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If the amplifiers output impedance is 50 ohms, and something else isn't causing an issue due to the higher power, the SWR will be the same weather it is on or not.

SWR is a ratio. x% of the power being transmitted is being reflected by the antenna back up the coax. It doesn't matter if the input is 1 watt or 1,000,000 watts, the same percentage of power will be reflected (assuming the antenna system including the coax can handle the power of course).

The only real issue you should have is if the amplifier is being driven hard it will be much more sensitive to SWR. You may consider getting an unun if you are worried about it. That will resolve any potential SWR issue.

How do you know your antenna is at 40 ohms of impedance? Have you hooked an antenna analyzer up to it? Most quarter wave antennas are at 35 ohms of impedance.

The DB

<blockquote data-quote="The DB" data-source="post: 392356" data-attributes="member: 21346">If the amplifiers output impedance is 50 ohms, and something else isn&#039;t causing an issue due to the higher power, the SWR will be the same weather it is on or not.SWR is a ratio.&nbsp; x% of the power being transmitted is being reflected by the antenna back up the coax.&nbsp; It doesn&#039;t matter if the input is 1 watt or 1,000,000 watts, the same percentage of power will be reflected (assuming the antenna system including the coax can handle the power of course).The only real issue you should have is if the amplifier is being driven hard it will be much more sensitive to SWR.&nbsp; You may consider getting an unun if you are worried about it.&nbsp; That will resolve any potential SWR issue.How do you know your antenna is at 40 ohms of impedance?&nbsp; Have you hooked an antenna analyzer up to it?&nbsp; Most quarter wave antennas are at 35 ohms of impedance.The DB</blockquote>

[QUOTE="The DB, post: 392356, member: 21346"] If the amplifiers output impedance is 50 ohms, and something else isn't causing an issue due to the higher power, the SWR will be the same weather it is on or not. SWR is a ratio. x% of the power being transmitted is being reflected by the antenna back up the coax. It doesn't matter if the input is 1 watt or 1,000,000 watts, the same percentage of power will be reflected (assuming the antenna system including the coax can handle the power of course). The only real issue you should have is if the amplifier is being driven hard it will be much more sensitive to SWR. You may consider getting an unun if you are worried about it. That will resolve any potential SWR issue. How do you know your antenna is at 40 ohms of impedance? Have you hooked an antenna analyzer up to it? Most quarter wave antennas are at 35 ohms of impedance. The DB [/QUOTE]

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