![]() ![]() So, these antennas can work reasonably well, especially on frequencies where full sized antennas are impractical such as VLF. ![]() A short antenna picks up less of the desired signal, but also picks up less of the surrounding noise. As long as the noise generated by the preamplifier is low, it doesn’t actually matter how efficient the antenna is. But receive antennas aren’t concerned with efficiency: you really just want to preserve the signal to noise ratio of the incoming signal. ![]() In this context, short antennas have a very low radiation resistance, so other losses tend to dominate, and you lose a lot of power as heat. A transmitting antenna is designed for efficiency: to send as much of the input power out as radio energy as possible. This article points out something which may not be entirely obvious until one thinks about it: antennas designed for transmission and reception have different goals. PA0RDT has developed a simple active antenna which has intrigued me. Because of a lack of suitable trees on my property, this means that I’ve had fairly compromised setups: I’ve gotten the most use from a simple 40m dipole which probably only averages about six meters in height.īut at least for receive there might be an interesting alternative. This means that I have to be fairly careful to use largely invisible or stealth antenna setups. Like many people, I live in a development with a fairly restrictive HOA. ![]()
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