LP-100A manual advice on VSWR measurement

At Where is the best place to measure feed point VSWR I discussed location of the VSWR meter and projection of its reading to another point on a known transmission line.

A correspondent has taken me to task and citing Telepost’s LP-100A manual: Continue reading LP-100A manual advice on VSWR measurement

Diamond X50N measurements – AIMuhf and AA-600

At Diamond X-50N #2 at VK2OMD I reported some details of a new antenna at VK2OMD, including some baseline measurements using a Rigexpert AA-600.

This article expands that information with some measurements made using AIMuhf, and gives some contrasts between the two tools.

The AA-600 measurements were made 26/11/2014, and AIMuhf a couple of months later on 29/01/2015. The system measured should have been identical, the feed line is 9.83m of LDF4-50A with N-type connectors at both ends. Continue reading Diamond X50N measurements – AIMuhf and AA-600

AIM 882 produces internally inconsistent results

 

AIMuhfI have had cause to validate the output produced by an AIMuhf measurement using AIM882 (current version, released about three months ago).

The test scenario is a pair of nominal 50+j0Ω loads on a Tee piece, connected to the AIMuhf by about 1m of RG58 coax and swept from 10 to 50MHz.

Screenshot - 16_01_2015 , 15_40_27

It is mental arithmetic that the VSWR should be very close to 2:1, and since the loss of the cable is quite low, VSWR should be almost uniform with frequency. Continue reading AIM 882 produces internally inconsistent results

Inexpensive utility rechargeable 9V battery pack for test instruments

There is often a need for a 9V battery for portable test equipment (NNA, Noise Bridge, Low R meter, Power Meter etc). A solution is a 8 cell NiMH pack.

BatteryPack9VAbove, a battery pack made from two Hobbyking 4 low self discharge AA cells. The packs come with JR servo connectors, and the pins are rewired to use the -ve from one pack and +ve from the other pack to one of the JR connectors. The other wires are connected via a 3A Polyswitch for s/c protection. A short JR to 2.1mm DC connector is made from a JR extension cable and 2.1mm connector. Continue reading Inexpensive utility rechargeable 9V battery pack for test instruments

Near-field field strength measurements using a diode detector

My recent article Near-field field strength measurements using the RFPM1 described a technique using VK3AQZ’s RF Power Meter which is based on the AD8307 log detector.

There are many ways to measure low level RF power or voltage, and this article describes methods that I have used using a simple diode detector attached to the HF loop, and measuring the DC output voltage using a small digital panel meter with 9V battery for a self contained measurement system with little risk of significant common mode current. Such a system can be hauled to some height and read remotely with a telescope.
Continue reading Near-field field strength measurements using a diode detector

Near-field field strength measurements using the RFPM1

Review of Boswell et al paper “Performance of a small loop antenna in the 3-10 MHz band” discussed measurement of near-field field strength for measurement of performance of a small transmitting loop (STL).

This article describes a method of performing near-field field strength measurements using a portable RF power meter (RFPM1) and a small untuned square loop. Continue reading Near-field field strength measurements using the RFPM1