Tom Rauch wrote:
> > The term "UHF" is a complete misnomer in discussing these connectors. They
> > are strictly HF devices. VSR above around 140 MHz is too high. The better
> > types use PTFE, bakelite or similar insulation (won't melt when heated
> > with a soldering iron).
>
> The impedance bump in a UHF connector is confined entirely to
> the area of the female about 1/2 inch long, assuming a hood is
> used on the female's rear. The impedance of that bump is about
> 30-35 ohms.
>
> The VSWR error from using a single connector, assuming the 30
> ohm impedance and a VP of .5 is 1.028:1 at 50 MHz.
>
> It is only 1.25 at 400 MHz!
>
> That's why you find UHF connectors used on landmobile radios up
> to 400 MHz and higher. The impedance bump, and loss, of a UHF
> connector can be pretty much ignored up to 250 MHz, and often is
> negligible above 250 MHz if the connector has partial air dielectric
> in the female section.
I had always assumed this fact resulted from commercial imperatives
rather than engineering ones.
I had a look in the Suhner catalogue:
Impedance - "undefined"
Working voltage - 750 v
Test voltage 2500/50 Hz.
Freq range DC-200 MHz.
Insulation 5 G-ohm
Current 10A max.
By comparison a 50 ohm "N" has a range of 18 GHz (75 ohm "N" 1.5 GHz due
to impedance bumps).
Note that Suhner is top quality, the Taiwanese route is around 6 dB
down.
Inherent in any "UHF" connector is the performance of the cable making
up part of the connector.
Cheers,
Ian ZS6BTE
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