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TelePost LP-100 Manual

Digital vector hf wattmeter
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LP-100
Digital Vector
HF Wattmeter
Operating &
Assembly Manual
April 2007
TelePost Incorporated
Rev. C20
1

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Summary of Contents for TelePost LP-100

  • Page 1 LP-100 Digital Vector HF Wattmeter Operating & Assembly Manual April 2007 TelePost Incorporated Rev. C20...
  • Page 2 E.I. du Pont de Nemours and Company. PICmicro® is a registered trademark of MicroChip Technology Inc. Material in this document copyrighted © 2007 TelePost Inc. All rights reserved. All firmware and software used in the LP- 100, LP-100 VCP and LP-100 Plot programs copyrighted © 2004-2007 TelePost Inc. All rights reserved. MicroCode...

  • Page 3: Table Of Contents

    Table of Contents Introduction ......................4 Parts List......................... 5 Assembly Instructions .................... 8 Initial Checkout ....................16 Setup/Calibration ....................18 Operation......................22 Circuit Description ....................26 Schematic ......................28 Troubleshooting ....................30 Software........................ 32 Specifications and CAL Table ................34 Warranty ......................

  • Page 4: Introduction

    As a convenience to any LP-100 owner, TelePost will do the chip swap and a free recalibration if the owner returns the LP-100 to TelePost at his shipping expense, and pays for return shipping ($12 for Fedex Ground insured).

  • Page 5: Parts List

    Parts List - Subject to change without notice. Pre-installed SMT parts Part No. Description C9,10,12,13 0.01uF 50V R4,18 Resistor 26.7 1% .25W R5, 12 Resistor 49.9 1% .5W R6,21 Resistor 56.2 1% .25W R9, 27 Resistor 56.2 1% .5W R10, 20 Resistor 422 1% .25W Resistor 174 1% .25W Resistor 120 1% .25W...
  • Page 6 Part No. Description R19,29 4.7 5% 1/4W yel-viol-gold 150k 1% 1/8W br-grn-blk-or-br R23,25 10k 1% 1/8w br-blk-blk-red-br 6.34k 1% 1/8W blu-or-yel-br-br 100 5% 1/8W br-blk-br 174 1% 1/8 or 1/4W br-viol-yel-blk-br 57.6 1% 1/8 or 1/4W grn-viol-blu-gold-br (blue body) 120 5% 1W br-red-blk-blk-br (brown or rust colored body) Omron G5V-2-H1-DC5 CEM-1212C Piezo transducer SW1, 2, 3...
  • Page 7 Hardware Part No. Description 4-40 x 1.5” (3.81cm) threaded standoff (.625” (1.59cm) on serial #s after 200) 4-40 x 0.75” (1.91cm) machine screw (serial #s after 200) #4 self-tapping screws – 1/4” (6.35mm) – plated (for coupler) #4 lockwashers (9 for coupler, 3 for main chassis) (11 for coupler, 3 for main chassis starting about serial # 350) #4 split lockwasher for coupler PCB 4-40 x 3/8”...

  • Page 8: Assembly Instructions

    Note: DO NOT use this manual for assembly of kits with serial numbers before #101. Use LP-100 Manual Rev. B listed on the LP-100 webpage at instead. Some www.telepostinc.com/lp100.html...
  • Page 9 Digital Multimeter NOTE: The LP-100 is what I would call an intermediate level kit. If care is taken, you should have no difficulty building it. I would peg the assembly time at about 8 hours total, plus some reading through the manual in advance, and some time for calibration. Take your time, and double-check your work.
  • Page 10 Assembly cont’d Step-by-step assembly instructions for main board. Below is a picture of the assembled PCB. The SMT parts come pre-installed. It is recommended that you print this manual to allow for easy reference while building, and to allow you to check off the steps as you complete them.
  • Page 11 Assembly cont’d Install miscellaneous parts such as resonator, Piezo transducer, transistor, diodes, etc. NOTE: Remove the protective covering on the transducer before using. Also, the “+” lead goes to the side with the jumper, per the placement guide. The outside leads of the resonator are interchangeable.
  • Page 12 Step 2. Power the board up again, and verify that you are seeing the “splash” screen with version and copyright information, followed by the main LP-100 screen. The main screen should look like the screen on the photo at the top of the “Operation” section of this manual.
  • Page 13 Assembly cont’d Step-by-step assembly instructions for the coupler. Refer to the drawing and pictures during assembly of the coupler. The top picture is courtesy of Dario, N5QVF, and the lower right one is courtesy of Stan, W5EWA. The sequence of pictures below is from Jack K8ZOA. Jack developed a clever way to ensure proper winding of the cores, both for spacing and coverage of the windings.
  • Page 14 Assembly cont’d Construction of the coupler consists of only a few steps. The main components are the transmission line, toroidal transformers and the attenuator PCB. The most critical step is the winding of the transformers. They are wound with 26 turns each of #20 enameled wire. The cores are wound in opposite directions, i.e.
  • Page 15 Assembly cont’d Prepare the two pieces of coax as shown in the diagram. Make sure that the shield wires don’t short out to the center conductor on either end. RG-142 is double silver shielded. Leave a little shield showing on one end as shown in the pics above, and then wrap a short pigtail of wire around it.

  • Page 16: Initial Checkout

    Assembly cont’d Solder the 12 SMT resistors onto the attenuator board as shown. Don’t be afraid of these parts. These are VERY big parts as SMT goes. The resistor values are printed on the resistors. Use a fine tip on the soldering iron, and tin ONE of the PCB pads for each resistor with a small amount of solder before attempting to solder the resistors.
  • Page 17 Final Checkout and Assembly Before going through the Setup screens, it is necessary to verify that the remaining basic circuits are working. Power up the LP-100, and verify that the current draw is correct. (160 mA ).

  • Page 18: Setup/Calibration

    (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.
  • Page 19 The next screen is the Gain/Phase Zero screen. This allows for band-by-band balancing of the gain and phase detectors. To do this, connect your dummy load to the ANT connector on the LP-100 coupler. Starting with the lowest band you can transmit on, key the transmitter.
  • Page 20 Before adjusting either the Mstr or Fine trims, it is necessary to provide an accurate means of measuring power that is independent of the LP-100. The simplest approach to this is to borrow a high quality meter like a Bird or Alpha to use as a reference, and connect it between the LP-100 and dummy load with a UHF male-male adapter.
  • Page 21 PLED display connector. It is imperative that this screw not be longer than ¼” (6.35mm) or it will short out the connector. If you wish to add a power switch to the LP-100, you can do so at this time. I provided a 2-pin header to wire the switch to using a plug.

  • Page 22: Operation

    Direct/Field Strength mode is similar to dBm mode except that it is calibrated to display power from –15 dBm to +33 dBm. There is no return loss in this mode because it does not utilize the coupler. Power is supplied directly to one of the inputs on the back of the LP-100.
  • Page 23 Slow (peak) is best for CW or SSB operating. Note: The Peak Mode is VERY fast, and can respond to a lip smack, mic button click, etc. Don’t be alarmed by this… it is normal, and allows the LP-100 to provide an accurate indication of peak power.
  • Page 24 Normal Operation In normal operation, the LP-100 is left in the Normal mode. For SSB or CW operation, you should use the Slow (or peak-hold) Power mode. This mode will show peak power and SWR and hold them for the preset hold time unless a higher peak is detected, at which time the timer resets.
  • Page 25 For amplifier tuning, you should switch to Tune mode for fast update of both bargraph and numerical readout. The bargraph sampling in the LP-100 is about 100 samples/second, and it will display a single dit at 60 wpm, or a string of pulses as with a pulser or keyer set for high speed.

  • Page 26: Circuit Description

    The LP-100 is unique in it’s design in several regards. Refer to the following block diagram during this discussion. First, instead of using a coupler that produces forward and reflected power signals, the LP-100 uses a pair of transformers that sample current in the transmission line and voltage across the load.
  • Page 27 Circuit Description cont’d Finally, the PIC provides a standard RS-232 serial interface for remote control and monitoring of the LP-100. Functions of the LP-100 can be controlled from a Windows® “Virtual Control Panel” program, either locally or over a network connection, including the internet.

  • Page 28: Schematic

    Schematic Page 1...
  • Page 29 Schematic Page 2 Coupler Schematic...

  • Page 30: Troubleshooting

    Below are some problems that have been reported and solutions. If you still have a problem, I am always available by email at larry@telepostinc.com and the newly formed LP-100 Yahoo Group is available at http://groups.yahoo.com/group/LP-100/ For excessive current, always check for solder bridges and proper orientation of ICs first. If a step calls for more than one IC to be added and current is excessive, remove the ICs and re-install one-by-one until you narrow the source of the high current.
  • Page 31 These adapters are both much cheaper than the ones typically sold at computer stores, and should work well. I have been asked about a USB port for the LP-100, and it would be easy to do, but since all ham software has native RS-232 com support, and older machines don’t have USB ports, I think a RS-232 port with an inexpensive USB adapter where needed is the most flexible choice.

  • Page 32: Software

    Baud Rate to 19,200 (under Options). When all of this is done, click on Load>Program. You will see a message to Reset the PIC. This is done on older firmware by cycling the power to the LP-100. On firmware after ver. 1.1.47b, you can do a software reset by entering Setup (hold Mode button for 1 second) until the first CAL screen is displayed, release the mode button and then press Alarm.
  • Page 33 LP-100 Plot Plot version 0.99 is available for download on the LP-100 Current Software page. An html help file is also available there with instructions for installation and use.

  • Page 34: Specifications And Cal Table

    Offset Trim Master Power Trim Gain Slope Trim Phase Slope Trim Lo/Hi Power Trim Reference Log the initial CAL constants for your LP-100 in this table. If you ever make changes, you can log additional constants in the spaces provided.

  • Page 35: Warranty

    If failure occurs within the warranty period, return the LP-100 to TelePost Inc. at your shipping expense. The device will be repaired or replaced, at our option, without charge, and returned to you at our shipping expense. Repaired or replaced items are warranted for the remainder of the original warranty period.
  • Page 36 Appendix A...

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