109

Manuals – Specifications – Links – Pictures

The Tektronix Type 109 is a pulse generator introduced in 1962.

It uses a GR-874 50 Ω output connector and has a specified rise time of 250 ps.

Key Specifications

Rise time	250 ps
Pulse frequency	550 to 720 Hz
Pulse length	0.5 ns to 100 ns with a single charge line between the two charge line connectors, or up to 300 ns at half pulse rate with one open-ended charge line (other connector grounded)
Pulse amplitude	Internal supply: 0 to 50 V variable in three ranges (0.5 V, 5 V, 50 V), positive or negative, or external up to ±300 V

Internals

The 109's operating principle is that of a charged transmission line pulse generator with a mechanical reed switch and external 50 Ω transmission line/lines attached through two GR-874 50 Ω connectors. The length of the external cables determines the impulse width. Using two transmission lines of non-equal length, alternating pulses having different width can be produced. Alternatively, an R-C network can be used to create pulses with R-C decay characteristic but longer duration.

The pulse-generating switch in the 109 is a mechanical mercury switch, which limits pulse frequency to about 600 Hz. Moreover, this switch has a relatively short life time (200 hours) — if the operator forgets to shut the 109 down over the weekend and some holidays, the reed switch will need replacement. Component News 259, 5 May 1978 says:

The most critical usage of mercury reed switches is in Tek's Type 109 Pulse Generator. (The 109 is used in-house for calibrating virtually all our product lines.) Unfortunately, there are no plans to replace this instrument line, which is dependent on the 260-0282-01 mercury reed switch for a 250 ps rise time pulse capability. To make matters worse, these switches are single-sourced from C. P. Clare, who must import them from Belgium. We are also having problems obtaining quality parts. (The raw switch costs approximately $5, but when the cost of rejects and added tooling are figured in , the cost per switch approaches $55.)

The internal voltage source is adjustable from 0 to 50 V in three ranges (0.5 V, 5 V, 50 V), either positive or negative. Using external voltage sources, pulses up to 300 V of either polarity are possible, including alternating positive/negative pulses.

Repair issues

Be aware during servicing that the thermal breaker is on full mains and has no protection cover!

Links

• Jim Williams, Linear Technology Application Note 120, "1 ppm Settling Time Measurement for a Monolithic 18-Bit DAC" - see Appendix H (p.30)
• Report comparing RG-58 with RG-174 using Tek 109 and Tek 661 (PDF)
• Tek 109 page @ amplifier.cd

Pictures

• 

  Front view

• 

  Right internal

• 

  Left internal

• 

  Rear view (connector not original)

• 

  flying spot caught with 7904, S6, 7T11, 7M11. 2.5 V_pk, T_r=240 ps

• 

  schematic

• 

  017-067 Charge network for 109

• 

  017-067 Charge network for 109 (description)

• 
• 
• 

  top

• 

  bottom