Wattage difference with new coax?

[husker]

So I ordered new RG-213 jumpers and now my deadkey went down! I went from a normal 10 watt ( 2510) to 7 3/4 with the new jumpers...anyone have any ideas?? Also my SWR dropped a tad, but it was so low anyway it's not really a factor

[BionicChicken]

The SWR dropping, however slight, can change the power reading. Higher SWR will usually show a radio as doing more wattage. Hook a radio up to an antenna with high SWR and usually you'll see the meter peg on the radio when you key.
If the SWR was "so low" how did you determine it went down some? Perhaps trying another meter or swapping the antenna for a dummy load might shed some light on the subject.

BC

[Sandbagger]

Feb 5, 2009 8:22:03 GMT -5 BionicChicken said:

The SWR dropping, however slight, can change the power reading. Higher SWR will usually show a radio as doing more wattage. Hook a radio up to an antenna with high SWR and usually you'll see the meter peg on the radio when you key.
If the SWR was "so low" how did you determine it went down some? Perhaps trying another meter or swapping the antenna for a dummy load might shed some light on the subject.

BC

Changing the length of the coax will alter the point where the standing waves peak. If a watt/SWR meter is placed in one point in the feedling, and then moved to a different point, the reading will usually change. It will be more noticable if you have a higher SWR to begin with, as the magnitude of the standing waves will increase.

This phenomenon is largely responsible for the myth that cutting coax can tune your SWR (which is strictly a function of antenna impedence). While changing the place in the feedline where the meter is may make the SWR appear to change, in actuality, the actual SWR is not changing but the standing wave peak in the cable relative to the location of the meter will change making it look as if the SWR (and by extension the wattage reading) had changed.

That's why wattage readings are only truly accurate when measured into a purely resistive 50 ohm load.

[husker]

Interesting, so I was 1:1.2 and with the new cable it didn't even move. Also the new cable is 18 in and the old one was 3 feet....It only affects the cable that runs from the radio to the...ah...amp the rest of the jumpers have no effects at all.

[kr750]

thinking of geting new coax..i got the old 58u fome radio shack from the 70s..what about Astatic RG8X? .i see all kinds of crap on ebay...not sure what to get.....