i have a rtl sdr 3 years old. not hf .. i did the mod on youtube.. posted below.. it seems to work good.. but got to work on the noise.. image below shows how bad the birds are flyin around. the humps are a fm station i think. all over the place ... but it is RX HF and not to bad .. about 75% out of 98%. less on the main radios and such ... will off to figure out the filtering.. they video below has a noise filter . would need to get a few caps.. but so far followin what he has shown.. as i dont speak spanish.. its working good.. hint 1 .... if you do this. the little caps you will take off... heat the chip side. if u dont and flick it.. the solder pad may go with the cap... guess what... toast... go slow easy take your time dont have a headache or anyone around.. small iron ... next to nothing for solder... you will be ok .. the 4 to 1 balun.. i have no idea if works. i had a little yellow core. about 1/3 inch dia. wond 6turns on it. and hooked it as a 4 to 1 .. the balun side goes to dongle. the coax side goes to antenna.. your using it backwards it seems.. that is ok to do .. i see he wound his mor elike a transformer i think.. i will have to try it that way and see.. ideas on this please post.. help is always needed and thankful for it.. the 1m cap. not sure if makes a diff. i think its there to smooth out the power a little and filter it.. i have no idea its just a guess.. image below tho shows it is working.. it needs filtering big time.. but hey one step at a time.. if you have idea for a xtern filter like the one in the video below.. let me know.. if its easier to build. i will give it a go if i have the stuff. any ideas hints tips tricks toss them out here.. again its not purfect. its not a $3000 RX. but it works good for me ..