Note
One of a pair of VHF receiving converters, the other being the two-meter SBA-300-4. Both were designed specifically for the SB-300/301 receivers, but can be used with any receiver having similar characteristics. A separate power source would be required for use with the SB-303. The outputs of the converters are connected to two rear panel jacks on the receiver—VHF #1 and VHF #2. It doesn’t matter which converter is connected to which jack, as long you know which is which.
The converters could be mounted to the rear panel of the receiver, if desired. Rear panel mounting holes are provided, except on very early versions of the SB-300.
The converters may be used individually, or may be plugged together, as loop-through power is provided. Power is supplied from the receiver.
The converter covers a two megahertz segment of the six-meter band, with output on the 10-meter band. Refer to specifications below.
Crystal Frequency and Coverage
Converter Crystal Coverage
20 MHz 48 to 50 MHz
21 MHz 49 to 51 MHz
22 MHz 50 to 52 MHz (supplied)
23 MHz 51 to 53 MHz
24 MHz 52 to 54 MHz
If a crystal other than 22 MHz is installed, it will be necessary to readjust coil L6.
Crystal Characteristics
Type: HC-6/U
Load capacitance: 12.8 pF
Internal capacitance: 6 pF
Series resistance: 30Ω
Drive level: 8 mW
Mode of operation: 3rd overtone
Sensitivity:
AM: Better than 0.1 microvolts for 6 db at 3750 Hz bandwidth
SSB: Better than 0.1 microvolts for 10 db at 2100 Hz bandwidth
CW: Better than 0.1 microvolts for 15 db at 400 Hz bandwidth
Noise figure: 5 db or less at 3750 Hz bandwidth
Bandpass: Essentially flat over any 2 MHz segment between 48 to 54 MHz
Frequency:
Input: 48 to 54 MHz (50 to 52 MHz with supplied crystal)
Output: 28 to 30 MHz
Image rejection: 50 db or better at 6 MHz
IF rejection: 40 db or better at 28 MHz
Crystal: 22.0000 MHz ± 0.005%, 3rd overtone, supplied
Power requirements: 130 VDC at 12.5 mA, and 6.3 VAC at 815 mA. Power is normally supplied by the receiver
Tubes: (1) 6DJ8, (1) 6EA8
Photos, general information and specifications from "Heathkit: A Guide to the Amateur Radio Products," by Chuck Penson, WA7ZZE. Used with permission.
