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?

ShieldedTwin

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.

Analysis

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