Amateur Radio

SWR Meter - Easymatch

The 'Easymatch' has a length of solid copper wire as its transmission line. The diode leads,

Easymatch

running parallel to the transmission line, double as sensing lines.

A salvaged 100µA meter is used as the indicator, along with a 47KΩ potentiometer for sensitivity adjustment.

Easymatch Schematic

There is no indication till a load is connected.

Related post: SWR Meter - Pencil Box
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SWR Meter - Pencil Box

This SWR Meter is housed in a pencil box. The transmission line is a length of TV hardline. Sensing

Pencil Box

lines are hook-up wires, run close to the centre conductor through longitudinal holes made in the foam dielectric.

Pencil Box Schematic

A tuning indicator (salvaged from an old Philips transistor radio) is used as the indicator, along with a 47KΩ potentiometer for sensitivity adjustment.

Related post: SWR Meter - Minimatch
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SWR Meter - Minimatch

The 'Minimatch' differs from the 'Monimatch' with respect to its transmission line (RG-58/U
used instead of stripline-on-PCB).

Minimatch

Two lengths of hook-up wire, running in parallel inside the braid, are the sensing lines.

Minimatch Schematic

SWR Meter - Monimatch

This SWR Meter is identical to the 'Monimatch', published in ARRL's 'Understanding
Amateur Radio'.

Monimatch

It was not difficult to follow the 'stripline-on-PCB' design.

Monimatch Schematic

A 100µA meter reads 'forward' or 'reverse', based on the toggle switch position.

A 47KΩ potentiometer is used for sensitivity adjustment.

Related post: SWR Meter - Easymatch
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Low-cost ½ λ Dipole for HF QRP rigs

Here’s an economical dipole for simple QRP HF homebrew rigs. It’s a one-piece radiator/feeder arrangement made of surplus insulated telephone drop wire with twin copper-clad steel cores.

Low Cost ½ λ Dipole

The cores are separated to get the λ/2 radiating length and then tied together with string to arrest further separation.

Telephone Drop Wire

The string could be done away with, and the λ/2 length yet maintained, using the reliable 'Underwriters Knot'.

Underwriter's Knot

The end insulators are scrap bakelite pieces, drilled to take the wire and string. Banana plugs are used at the rig-end.

Works real good when strung high up between two trees or other supports.
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Improved 7 MHz QRP CW Rig

This QRP CW transmitter's output is of the order of 5W.

Improved 7 MHz QRP CW Rig

Fairly comfortable QSOs are possible with the higher power level. The driver and the final transistors require heat sinks. The aluminium enclosure serves as the heat sink for the final.