SMA connectors - max power?

**Studio1** · 01-10-08, 07:49 AM

How much RF can a standard SMA connector cope with? I've been trying to find some data on them but only really found max frequency. Apparently there is a "Super SMA" which goes out to 26 GHz or so, and can handle 150 watts of RF.. but I need info on the standard range, if anyone knows or can suggest a source.

**ssrattus** · 01-10-08, 08:47 AM

Amphenol RF- SMA Connector Series

Appears that the peak voltage is the specification quoted and the power can be worked out from its impedance, assuming a matched system, ie low vswr.

**Studio1** · 01-10-08, 08:05 PM

Quote:

Originally Posted by ssrattus

Amphenol RF- SMA Connector Series

Appears that the peak voltage is the specification quoted and the power can be worked out from its impedance, assuming a matched system, ie low vswr.

Damn. That means I have to use my brain to work it out

**trash** · 03-10-08, 10:17 AM

It's all quite simple under ideal conditions.

P=(V^2)/(2*Z)
P Power
V peak voltage
Z impedence

You need to evaluate connectors independantly, as different brands can
have different performance.
Typically it's the strike voltage of the dielectric which is usually higher than
air. But air gaps in the connector's dielectric connection is the weak point.
Worst case you can always work with air dielectric. For SMA connectors, it's about 2mm radius from core to shield. This is approximately 2000V strike.

2000^2/100= 40kW peak. For dry air and a matched load. Ideal conditions.

Air is humid, dust gets into the connectors and if the connector is not quite 50 ohms or there is a termination fault, things can go VERY wrong.

Reality is more like 2.5kW peak ! And still this is not average power handling.
That then relies on the electrical connections themselves and the ability to
pass current without heating up and causing more mismatch problems.

Generally, a standard SMA connector is quite capable of handling frequencies up to 50GHz (and higher) and powers up to 100W.

The best way to test the limits is to melt a few yourself, mythbusters style.
You'll know where the limitations really are compared to a safe working load.

**Studio1** · 03-10-08, 04:41 PM

Quote:

Originally Posted by trash

It's all quite simple under ideal conditions.

P=(V^2)/(2*Z)
P Power
V peak voltage
Z impedence

You need to evaluate connectors independantly, as different brands can
have different performance.
Typically it's the strike voltage of the dielectric which is usually higher than
air. But air gaps in the connector's dielectric connection is the weak point.
Worst case you can always work with air dielectric. For SMA connectors, it's about 2mm radius from core to shield. This is approximately 2000V strike.

2000^2/100= 40kW peak. For dry air and a matched load. Ideal conditions.

Air is humid, dust gets into the connectors and if the connector is not quite 50 ohms or there is a termination fault, things can go VERY wrong.

Reality is more like 2.5kW peak ! And still this is not average power handling.
That then relies on the electrical connections themselves and the ability to
pass current without heating up and causing more mismatch problems.

Generally, a standard SMA connector is quite capable of handling frequencies up to 50GHz (and higher) and powers up to 100W.

The best way to test the limits is to melt a few yourself, mythbusters style.
You'll know where the limitations really are compared to a safe working load.

Thanks Trash, LOL ... I was actually being facetious when I said I'd have to use my head to work it out. The math isn't an issue, I do it all the time.
I'm just in a lazy mood

I'm considering using SMA on the output of a 40 watt FM exciter (88-108 MHz) so I think it will survive.
Ordinarily I'd use BNC but I have some nice SMA cables and connectors sitting here that would be ideal for the application.

01-10-08, 07:49 AM	#1 (permalink)
Studio1 Senior Member iTrader: (0) Join Date: Jan 2008 Location: Inside the toaster Posts: 484 Spent time on board: 3 Days and 11:13:34	SMA connectors - max power? How much RF can a standard SMA connector cope with? I've been trying to find some data on them but only really found max frequency. Apparently there is a "Super SMA" which goes out to 26 GHz or so, and can handle 150 watts of RF.. but I need info on the standard range, if anyone knows or can suggest a source.

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01-10-08, 08:47 AM	#2 (permalink)
ssrattus Super Moderator iTrader: (0) Join Date: Jan 2008 Posts: 1,233 Spent time on board: 3 Weeks, 6 Days and 6:47:02	Amphenol RF- SMA Connector Series Appears that the peak voltage is the specification quoted and the power can be worked out from its impedance, assuming a matched system, ie low vswr.

03-10-08, 10:17 AM	#4 (permalink)
trash Senior Member iTrader: (0) Join Date: Jan 2008 Posts: 346 Spent time on board: 2 Days and 19:58:29	It's all quite simple under ideal conditions. P=(V^2)/(2*Z) P Power V peak voltage Z impedence You need to evaluate connectors independantly, as different brands can have different performance. Typically it's the strike voltage of the dielectric which is usually higher than air. But air gaps in the connector's dielectric connection is the weak point. Worst case you can always work with air dielectric. For SMA connectors, it's about 2mm radius from core to shield. This is approximately 2000V strike. 2000^2/100= 40kW peak. For dry air and a matched load. Ideal conditions. Air is humid, dust gets into the connectors and if the connector is not quite 50 ohms or there is a termination fault, things can go VERY wrong. Reality is more like 2.5kW peak ! And still this is not average power handling. That then relies on the electrical connections themselves and the ability to pass current without heating up and causing more mismatch problems. Generally, a standard SMA connector is quite capable of handling frequencies up to 50GHz (and higher) and powers up to 100W. The best way to test the limits is to melt a few yourself, mythbusters style. You'll know where the limitations really are compared to a safe working load.

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