Note
The SB-610 is essentially an HO-10 put into a new cabinet, but there were a few differences worth noting. The SB-610 uses only four tubes (excluding the CRT), because the power supply is solid state. As in the HO-10, no PC boards are used—all wiring is point to point.
The front panel SWEEP function control selects a standard internally generated sweep, an RF trapezoidal or RTTY display. A clamp function may be selected by pulling out on the SWEEP FREQ control. When activated, the clamp will pull the dot off the screen when no signal is present. This prevents burning of the CRT.
A rear panel attenuation control can be used to compensate for a range of RF power levels and will keep the displayed signal within the bounds of the CRT.
Unlike the HO-10, the SB-610 provides vertical amplifier wiring options to accommodate any receiver IF from 455 kHz to 6 MHz for use in analysis of received signals. An option is also available for 1 kHz to 150 kHz operation for RTTY use, or for use as a simple oscilloscope. Since the correct parts may be very hard to find, these options are not easy to change after the fact, and there is no simple field check to determine which option has been chosen. However, conversion to the oscilloscope/RTTY option is easy since it requires only the removal of parts.
The frequencies of the two-tone generator are 1500 and 1950 Hz. You can choose a single tone output (1500 Hz) or the two-tone signal. Both frequencies are at 50 mV nominal Note: The 6J11 compactron tone generator tube is expensive and sometimes found to be missing. This tube serves only to generate the two-tone frequencies. Even without the 6J11, all other functions of the SB-610 will operate correctly.
Rear panel connections include a pair of loop-through SO-239s for RF input and output, a pair of loop-through RCA jacks (exciter input for linearity checks), an RCA jack for tone output, and RCA jacks for vertical and horizontal input (for RTTY or oscilloscope use).
The 610 is finished in Heath’s standard two-tone green wrinkle paint and matches the rest of the SB line. Heath sold tens of thousands of SB-610s. They are not rare, and they turn up frequently at swap meets.
Caution: Handle cathode ray tubes (CRTs) with great care.
Warning: Lethal voltages present when operating.
References:
Review. QST. Jul 1972, p. 49.
Review. 73 Amateur Radio. Dec 1966, p. 54.
Clamp and attenuator mods. 73 Amateur Radio. Apr 1969, p. 42.
Use with SX-101A. CQ. Oct 1969, p. 74.
Use of Drake TR-4. Ham Radio. Jan 1971, p. 62
Reducing baseline ripple. QST. Dec 1972, p. 47.
Use for RTTY. Ham Radio. Sep 1974, p. 70.
General article. QST. Dec 2017, p. 104.
VERTICAL AMPLIFIER
Input resistance: 100kΩ
Sensitivity (untuned, per inch of vertical deflection):
10 Hz to 400 Hz: 2.0 volts
400 Hz to 10 kHz (RTTY): 1.0 volt
10 kHz to 455 kHz: 500 mV
Sensitivity (tuned, per inch of vertical deflection):
455 kHz: 70 mV
1600 to 2475 kHz: 200 mV
3000 to 3055 kHz: 400 mV
3395 kHz: 500 mV
5000 to 6000 kHz: 600 mV
HORIZONTAL AMPLIFIER
Frequency response: ±3 db from 3 Hz to 15 kHz
Sensitivity: 800 mV per inch of deflection
Input resistance: 1MΩ
SWEEP GENERATOR
Type: recurrent, sawtooth
Frequency: 15 to 200 Hz
GENERAL
Frequency coverage: 160 through 6 meters (50-75Ω coaxial input)
Signal limits: 15 watts to 1000 watts (5 watts with QRP option)
Rear panel attenuation: up to 24 db in 8 db steps
Power requirements: 120/240 VAC, 50/60 Hz. 35 watts
Tubes: (1) 6BN8, (1) 6C10, (1) 6J11, (1) 6EW6, (1) 3RP1A CRT
Photos, general information and specifications from "Heathkit: A Guide to the Amateur Radio Products," by Chuck Penson, WA7ZZE. Used with permission.
