Manual For Optoelectronics Xplorer

1. Manual For Optoelectronics Xplorer 5

BACKGROUNDThere exists in circulation a review of the Optoelectronics M1frequency counter from 1994. This review is available from, amongothers, this reviewis somewhat out of date, and the device currently being sold as the M1is substantially different from that discussed in the review. Havingrecently purchased such a device, I would like to provide more currentinformation.I would like to begin by providng some background information on thevarious models of Optoelectronics hand-held frequency countersavailable. This information and more is available from theOptoelectronics web site, at However,in light of Optoelectronics' apparent tendency to change models whilekeeping the name the same, it seems that it may be useful to note someof the more prominent features of the current model, to allow a futurereader to determine if these models have changed since this articlewas written.Scout: The scout has three switches and button on the front panel,with the button rightmost.

It has a range from 10 MHz to 1.4 GHz, 400memories, and selectable filter, capture, and gate. The main featureof the scout is that it automatically tunes some scanners, and itsability to bee/vibrate when a new frequency is acquired. $449.Mini Scout: This model is like the scout, but without the memories,backlight, or beeper. $249.Cub: The case appearance is like that of the Scout, with threeswitches and one button. Range is from 1 MHz to 2.8 GHz. The gate isselectable, and a 1-250 MHz range is available.

$149.3000A+: A very decorated case with blue and red highlights on it, asopposed to the plain cases of the others. Range from 10 to 3000 MHz.Four vertical switches and two horizontal on the left, and threebuttons on the right. Four ranges, three memories, built in highpassfilter. Provides measurement of Period, Ratio, and Intervals.

Manual For Optoelectronics Xplorer 5

$350.M1: Black case with four buttons and no switches. Range from 50 Hzto 2.8 GHz, with a 10-250 MHz range and a 50Hz-40MHz range. 100memories.OVERVIEWI wanted a frequency counter for two uses, off-the-air RF measurementsand benchtop use. Of the Optoelectronics models, only the M1 and3000A provided measurements below 10 MHz or so. I selected the M1over the 3000A based on the aforementioned reviews by Brian Mork.The current M1 is substantially different from that previouslyreviewed.

The most obvious differences are the change of the case fromswitches to buttons, and the increase in the number of memories from 3to 100. More subtle differences also exist.OPERATIONThe left button turns the power on and off. Holding it down for twoseconds turns on the backlight.

The backlight remains on untilmanually turned off. It does not time out and turn off after acertain period of inactivity.The third button selects the range. Three ranges are available. TheA range is a 1 Mohm input, for measuring signals between 50 Hz and 1040 MHz. (in practice, mine works down to about 10 Hz). The B rangeoperates from 10 MHz to 250 MHz with a 50 ohm input.

The Prescalerange operates from 30 MHz to 2.4 GHz. The device always powers on inthe Prescale range.The second button selects the gate. In the A and B ranges, 2 to 7decimal places (in a MHz scaled readout) are availble, with gate timesof 100us to 10S, respectively.

Strangely, the instruction manualfails to list the most accurate setting in its list of gate times,though the catalog lists it. In the prescale ranges, 2 to 5 decimalplaces are available, and the gate times range from 6.4ms to 6.4s.The fourth (rightmost) button selects the mode. The power-up mode isthe standard one, in which a count is taken constantly. The secondmode is 'filter' mode, in which a frequency is displayed only when theinternal processing is satisfied that there is a genuine signalinstead of noise. The third mode is Capture, in which the filter isactive and all unique recorded frequencies are stored to an internalmemory.

The fourth mode is Recall, in which the second and thirdbuttons scroll through the recorded frequencies.There is a bargraph on the display which gives an indication of thetotal RF energy received, in arbitrary nonlinear units of'approximately 3 dB'. It seems inactive in the A range, and functionsonly in the B or prescale ranges.GENERAL COMMENTSThe display always reads in units of MHz. This means that the counterisn't as useful as you might think for low frequency measurements.

Ifyou're reading something at around 50 Hz, the longest gate time willstill get you only three figures in your answer. That's notparticularly good. Therefore, though the stated specifications godown to 50 Hz, and I've found that it will actually count down toabout 10, it's not that useful below the tens of kHz range.The use of a button to select the range seems like a misfeature - onecannot power on the device in the 1 Mohm range, so one needs todisconnect any direct connection to the device when it is powered onin order to avoid damaging it. This would not have been a problemwith a switch. No functionality is lost, but having to disconnect thecable every time I turn on the counter is mildly bothersome.There has been some question as to the utility of providing more than6 digits with a 1ppm timebase.

This is useful because the displaydoes not scale, but always puts the decimal point at MHz with three orfour digits to the left of the decimal. When measuring a 10 kHzsignal, for example, the leftmost four digits will all be zero/blank.Unlike the previous M1, and possibly some other Optoelectronicsmodels, filter or capture mode does not require arming. Signals aredisplayed or written to memory whenever they pass the filter. Thefilter also seems to become more selective as the gate time isincreased.

The behavior when all 100 memories are full is not clearto me, as I have come nowhere close to filling them.The gate is not selectable in Capture mode; three digits after thedecimal point (and the corresponding gate time depending on the range)are always used. Pressing the gate button has no effect.

This meansthat capture mode isn't good for much when using the A range forlow-frequency signals.The battery indicator is not actually a 'low battery' indicator, butis instead a 'no battery' indicator. It does not turn on when thebatteries are getting low, but instead turns on after the unit hasstopped operating due to low battery power. This behavior seems lessthan useful, and the indicator might as well be absent.The new manual is no longer folded 8.5x11' sheets. It is now folded4.25x11' sheets. No schematic is included.SPECIFICATIONSThe inconsistency in the 50 ohm maximum input power is still there -it says 15 dBm or 50 mW, and 15 dBm is still 32 milliwatts, not 50.The A-range maximum input power is listed as 50 V AC+DC. Thecapacitance on the 1 Mohm input is listed as 30pf.frequencies(hz) range sensitivity1k-10M A.