VK3FI QRSS on 473kHz – 19/06/2014

Some four months ago I sent VK3FI in Mildura a QRSS keyer to try on his 600m beacon. The keyer hardware and message content are described at Simple Morse beacon keyer for VK3FI on 600m.

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Above is a capture with Spectran received at my location in Bowral tonight 760km east of VK3FI, QRSS3 on 473.000kHz (well perhaps 2Hz higher, Dial freq 472.2kHz USB for the above display). Continue reading VK3FI QRSS on 473kHz – 19/06/2014

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

Equivalent circuit of small transmitting loop with auxiliary loop feed

A common method of feeding a small transmitting loop is to use a small auxiliary input loop. This is sometimes referred to as the “Faraday feed”, implying a shielded feed loop though many so-called shielded loops are not effective (Duffy 2007), but the loop does not need to be shielded nor does there need to be a metallic connection to the main loop.

This article looks at an equivalent circuit. Continue reading Equivalent circuit of small transmitting loop with auxiliary loop feed