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Old November 21st 06, 02:52 PM posted to rec.radio.amateur.boatanchors
Scott Dorsey Scott Dorsey is offline
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First recorded activity by RadioBanter: Jul 2006
Posts: 774
Default Drake R4-C antenna connector question

COLIN LAMB wrote:
It should be stated that the PL-259, a favorite of the ham world, is not a
constant impedance, either. Some hams go nuts if they see you use one of
those on 2 meters or higher. However, it is simple enough to calculate the
impedance bump at a particular frequency simply by determining the impedance
(using the ratio of diameters and the length of the connection), then
determining what that bump is at a particular frequency.


PL-259 _is_ constant impedance, it's just not exactly 50 ohms. But it's
closer to 50 ohms than the RCA is.

I did that once, to show a friend that he should not lose sleep over the
connector. It is like inserting a 1" length of 75 ohm coax in a 50 ohm
line. Remember that 50 ohm coax is not necessarily 50 ohms. It is a
nominal impedance, which means it might be 50 ohms, or 52 ohms or even 53
ohms. So, if you are worried about the connector, you should measure the
coax to see what impedance you really want.


Not to mention measuring the antenna! But with coax, the number in the
manufacturer's catalogue is probably correct (but in a lot of cases it
is NOT the same as the number in the Radio Guide!)
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."