This article documents my build of Lou Destefano’s (VK3AQZ) RF Power Meter kit.
The power meter is based on probes using an AD8307 logarithmic detector.
Above, the RF Power meter with two probes. (The ferrite sleeves were not part of the kit.) Continue reading VK3AQZ RF power meter (RFPM1)
The subject question is often asked, and the usual responses are mindless recitals of Rules of Thumb (RoT).
In the light of the discussion at Feed line length affect on VSWR and The half waves of coax rule for measuring VSWR accurately, lets consider the subject question and develop a rational answer. Continue reading Where is the best place to measure feed point VSWR
VK2XSO posted a sweep of “Return Loss (SWR) (the lower plot) from 500 to 2500MHz of a 50Ω load through ~5m of RG59” apparently to demonstrate his knowledge of transmission line basics. As he says “here are also many other things we can deduce from looking at these two lines.”
For students of transmission lines, some deductions… Continue reading Exploring VK2XSO’s transmission line example
Many years ago I bought a Tigertronics Signalink USB, principally for measurements using FSM and NFM.
A nuisance with the device is the lack of a simple means of disabling PTT. This is particularly important if the system is being used for noise figure measurement with an expensive calibrated noise source which will not withstand transmitter output.
This note describes the fitting of a front panel PTT disable switch. Continue reading Signalink USB PTT disable
Many years ago I bought a Tigertronics Signalink USB, principally for measurements using FSM and NFM.
The Signalink USB turned out to be a disappointment for several reasons but the main one was that the noise floor was almost 20dB higher than an ordinary $10 Creative desktop sound card. Continue reading Signalink USB noise floor improvement
Hams often speak of inline RF wattmeters as being ‘averaging’, but are they? Continue reading Are inline RF wattmeters really averaging
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
NFM has been updated to v1.18.0.
It includes for user convenience, a noise measurement uncertainty calculator based on the discussion of uncertainty of the noise sampling process at (Duffy 2007b) and the calculator at (Duffy 2007c)
Much is written about the virtues of some types of coax connectors over others.
Continue reading Coax connectors and accurate / repeatable measurements
A common method of making Noise Figure measurements of a receiver is to use a noise generator of known noise power. The output power of the DUT is measured with the generator off (NoiseLo) and on (NoiseHi), a Y factor calculated, and from that Noise Figure is calculated.
Continue reading Using an attenuator for NoiseLo/NoiseHi in NFM
