Category: Antennas

Design / build project: Guanella 1:1 ‘tuner balun’ for HF – #1

This is a project to design and build a Guanella 1:1 (current) balun for use on HF with wire antennas and an ATU.

First part in the series…

 

For use with a tuner, the most important design criteria are:

  • high voltage withstand;
  • high common mode impedance;
  • generous power handling given our 400W PEP limit, possibly 1kW in the future.

Continue reading Design / build project: Guanella 1:1 ‘tuner balun’ for HF – #1

Last update: 13th February, 2017, 4:38 AM

WIA 4:1 current balun – further explanation

4-101a

I mentioned in my article WIA 4:1 current balun that the use of a single toroidal core in the above graphic compromises the balun. This article gives a simple, but more detailed explanation for the technically minded of why the shared magnetic circuit ruins the thing.

Continue reading WIA 4:1 current balun – further explanation

Last update: 30th March, 2020, 8:23 AM

Do SWR meters make you stupid

Eric Nichols, KL7AJ, published a manifesto entitled “SWR Meters Make You Stupid” announced on eHam in March 2010. Eric is clearly a disciple of Walt Maxwell (W2DU SK), his first announcement states By popular demand, my complete treatise on transmission lines. Approved by Walt Maxwell, W2DU as if Walt’s blessing was an imprimatur from the ham radio church.

Continue reading Do SWR meters make you stupid

Last update: 23rd February, 2014, 10:10 AM

Cobwebb antenna impedance matching scheme

From time to time, correspondents have asked how the Cobwebb antenna works, and particularly how the impedance matching scheme works.

Firstly, what is the Cobwebb?

It is an innovative antenna for small spaces, quite compact and as I recall originally intended to cover five amateur bands from 20-10m.

Continue reading Cobwebb antenna impedance matching scheme

Last update: 16th February, 2014, 7:53 PM

Common mode current and coaxial feed lines

An antenna feed line is intended to convey energy from the transmitter to the antenna, and usually without giving rise to radiation itself.

The term “common mode” comes from consideration of the currents on an open two wire line, and it refers to the net  or unbalance current, ie the current that would give rise to external fields, to radiation.

This article looks at the equivalent common mode current in a coaxial transmission line.

Continue reading Common mode current and coaxial feed lines

Last update: 21st December, 2014, 7:45 PM

RG174 for portable HF operation

There are frequent recommendations of RG174 for portable stations (eg SOTA), usually running QRP, principally because it is light and easy to wind up into a small package to fit into a pack. RG174 commonly uses silver coated steel (SCS) centre conductor, sometimes copper clad steel (CCS), sometimes copper.

Continue reading RG174 for portable HF operation

Last update: 4th October, 2020, 4:19 PM

Wire dipole on 160m

Discussion with a correspondent recently ranged onto the effect of some conductor materials in antennas. This posting reports the feed point impedance and internal efficiency (meaning power not turned into heat in the structure divided by power input at the feed point) of a 160m half wave dipole (80m long, centre fed, 20m above average ground and using 2.6mm diameter single core wire).

Continue reading Wire dipole on 160m

Last update: 8th November, 2015, 3:55 PM