The Jerrold Model 704 (including its variants the 704A and the 704B) holds a special place in the history of the cable television industry. During the 1960s, when most cable TV systems were carrying twelve channels (2-13), the 704 was the most popular signal level meter in use. An entire generation of system techs came of age using the 704.
The 704 incorporated a continuous tuner capable of tuning 54 to 220 MHz band. VHF Channels 2-13, and the FM broadcast band, were indicated. Although the meter was capable of tuning midband channels (98, 99, 14-22), they were not indicated on the tuning dial; only the corresponding off-air bands (aviation, amateur, telephone) were indicated.
The meter was not capable of tuning UHF, superband, or subband channels. To address the need to tune to these bands, Jerrold offered an adapter known as the TK-Channel Adapter This device was connected between the incoming test signal and the 704 input connector.
This device block-converted a desired band of frequencies to a band within the 704's tuning range. Richard Kreeger (who contributed one of the photos on this page) believes this adapter was designed to up convert the 5-47 MHz spectrum to 105-147 MHz. Kreeger also notes that "it was a unity gain device so it would read these signals directly from a level standpoint."
Graham Stubbs, in his article "Workhorse to Icon: The 704 Jerrold Field Strength Meter," states:
For the "K" channels, used by Jerrold as part of a scheme to effect adjacent channel operation in the early 1950’s, a special adaptor was provided which mounted on the outside of the cabinet.
Jerrold also offered a 300-ohm to 75-ohm transformer. This device matched a 300-ohm source (e.g., a dipole antenna) to the 75-ohm input of the 704B so that the 704 could be used to measure the field strength of an electromagnetic field.
The 704 has long since passed from the scene, but its memory lives on to this day, kept alive by an organization of mildly insane senior citizens known as the Loyal Order of the 704. Each year, during the annual SCTE Cable Tec Expo, the Loyal Order meets for an evening of ritual conviviality accompanied by the 704's mascot, a pink plastic flamingo named Pinky.
Model 704B with TK-Channel Adapter Module and Manual
Note the TK-Channel Adapter attached to the right side of the cabinet, connected via a coaxial cable to the 704B input connector.
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| Photo: Richard Kreeger | High resolution |
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Accessories used with the Model 704B
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Photo: Jim Cruth
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High resolution
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Photo: Jim Cruth
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High resolution
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Jerrold TK-Channel Adapter
The six-pin Cinch Jones connector connects to the power supply via a Y-cable.
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Jerrold 300-72-Ohm Transformer
Matches a 300-ohm source (e.g., a dipole antenna) to the 75-ohm input of the 704B.
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Model 704 (S/N 0101) with Manual
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| Photo: Ned Fenimore | |
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| Photo: Ned Fenimore | |
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| Photo: Ned Fenimore | |
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| Photo: Ned Fenimore | |
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| Photo: Ned Fenimore | |
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| Photo: Ned Fenimore | |
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| Photo: Ned Fenimore | |
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| Photo: Ned Fenimore | |
Model 704A (S/N 1101) with 300-72-Ohm Transformer
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| Photo: Jim Cruth | |
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| Photo: Jim Cruth | |
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| Photo: Jim Cruth | |
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| Photo: Jim Cruth | |
Model 704B (S/N 7365) with photos of internal construction
The following photos show various views of a 704B dating from approximately 1968. This particular 704B was owned by Illinois Teachers College Chicago-North (now Northeastern Illinois University). It was retired from the University's inventory in the 1990s.
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| Photo: Neal McLain | |
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| Photo: Neal McLain | |
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| Photo: Neal McLain | |
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| Photo: Neal McLain | |
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| Photo: Neal McLain | |
| Meter, calibrated in microvolts and decibels ("DB"). In this case, "DB" in not synonymous with "dBmV" (or "dBj" as Jerrold calls it) for reasons explained in Section I-2(e) of the Operation and Maintenance Manual. |
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| Photo: Neal McLain | |
| Tuner, calibrated in frequency and channels 2-13. |
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| Photo: Neal McLain | |
| Range switches, calibrated in microvolts and dBj. |
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| Photo: Neal McLain | |
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| Photo: Neal McLain | |
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| Photo: Neal McLain | |
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| Photo: Neal McLain | |
Mallory IF Strip — probably a standard assembly
designed for the consumer television market. |
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| Photo: Neal McLain | |
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| Photo: Neal McLain | High resolution |
Note the six-pin male Jones connector for power input.
This connector mates a female connector on the power supply. |
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| Photo: Neal McLain | |
| Power supply module. |
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| Photo: Neal McLain | |
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| Photo: Neal McLain | |
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| Photo: Neal McLain | |
| Cover closed for transportation. |
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| Photo: Neal McLain | |
| Rear view showing storage compartment for line cord and shoulder strap. |
Instruction Manuals
