Most cheap USB radio sticks start around 24 MHz, which leaves out AM radio, the shortwave bands and the amateur-radio HF bands. The RTL-SDR Blog V4 adds them with a built-in upconverter, for about the price of the older sticks. This guide explains what that gets you, what you will and won't see, and how to sweep it in Consentiva.
How the V4 reaches HF
The tuner chip in these sticks can't tune below about 24 MHz. The V4 adds a small mixer in front of it: a signal at 7 MHz is shifted up by 28.8 MHz to 35.8 MHz, where the tuner can receive it. You don't have to do anything. Tune to 7 MHz and the stick handles the shift and switches its inputs for you, through the same antenna jack. It also has notch filters for broadcast AM, FM and DAB signals that the app switches automatically while you sweep.
What lives between 1 and 30 MHz
- AM broadcast, about 0.5 to 1.7 MHz (the bottom of the range is below Consentiva's 1 MHz lowest channel, so you see the upper part).
- Shortwave broadcasters, in bands between about 2.3 and 26 MHz.
- Amateur radio, including the 40 m band (7 to 7.3 MHz), 20 m (14 to 14.35 MHz) and 10 m (28 to 29.7 MHz).
- Time signals: the US station WWV transmits on 2.5, 5, 10, 15 and 20 MHz, a handy known signal to check that HF is working.
- Man-made noise: broad humps and combs of interference from electronics near the antenna.
The antenna matters more than the receiver
At HF the wavelength is tens of metres, and a telescopic whip is a poor match. Indoors you will mostly see noise. For better results use a long wire (5 to 20 m) outdoors, as far from electronics as you can, or a purpose-made HF antenna. Keep the same antenna for every walk so readings compare, and record it in Consentiva's Antenna setting.
Sweeping HF in Consentiva
- Plug the V4 into an Android phone with Chrome (or a laptop with Chrome or Edge).
- Open the app, choose RTL-SDR Blog V4 under Receiver and the HF / shortwave 1-30 MHz range.
- Start the walk. Known signals such as WWV should appear as steady peaks, strongest in the evening on the higher bands.
HF levels change with the time of day and the season because signals bounce off the ionosphere, so Consentiva's baseline for HF is for that hour, not a fixed number.
Be realistic
V4 support in Consentiva is a beta: it was written from the RTL-SDR Blog's own driver and tested against a simulated stick, not yet on a real V4. The 8-bit converter limits the dynamic range, so a strong nearby station can overload it. Lower the gain if every channel looks lit up. A walking survey at HF shows what is present, not who is transmitting; many signals here are legitimate broadcasters and hobbyists. See what to buy and RF meter vs spectrum analyzer.
Common questions
Does the RTL-SDR Blog V4 need an extra converter for shortwave?
No. Below 28.8 MHz the V4 uses a built-in upconverter that shifts the signal up before the tuner sees it, so AM and shortwave work through the same antenna jack. Older RTL-SDR sticks start at about 24 MHz.
Which Consentiva setting sweeps HF?
Choose RTL-SDR Blog V4 under Receiver and the HF / shortwave 1-30 MHz range. A plain RTL-SDR stick can't be used for that range, and the app will say so.
Is V4 support verified on a real stick?
Not yet. It is a beta, written from the RTL-SDR Blog's own driver and tested against a simulated stick. If a band looks wrong, send a report from the walk.
Why is HF so noisy in a city?
Switching power supplies, LED lighting, chargers and Wi-Fi gear all make interference at HF, and a short antenna indoors picks it up. A longer wire antenna outdoors, away from electronics, helps most.