South Africa, Cuba, Brazil, Ecuador, Australia, New Zealand, Mongolia, Kamchatka, Japan. I can receive and transmit pretty much DC to daylight but my favorite is tracking and working the satellites. I listen to Pandora most times (just a few too many people with shit for brains on the air, I choose to avoid) but listen around and tune into stations that are working special event call signs just for fun. Right now I'm monitoring some weird looking data/burst signals spanning from 250kHz to 300kHz using the FunCube Dongle Pro+ and SDR# comparing those signals with the HamitUp and all using a 6' piece of wire draped over a curtain rod as the antenna.

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wow just a 6' foot piece is effective.. one thing i have wondered about is .. is the fun-cube / pro+ different from the RTL-SDR dongle? and is it a drastic difference if at all ? i have been exposed to ham radio but have not apparently learned enough.. i know i have many questions but am a good learn and ready to get it figured out

thanks

Matt B

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The big difference between the RTL an the Fun-Cube is the price but the performance on the Fun-Cube is way better since it has a better front end and individual SAW filters per band segment which helps the front end mask nearby energy from unwanted bands. The Fun-Cube does not process any where near as wide of bandwidth as the RTL so as a bonus, the FCD+ operates on a wide range of computers including my old Dell laptop which greatly improves the appeal across more users. That said, the RTL is super ubiquitous and DIRT cheap and with the addition of some filters and preamps would operate just as well in weak signal ops but is good enough stock for many of the local and aircraft signals. I haven't experimented too much with the RTL but I certainly appreciate what it does for the community and frankly speaking, why I started watching HAK5 Darren and Shannon and monitor this forum. I also have to admit I also now know how to spell "pentest". :wink:

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