TelePost LP-100 Manual Download Page 18

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Setup/Calibration

Note: This section assumes you are using firmware version 1.1.1 or later, and of course the upgrade PIC processor. If you own a kit
from the first production run (serial # 100 or older), then it is highly recommended that you upgrade to the new processor before
calibration to avoid having to calibrate twice. This is a no charge upgrade (except for shipping cost).

Enter the Setup mode again as described in Initial Checkout. Below you will see a picture of each Setup screen along with a brief
synopsis of what it does and what the controls adjust. Remember, for firmware 1.1.45 or later, it is a single, long, Mode button press.

Reference screen. Displays the reference voltage from the gain/phase detector, as well as the RSSI
voltage (Received Signal Strength Indicator) from the AGC chip used in the frequency counter preamp.
This voltage is proportional to the log of the RF input power to the LP-100. The screen also shows
temperature in Deg F & C. There are no adjustments for this screen.

This screen allows you to enter the actual impedance of your dummy load. This will result in a more
accurate calibration if your dummy load is other than exactly 50.0 ohms.

This adjustment is used to calibrate the zero point (or offset) of the magnitude and phase detectors. The
adjustment is semi-automatic in that you don’t have to make any adjustments. The process requires you to
briefly transmit into an accurate 50 ohm dummy load on each band in sequence, and to press the Alarm/Dn
button to save the correction for each band.

This adjustment is used to calibrate the slope of the phase detector. It is simply done by inserting a line with
known delay into the Current input of the LP-100, and transmitting into a high quality 50 ohm dummy load.
The controls are then adjusted so that the display correctly shows the line delay. If coax of known Velocity
Factor is used, the line length in degrees can be simply calculated.

This adjustment is used to calibrate the slope of the gain detector. It is accomplished by transmitting into a
25 ohm load and setting the Trim for a reading of 25.0 (or whatever the actual load resistance is if it’s not
exactly 25.0).

Allows adjustment of the accuracy of the op-amp detector and ADC to provide correct conversion values at
low power levels. The screen shows the output voltage of the detector, and the Trim level is set by
adjusting for zero voltage with no RF power applied.

Adjusts overall power accuracy of the LP-100. This adjustment affects all frequencies equally, and is made
by comparing the LP-100 power reading with an accurate reference. Acceptable reference measurement
devices can be inexpensively made, and will be described later.

Same as above, but adjusts the displayed power reading on a band-by-band basis. The built-in frequency
counter detects the band you’re on, and stores the CAL constant for each band automatically for 12 bands
from 160m through 4m. The counter works from 50 mW to 2500W.

This screen is used to match the readings of the low power and high power ADC inputs. It is done at a
power level below 320W, which is the point at which the low power input reaches maximum. Its purpose is
to allow compensating for any error in the 1% precision divider parts used in the high power input.

NOTE:

Moved up between Offset and Master on ver. 1.1.47c and later.

This screen allows setting the SWR Alarm power threshold and Power display type. The alarm threshold is
used mainly in contesting stations with multiple transmitters to prevent false alarms when energy from
another transmitter is picked up by an antenna. The choices are 0,0.1, 1.0, 10.0 and 100.0 W. The power

This screen allows selection of the correct cable compensating table to match the connecting cables you
are using. Early LP-100s used RG-174U, but a change was made to RG-58U starting wit serial # 101.

Starting with serial #400, this menu was changed to a serial number selection, and covers any hardware
change between versions instead of just cables. In the case of the 5

run, it covers the change in response

of a slightly different model power combiner.