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5

See SigiWiki: This wiki is intended to help identify radio signals through example sounds and waterfall images. Most signals are received and recorded using a software defined radio such as the RTL-SDR, Airspy, SDRPlay, HackRF, BladeRF, Funcube Dongle, USRP or others. https://www.sigidwiki.com/


4

The gain becomes an issue only if its ridiculously low. The main purpose of an LNA is to lift the signal well above any noise of the following stages, and often that can be done with a gain of several dB. However, the fact that they didn't advertise it, makes it suspect.


3

Here's one from the designer of fldigi. http://www.w1hkj.com/modes/index.htm


3

If I were to design an amplifier, I would always design an amplifier with low noise anyway. Nope! For a power amplifier, you'd do a different tradeoff; the noise figure of that amplifier nearly doesn't matter at all, whereas the capability to produce a high output power does very much. Same goes for other aspects of amplifiers, things like linearity/...


2

20-25 meters of RG-6 coaxial cable has significant loss at 739 MHz. RG-11 coax has significantly lower loss than RG-6. Unless there is an issue with your LNA, I expect that replacing the RG-6 with RG-11 will give you the signal boost that you are looking for. What you could do in lieu of replacing the coax is add a low-noise preamp right at the dish, to ...


2

These specifications mean: VHF yagi antenna This tells you the general kind of antenna it is: a Yagi intended to operate at VHF: "very high frequency". 12dBic gain This means that in the antenna's direction of maximum gain, it will receive 12dB more power than a theoretical circularly polarized antenna which receives power equally from all directions....


2

It's hard to say whether your active antenna would work properly if provided with 3.3 VDC instead of 5 VDC. I doubt that any damage would be done, but I'm not the engineer that designed the antenna. You might consider adding a boost regulator (and the other parts it requires) to your circuit, which could convert 3.3 VDC to 5 VDC. Here's such a part, ...


1

Phil's answer is sound from a technical perspective since there is not sufficient data to fully answer the question. From a more pragmatic perspective, if you wish to increase the 12 dB SINAD sensitivity of your receiving system, you should: Minimize feedline losses Increase the gain of your antenna Your required 5 dB improvement in sensitivity is usually ...


1

300 kHz channel at 436 MHz sounds a lot like your spectrum analyzer might be seeing that are at twice the frequency – 872 MHz would be a typical 2G cellular network frequency, and 300 kHz might be around the bandwidth of a 2G channel. Try and tune to your SA to 872 MHz.


1

If the antennas are cheap and easy to build, why not build two and use one for TX and one for RX, then use a common RF sense antenna switch such as MFJ-1707 to switch between the two. This allows you to have one coax to your transceiver and two antennas. Control lines for switching are also accommodated in many of these types of antenna switches. Typical ...


1

Whether you can use an omnidirectional antenna to replace a directional antenna depends entirely on the minimum signal-to-noise ratio required by the receiver, and the amount of noise arriving from directions other than the wanted signal. Without this information, your question does not have a yes-or-no answer. And if you are going to go to the effort of ...


1

Is there any way to independently test the two parts of the circuit -- the antenna and the amplifier? Perhaps use a 1 megaohm through-hole resistor to directly connect your RF source to the big "antenna feed" pad, completely bypassing the antenna, to test the amplifier section? It appears to me that the version 1.1 circuit board has a ground pour covering ...


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