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High Frequency Measurements Web Page
Douglas C. Smith

 Address:  P. O. Box 1457, Los Gatos, CA 95031
 TEL:      800-323-3956/408-356-4186
 FAX:      408-358-3799
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Technical Tidbit - December 2008
Inexpensive Protective Caps for BNC and SMA Connectors
(also known as vacuum port caps for automobile engines)

bag of vacuum port caps for car engines

Figure 1.
A Bag of Vacuum Port Caps for Automobile Engines

Abstract: Sometimes a device intended for one use is also suitable for another and often provides an inexpensive solution to a problem as well. An inexpensive and readily available source of protective caps for BNC and SMA connectors is discussed.

Discussion: Figure 1 shows a small bag of assorted vacuum port caps (Pico part #7029C, ), intended for use on intake manifolds in automobile engines, that was purchased for a few US dollars. It turns out that some of the caps can be used to protect BNC and SMA connectors. Figure 2 shows a small 1/8 inch white cap and a larger 3/8 inch yellow cap that just fit snugly over SMA and BNC connectors respectively. Four of the yellow caps can be used on the BNC inputs of an oscilloscope to keep out dirt and protect from mechanical damage. These caps do the same job as the plastic caps used for the same purpose by equipment and connector suppliers, but at a very low cost.

caps for BNC and SMA adapters

Figure 2.
Two Caps Suitable for Protecting SMA (left) and BNC (right) Connectors

Figure 3 shows a large bag containing 1000 of the yellow caps (Pico part #7024A, ). At this quantity the cost per cap is only about US$0.05!

large bag of BNC caps

Figure 3. Large Bag Containing 1000 Caps Suitable for Protecting BNC Connectors

Summary: Vacuum port caps for automobile engines make great inexpensive protectors for SMA and BNC connectors. They are low cost and very effective. Every lab should have a bag or two of these!

Additional articles on this website related to this topic are:
  1. July 2002, Inexpensive, but Useful Test Equipment
If you like the information in this article and others on this website, much more information is available in my courses. Click here to see a listing of upcoming courses on design, measurement, and troubleshooting of chips, circuits, and systems.

Click here for a description of my latest seminar titled (now available online as a WebEx seminar):

EMC Lab Techniques for Designers
(How to find EMC problems and have some confidence your system will pass EMC testing while it is still in your lab).

D-104 mike
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Copyright © 2008 Douglas C. Smith