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
A correspondent has been tearing his hair out trying to replicate my VSWR plots of some STL.
Above is an example where the Z0 has been set to 0.0901847Ω which is the feedpoint impedance of the loop at resonance. Continue reading 4NEC2 plots of STL VSWR
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
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
Precise RF have announced two small transmitting loops for amateur radio, this article looks at the Precise High Gain Loop.
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