I have been experimenting too with an RTL-SDR dongle now for a few
weeks. I currently use a transverter to listen to lf/mf/hf. This transverter
upshifts the spectrum with 100 MHz.
Although the RTL-DSR is rather deaf when
used on 2m or 70 cm (compared to my ham equipment) when used for HF it is
sensitive enough with a pa0rdt active antenna.
I can also use it on 472. But
there I have to use my 472 KHz narrow band filter to keep out mf, especially
Radio Mario @ 675 Khz. And although the dynamic range is not stellar, as far as
I can determine reception on 472 is
very comparable to my ft817..
Grahams pointer to the direct sampling option
got me interested. Time to let the nice people from dealextreme send me another
on for EUR 10 so I can ‘experiment’ with it.
Some
interesting websites/video’s about the direct sampling
implementation:
http://ttrftech.tumblr.com/post/36283680013/rtl2832u-dongle-mods-for-7mhz-reception-with-gqrx
and
http://mikikg.wordpress.com/2012/08/22/prepravka-dvb-t-usb-prijemnika-sa-rtl2832u-za-hf-0-28mhz/
First site is in Japanese, second in Croatian, but Google
(translate) is your friend.
It is very nice to get an instant overview of 2 MHz of spectrum. I
have been plagued by ever increasing QRM here, which forced me to place a
magnetic loop antenna in my backyard to get any reception at all. QRM now is
S9+10 dB form 100 KHz to nearly 50 MHz. I have not been able to find out what
causes this (not generated in my house). See attached screenshot for a part of
the spectrum around 80 meters. This
wavy pattern can be seen everywhere from nearly DC to 50 MHz, with some
clean area’s in between. Sometimes the QRM stops waving – straight lines for
several seconds and then the waving restarts.
I am very jealous of other hams showing waterfall patters where
everything between real signals is dark blue... :-(
Anybody ANY idea what might cause this kind of QRM?
73’s Minto pa3bca
