Meters and testers

On this page I would like to present meters and testers.

Frequency Counter
 
If you have actually no space on the front of your self-construction transceivers for a frequency display, the Small Wonder Labs Freq-Mite by Dave Benson, K1SWL, is the correct for you. On the front only the space for a tracer is required. The output of the frequency takes place thereby as CW word with three or four digits, whereby the signal is supplied easily to the AF signal. Due to its size of (3.2 × 4.5 cm) and the adjustable frequency offset each self-construction equipment thereby can actually be re-tooled. The maximal computable frequency is 32.767 MHz. These frequency counters be based on a PIC circuit. The counter was available by Dave Benson, K1SWL, Small Wonder Labs, which already closed.

For all those, which do not get along without a "correct" frequency display, I can recommend the Almost All Digital Electronics (AADE) DFD1. Unfortunately, this manufacturer is out of business. It's based on a PIC circuit and a LC display. The maximal measurable frequency amounts to 40 MHz, whereby the adjustable frequency offset is adjustable in steps of 500 kHz to 16 MHz. Additionally still some symbols for the frequency (kHz, MHz, GHz) and the operating mode (USB, LSB, AM, FM, FAX, FSK, CW) are representable. The 8 × 3.6 cm large circuit board can operate with voltages between 8 and 20 V and uses a current of approximate 20 mA.

I had the problem to build somehow a counter or similar into a transceiver with VFO tuning over a 10-turn potentiometer however without frequency counters. Old pictures in American magazines occurred to me again. With the devices illustrated the control and frequency display were combined, . Well clearly! Thus with most of my devices the main tuning knob against a new tuning with scale were exchanged in each case. These new knob had a ratio from 1:3. As result a "counter without current" developed. With calibration uniquely a table with the relations is noted by counter reading and actual frequency. This table, which sticks with me on the top side of the transceivers, permits exactly an statement to the frequency up to 1 kHz. For all those, which are more interested in operation and fewer in a display of the frequency on the last cycles per second is exactly interested, for that is this version the best way. Different electronic companies offer fine tuning knobs with a ratio from 1:3 and in different size.

SWR/Power/Voltage Meter
 
A number of reading meters avaible in the surplus stores. Most of these are FM tuning meters, but some are calibrated for use in CB transceivers. These meters are easy to take apart for substitution of a new meter scale and the other left over for a SWR Meter. The circut can be use a small PC board or ugly construction. The circut from the source below shown here is sensitive to make is suitable for power levels from 350 mW to 25 W. The diodes rectify the forward or reflected voltage (selected by switch) to provide a dc voltage for the meter. Trimmer capacitors an the 330 pF form a voltage divider. These trimmer are used to null the bridge with a 50 Ω load connected to TRX or ANT jack.
Source: Doug DeMaw, W1FB: Build this QRP omni box. QST 11/1987, p. 18

The WM-2 by Oak Hills Research (OHR), Founder Doug DeMaw, W1FB, is a bi-directional power meter. It can measure the output power of the transmitter as well as the reflected power of the antenna resp. tuner down to 5 mW. The WM-2 works with each DC voltage between 9 and 13.8 V. Because the internal electronics has a very small power consumption, typically is about 1.2 mA, therefore the use is possible also over long time with the internal 9-V-Batterie.
Very pleasantly I feel the large, easily readable scale. With the WM-2 you can measure the power within three ranges (100 mW, 1 W, 10 W) with an accuracy of 5 % of the final value. The WM-2 is suitable for measurements in the frequency range from 300 kHz to 54 MHz. Input and output are implemented with SO239 jacks.
Difficulties with many RF measuring instruments always prepares the calibration. With the WM-2 this is ingeniously solved. For the calibration no RF generator is necessary. It hands the anyway existing DC voltage for all three ranges!
Measuring with the WM-2 is simple: In the switch position FWD the forward power minus the the reflected power is always indicated. In the switch position REF only the reflected power is indicated and the WM-2 is suitable for adjusting tuners. When measurements always begins in the largest measuring range. Only if the displayed power is under a tenth of the maximum value, switch into the next lower range. Otherwise the pointer crashs at its mechanical terminator point.
In the meantime I still made a few modifications at the WM-2, which facilitates the work with it.

Normaly you use to measure small RF voltages up to 30 MHz a RF voltage meter. But you can use also a simple probe, the QRPproject RF/AF probe. Merely an easy digital multimeter is necessary. The probe is usable for measurements above U_SS = 25 mV, U_eff = 8,9 mV, P = 1,6 µV, P = -28 dBm.
You can convert the measuredly voltages fast with the standard diagrams into the existing voltage or power. Besides the probe is also usable for AF measurements. The probe with calibration curves was buyable from QRPproject (QRP-Shop).

Antenna Analyzer
 
The MFJ Enterprises MFJ-259B by Martin F. Jue, K5FLU, is an easy to operate, versatile test instrument for analyzing nearly any 50 Ω RF system on frequencies between 1.8 and 170 MHz. In addition the MFJ-259B can be used as a signal source and as an accurate frequency counter. The MFJ-259B combines four basic circuits: a wide range oscillator, a frequency counter, a 50 Ω RF bridge and a microcontroller. This combination of circuits allows measurement of the SWR (referenced to 50 Ω), magnitude of the impedance, components of the impedance (resistance and reactance), of any load connected to the antenna connector. By connecting a signal to the BNC jack labeled frequency counter input it is possible to determine its frequency. The MFJ-259B provide a sine-wave signal of approximately U_PP = 3 V to any load in series with a 50 Ω internal resistance. The MFJ-259B is also portable. It can be used with an external low voltage supply or with an internal battery pack.
If your device is out of order, so you can download technical documentations for MFJ-259 and MFJ-259B. The manual for the MFJ-259B is available only on the webpage by MFJ Enterprises (www.mfjenterprises.com).
Addendum: MFJ Enterprises was closed at the end of April 2024.

The antenna analyzer SARK-110 by Melchor Varela, EA4FRB, is able to determine impedances in the frequency range of 0.1 to 230 MHz. The measured values are graphically displayed on an OLED display. It can measure resistive and reactances of series and parallel impedances, absolute magnitude and phase angle of impedances, standing wave ratio, return loss, insert loss, and equivalent series and parallel capacitances and inductances.
The analyzer was available by the Funkkiste (www.funkkiste.de), but its closed at the end of September. It is, according to the SARK-110 webpage also available by others.

Component tester
 
A small, but very useful device, develops after short work from this kit. It is te Almost All Digital Electronics (AADE) L/C Meter IIB. Unfortunately, this manufacturer is out of business. There is NOTHING comparable for this price on the market! Solder the fewer parts together and the kit will work. No alignment is necessary.
Display ranges: 1 nH to 100 mH, 0.01 pF to 1 µF, automatic ranging.
Accuracy: typical 1 %, self calibrating.
Display: 16 character LCD module with four digit resolution of the measured value, direct display in engineering units (for example Lx = 1.234 uHy), jumper option to display pF, nF, µF (for example 10 nF instead of 0,01 µF).
In the meantime I still made one modification at the L/C Meter, which saves the battery live.

Network analyzer
 
The Box 73 FA-NWT1 (www.box73.de) based on the NWT by Bernd Kernbaum, DK3WX. The distribution was discontinued so the device is now available only from second hand. It is a computer-based RF measuring instrument, which is nearly an all-rounder. The FA-NWT1 contains, it is true, "only" a sweeper, a sinus-wave generator and a power meter for frequencies always from 100 kHz to 160 MHz. But if you plug in some simple extensions, further measurement process can be mastered. For example after plug in a reflection measuring head you can meassure the standing-wave ratio (SWR) at antennas or after plug in a 50-Ω-series resistance you can determining and graphically represent the impedances of units. The measuring capabilities are nearly unlimited.
FA-SAV is the name of a spectrum analyzer add-on for the FA-NWT1, which was also obtainable by Box 73. It is usable for spectral measurements in two frequency ranges (1 to 75 MHz and 135 to 148 MHz) as well as three bandwidths (300 Hz, 7 kHz, 30 kHz).
The suitable software came from Andreas Lindenau, DL4JAL, and runs under Windows and Linux.

Also the Box 73 FA-NWT2 (www.box73.de) based on the NWT by Bernd Kernbaum, DK3WX. The FA-NWT2 is the further development of the FA-NWT1. It is a computer-based RF measuring instrument, which is nearly an all-rounder. The FA-NWT2 contains a sweeper, a sinus-wave generator and a power meter for frequencies always from 100 kHz to 160 MHz. The new version also included switchable attenuators and a directional coupler (optional), eliminating the need for externally connected additional extentions. The FA-NWT2 is available as a kit with an edited and printed housing. All SMD components are already soldered, only a few wired components have to be soldered. The power is supplied via the USB conversation from the already required PC. The suitable software comes from Andreas Lindenau, DL4JAL, and runs under Windows and Linux. German (standard) or English (parameter -len) can be chosen as the language for the user interface.

Generators
 
Sometimes it is necessary to produce a wide-band noise. I use for it a noise generator, which was meant actually for an Noise generator. The construction on a universal circuit board with stripy circuit paths facilitates the construction. The interruptions in the conductive strips I realized with a 4 mm drill. I turned these with the hand, until the conductive strips in the appropriate place was interrupted. I replaced the original transistors by RF transistors from the junk box. A strong noise can be achieved by this small device over the whole short wave frequency-area. The specification of this device is available.

Exact reference frequencies are necessary among other things for frequency counters. Otherwise you cannot trust the measured values. A GPS-guided 10 MHz frequency standard can be developed at minimum expenditure with the small module RS-GGO10M-TG. In order to achieve all in the data sheet specified characteristics, some general information should be considered.

DC/Power Meters
 
For the simultaneous measurement of the current and the voltage, I have always used two separate measuring instruments. A much more elegant solution is the Voltcraft PM-60-A. It can be switched on to the circuit via 2 pairs of wires. Attention! The measuring resistance lies in the negative line. Therefore, you must never ground both negative connections at the same time. The device can be attached with a clamp or with 2 magnets, which is not in the operating instructions.
In the 1. line of the LC display, voltage and current are constantly displayed and at the end of the 2. line the power. The front display value in the 2. row changes. These include the charge in Ah and the energy in Wh, both of which can be used well when charging accumulators. A separate power supply is not required, even if the device can be supplied with 5 V via a MicroUSB plug.
Measuring ranges/resolution: Voltage 5 to 60 V/0.01 A respectively 0 to 60 V/0.01 V; Current 20 A/0.01 A; Power 3600 W/0.1 W; Energy 9999 kWh/0.1 Wh; Load 99999 Ah/0.01 Ah
Recording: Rate 30 to 180 seconds; Time < 75 hours; Data records < 1500
Operating voltage: 5 to 60 V/12 mA bzw. 5 V/12 mA;
Dimensions: 7.5 cm × 4.5 cm × 2.3 cm
Supplier: Conrad Electronic www.conrad.de, Item no. 1499842

Options
 
Sometime you need for tests on a transmitter or for comparative measurements a Dummy loads. Of course you can buy it nearly everywhere. Such "monsters" are however not necessary for QRP power! What should I do as QRPer e.g. with an enormous and expensive dummy load for 50 or 100 W or more? Therefore I would like to tell you a few suggestions for small and cheap dummy loads.
A commercial variant (picture left) is offered as terminal resistor for measuring instruments. They exhibit for 50 Ω and can handle up to 1 W.
If you want to build your own dummy load, then it seems to fail first because of the offered resistors. 50 Ω resistors with the necessary power are require large heat sink. Take therefore simply different resistors! Remind you of the Ohm's law and the parallel and/or series connection of resistors. In each good electronic shop you can buy non-inductive resistors for 0.25 W or 0.5 W. In some stores also such for 1 W or 2 W. Resistors made from carbon or metal oxid are good usuable. You can reread a few possible combinations here. If you solder this resistors to a suitable plug (picture right), then you receive a outstanding dummy load. In addition, you can solder SMD resistances on a PCB. No borders are set to your fantasy!