>>> LOA5C RF SOURCE <<<

  The assembly shown in Figures 1 and 2 is a broadband RF source that covers 62.5 to 500 MHz with 3 jumper settings of the onboard ECL Prescaler IC.   The LOA5C Circuit Diagram of Figure 3 is included to clarify assembly operation.  The frequencies in these bands are set by tuning the onboard VCO between 500 and 1000 MHz  (1.5 V < V-T < 13.00 V).   Figures 4 through 6 show the LOA5C Output Power of each Band.  Tables 2 through 7 show the power level of the 2nd and 3rd harmonic of the LOA5C measured with a spectrum analyzer.  To use this RF source for receiver testing, add 60 to 120 dB of attenuation on the output, and, if necessary, a LOW PASS FILTER to attenuate the 2nd and 3rd harmonic.  To drive the LO Port on a double balanced mixer, add 3 dB to10 dB of attenuation between the LOA5C output and the input of a MWA23 or HUA23 VHF/UHF amplifier.  For swept frequency and FM applications, the VCO Driver, VCOTC, is required.  A  complete RF Generator can be viewed by clicking on this hyperlink, RF Generator.

  Table 1 shows what frequency band is selected when a short is  installed on or removed from the 2 pin headers, J1 and J2, of Figure 2.  A short installed on the SB header of Figure 2 puts the ECL Prescaler IC in the stand by mode resulting in no output until the short is removed.

Band Divide Ratio Header J1 Header J2 Header SB VCO @ 500 MHz VCO @ 1000 MHz
A 8 OPEN OPEN OPEN 62.5 125
B 4 OPEN SHORT OPEN 125 250
B 4 SHORT OPEN OPEN 125 250
C 2 SHORT SHORT OPEN 250 500
-- -- -- -- SHORT No Output No Output

Table 1, Band Select

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Figure 1, LOA5C Printed Circuit Assembly Side 1

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Figure 2, LOA5C Printed Circuit Assembly Side 2

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Figure 3, LOA5C Circuit Diagram

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Figure 4, Divide Ratio 8 (Band A) Output Power Plot

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Figure 5, Divide Ratio 4 (Band B) Output Power Plot

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Figure 6, Divide Ratio 2 (Band C) Output Power Plot

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  This first group of three Spectrum Analyzer measurements were performed with the VCO set to 500 MHz (V-T = 1.52 VDC)

 

FUNDAMENTAL

2ND HARMONIC

3RD HARMONIC

OUTPUT FREQUENCY (MHz)

62.5

125.0

187.5

OUTPUT POWER (dBm)

-2.02

-48.96

-10.83

 Table 2, ECL Prescaler IC set to divide by 8

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FUNDAMENTAL

2ND HARMONIC

3RD HARMONIC

OUTPUT FREQUENCY (MHz)

125

250

375

OUTPUT POWER (dBm)

-1.76

-50.12

-10.76

 Table 3, ECL Prescaler IC set to divide by 4

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FUNDAMENTAL

2ND HARMONIC

3RD HARMONIC

OUTPUT FREQUENCY (MHz)

250

500

750

OUTPUT POWER (dBm)

-1.26

-16.8

-22.27

 Table 4, ECL Prescaler IC set to divide by 2

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  This next group of three Spectrum Analyzer measurements were performed with the VCO set to 1000 MHz (V-T = 12.94 VDC).

 

FUNDAMENTAL

2ND HARMONIC

3RD HARMONIC

OUTPUT FREQUENCY (MHz)

125

250

375

OUTPUT POWER (dBm)

-1.7

-31.1

-10.8

 Table 5, ECL Prescaler IC set to divide by 8

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FUNDAMENTAL

2ND HARMONIC

3RD HARMONIC

OUTPUT FREQUENCY (MHz)

250

500

750

OUTPUT POWER (dBm)

-1.07

-26.8

-17.2

 Table 6, ECL Prescaler IC set to divide by 4

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FUNDAMENTAL

2ND HARMONIC

3RD HARMONIC

OUTPUT FREQUENCY (MHz)

500

1000

1500

OUTPUT POWER (dBm)

-5.45

-15.47

-45

 Table 7, ECL Prescaler IC set to divide by 2

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RF Generator

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