ERP - Power Out Before Tuner and Power Measured After Tuner

[AussieLand]

I had a discussion with a Ham mate some time ago about the power output measured directly after an antenna tuner. He stated that the power after the tuner would be greatly reduced, when tuning an antenna with a high SWR.

Not sure if I agree with him, but, I'm wondering if I was to measure the power before the tuner and after the tuner, would I get a good indication of what was happening?

Also would there be a (great) power loss at the balun before the power gets radiated from the antenna?

 

[prcguy]

This all depends on the tuner and its internal losses. The tuner is just acting as an impedance matching device and they can be pretty efficient over a large frequency range. Losses may be worse at high power where components can heat up.

You can test efficiency with a wattmeter at the input of a tuner then use various non inductive resistors like 200 ohm, 600 ohm, etc. at the output then measure the RF voltage across the resistor with an oscilloscope and calculate output power to compare with input power.

 

[AC9KH]

I had a discussion with a Ham mate some time ago about the power output measured directly after an antenna tuner. He stated that the power after the tuner would be greatly reduced, when tuning an antenna with a high SWR.

Also would there be a (great) power loss at the balun before the power gets radiated from the antenna?

I don't agree with greatly reduced, but there is some losses in the tuner. And some tuners are more efficient than others, for example a L-network will typically be more efficient than a T-network.

There is also some loss in your balun, and that can also vary depending on the frequency and type of core used. But it will not be a great loss, it is pretty much negligible.

 

[merlin]

Everything beyond the output connector will have some loss. Through a 'tuned' tuner, you should be down about 1.4 to 2.2 Db.

 

[AC9KH]

Everything beyond the output connector will have some loss.

Yeah, even an antenna switch for switching from one antenna to another will have an insertion loss of ~0.2dB. Amplifiers are another source of insertion loss. My amplifier on standby has loss of 3dB, which is worth about 1/2 an S-unit on the receiving end. Compared to a typical 100W (SSB PEP) HF radio direct to the tuner, have to run 200W with the amplifier just to overcome its insertion losses compared to the radio straight-up. And increase the power to 400W to get an additional 1/2 an S-unit on the receiving end compared to the radio straight-up at 100W.

Ohm's Law cannot be revoked or defeated.