[Elecraft] OT: SO-239 Connector Selection

[Wes Stewart]

I agree with Tom.  The biggest problem, from my perspective, with the "UHF" connectors is the variability of attachment to the cable.  I have no experience with crimp varieties, they may mitigate the issue, but the solder on types are ripe for trouble.

The other problem with them if you are trying to do any precision measurements---an oxymoron I suppose---is that any decent instrumentation will have type N connectors, thus adapters are necessary.  Again at HF I would just include the adapter as part of the thing I was testing and not worry about it.

Wes  N7WS

--- On Thu, 7/22/10, Tom W8JI <w8ji at w8ji.com> wrote:

> In some connector applications ... particularly power
> dividers and other applications that are "impedance-
> conscious" ... SO-239 / PL-259" connectors are not
> suitable.

This is NEVER the case at 30 MHz and lower, so long as connection to the 
connector are properly done. The total impedance bump length in a UHF female 
to UHF male pair is about the length of the center pin of the female.

All of the problems are in the female, and the length of the problem area is 
confined to the spread area of the female that fits over the male pin. That 
area is about 35 ohms impedance, not a large mismatch.

The effect of that is virtually immeasurable on 30 MHz. If connections to 
the SO-239 are 50 ohms, the SWR caused by a SO-239 would be 1.006:1.

If anyone has a problem using a single SO239 PL259 pair below 50 MHz in 
anything but the most critical measurement systems, they did something else 
wrong. This would include filters, combiners, splitters, and loads. 1/2 inch 
at 35 ohms is nothing below UHF.

73 Tom