Wanting to dip into software defined radio I bought a genuine RTL SDR v3 last fall & was excited to see what I could receive. Much to my disappointment all I was getting were local FM broadcast stations, weather in the 162 mhz range and 2 strong local AM stations. My main interest is in shortwave and the signals I was looking for were nonexistent. Fast forward to this week, I upgraded my outside long wire antenna and took another shot at SDR. First of all the noise level went way down and I tuned in WWV on 5 mhz no problem. Then other shortwave broadcast stations like WWCR and a religious station on 9330 khz came in very well. So this was a huge improvement in my experience with the RTL & SDRsharp software. What I can't figure out is why my AM broadcast band hasn't improved at all. Plus 40m and 80m amateur is very poor. Just received a couple of CW signals (no voice/SSB) around 7 mhz after tuning around for over an hour. I'm now hoping to improve things to bring these signals in as well. Any suggestions? Also is there any other software that will work with the RTL SDR that I could try that will work well on the shortwave bands? I know that SDRsharp has the "direct sampling" mode that some other programs might be lacking. Thanks in advance
My Experience With RTL SDR V3
- Thread starter SatHunter
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AB5ID
Member
Are you able to compare with a known good radio to rule conditions, antenna , etc. ?
FlyingGerman
Member
I'd also be interested in the electrical setup of your antenna.
Are you going direct or are you using a balun transformer to adapt the
antenna impedance?
Long wires usually have a foot point impedance of 240 ohm while your
receiver/transceiver should have 50 ohm or in the case of the SDR dongle
it would be 75 ohm if you have the one I'm thinking of.
That might contribute to the issues you're seeing.
Are you going direct or are you using a balun transformer to adapt the
antenna impedance?
Long wires usually have a foot point impedance of 240 ohm while your
receiver/transceiver should have 50 ohm or in the case of the SDR dongle
it would be 75 ohm if you have the one I'm thinking of.
That might contribute to the issues you're seeing.
I am. I'll do a comparison with my Tecsun, Sangean and Grundig later today. I know generally I have excellent results on MW with my variety of radios and basically no reception at all on broadcast band with my SDR setup.
Not really a major concern, my main interests are SW and 20m - 80m amateur.
Well I'm sure you set the sampling mode to Direct Sampling (Q Branch), but yeah, I had less than stellar results as well even when hooked up to my Amplified Palomar Loop Antenna.
I ought to just stay out of this, as I am a newbie...
That said, when I look at the www.rtl-sdr.com web site, and look at a table of 7 various SDR models, including the RTL-SDR (R820T), and their bandwidth, the RTL-SDR says 24 MHz - 1766 MHz.
So, I would expect it to work for VHF and UHF, but AM band, MW stuff, and lower freq Ham / SW would all be well outside of the primary pass band for in spec signal reception.
The table shows that there are other models that clearly do have an extended pass band into the lower frequencies.
Additionally, I've seen "up-converters" to shift the lower frequencies up to a better operating range for the RTL-SDRs, again leading one to believe that their out of the box performance on the low end might be marginal at best.
Just some thoughts...
JC
That said, when I look at the www.rtl-sdr.com web site, and look at a table of 7 various SDR models, including the RTL-SDR (R820T), and their bandwidth, the RTL-SDR says 24 MHz - 1766 MHz.
So, I would expect it to work for VHF and UHF, but AM band, MW stuff, and lower freq Ham / SW would all be well outside of the primary pass band for in spec signal reception.
The table shows that there are other models that clearly do have an extended pass band into the lower frequencies.
Additionally, I've seen "up-converters" to shift the lower frequencies up to a better operating range for the RTL-SDRs, again leading one to believe that their out of the box performance on the low end might be marginal at best.
Just some thoughts...
JC
<< The kit I purchased from Amazon >> will do AM-BCB, but marginally. At 1:44 in the video below, you'll see the quality level I was getting on a station about 85 miles away. But again it was with a tuned, directional amplified antenna. So no, I don't recommend them for BCB-DXing, but for VHF they are pretty damn good.
It's coverage is: 500 kHz to 1.7 GHz --- But it does say below 24Mhz WITH REDUCED PERFORMANCE
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85 miles is quite respectable for a device which is basically a glorified hack and is produced to an incredibly low price point. If it was designed to cover a larger section of the spectrum and NOT OPERATE at a reduced PERFORMANCE, it wouldn't be available at the low, low << amazon price of 39.99 CLICK HERE >>, with absolute garbage being called an antenna with it.
Taking it all into consideration, it really shouldn't be doing what it is. There are a great many people here who have done amazing things with it, and have really pushed them to the bleeding edge. People buy what amounts to an "as seen on TV" kit that does everything for a modest price, then either gripe or malign the device or it's output when it under performs their lofty expectations. They come on here and click every button on the top-bar of the editing window to muddy the waters and "offer their opinion" about why "It didn't work for them", and don't really go and explore why it didn't work for them or they just want the baby, and not the labour pains. It may help them to vent, but it doesn't help the person who is on the edge, who may have drastically different outcomes. The device they wanted doesn't come bundled on Amazon for what amounts to a half tank of gas, it is usually closer to a mortgage payment.
Take your time, don't make rash decisions, evaluate your use case and make incremental changes to your setup. You may find that hoping that software can take the place of hardware (like expecting the direct sampling to work wonders, which it may - or may not) may actually be leading you astray, and using a hardware solution like an upconverter might yield you better results.
First and foremost lesson I can provide to you is, throw away the stock antenna and wiring, unless you're within clear vision of the transmitter you're looking to listen to. Look at what you said, yourself
Taking it all into consideration, it really shouldn't be doing what it is. There are a great many people here who have done amazing things with it, and have really pushed them to the bleeding edge. People buy what amounts to an "as seen on TV" kit that does everything for a modest price, then either gripe or malign the device or it's output when it under performs their lofty expectations. They come on here and click every button on the top-bar of the editing window to muddy the waters and "offer their opinion" about why "It didn't work for them", and don't really go and explore why it didn't work for them or they just want the baby, and not the labour pains. It may help them to vent, but it doesn't help the person who is on the edge, who may have drastically different outcomes. The device they wanted doesn't come bundled on Amazon for what amounts to a half tank of gas, it is usually closer to a mortgage payment.
Take your time, don't make rash decisions, evaluate your use case and make incremental changes to your setup. You may find that hoping that software can take the place of hardware (like expecting the direct sampling to work wonders, which it may - or may not) may actually be leading you astray, and using a hardware solution like an upconverter might yield you better results.
First and foremost lesson I can provide to you is, throw away the stock antenna and wiring, unless you're within clear vision of the transmitter you're looking to listen to. Look at what you said, yourself
You have your first step on the path. I'm glad you took another shot at it, getting that included trash of an antenna away from the front end of your device helped you, keep working at it.
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I have it connected directly to the antenna. I've been reading posts here about balun but I'm not exactly sure how to set one up or which one to buy that will work with the RTL SDR
slicerwizard
Member
From the RTL-SDR Blog V.3 User Guide:
"The result is that 500 kHz to about 24 MHz can be received in direct sampling mode.
Direct sampling could be more sensitive than using an upconverter, but dynamic won’t be as good as with an upconverter. It can overload easily if you have strong signals since there is no gain control. And you will see aliasing of signals mirrored around 14.4 MHz due to the Nyquist theorem. But, direct sampling mode should at least give the majority of users a decent taste of what’s on HF. If you then find HF interesting, then you can consider upgrading to an upconverter like the SpyVerter (the SpyVerter is the only upconverter we know of that is compatible with our bias tee for easy operation, other upconverters require external power).
Note that [the V3] makes use of direct sampling and so aliasing will occur. The RTL-SDR samples at 28.8 MHz, thus you may see mirrors of strong signals from 0 – 14.4 MHz while tuning to 14.4 – 28.8 MHz and the other way around as well. To remove these images you need to use a low pass filter for 0 – 14.4 MHz, and a high pass filter for 14.4 – 28.8 MHz, or simply filter your band of interest."
That means:
Direct sampling has less dynamic, has no gain control, is easily overloaded, has aliasis, needs filtering ...
So it's a useful addon but not the best solution for MW to SW listening.
"The result is that 500 kHz to about 24 MHz can be received in direct sampling mode.
Direct sampling could be more sensitive than using an upconverter, but dynamic won’t be as good as with an upconverter. It can overload easily if you have strong signals since there is no gain control. And you will see aliasing of signals mirrored around 14.4 MHz due to the Nyquist theorem. But, direct sampling mode should at least give the majority of users a decent taste of what’s on HF. If you then find HF interesting, then you can consider upgrading to an upconverter like the SpyVerter (the SpyVerter is the only upconverter we know of that is compatible with our bias tee for easy operation, other upconverters require external power).
Note that [the V3] makes use of direct sampling and so aliasing will occur. The RTL-SDR samples at 28.8 MHz, thus you may see mirrors of strong signals from 0 – 14.4 MHz while tuning to 14.4 – 28.8 MHz and the other way around as well. To remove these images you need to use a low pass filter for 0 – 14.4 MHz, and a high pass filter for 14.4 – 28.8 MHz, or simply filter your band of interest."
That means:
Direct sampling has less dynamic, has no gain control, is easily overloaded, has aliasis, needs filtering ...
So it's a useful addon but not the best solution for MW to SW listening.
AB5ID
Member
Thanks for pointing it out. I'm ordering one today! Quick question: can they be used with a radio or just with a SDR setup? Does an outside ground improve reception quality/strength when using one of these devices?
The device states it can be used with ..."any HF Capable Radio".
As you are using a long wire, you should be using this as well in your signal path.
Here is 59 pages of goodness that i've seen several links to about the many aspects of baluns, ununs and chokes.
Thank you very much, looking forward to trying it. And looks like a great link to find out just how these things work
I don't mind putting more money into a more capable SDR device for HF.
Any recommendations? I can't find the Airspy units here
I wanted one badly. Can't find Airspy in this part of the world. Not having any luck even on eBay
Canada. If there is a retailer in Canada (or North America for that matter) that sells them I would order one today as well
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