>>> LOA5C RF SOURCE <<<
The assembly shown in Figure 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 the lower 2 white jumpers of Figure 2 are installed or removed. The top white jumper puts the ECL Prescaler IC in the stand by mode (SB) when installed.
| Band | Divide Ratio | Jumper J1 | Jumper J2 | Jumper SB | VCO @ 500 MHz | VCO @ 1000 MHz |
| A | 8 | OFF | OFF | OFF | 62.5 | 125 |
| B | 4 | OFF | ON | OFF | 125 | 250 |
| B | 4 | ON | OFF | OFF | 125 | 250 |
| C | 2 | ON | ON | OFF | 250 | 500 |
| -- | -- | -- | -- | ON | 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)
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|
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).
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|
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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