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Spikes on HF frequency

Posted: Sat Jun 29, 2019 6:18 pm
by 00EE00
Good day, I'm new in signal receiving and etc, just purchased RTL SDR V3 kit and when connecting antenna getting huge spikes everywhere on HF range. In medium, long waves is impossible even consider to detect signal.

Kit Longest Antenna off
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Kit Longest Antenna on
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On higher frequency (starting about 10Mhz+) can listen radio, but still it is supposed to be constant noise level at ~-50db?
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Also tried with 20 meter cable, situation is not getting better on low frequency. Settings is done by the rtl guide.

Re: Spikes on HF frequency

Posted: Mon Jul 01, 2019 4:42 am
by rtlsdrblog
Those spikes are probably from computer noise, or perhaps from the dongle itself. They will normally go away once an antenna is connected.

But the antenna you're using is not for HF signals (you seem to be using the dipole?). The dipole is only sized for VHF/UHF signals. For HF you need a large antenna, like a long wire 5 meters+. Or a magnetic loop antenna if size is an issue.

The dipole is simply too small to get good HF reception.

The lower range of the V3 is about 500 kHz, it doesn't support long wave.

Re: Spikes on HF frequency

Posted: Mon Jul 01, 2019 1:32 pm
by 00EE00
rtlsdrblog wrote:
Mon Jul 01, 2019 4:42 am
Those spikes are probably from computer noise, or perhaps from the dongle itself. They will normally go away once an antenna is connected.

But the antenna you're using is not for HF signals (you seem to be using the dipole?). The dipole is only sized for VHF/UHF signals. For HF you need a large antenna, like a long wire 5 meters+. Or a magnetic loop antenna if size is an issue.

The dipole is simply too small to get good HF reception.

The lower range of the V3 is about 500 kHz, it doesn't support long wave.
Yes, I'm using horizontal dipole. With supplied kit antenna I can decent receive on the evening or night frequency until about ~12-15Mhz. But also tried horizontal dipole with 20 meter long wire between buildings (also tried splitted for dipole 10m + 10m wire) and situation is not getting any better with radio below 7Mhz. It is heavily drowning in noise waves (they are -50, -40db) like 2 and 3 picture (looks like pulse amplitude modulation or etc).

Also in the spectrum receiving what it looks mirrored strong stations, lets say about 15mhz+. Is some stations overloading dongle?

EDIT:
also example of kit antenna dipole on the ground in the balcony where is no electric equipment near it, running laptop from battery:
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and this noise waves starting to happen when it raised only 1 meter higher
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Re: Spikes on HF frequency

Posted: Mon Jul 01, 2019 4:26 pm
by hotpaw2
Those periodic spikes and waves look like the symptoms of electronic switching RF noise.

This kind of RF noise can be generated by LED lights, power supplies, network equipment (cable modem, WiFi/ethernet hubs, etc.), PCs, monitors, printers, and etc. Not only in your place, but from inside any nearby buildings in your neighborhood as well. Perhaps even from your laptop.

To test for RF noise near your setup, take your RTL-SDR plus an antenna to some open field or park several hundred meters from the nearest building or electric power source, and re-check the spectrum. To see if the RF noise is from your own place, kill your main power circuit breaker. If the noise drops, you are generating it (your LED lighting, network, etc.), and can hunt it down. If it doesn't, it's from your neighborhood.

Re: Spikes on HF frequency

Posted: Thu Jul 04, 2019 3:50 am
by radiolistener
Most of all is that source of these spikes is some electric equipment in your home, or your neighbors.
Usually this is something with switching power supply.
Also, some cheap low quality LED lamps and cheap USB chargers can produce such noisecause it.

Also malfunction mercury-vapor lamps near your home can produce such noise.

Try to power off your home electric equipment, especially powerful with switching power supply.

Re: Spikes on HF frequency

Posted: Thu Jul 04, 2019 5:03 pm
by 00EE00
Identified major contributor to noise waves/spikes is probably stationary computer PSU as it currently not powered on only plugged to wall socket. Will try again with long wire antenna when weather is decent for low frequency reception. For now with kit antenna indoors when PSU unplugged:

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Re: Spikes on HF frequency

Posted: Fri Jul 05, 2019 5:46 am
by radiolistener
then you're needs to replace power supply of your computer. Normal PSU should not produce so high noise. May be this is some cheap Chinese PSU, if so then look for branded one.

Re: Spikes on HF frequency

Posted: Wed Aug 28, 2019 8:50 pm
by TomLine
I had a monster spike at 28 or 29 Mhz. Started unplugging everything in the house. It was a cheap 10/100 data repeater under my desk humming like crazy! Not sure if it was the power supply, the repeater itself, or the cat5 cables. It was REALLY putting out the noise. But power cycling things around the house was really helpful for sure.

Re: Spikes on HF frequency

Posted: Wed Aug 28, 2019 10:16 pm
by Username
Hi
Sry I am tiered what kind of SDR did you use?
Looking for the USB Hub I use the is good and I have quite no noise with.
I also use from Delock there "Premium" USB 3.0 Cable who are shield to.
Dont use there USB Isolator the use a Plastic Case and you need to desolder some stuff to keep the noise out.