I tried an antenna that you may be interested in, it tunes up very well with my rig using an antenna tuner,it does not need radials like a 1/4 wave vertical antenna does

40 meter short coil loaded dipole antenna. The goal will be to keep the total length under 40 feet

Coil, 78 turn of insulated copper wire no spaced, awg #18 - equivalent to 1mm diameter or 0,8 mmq, wound on plastic support 50mm diameter,coil drawing

I decided that for this winter, the vertical would become a dedicated 80m antenna

I use the following dimensions, 40m Trap 63/16 - 80m Trap 140/42 millimeters before/after heat treatment

Having made lots of dipoles, but never a trapped antenna, i started by doing some reading on the subject Coax traps wound on thin plastic formers would be cheap and lightweight

For this model the details as given by the arrl antenna handbook, with a 75-ohm twin-lead feeder the swr with this antenna is under 2 to 1

Never has there been a more true, tried and tested design for 40/80m than the w3dzz

A coaxial-cable trap dipole antenna installed in the attic provides a surprisingly effective solution to HF operation on the 10, 15, 20, 30, 40, and 80 meter

What are the advantages of an air core coil? its inductance is unaffected by the current it carries

I opened the traps and found the two driven element traps broken and the 10m coils blackene

The following is a design tool which calculates the inductance of an air core inductor

Utilizzo cavo coassiale del tipo RG8U su cui ho fatto esperienza nella costruzione di numerose trappole

The advantages of a vertical are that they take up little space and that the beam angle is very low

Many hams who want to work the low bands need an effective antenna thatfits on a small lot

the solution build an antenna for 40 and 80 the roof on the building is not that big that i could install a full size dipole or inverted v

dissatisfied with my choice of capacitors, they were too small for more than about a hundred watts, and the ganged capacitor was in pretty sad shap

This page describes the design and construction materials i used to build a coaxial cable trap

The article is an analysis of an antenna trap where a coil is formed of a length of coax cable

The loading coil inductor that I built for my center-loaded 160 meter 1.83 MHz vertical antenna

Multiband Antenna DesignParallel-resonant circuits calledtraps are widely used to isolate partsof multiband antennas to make the antenna resonant on different frequencie

Coax traps are cheap, easy to assemble in a reproducible manner, very rugged, perfect for portable or permanent operation, on dipoles, inverted-V's etc

The Coax trap program computes design parameters for the construction of coaxial traps for HF usage

Circuit network that can perform either of two functions in an antenna system, depending on whether the traps are resonant at the operating frequency

The coil design is one of the most difficult and important parts of the coilgun

This calculator computes the inductance of a wire coil

I have owned an at-auto since they were first released and its given good service. one area that it let me down was 10m

Con questo articolo vorrei descrivere la sequenza delle operazioni che solitamente svolgo quando costruisco le trappole per le bande HF

Studiare un sistema accoppiato d'antenne mi sono imbattuto nell'arcinoto modo di tagliare un coassiale esattamente lambda/4

Here applies to a A4s triband antenna, but the reasoning can be made for any multi-band yagi or verticaL

High-Q coil inductors have something in common: the length of the coil can only be slightly longer than its diameter. In other words, high-Q coils have cube-like dimensions

Air-dielectric inductors can be made quite easily at home

The inductance and self capacitance of a helical coil can be determined by entering its dimensions in the boxes above. The length of wire used is also calculated

This calculator requires the use of Javascript enabled and capable browsers. The purpose of the calculator is to determine the capacitance value of the jar capacitor needed for the circuit's coil

Una trappola per gli 80mt con del filo di 2 mm avvolgendo 40 spire su un diam. di 50 mm e spaziate 3 mm interponendo un condensatore da 100Pf 10 kv

For tuning of the traps for this project with MFJ antenna analyzer is util a though

L'operazione di sintonizzazione avviene scostando tra loro, leggermente, le spire dell'induttore

Questo circuito permetterà di fare oscillare qualsiasi bobina, da un minimo di 10000 Hz fino ad un massimo di 400 MH

Wire dipole antenna that works on 40 30 and 17 meters band

A tuneable power adjustable transmitter and either an swr meter and a decent 50 ohm resistor

Coaxial cable antenna traps for a multi-band trap antenna

This is an easy to build coil with variometer

This single-layer coil inductance calculator uses the Lundin's formula [5] for which the maximum relative error is stated to be less than 3 ppm

The following is a design tool which calculates the inductance of an air core inductor

Enter desired frequency MHz, Results inductance L (uH) Capacitance C (pF)

Calculator the inductance of a single layer, air core coil in microHenries