If you are casually listening to the radio, you probably tune into a local station and with modern receivers and FM modulation, the sound quality is good. But if you are trying to listen to distant or low-powered station, there’s a lot of competition. Our modern world is awash in a soup of electronic interference. [Electronics Unmessed] tells — and shows — us how much noise can show up on a SDR setup and what simple things you can do to improve it, sometimes tremendously.
According to the video, the main culprit in these cases is the RF ground path. If you have a single antenna wire, there still has to be a ground path somewhere and that may be through the power line or through, for example, a USB cable, the host computer, and its power supply. Unsurprisingly, the computer is full of RF noise which then gets into your receiver.
Adding a counterpoise makes a marked difference. A low inductance ground connection can also help. The counterpoise, of course, won’t be perfect, so to further turn down the noise, ferrite cores go around wires to block them from being ground paths for RF.
The common cores you see are encased in plastic and allow you to snap them on. However, using a bare core and winding through it multiple times can provide better results. Again, thanks to the SDR’s display, you can see the difference this makes in his setup.
None of this is new information, of course. But the explanation is clear, and being able to see the results in a spectrum display is quite enlightening. Those cores essentially turn your wire into a choke. People think that grounding is simple, but it is anything but.
The only radio I like listening to is shortwave. There is a joy in listening to random radio broadcasts from around the world. Some from Asia, some from Eastern Europe, some from Africa. I do not understand a word but its still fun.
One of these days I plan on putting a directional antenna on a my rtl-sdr and seeing what I can pick up. I absolutely love the late nights under the stars, on my roof with a laptop and SDR, trying to pick up random broadcasts. Just love it!
I too love tuning around the bands and listening to random broadcasts from all over the world, I discovered Google translate on a mobile device or tablet does a reasonably OK job of live transcribing and translating strong broadcasts too.
The first link leads to a startrek fan video?
But on topic – this is a really nice article, so often especially with RF very simple measures can be used to improve things and it’s good to keep getting reminders and other tips and tricks.
‘counterpoint’ -> ‘counterpoise’
Nothing would work against Radio Maria
Al: This may be a generational thing. Younger listeners who are accustomed to consumer electronics (no noise on the smart phone!) often object to the noise coming from a simple direct conversion (HDR!) receiver. But those of us who grew up with analog shortwave receivers knew that a certain amount of noise was a necessary part of the game, and in fact was one way to test the sensitivity of the receiver. When you connected the antenna, did the noise level go up? If so, you were hearing the “band noise.” Some of it was from thunderstorms in Brazil, some from the weed-whaker down the road, some from remnants of the big bang. Sure, you could decrease the gain of the receiver to the point that this band noise is no longer audible. You will be able to listen to Brother Stair with no noise. But that weak station coming in from far-off Ulan Bator might no longer be audible. FM was another way to eliminate the noise. Personally, on an HDR analog homebrew shortwave receiver, I like the noise. It lets me know that the receiver is working.
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Did you not know that End-fed half wave antennas need no counterpoise ????
The don’t obey Ketchup’s Law
(if needed….. /s or JOKE)
Will we EVER get a edit button???
“They don’t”
The counterpoise still exists even if you use an EFHW . If you omit a physical counterpoise line(s) , it still exists as your outer surface of your coax feed line. This gets back to your receiver. It is known as the i3 current. Now no harm done if this RF current doesn’t bite you when you transmit. But, consider how much local noise you are now picking up from indoor appliances, wall warts,etc (see Bill’s comments, above).
Does this really happen? Several of our local hams constructed EFHW ‘s with 49:1 XFORMERs . Counterpoise connected, noise dropped audibly.