TXTVb - 70cm ATV Test Generator (PDF) - Ham TV · TXTVb - 70cm ATV Test Generator ... fire up the...
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P. C. Electronics 2522 Paxson Lane Arcadia CA 91007-8537 USA ©2014 Tel: 1-626-447-4565 m-th 8am-5:30pm pst (UTC - 8) Tom (W6ORG) & Mary Ann (WB6YSS) Email: ATVinfo @ hamtv.com Web site: http://www.hamtv.com TXTVb - 70cm ATV Test Generator A low cost ($30), low power 70cm ATV generator can have many uses in the shack and for demo’s. The TXTVb board will put out 1 to 10 milliwatts with DC inputs of 8 to 14 Vdc @ 40 mA. For portable, it can run on a 9V alkaline battery for over 8 hours. Any time you think your receive system isn't working or you want to do some fine tweaking, fire up the test generator and you have a solid crystal controlled signal - no need to have to wait until a local ATVer is around to send a picture your way. Put the board in a Hammond 1590C die cast aluminum box, run the DC through a feed thru cap, and bypass the video in jack with a 33 pF cap with short leads to prevent too much radiated RF from being stronger than what comes out of the RF jack. It would take about 60 dB attenuation to get down to P4-P5 levels with a direct connection to the receiver - tough to get inside the box with resistors. A low cost solution is putting a 50 Ohm resistor to ground with short leads directly on the RF Jack and playing with the placement of a short “gimmick” pick up wire on the center pin of the jack for the desired level. More practical would be to make a RG174 coax connection between the board and jack, then a good fixed or variable attenuator in the external coax line then you can use the generator full power for other uses. The board comes stuffed and sol- dered up to a point as it was originally designed to drive 144 MHz transverters for higher bands. Contact Interna- tional Crystal Mfg. ordering catalog #473370, crystal frequency is Fo/4 MHz - 800-725- 1426. Example, for 439.25, crystal is 109.8125 MHz type HC-50U, Want to play with ATV antennas? Connect the 10 mW from the board directly to the RF jack. Put the test generator on top of your car with a ground plane or dipole, park it down the street at least 75 yards to make sure it is in the far field, and that you have line of sight with no other cars in between. Set up a TV on an extension cord at the curb and a connect a DC voltmeter to the AGC then tweak away or compare gain if you have a step attenuator you can put in the coax line so you can set for the same AGC voltage as with a reference antenna of known gain. TXTVbTG Parts Kit includes: L1 = 8.5 turns #22 buss wound on a 10-24 screw as a form, L2,3,4 = 1.5 turns; RF1, 2, 3 = 2N5770; C3 = 56 pF, C8 = 18pF; RF2 emitter bypass replaced with a 18 pF; C13 is replaced with a 1 pF; C10 and replace with 2-8 pF variable cap. W6ORG © 5/2014 RF2 RF1 RF3 16Vz 1N4745 - + +12 to 14.0 Vdc 100 + RF OUT 50 Ohms 220 15 270 3.3K 220 2N5770 100 100 Video gain + 220 1K 1N751 5.1Vz 2N2222 2N2907 2.2K 1K Blanking Pedistal 1N914 1N914 1N914 100 Adj 33 100 1K V VIDEO INPUT Sync 220 .001 10K 330 100 68K 4.7K 4.7K 10 2N5770 OSC 1N5711 Xtal Final P 2N2219A Modulator .1 + 22 220 4.7K 100 100 1 uH 1 uH 2N5770 4.7K 100 100 Level FMA5 Sound Input .001 + 10 270 .001 1K + 1 1 2 8 6 4 680K .1 .1 EL4581CN Sync Sep. 5.1V >.7V >.5V L1 8.5T L2 1.5T L4 1.5T C3 56p 18p C8 18p L3 1.5T C13 1p C10 2-8p TXTV b Test Generator © 2006 C1 3-20p C11 3-20p C6 1-4p TP1 TP2 RF TP
Transcript of TXTVb - 70cm ATV Test Generator (PDF) - Ham TV · TXTVb - 70cm ATV Test Generator ... fire up the...
P. C. Electronics 2522 Paxson Lane Arcadia CA 91007-8537 USA ©2014
Tel: 1-626-447-4565 m-th 8am-5:30pm pst (UTC - 8) Tom (W6ORG) & Mary Ann (WB6YSS)
Email: ATVinfo @ hamtv.com Web site: http://www.hamtv.com
TXTVb - 70cm ATV Test GeneratorA low cost ($30), low power 70cm ATV generator can have many uses in the shack and for demo’s. The
TXTVb board will put out 1 to 10 milliwatts with DC inputs of 8 to 14 Vdc @ 40 mA. For portable, it can runon a 9V alkaline battery for over 8 hours.
Any time you think your receive system isn't working or you want to do some fine tweaking, fire up thetest generator and you have a solid crystal controlled signal - no need to have to wait until a local ATVer isaround to send a picture your way. Put the board in a Hammond 1590C die cast aluminum box, run the DCthrough a feed thru cap, and bypass the video in jack with a 33 pF cap with short leads to prevent too muchradiated RF from being stronger than what comes out of the RF jack. It would take about 60 dB attenuation toget down to P4-P5 levels with a direct connection to the receiver - tough to get inside the box with resistors. Alow cost solution is putting a 50 Ohm resistor to ground with short leads directly on the RF Jack and playingwith the placement of a short “gimmick” pick up wire on the center pin of the jack for the desired level. Morepractical would be to make a RG174 coax connection between the board and jack, then a good fixed or variableattenuator in the external coax line then you can use the generator full power for other uses.
The board comesstuffed and sol-dered up to a pointas it was originallydesigned to drive144 MHztransverters forhigher bands.Contact Interna-tional Crystal Mfg.ordering catalog#473370, crystalfrequency is Fo/4MHz - 800-725-1426. Example,for 439.25, crystalis 109.8125 MHztype HC-50U,
Want to play with ATV antennas? Connect the 10 mW from the board directly to the RF jack. Put thetest generator on top of your car with a ground plane or dipole, park it down the street at least 75 yards to makesure it is in the far field, and that you have line of sight with no other cars in between. Set up a TV on anextension cord at the curb and a connect a DC voltmeter to the AGC then tweak away or compare gain if youhave a step attenuator you can put in the coax line so you can set for the same AGC voltage as with a referenceantenna of known gain.
TXTVbTG Parts Kit includes: L1 = 8.5 turns #22 buss wound on a 10-24 screw as a form, L2,3,4 = 1.5 turns;RF1, 2, 3 = 2N5770; C3 = 56 pF, C8 = 18pF; RF2 emitter bypass replaced with a 18 pF; C13 is replaced witha 1 pF; C10 and replace with 2-8 pF variable cap. W6ORG © 5/2014
RF2RF1
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16Vz
1N4745
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Sync
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TXTV b Test Generator© 2006
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P. C. Electronics 2522 Paxson Lane Arcadia CA 91007-8537 USA ©2014
Tel: 1-626-447-4565 m-th 8am-5:30pm pst (UTC - 8) Tom (W6ORG) & Mary Ann (WB6YSS)
Email: ATVinfo @ hamtv.com Web site: http://www.hamtv.com
TXTVb - 70cm ATV Test Generator
ASSEMBLY PROCEDURE:Refer to the board pictorial on right
1. Remove trimmer caps C5, C10 and C13.2. Install and solder the kit of parts in their respective locations:
A. Install the 8.5 turn coil at L1 and the 1.5 turn coils inL2,3 and 4and space the bottom of the coils 1/16” above the board. Aftersoldering, verify that L1,2 and 4 read greater than 1K with respectto ground with an ohm meter and adjust if a short is found.
B. The 2N5770 are inserted into the board with the flat side facingtoward the crystal end.
C. Install the 18pF disc caps at C8 and replace the 220 or .001 emitterbypass cap with one at the emitter of RF2.
D. Install the 56pf disc cap at C3. Install the 1pF disc cap at C13.Install the 2-8 pF variable cap at C10.
E. Install the 100 Ohm carbon trim pot at the video input or run 3wires to a panel mounted 100 Ohm carbon pot.
F. Connect the output coax to a RF Jack or antenna. Fold back thebraid and attach to the connector in the same manner as we have
done on the board. Do not use pigtails. Solder directly to the ground of the jack as close to the center aspossible. We suggest only using a Type N or BNC at 70cm. Check for 100 ohm reading.
TUNE UP:Plug in a HC-50U crystal for the desired 70cm frequency. Output frequency is crystal frequency times 4.1. Preset the PEDestal pot to full CCW and the RF LEVEL to full CW. No video plugged in. Connect RF out
to a 50 ohm load.2. Turn on +12 to 13.8 Vdc and peak C1 at TP1 with a DC Voltmeter. It should read greater than .5 Vdc.3. Peak C8 first, then C10 and C11 for maximum DC voltage at the RF OUTPUT test point (top of 4.7K).
Then go back and fine peak each. DC voltage should be about .3Vdc. Note this voltage then multiply it by.75. Set the Pedestal Pot to this calculated voltage. Once set, it should not be readjusted unless you want torepeak the trimmer caps or change the DC applied voltage more than 1/2V in which case always start over atstep 1.
4. Plug in the video source and adjust the VIDeo gain pot for best picture without white smearing.
RF TP
C11
(18 pF)
RF1
RF2
RF3
P. C. Electronics 2522 Paxson Lane Arcadia CA 91007-8537 USA ©2014
Tel: 1-626-447-4565 m-th 8am-5:30pm pst (UTC - 8) Tom (W6ORG) & Mary Ann (WB6YSS)
Email: ATVinfo @ hamtv.com Web site: http://www.hamtv.com
TXTVb - ATV Exciter for 2 Meter TransvertersThe TXTV ATV exciter board is designed to generate 10 to 100 milliwatts on various frequencies
depending on selection of inductors and capacitors. 2 meter input Transverters for higher bands can add theATV mode with this board. Sound can be added by running a shortRG174 coax from the output of a FMA5-G 4.5 MHz soundsubcarrier board to the solder pad marked S on the TXTV board.The board(s) should be mounted in a die cast aluminum box toprevent stray radiation on cable channels 16 to 18.
The board comes stuffed and soldered up to a point with akit of parts for the 2 meter application. Stuff and solder therespective parts in the board as shown at right: RF1, 2, 3 =2N5770, L1=.22uH, L2,3,4=6.5 turn coil - space above the board1/16” and verify no short to the ground plane with an Ohm meter,C2=22 pF, C3=100 pF, C7=10 pF, C8=22 pF, C12-10 pF andvariable cap C13 is removed and replaces with a 4.7 pF fixed cap.Solder the RG174 50 ohm coax from the RF OUT solder pad onthe bottom of the board to a RF chassis mount jack and check forshorts. Run a wire from the + solder pad to a 1000 pF feedthroughcapacitor or a jack that is bypassed with 1000 pF. Run a wire fromthe V solder pad to a Video in jack. Plug in a crystal selected forthe right ATV output frequency - ie. 1289.25 in a 144.0 to 1296.0transverter would be 68.675 MHz and outputting times 2 on 137.25MHz. Do not transmit ATV on weak signal frequencies.
Tune up: No video plugged in, output pot full CCW, andthe pedestal pot full CCW, +13.8V, connect a DC voltmeter to the
RF2RF1
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test point (top of 100 ohm resistor) andpeak the oscillator trimmer cap. Thenpeak the next two trimmer caps formaximum at the doubler 2X test point.Finally peak the two output trimmer capsat the output RF test point. Connect theoutput to the transverter and adjust theRF output pot for 90% of the rated outputof the transverter or final amp. Fine peakthe last to trimmer caps for maximumoutput, then reset the pot to 90% power.Note this power and then set the pedestalpot for 60% of that. This sets the videoto sync ratio and compensates for anysystem gain compression. Plug in thevideo and adjust video gain for best pix.
W6ORG (c) 2014
