Restoring a vintage tube radio or aligning older telecom and network gear usually calls for an RF signal generator. The tricky part is choosing among used units that differ widely in price, frequency coverage, and included documentation. Here's how to pick.
Quick Take
Comparing these four used RF signal generators for network, cable, and telecom bench work comes down to three questions: how much you want to spend, how high a frequency you need, and whether an original manual matters to you. The two Knight KG-650 units cover the budget side at $45 each, offering a tube-era circuit you might use for radio restoration. The HP 8654B, at $116.96, adds a much wider 10-520 MHz range for higher-frequency telecom tasks. The HP 606A, at $161.10, is the priciest and tops out at 65 MHz.
Listed Price Comparison
| Model | Price | Price Bar |
|---|---|---|
| Knight RF Signal Generator Vintage Tube Radio Test Equipment USA (First) | USD 45.00 | |
| Knight RF Signal Generator Vintage Tube Radio Test Equipment USA (Second) | USD 45.00 | |
| HP 8654B Signal Generator 10-520 MHz Vintage RF Test Equipment | USD 116.96 | |
| Hewlett-Packard 606A Signal Generator Vintage RF Test Equipment With Manual | USD 161.10 |
The price spread from $45 to $161.10 creates a $116.10 gap between the most and least expensive options.
Decision Matrix
| Your priority | Best fit |
|---|---|
| Lowest listed price | Knight KG-650 (either of the two identical units) |
| Widest frequency range | HP 8654B |
| Included documentation | HP 606A |
If price is the deciding factor, one of the two Knight units will do. If you need to go beyond the AM and shortwave band, the HP 8654B offers a higher reach. If you want documentation with your vintage generator, the HP 606A is the one to pick.
Product Notes
Knight RF Signal Generator Vintage Tube Radio Test Equipment USA (First Unit)
Choosing the first of the two Knight KG-650 units gives you the lowest-priced RF generator in this group, an easy entry point for vintage radio repair. The unit features RF coarse and fine tuning, internal/external modulation, an audio input, and a metal cabinet, with front panel lettering that remains readable and knobs that appear original. The main limitation is the untested condition and the limited included contents: only the generator itself, with no manual or accessories listed. If you're comfortable troubleshooting vintage electronics, this budget path is worth considering.
Knight RF Signal Generator Vintage Tube Radio Test Equipment USA (Second Unit)
The second Knight KG-650 unit is identical to the first and also sits at the low end of the price scale, giving you another opportunity to pick up this classic Allied Radio tube-era generator without paying more. It includes RF coarse and fine tuning, internal/external modulation, and an audio input, all in a metal cabinet. Normal scuffs and dust are expected, and the front panel lettering remains readable. Like the first example, it is sold untested and includes only the generator, no manual or accessories. Use it as a backup if the first unit is gone, or as a project unit for a restoration.
Hewlett-Packard 606A Signal Generator Vintage RF Test Equipment With Manual
The Hewlett-Packard 606A Signal Generator is the highest-priced unit in this set, and its main draw is a complete vintage package: the unit includes an original operating and service manual. The heavy metal enclosure, large analog frequency dial covering 50 KC to 65 MC, and two meters for percent modulation and DBM/volts give it a substantial bench presence. Visible wear on the enclosure paint and sides is noted, but no major dents are mentioned. The unit is untested, so treat it as a collector-oriented purchase that still needs verification before regular use.
HP 8654B Signal Generator 10-520 MHz Vintage RF Test Equipment
The HP 8654B Signal Generator is the middle-priced option and stands out for its 10-520 MHz frequency coverage, far higher than the 606A's band. That makes it a practical fit for telecom and network testing where you need to generate signals in the VHF range and beyond. The aged leather handle is intact, and the main controls and connectors appear present. Surface dirt, scuffs, and oxidation are visible, and the unit is untested. It does not include accessories or packaging, so you'll likely need to supply your own cables and a power cord.
Bottom Line
Before you decide, keep in mind that both Knight units share the same untested status, so the real differentiator between the two is availability, not capability. The HP choices split cleanly: the 606A is the higher-priced unit and operates in a lower frequency band, while the 8654B covers a wider range at a lower price. Weigh those tradeoffs against your budget and the type of RF work you plan to do.
Final Recommendation by Use Case
- Budget bench work: Pick one of the Knight KG-650 units.
- High-frequency telecom and network testing: Choose the HP 8654B for its extended range.
- Classic HP with documentation: Go with the HP 606A if you want the original manual with your vintage generator.
