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i meant electrical half wave length . my bad
this comment on another forum seemed odd to me is why i asked ....

"In a mobile there is no matching network. The only way to match your impedance ( just as a gamma does ) is to alter the coax length. Mind you swr of the antenna itself will not change, but your amp will me much happier seeing a 50 ohm load, run cooler and less chance of blowing pills. I have found that in most all single antenna installs that I have done 15 ft of 213 was the sweet spot. the wifes pick up has 7.5 ft of 213. mfj read 50 ohms 1.0 swr. same with the work truck with 15 ft. when we had 18 or 12 feet the ohms were roughly near 70. When ohms are 70, x=2 you will not read 1.0 swr on the mfj, even though your antenna will be perfectly tuned. the bird will also show more reflect under the same situation. depending on what coax you use may change length. it depends on what velocity factor the coax is."

thanks for the replies

<blockquote data-quote="BOOTY MONSTER" data-source="post: 339190">i meant electrical half wave length . my bad <img src="https://cdn.jsdelivr.net/joypixels/assets/8.0/png/unicode/64/1f609.png" class="smilie smilie--emoji" loading="lazy" width="64" height="64" alt=";)" title="Wink&nbsp; &nbsp; ;)"&nbsp; data-smilie="2"data-shortname=";)" />this comment on another forum seemed odd to me is why i asked ....&quot;In a mobile there is no matching network. The only way to match your impedance ( just as a gamma does ) is to alter the coax length. Mind you swr of the antenna itself will not change, but your amp will me much happier seeing a 50 ohm load, run cooler and less chance of blowing pills. I have found that in most all single antenna installs that I have done 15 ft of 213 was the sweet spot. the wifes pick up has 7.5 ft of 213. mfj read 50 ohms 1.0 swr. same with the work truck with 15 ft. when we had 18 or 12 feet the ohms were roughly near 70. When ohms are 70, x=2 you will not read 1.0 swr on the mfj, even though your antenna will be perfectly tuned. the bird will also show more reflect under the same situation. depending on what coax you use may change length. it depends on what velocity factor the coax is.&quot;thanks for the replies <img src="https://cdn.jsdelivr.net/joypixels/assets/8.0/png/unicode/64/1f642.png" class="smilie smilie--emoji" loading="lazy" width="64" height="64" alt=":)" title="Smile&nbsp; &nbsp; :)"&nbsp; data-smilie="1"data-shortname=":)" /></blockquote>

[QUOTE="BOOTY MONSTER, post: 339190"] i meant electrical half wave length . my bad ;) this comment on another forum seemed odd to me is why i asked .... "In a mobile there is no matching network. The only way to match your impedance ( just as a gamma does ) is to alter the coax length. Mind you swr of the antenna itself will not change, but your amp will me much happier seeing a 50 ohm load, run cooler and less chance of blowing pills. I have found that in most all single antenna installs that I have done 15 ft of 213 was the sweet spot. the wifes pick up has 7.5 ft of 213. mfj read 50 ohms 1.0 swr. same with the work truck with 15 ft. when we had 18 or 12 feet the ohms were roughly near 70. When ohms are 70, x=2 you will not read 1.0 swr on the mfj, even though your antenna will be perfectly tuned. the bird will also show more reflect under the same situation. depending on what coax you use may change length. it depends on what velocity factor the coax is." thanks for the replies :) [/QUOTE]

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