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An Introduction to 4m - Part 2

An Introduction to 4m - Part 2 of 2

Antennas

For FM contacts use a vertical antenna. A simple ground plane works well, and mobile whips are available from many distributors in the UK. End-fed half-wave antennas, mostly the J-pole or variants, are favoured by many operators.
There are a number of homebrew designs around on the internet, The Four Metres Website has several. The principal two commercial antennas in use for base stations are probably the Sandpiper 5/8 wave “Ringbase” and the Sirio CX4 J-pole.

For SSB/CW a horizontal antenna is a must. A dipole will bring local contacts and the usual range of VHF antennas has been designed for 4m. The simplest include the halo, Moxon rectangle and the mini-beam made by Alton Antenna Arrays.

  • G0KSC has a website for those interested in Yagi antennas and contains a selection of designs to build, together with a shop to buy parts.
  • InnovAntennas is his commercial venture and sells ready-made antennas.

Other manufacturers and distributors of antennas include Nevada, Vine Antennas and Moonraker.

Equipment

The Four Metres Website has several articles on 4m equipment.

For FM-only working:

Converted PMR radios will provide 20 – 50 watts but may not be rated for continuous use and a small fan is a wise addition. The Philips FM1000 series is very popular, and Simoco, Tait and others are available.
Commercial offerings are mainly from China: Anytone 5189, Wouxun KG-UV950PL multiband mobile, KG-UV6DL and KG-699E handies. The handies will benefit from an improved whip antenna compared to that supplied.

For SSB/CW working:

Current transverters from 28MHz are available from Spectrum communications and OZ2M. Others have been advertised on Ebay but success with these has been variable.
Older units such as Microwave Modules, G3WPO and Practical Wireless designs from 1980s/90s are sometimes available second-hand.
FPARC member G3WIE has recently completed and proved a new open-source transverter design.

Multimode working:

The ICOM 7100 is the first multiband multimode rig to support 4m by design, and has good reviews. It is reported to require 20A at 12v to produce 50W.
Elecraft have announced (2014) transverters that fully integrate with their K3 and KX3 transceivers.
The Yaesu FT847 can be modified for 4m operation but performance has been open to question.

Amplifiers:

Philips A200 amplifiers are available on the surplus market and the E0 variant works well on 4m providing 70W or so on FM. It can be modified for linear operation.
TE Systems (USA) manufacture linear amplifiers suitable for 4m.
dutchrfshop.nl and hf-electronics.nl have linear amplifiers ready-built/ kits and a range of useful components for homebrewers.
There are a number of designs for homebrewing. The Four Metres Website has details.

Ancillary equipment:

A SWR meter is important for checking that your antenna is functioning correctly and for monitoring your transmitter output power. Many HF SWR meters, even older ones from rallies, will work successfully on 4m though their power calibration should be checked if you wish to rely on it.

A dummy load is useful for testing. These can be made with a low-inductance power resistor on a heatsink. Suitable resistors are available from dutchrfshop.nl (eg a 250W RF-specified resistor) and component distributors such as Farnell (eg the Bourns PWR220T-35-50R0J resistor is rated at 35W).

Page content by Chris G3WIE and Ted G3XUX gratefully acknowledged.

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