TelePost LP500, LP-700 User Manual

1

LP-500 / LP-700

User Guide v3.1

Connections…

Power: 12-16 VDC @ 800 mA maximum, center pin positive, 2.5mm. The cable either has a white stripe on the positive wire, or ridges on the negative
wire, depending on the cable supplied. The meter also has a protection diode to prevent damage in case of reverse polarity. If unsure, use multimeter to
check the wiring before plugging it into the meter. The meter has a built in replaceable 1A fuse on the PCB for protection. We recommend a well
regulated supply with a 1A to 1.5A rating. An alternative is to use the accessory 12VDC jack on the rig if it can handle the current. You can also use a
12VDC power distribution strip like RigRunner connected to the main station DC supply. Sharing the meter power with other devices when the supply is
marginal could result in ripple caused by the high current switching of the LED backlight between on and off states.

PTT: For older amplifiers, loop the PTT (send, amp keying) between your amplifier and rig through the LP-500 using RCA connectors. Two isolated pairs
of connectors are provided for connecting two amplifiers. Use either pair for either amplifier.

Test Tones: Audio output for built in test tones. 3.5mm mono. Connects to the MIC or LINE input of the rig. An attenuator will be needed in the case of
mic input, as well as galvanic isolation (transformer). Interfaces designed for a sound card based RTTY setup should work well for this. We plan to offer
an interface box for this type of connection in the future, which will allow hot-switching between the mic and LP-500, isolation and level balancing
between them. This will ensure that testing can be done at normal speech levels.

USB 2.0: Connects to computer using standard USB cable (Type A to Type B connectors). Used for flashing firmware and interfacing to LP-500 VM and
Utility programs. Can be connected to USB 2.0 or 3.0 jacks on PC. No special drivers are necessary since the standard Windows drivers are used.

Couplers: Connect to corresponding jacks on the coupler(s) using supplied or user provided CAT5/6 shielded Ethernet cables. See Fig.1 below.

2

Overview

Fig.1. Shows installation with two couplers and PTT Alarm connections. The use of two couplers allows viewing of amplifier linearity with a trapezoidal

display. PTT Alarm connections are optional and designed mainly for older amplifiers with no built in protection.

The LP-500 Digital Station Monitor combines a state-of-the-art wattmeter and SWR meter with a task specific oscilloscope and spectrum analyzer, all
using a large, bright color TFT display. In the case of the LP-500, the display size is 5” diagonal. The LP-700 display size is 7” diagonal. Otherwise, the
two meters are the same. Any reference to the LP-500 in this manual also applies to the LP-700. The LP-500 also employs a low distortion audio signal
generator with a number of complex signals available, plus the ability to allow users to create their own test signals. The instrument can be used to
monitor the outputs of four different transmitters, or the inputs and outputs of two amplifiers as well as other combinations. The intent is for the user to be
able to monitor many aspects of his transmitted signal and ensure that his station is operating as cleanly as possible.

While it doesn’t completely replace dedicated oscilloscopes and spectrum analyzers, it performs almost all the tasks one would employ these
instruments to do, but does it much more conveniently, cost effectively and in many cases with better results.

While the LP-500 is a complex piece of test equipment, every effort has been made to make operation as simple as possible, with many automated or
linked functions. Operation of the LP-500 is mostly controlled through the six pushbuttons, but in the scope and spectrum modes there are a number of
touch screen controls, as well as a rotary digital encoder control. The six main buttons are associated with six “soft” buttons, which can also be
controlled via the touch screen.

The main modes of operation… Power/SWR meter, Waveform Scope and Spectrum Display… are controlled by the Mode button. The Mode button
remains in all modes, as does the Channel selection button. The 3rd button controls the range or gain of the meter in each mode. The other buttons are
soft keys whose function changes with mode.

A detailed list of modes and controls follows on the next pages, which will help the user get the most out of this meter.

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Power/SWR Mode…

Power/SWR

Waveform

Spectrum

CH Auto

CH 1
CH 2
CH 3
CH 4

Rng Auto

Rng 5
Rng 10
Rng 25
Rng 50

Rng 100
Rng 250
Rng 500

Rng 1K

Rng 2.5K

Rng 5K

Rng 10K

(per channel)

AL Off
AL On

(per channel)

Peak Hld
Average

Tune

Setup

Normal

The above picture shows the Power/SWR mode, with menu choices listed below each button. The bottom choice in each list wraps around to the top.

Note: The pictures in this section were taken from v2.12 of the firmware and have changed slightly in later versions. The later versions have added a
peak hold power readout in the lower right.

Mode Button: Changes mode.
CH Button: Selects among the 4 coupler channels, and also offers an Auto Channel selection, which displays the channel with the highest power

reading. This mode is very useful for SO2R type contest operation. When in CH Auto, the current selected channel is displayed to the right of the SWR
bargraph, along with the current power and SWR alarm settings for that channel.

Range Button: Selects the desired bargraph range between 5W and 10KW in 11 steps, and also offers an Auto-Range choice.
The selection is indexed to the current channel selection and is saved in memory. As the range changes, the bargraph legends also change so that you
always graphically see the correct range and bargraph length. When changing to a higher range, there is some hysteresis built in so that the meter will
stay at the higher range unless power drops a certain percentage. This is done to prevent “hunting” on the edge of two ranges while operating, and
especially while tuning. Note: This choice can’t be changed when the CH button is in Auto.

Alarm Button: Selects the alarm status for each channel and is saved in memory. The alarm settings for the current selected channel are displayed to
the right of the SWR bargraph below the Auto CH display. This is true whether the channel is manually or automatically selected. These values are
entered on the Setup screen. If the alarm is tripped, the display indicates which channel tripped the alarm, and the chime sounds as well, with 1 chime
for CH1, 2 chimes for CH2, etc. The sequence repeats continuously until you stop transmitting, the fault is cleared or the alarm is set to OFF. The Alarm
P or Alarm S displays will change to red to indicate whether the trigger was due to a power fault or SWR fault. Note: This choice can’t be changed when

the CH button is in Auto.

Peak/Avg/Tune Button: Determines whether Average, Peak Hold or Tune power is fed to the large numeric power display. The hold time for Peak Hold
is adjustable in Setup. Tune is just peak hold with a very short hold time. Note: Smaller values of average and peak power are always displayed at the
end of the average and peak power bargraphs with 1W resolution.

Setup Button: This is a special button and displays a screen with all the adjustable user preference items. This will be covered as a separate mode later
in this guide. Tapping this button once changes to Setup mode, tapping again returns to Power/SWR mode. Tapping the Mode button will also return to
Power/SWR mode.

“Adjust” Knob: This controls an optical encoder which currently has two functions… to facilitate call sign entry in Setup by allowing the user to scroll
through alphanumeric characters, and to control the sweep rate in WFM mode when setting a User Preset. It does not function in factory presets. Slowly
turning this knob will result in smoother operation than rapid turning.

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Waveform / ‘Scope Mode…

Power/SWR

Waveform

Spectrum

CH 1
CH 2
CH 3
CH 4

Rng Auto

Rng 5
Rng 10
Rng 25
Rng 50

Rng 100
Rng 250
Rng 500

Rng 1K

Rng 2.5K

Rng 5K

Rng 10K

SSB F

SSB S

CW
PSK F
PSK S
User 1
User 2
User 3

Wfm
½ Trap
Scope

Wfm/Trap

AM Mod
Wfm/Pwr

2 Tone+
Wnoise+

Pnoise+

2 Tone

WNoise

Pnoise
400 Hz

1 kHz

User 1
User 2
User 3
User 4

Mode Button: Changes mode.
CH Button: Selects among the 4 coupler channels. CH Auto is not offered in the ‘scope mode to avoid confusion. The channel selection for the ‘scope

mode is independent of the Power/SWR mode.
Range Button: Selects the desired power range between 5W and 10KW in 11 steps, and also offers an Auto-Range choice.

The selection is indexed to the current channel selection and is saved in memory. As the range changes, the vertical voltage legend changes as well to
indicate actual peak voltage at the output connector of the coupler. As with the Power/SWR mode, there is some hysteresis built into the auto-ranging.

Sweep Button: Selects the horizontal sweep rate / scaling. There are 5 presets… which select a combination of sweep rate and trigger mode optimized
for the indicated mode, as follows:

SSB Fast... 1.0 msec/division, Normal trigger
SSB Slow… 2.0 msec/division, Normal trigger
CW… 1.0 msec/division, +/- trigger (more on this below).
PSK Fast… 5.0 msec/division, Normal trigger
PSK Slow… 10.0 msec/division, Normal trigger

Note: The +/- trigger mode displays a split screen of the CW waveform with positive edge triggering on the left side of the screen and negative edge
triggering on the right edge. This provides more resolution for viewing the detail of the leading and trailing edges of the keying waveform.

In addition, there are three USER sweep settings which allow the user to select his own combinations of sweep rate and trigger style. More on this in the
Touch Screen Controls section.

Test Tone Button: This button selects the desired test signal to be fed to the transmitter. Choices are:

2 Tone+… Two tones plus “subcarrier” (Spectrum Mode)
Wnoise+… White noise plus subcarrier (Spectrum Mode)
Pnoise+… Pink noise plus subcarrier (Spectrum Mode)
2 Tone… Standard two tone test signal
Wnoise… White noise
Pnoise… Pink noise
400 Hz… 400 Hz sine wave
1 kHz… 1 kHz sine wave
User 1,2,3,4… These select custom tones that the user can record and save to memory in standard .wav format.

The test tone output of LP-500 is unbalanced line level audio with a source impedance of 250 ohms. This can be directly fed to the line input of most
radios. We are developing an interface box which will convert this audio to mic level balanced output, with a switch and attenuator to allow matching the
LP-500 output to a microphone and switch between them.

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Waveform / ‘Scope Mode, Continued…

Trg Norm, Trg +, Trg -, Trg +/-, Trg Off

1.0 ms/div, 2.0 ms/div, 5.0 ms/div, 10.0 ms/div

Cursor 1, Cursor 2, Peak Marker, Cursor Off

Freeze, Unfreeze

Descriptions below refer to these pictures and the one at the top of the previous page.

½ Trapezoid CW Envelope WFM / Trapezoid

AM Modulation WFM / PWR

Wfm Style Button: Selects the desired ‘scope display from these choices…
Wfm: Standard ‘scope display… shown top of previous page.

½ Trap: Top half of a trapezoidal display plots exciter output vs. amplifier output and displays a triangular image that easily shows when the output of the
amplifier becomes nonlinear, ie. flat tops and no longer provides the same gain as at lower power. Also shows other distortions of the input signal. Using
half the normal trapezoid allows displaying twice the vertical resolution.

Scope: Shows the modulation signal, ie. demodulated audio. Not shown.
Wfm/Trap: Split screen of the transmitted waveform on the left of the screen and trapezoid on the right side.
Wfm_Pwr: Displays the transmitted waveform on the left of the screen, and Power/SWR on the right side.

Touch Screen Controls…

The touch screen serves a couple functions. It adds additional buttons that the
user can access by pressing with his finger or a stylus, and it allows the user to
control cursors which allow the user to make voltage and time measurements.

Cursor Button: Pressing this button cycles through four cursor modes.
Selecting Cursor 1 displays a blue crosshair, which allows the user to set a
position on the waveform in either voltage or time, or both. The corresponding
voltage and the total time from the left edge of the display are displayed
numerically. Selecting Cursor 2 adds a second cursor with green crosshairs. In
this mode, the numerical readout shows the time difference between Cursor
1 and Cursor 2. The voltage displays 0. Pressing the cursor button again turns
on the Peak Pwr Markers. The fourth position is OFF.

Freeze Button: To aid in setting the cursors and making measurements,
pressing this button causes the waveform to freeze.

Trigger Button: This button selects the trigger mode when one of the USER sweep presets is selected. The selection is saved as a custom user preset.
The button only works when a USER preset is selected, but always displays the current trigger setting, even in factory sweep preset positions.

Sweep Button: Selects the desired sweep rate when the Sweep preset is set to one of the USER choices. The setting is saved in memory along with
trigger mode. The sweep rate can be modified by rotating the Adjust knob to any desired value.

Power Display: A numeric display below the Sweep button which shows the current transmitted power level. When moving Cursor 1, the power display
shows calculated power based on the cursor position rather than transmitted power.