Month: June 2017

Kenwood R-5000 thermals

I have a Kenwood R-5000 that is now 30+years old and warrants a check of its health.

R-5000s are infamous for VCO problems, the early production used ‘yella glue’ to stabilise the VCO components and that decomposed into corrosive components that damage the electronic parts. Repair is not usually economically rational.

This is one of the later model R-5000s that used the hard white adhesive which has remained stable.

The R-5000 is built on phenolic PCB and operates at relatively high temperature for a simple receiver, reflecting the power consumption of synthesisers of the 1980s.

 

Above, the case temperature is up to 20° above ambient over the power transformer (upper right of pic).  Continue reading Kenwood R-5000 thermals

Last update: 11th April, 2022, 7:22 AM

Estimating the voltage impressed on the tuning capacitor of a small transmitting loop

The ‘net abounds with calculators for design of small transmitting loops (STL), and most estimate the voltage impressed on the tuning capacitor. Most of these calculators give an incorrect estimate.

This article describes a measurement based approach to estimating the capacitor voltage for a STL.
Continue reading Estimating the voltage impressed on the tuning capacitor of a small transmitting loop

Last update: 6th June, 2017, 11:50 AM

A QRP small transmitting loop evaluation

The ‘net abounds with articles describing easy to build low cost small transmitting loops (STL).

This article describes measurement of a STL for 4MHz using RG213 coaxial cable for the main loop and its tuning capacitance, and a smaller plain wire loop for transformation to 50Ω. Continue reading A QRP small transmitting loop evaluation

Last update: 6th June, 2017, 10:27 AM

Precise RF small transmitting loop

Precise RF have announced two small transmitting loops for amateur radio, this article looks at the Precise High Gain Loop.

Description

The antenna is described at (Precise RF 2017).

Above is an extract from a table in the brochure comparing the subject antenna to some others.

On a quick scan, the standout figure is gain of 2.8dBd presumably at a loop height of 4.57m (15′), and without qualification of frequency. Elsewhere in the brochure there is a note that 80m requires an optional ‘resonator’… presumably a larger loop.

Lets review the meaning of dBd

The ITU Radio Regulations (ITU 2012) gives us a definition for antenna gain that captures the meaning of dBd that is accepted by most regulators and industry world wide.  Continue reading Precise RF small transmitting loop

Last update: 5th June, 2017, 8:26 AM