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The kits described in this section use the theory of antennas as surface wave transmission line (SWTL) devices together with  symmetry to create designs capable of high common mode rejection ratio (CMRR), low distortion and low noise in order to build receive-only antenna systems and measurement equipment. SWTL theory is markedly different from what has previously been  commonly used for antennas and transmission lines. It has fundamental implications which are not commonly recognized.

Although  classic short-dipole theory is used in places to model these antennas, the SWTL model does not agree with the idea of current at the ends of a dipole falling identically to zero. Rather the actual seat of radiation resistance appears to be in a volume of space beyond the dipole tips. For transmission lines, the common Maxwell/Heaviside TEM model is shown to be inconsistent with other more fundamental theory and does not give the same insight as SWTL theory. Please see the citations for more detail.

These designs are intended to produce practical receiving systems which can best deliver the signal-to-noise-ratio (SNR) available from incoming propagating waves, those originating from distant transmitters and sources,  to become dominant in a receive system's detector at typical amateur radio locations. These designs are particularly focused on the spectrum from the audio frequency (AF) through the high frequency (HF) ranges.

This section describes several broadband receiving antenna systems which use active preamplifiers.  They have in common that each includes a symmetrical interface for use with a symmetrical (balanced) antenna system.  These are all non-resonant systems intended for broadband operation having medium to high impedance feedpoint connections. Most are probe antennas rather than matched structures such as are  used for transmitting.  Though the preamplifiers involved may also be usable with low impedance and matched structures  this is not a design goal.  Better solutions likely exist. These systems also have in common that there is no feedline between the attachment point of the two monopole conductors and the preamplifier. Thus there is no possibility of unwanted noise ingress or imbalance deficiency as there is for many other types of receive antennas.

A common goal of these systems is to obtain very high CMRR so that unwanted local noise and signal ingress does not degrade the incoming SNR.  The best of these designs can provide more than 40 dB better balance, greatly more than conventional passive methods such as ferrite baluns.  This extra common mode immunity is proving essential to creating low receiving  system noise floor & temperature  which can be necessary in some environments.

A Field Probe is included in this section. While not intended to be a long term antenna solution it can be a useful tool for identifying the best available location for one of the antenna systems: this will be a location that optimizes SNR for ionospherically propagated signals while minimizing coupling to unwanted  local noise sources.

Deployment of any of these receiving systems should be considered an ongoing project, not as a simple, one-time solution.  The  designs only make the goal of low receive system noise floor and maximum SNR more possible- they  don't guarantee it. Without proper deployment any of these can be a miserable failure.

Some of the preamplifiers include frequency shaping or filtering to better match the reality of over-air broadcasts worldwide and the limited dynamic range of modern software defined radio (SDR) equipment.

To understand these several receive antenna designs  it may be helpful to consider that antenna systems may not behave as is commonly believed and that  the SWTL theory being applied may not be what is commonly accepted.
If these assertions are surprising  and assembling  one of these antenna system kits is being considered, please read all the background FIRST. This includes but is not limited to

A New Antenna Model

Notes on Improving Station Noise Performance

Introduction to the Propagating Wave on a Single Conductor

Another Look At Transmission Lines (draft article for Radcomm+)   and Accompanying Figures .


Some Thoughts on HOA Antennas

Loop over Earth Antenna

On the Response of an Active Dipole, Winter 22 RadCom+ (RSGB membership required)

Active Antenna Projects DL4ZAO

Whip_Tipps DL4ZAO (Google Translation)

The ultimate goal of the systems shown here is to come as close as reasonably possible to delivering the SNR available from an incident wave to a receiver's detector.  For practical reasons this is never perfectly achieved due to the limitations of  real components. This should be thought of as an ongoing process that is unique to each location.

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