HF Reception

Main forum to discuss RTL-SDR related topics.
ejones
Posts: 15
Joined: Fri Jul 17, 2015 9:39 pm

HF Reception

Post by ejones » Fri Jul 17, 2015 9:50 pm

i am unable to receive shortwave transmissions.
would the problem be that i have an adapter that goes to 75 ohm TV coax and then a 75 to 300 ohm matching transformer witch goes to twin lead that goes to a dipole.
i have set up the software to manufacturer specs.

rtlsdrblog
Site Admin
Posts: 2281
Joined: Mon Nov 19, 2012 11:54 pm

Re: HF Reception

Post by rtlsdrblog » Sat Jul 18, 2015 1:56 am

What are you using to receive short wave? An upconverter or direct sampling mod or...?

What frequency is your dipole tuned to? If it's tuned to VHF you won't get anything.

ejones
Posts: 15
Joined: Fri Jul 17, 2015 9:39 pm

Re: HF Reception

Post by ejones » Sat Jul 18, 2015 2:30 am

webpage/ http://www.ebay.com/itm/US-100KHz-1-7GH ... 1e9b323bd1
as seller instructions. In the software options, please use the program of SDR # with RTL configured to direct sampling of the signal Q, as shown in the following picture, so that the radio can work in Ham Bands.

i built the dipole with 50 ft of twin lead and galvanized steel wire and is resonant from 3 to 30 MHz with my 1971 solid state receiver.
i have had openings on the 80 meter band from Canada and Mexico.

most of my equipment is old stuff i have gotten cheap and works with directly with twin lead.

rtlsdrblog
Site Admin
Posts: 2281
Joined: Mon Nov 19, 2012 11:54 pm

Re: HF Reception

Post by rtlsdrblog » Sat Jul 18, 2015 2:56 am

Hmm sounds like you've set it up properly. That's a direct sampling modified RTL-SDR, so you might want to try turning on RTL AGC as well.

Are you able to receive any local AM broadcasts?

What is the TV adapter and transformer you are using? Some transformers designed for TV VHF use might not work at HF frequencies.

Try test things by plugging directly into the twin lead, or try string up a long wire antenna for a simple test.

P-40 Warhawk
Posts: 85
Joined: Thu Jun 26, 2014 11:55 pm

Re: HF Reception

Post by P-40 Warhawk » Sat Jul 18, 2015 12:07 pm

If I may stick my two cents in this . A TV transformer if you look at the speck on them have a bottom frequency of 5 MHZ . Their is a bigger problem and is they are not real matching transformers . All they are is a PCB with two tracks on them , one being a little longer than the other . You can check this out by using a volt ohm meter , Just see if you have continuity between one of the primary and any of the secondary wires coming out if you do it's not a transformer . If it was a transformer their would not be any continuity between the primary and secondary I went on line and found someone that make's matching transformers . Now I have seen the schematic of you device and I think you should have a rf amp going into a prescaler so the device can see a small segment of frequency at a time . For my direct sampling setup I use a MFJ-1020 active antenna , I live in Pensacola Florida and the best DX I got and probable couldn't do better was Siberia .

ejones
Posts: 15
Joined: Fri Jul 17, 2015 9:39 pm

Re: HF Reception

Post by ejones » Sat Jul 18, 2015 3:57 pm

i modified an old transformer to just pass thru to twin lead.
the device seems to to not even receive regular am radio. but VHF and UHF are really good with the police scanner dipole that it is also set up with.

ejones
Posts: 15
Joined: Fri Jul 17, 2015 9:39 pm

Re: HF Reception

Post by ejones » Sat Jul 18, 2015 4:26 pm

ok i found one problem my SMA adapter is missing the gold pin inside.

ejones
Posts: 15
Joined: Fri Jul 17, 2015 9:39 pm

Re: HF Reception

Post by ejones » Sat Jul 18, 2015 8:48 pm

i have heard you can make an RF amp from wall warts would anyone have information for that.

ejones
Posts: 15
Joined: Fri Jul 17, 2015 9:39 pm

Re: HF Reception

Post by ejones » Thu Jul 23, 2015 3:00 pm

got everything working now and have solved fm radio stations showing up on shortwave frequencies.
and now i see the noaa whether station 8 or 10 times on vhf. i am having also a hard time finding a prescaler.
i have been getting some very distant stations since replacing the adapters such as japan just without the RF amp.
also figured out the wall wart project is for VLF only.

for anyone that needs SMA adapters some come without the pin inside you can use a piece of copper wire.

P-40 Warhawk
Posts: 85
Joined: Thu Jun 26, 2014 11:55 pm

Re: HF Reception

Post by P-40 Warhawk » Thu Jul 23, 2015 9:37 pm

Try google.com also ebay.com last MFJ makes a prescaler witch is known as a preselector . I use a FM trap I got mine from Radio shack .

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