Synthetic fibre rope for antenna rigging

Fibre rope has applications in antenna rigging, typically for halyards and tails to support the ends of wire antennas such as dipoles. The use of fibre rope for guying applications has issues due to shrinkage when wet.

Much is made of the ‘best’ fibre rope for these applications, and the almost universal answer is black Dacron (Polyester) in small sizes from 2.5mmm to 6mm diameter. The smaller sizes are usually a braided construction, commonly known as venetian cord. Claims are that the Polyester rope is strong, UV proof and rot proof. Whilst Polyester rope is resistant to mild acids and alkalis, it is damaged by strong alkalis (such as might develop when an alkaline solution dries on the rope). Continue reading Synthetic fibre rope for antenna rigging

Effect of ground on HF horizontal dipole efficiency

New hams are often advised quite poorly, justified by the mantra that “any antenna is better than no antenna at all”. The more confident the advisor, the more jargon, the more unsupported, the more the advice is soaked up by eager newbies. Not just soaked up, but learned so the newbie can talk like the pro… even if they also do not understand the subject matter. Spruiking BS has always been a feature of ham radio.

Recent online discussion illustrated and recommended a 40m dipole strung on a timer fence at a height of about 1.5m to a new ham with a 10W power limit in search of good solutions from ‘experts’. Continue reading Effect of ground on HF horizontal dipole efficiency

Spoiling balun action with ‘shielded twin’

In a QST column in 2008, a correspondent asked the question

… I have the ladder line terminated to double coaxes that run about 12′ (4m) inside the house to an antenna tuner. Should this pair of coaxes be grounded at one end or both ends?


The Doctor gave a detailed diagram (above) and his advice was… Continue reading Spoiling balun action with ‘shielded twin’

Analysers – help or hindrance

A ham posted online:

I spent several happy hours this weekend building the DE of the 6M Quad described in the June 2014 QST, p 30. When I got it completed, I put the antenna analyzer on it, expecting to find a nice resonance in the 50-51Mhz region and an impedance of 120 ohms or thereabouts. To my surprise, the radiation resistance in the couple of dozen ohm range, and resonance, if that is what I can call it, depends on how am I holding the loop.

After a bit of QST bashing in the thread, he later reveals:

The trial with the analyzer was about 2′ of RG-8X with PL-259s on each end, to BNC jacks on both antenna and analyzer with adaptors.


Much as the chap expressed his lack of confidence in modelling tools, NEC reveals what is happening. Continue reading Analysers – help or hindrance