Heathkit Model IG-5280
RF Generator
Calibration Procedure
· If using the unit as a portable instrument, install a fresh set of 9-volt batteries and set the SOURCE switch (on rear of unit) to the BATT position.
· If powered using the IPA-5280-1 AC Power Supply, set the SOURCE switch (on rear of unit) to the LINE position.
· Disconnect all external components from the front panel terminals.
Ancillary Equipment Needed
AC VTVM
250 MHz Frequency counter
AM/FM Radio
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AMPLITUDE ADJUSTMENT
Refer to PICTORIAL 15 B
Illustration booklet page 4
( ) Set an AC VTVM to the 3 VAC scale.
( ) Connect the AC VTVM common lead to the generator chassis.
( ) Set the MODULATION OFF/ON switch to the ON position.
( ) Set the MODULATION AMPLITUDE control to maximum clockwise.
( ) Connect the AC VTVM signal lead to the emitter of transistor Q3.
[Center of circuit board in front of the 100 uF capacitor]
( ) Adjust the AMP / ADJ control for a 2-volt meter indication.
( ) Disconnect the AC VTVM leads.
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PRESET ADJUSTMENTS
· The coil slug adjustments which determine the lower end frequency of each band have been adjusted to precision standards at the factory. DO NOT ADJUST.
( ) Adjust the trimmer capacitor C12 adjustment screw clockwise until snug.
( ) Adjust the trimmer capacitor C12 adjustment screw counter-clockwise 1-1/2 turns.
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Using an AM/FM RADIO (option)
Range bands A through D
( ) Set the RF OFF/ON switch to the ON position.
( ) Set the AM/FM radio OFF/ON switch to the ON position.
( ) Set the AM/FM radio to the AM band.
( ) Allow both the RF generator and the AM/FM radio to warm up for 15 minutes.
( ) Connect a pair of test leads to the RF output terminals.
( ) Carefully tune the radio to a station of known frequency on the AM band between 800 and 1000 kHz.
· The frequency selected should fall directly on one the even calibration points, such as 800, 850, 900 or 1000 kHz.
( ) Set the MODULATION OFF/ON switch to the OFF position.
( ) Set the RANGE switch to the .31 – 1.1 A position.
( ) Set the RF AMPLITUDE control to maximum clockwise.
( ) Place the red terminal test lead near the loop or antenna lead of the AM radio, but do not connect it directly to the radio antenna.
( ) Set the FREQUENCY dial pointer to the exact frequency of the radio station.
( ) Adjust the radio volume to an audible level.
( ) Adjust the trimmer capacitor C12 until a zero beat is heard.
[Front of circuit board next to large variable capacitor]
( ) Adjust the RF AMPLITUDE control until the output is just high enough for a clear zero beat signal.
( ) Adjust the trimmer capacitor C12 until a zero beat is heard.
Range band E
( ) Set the AM/FM radio to the FM band.
( ) Carefully tune the radio to a station of known frequency on the FM band between 88 and 100 MHz.
· The frequency selected should fall close to one the even calibration points.
( ) Set the MODULATION OFF/ON switch to the ON position.
( ) Set the RANGE switch to the E 32 - 110 position.
( ) Set the FREQUENCY dial pointer to the exact frequency of the radio station.
( ) Adjust the MODULATION AMPLITUDE control about 20 degrees clockwise from maximum counter-clockwise.
( ) Connect a pair of test leads to the RF output terminals.
( ) Connect the test leads to the free ends of the radio FM antenna terminals.
( )* Adjust the FREQUENCY dial pointer back and forth and listen for the 1000Hz modulation tone.
· The tone will be weakest (null) at the correct frequency, and it will be louder on both sides of this frequency.
( )* Adjust the MODULATION AMPLITUDE control as required.
( )* Adjust the FREQUENCY dial pointer to where the tone is weakest.
( )* If the FREQUENCY dial pointer is not on frequency, adjust the dial pointer to the correct frequency.
( )* Adjust the trimmer capacitor C22 until the tone is weakest.
( ) Repeat the above five steps* until the dial pointer matches the radio station frequency.
( ) Set the AM/FM radio to the OFF position.
( ) Disconnect the test leads from the radio FM antenna terminals.
( ) Disconnect the test leads from the RF output terminals.
( ) Set the MODULATION OFF/ON switch to the OFF position.
( ) Set the MODULATION AMPLITUDE control to maximum counter-clockwise.
( ) Set the RF OFF/ON switch to the OFF position.
( ) Set the RF AMPLITUDE control to maximum counter-clockwise.
( ) Set the FREQUENCY dial pointer control to maximum counter-clockwise.
( ) Set the RANGE switch to the .31 – 1.1 A position
( ) Calibration procedure is complete.
* * * * * * *
Using a FREQUENCY COUNTER (option)
( ) Set the MODULATION OFF/ON switch to the OFF position.
( ) Set the MODULATION AMPLITUDE control to maximum counter-clockwise.
( ) Set the RF AMPLITUDE control to maximum clockwise.
( ) Set the RF OFF/ON switch to the ON position.
( ) Allow both the RF generator and the frequency counter to warm up for 15 minutes.
( ) Connect a pair of test leads to the RF output terminals
( ) Connect the test leads to the frequency counter input.
· Adjust the tuning slugs with an alignment tool.
· Adjust the trimmer capacitor C12 for the greatest overall accuracy.
· Remember that the other bands will also be affected.
( )* Adjust each band for the high frequency with the trimmer capacitor C12.
( )* Adjust each band for the low frequency with the coil slugs.
( ) Repeat the above two steps* until no change in the reading for the five bands.
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High Adjust Low Adjust
Band Frequency Trimmer Frequency Coil
( ) A 1.1 MHZ C12 .31 MHz L1
( ) B 3.2 MHZ C12 1 MHz L2
( ) C 11 MHZ C12 3.1 MHz L3
( ) D 32 MHZ C12 10 MHz L4
( ) E 90-110 MHZ C12 32-35 MHz L5
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Tuning frequency chart
· To adjust coil L5, for a higher frequency, carefully squeeze the turns together.
· To adjust coil L5, for a lower frequency, carefully spread the turns apart.
( ) Set the RANGE switch to the 10 – 32 D position.
( ) Adjust the FREQUENCY dial for a 17 MHZ output.
( ) Loosen the FREQUENCY dial knob setscrew.
( ) Set the FREQUENCY dial pointer at the 17 indication on the BD scale.
( ) Tighten the FREQUENCY dial knob setscrew.
( ) Disconnect the test leads from the frequency counter.
( ) Disconnect the test leads from the RF output terminals.
( ) Set the RF OFF/ON switch to the OFF position.
( ) Set the RF AMPLITUDE control to maximum counter-clockwise.
( ) Set the FREQUENCY dial pointer control to maximum counter-clockwise.
( ) Set the RANGE switch to the .31 – 1.1 A position
( ) Calibration procedure is complete.