Homebrew vlf receiver how to#
Homebrew vlf receiver series#

Basic electromagnetic theory is developed here as it relates to electrically small multi-turn loops at low frequencies. The loop sensitivity decreases as frequency decreases, becoming a formidable problem below 1 Hz. Applications such as geophysical research, oil exploration and survivable communications require maximum sensitivity of receiving loop antennas. Multi turn wire loops are often used as low frequency receiving antennas.

Sensitivity of Multi Turn Receiving Loops (by N4YWK).

Homebrew vlf receiver how to#

This article gives some ideas on how to use a simple unbalanced loop with a home-brew transformer to achieve most of the benefits of a shielded, balanced loop. Shielding adds distributed capacitance to the loop and reduces the Q, which in turn reduces the loop's sensitivity. You might find a quiet location in the 'back 40', put your loop out there, and then re-introduce the noise from the house when you connect the coax. An unbalanced, unshielded loop can also pick up conducted interference from the feed line.

The directional pattern becomes asymmetrical and the nulls off the side may be only a few dB down from the peak of the radiation pattern. Unfortunately a loop doesn't offer a good impedance match to a coaxial transmission line or to the input of most modern receivers.ДЄlso, unless the loop is balanced and shielded, the so-called antenna effect makes the loop act like a combination of a loop and a short vertical whip. They're compact, don't need to be high and in the clear, and their directional characteristics can be used to null out local noise or strong interfering signals. Loop antennas offer many advantages for LowFER reception.

Experiments on remote receiving loops (by K0LR).

Homebrew vlf receiver series#

A loading coil with a series of taps can be used, but a constantly adjustable inductor like a variometer will make tuning a lot easier. An antenna that's much shorter than a quarter wavelength will have a high Q and consequently a narrow bandwidth. In an environement with a lot of 'vertical objects' (trees etc.) close to the antenna inductive toploading can significantly increase the performance of a short vertical antenna. Vertical antenna with inductive toploading (by ON7YD).The polarisation of a 'standing' loop is vertical. These nulls are almost independent to the mounting height of this antenna. 'Magnetic' means that it is only sensible to the magnetic field vector and provides two sharp nulls at the broad sides, rectangular to the plane of the loop. One possible answer is to build a magnetic receiving loop. So I decided to erect an antenna which is able to cancel out this unwanted source. Here in North Germany all faint amateur signals on 137 kHz are covered by a curtain of LORAN-C sidebands from the island of SYLT (120 km NW from this site). 137 kHz ham band) is the presence of local noise sources. One major problem receiving long waves (e.g.