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Vintage Heathkit IM-2420 Benchtop 512 MHz Frequency Counter Kit
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Vintage Heathkit IM-2420 Benchtop 512 MHz Frequency Counter Winter 1981 Catalog - RF Cafe Cool Product

Vintage IM-2420 Benchtop Portable 512 MHz Frequency Counter in the Winter 1981 Heathkit catalog (p25).

This vintage Heathkit IM−2420, 512 MHz Benchtop Portable Frequency Counter kit is one of the latest unbuilt Heathkit kits which appeared on eBay. I have been saving the images in order to preserve the history (see image below). The constantly growing list is at the lower right.

One of the first instances I could find for IM−2420 being offered for sale was in the Winter 1981 Heathkit catalog, at a cost of $239.95 ($754.51 in 2021 money per the BLS) as a kit or $299.95 ($943.18 in 2021) assembled and tested. A comparable benchtop frequency counter today is the RISEPRO Benchtop Frequency Counter for 10 Hz-2.4 GHz, at a cost just south of $90.

"UHF capability up to 512 MHz, low frequency capacity down to 5 Hz and a budget-pleasing price are all yours when you choose the newest Heathkit Digital Frequency Counter. Service technicians and do-it-yourselfers will find its extended frequency range idea for servicing UHF 2-way radios now used by police and fire departments - as well as most other communications equipment.

Our engineers have designed more features and added capabilities into this laboratory quality Heathkit instrument. For example, the IM−2420 can do more than measure the frequencies of input signals - its period function can give cycle time in seconds, while the frequency ratio function provides the ratio between two input frequencies.

Make more accurate measurements: A Standby power switch can keep the crystal oven warm, giving you maximum frequency accuracy as soon as the IM−2420 is turned on. Proportionally-controlled crystal oven keeps the internal time base extremely accurate - within 0.1 part per million (ppm) - over a wide temperature range. The crystal-controlled time base provides excellent long-term stability, with drift controlled to less than 1 ppm per year. And the external time base jack allows the use of an external time base signal.

Four gate times and a large, 0.43 (1.09 cm)-high, 8-digit LED display provide the resolution you need to measure UHF signals. The pivoting stand places the IM-2420 at a comfortable, convenient viewing angle.

The IM−2420s excellent 4-15 mV typical sensitivity, over the entire 5-Hz-512 MHz range, allows counting of weak signals. Trigger level control assures stable counting when noise is present, and provides more accurate measurement of complicated waveforms. Effective limiting circuits at both inputs (5 Hz-50 MHz and 40 MHz-512 MHz) make sure counting is stable, even when the input signal level varies by as much as 60 dB.

Measure signals with a direct connection. Or, for frequency counts without a direct connection, order the SMA-2400-1 Swiveling Telescopic Antenna (right).

Extra protection is built into the IM−2420, too. Its rugged, compact metal cabinet provides improved shielding from radio-frequency interference (RFI). Full voltage protection assures worry-free counting.

  • Extra-wide frequency range for maintenance of UHF, VHF radios
  • Crystal-controlled time base for excellent long-term stability and accuracy
  • Features four gate times and 8-digit resolution to give you more precise readings
  • Provides you with two separate inputs and trigger level control for added versatility

Kitbuilding is easy: the IM−2420 takes as little as four evenings to build, with a fully detailed Heathkit manual to guide you along the way, step-by-step. ICs are standard and easily available, for faster servicing.

Kit IM−2420. Shpg. wt. 9 lbs.  . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 239.95

SM−2420, Assembled 5 Hz-512 MHz Frequency Counter, Shpg. wt. 9 lbs.  . . 299.95

Heathkit IM-2420 512 MHz Frequency Counter Kit Contents - RF Cafe

Heathkit IM-2420 512 MHz Frequency Counter Kit Contents

(eBay photo)

Heathkit IM-2420 512 MHz Frequency Counter Kit Parts - RF Cafe

Heathkit IM-2420 512 MHz Frequency Counter Kit Parts

(eBay photo)

Heathkit IM-2420 512 MHz Frequency Counter Printed Circuit Board - RF Cafe

Heathkit IM-2420 512 MHz Frequency Counter Printed Circuit Board

 (eBay photo)

Heathkit Winter 1981 Catalog Cover - RF Cafe

Heathkit Winter 1981 Catalog Cover

(worldradiohistory.com photo)

Heathkit IM-2420 512 MHz Frequency Counter Components - RF Cafe

  Heathkit IM-2420 512 MHz Frequency Counter Components

(eBay photo) 

Heathkit IM-2420 512 MHz Frequency Counter Rear Panel - RF Cafe

 Heathkit IM-2420 512 MHz Frequency Counter Rear Panel

(eBay photo) 

Heathkit IM-2420 512 MHz Frequency Counter Schematic - RF Cafe

 Heathkit IM-2420 512 MHz Frequency Counter Schematic

(eBay photo) 

Heathkit products were well known for the completeness of its instruction manuals, with clearly illustrated instructions. During the writing and editing process, Heathkit employees were given pre-production kits to take home and build, while annotating any difficulties or errors encountered. Doing so helped minimize the situation where the writer inadvertently assumes his own familiarity with the process is shared by the customer. Having built a few Heathkit products myself in the 1970s when I did not have a lot of experience with electronics assembly, I can attest to the user friendliness of the instructions. Heathkit still sells many of its vintage manuals for around $15, which is what you would pay on eBay. You can download the IM−2420 manual here.


Contact Info

Heath Company (Heathkit)

Operations: PO Box 15, Ottsville, PA 18942

R&D/Mfg: PO Box 3115, Santa Cruz CA 95063

Phone: +1 (831) 480-4368

E-Mail: info.2015@2015.heath.company



Posted September 22, 2021

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