Batboard

Anybody have an idea on how much transmitter power an N connector can realistically handle? I'm working with an AM broadcast transmitter, rated for 1-2kw output into 50 ohms, that has a female N for the antenna connector, and I'm worried that there could be too much voltage present for such small internal dimensions. I'm sure the dielectric can handle the power, but what about the comtact resistance of the center pin? Not much surface there to grab on to, compared to something like a UHF (PL-259) connector. We'll be running about 15 feet of 7/8 coax to the antenna switch and I know that coax can handle the power.

In "the old days", they just used two insulated threaded posts, perhaps #10 screws and nuts, and crimp/solder lugs on the end of the coax.

Thanks.

Bob M.

Thanks for finding that link. A 1000w signal, into 50 ohms, is about 224 volts, well within the voltage limit of the connector. But I bet when one adds the modulation, the p-p voltage goes somewhat higher. I'm still not happy with the relatively small contact area of the center contact; I'd be much happier with a UHF connector for this application. But I didn't design the transmitter !

Bob M.

Look farther down the spec sheet where you will find:

Peak Power Maximum 10 kW
Average Power Maximum .60 kW

The Motorola System Engineer that designed our system told us that he specified DIN and LC series connectors in our main transmit lines [at the output of 15 channel combiners] because the standard N connector should not be used above 500 Watts.

Actually if you look a bit closer, you'll see that the bottom section is for so-called "corrugated" N connectors. They don't give a power rating for the ordinary kind above, just a voltage rating. I was quite surprised to see that very tiny decimal point where it said .60 kw. That's why a leading zero is so nice to see. For all I know it could be 6.0 kw or even 60 kw and that dot is merely a spec of dirt !

But seriously folks, I'm more concerned about the contact resistance and actual surface area of the center pin. At least a UHF connector has some meat in it, and it engages with a greater insertion length than an N connector does.

Seems like a poor choice for connectors on a 1-2kw AM transmitter.

Bob M.

kcbooboo wrote:
But seriously folks, I'm more concerned about the contact resistance and actual surface area of the center pin. At least a UHF connector has some meat in it, and it engages with a greater insertion length than an N connector does.

Seems like a poor choice for connectors on a 1-2kw AM transmitter.

Bob M.

Actually, I agree. At higher frequencies (especially above 300MHz), the amount of outer shielding is more important then the size of the center pin for reducing coupler loss, thus the N-connector is great for higher frequency applications. At lower frequencies such as is common in AM, the PL-259 connector is probably a better choice.

Todd