Hi Kirk,
I could perhaps shed more light on this but I need to know
what freqcy are you using to test, and what is your VSWR.
Jim mentions 30 MHz, and he is correct as to what the avg. loss ( 1.0 dB )is
with various quality 213 cables @ 30 MHz, but I didn't see where you mention
testing at that freqcy. So my question is where would you like to test it, what
freqcy?
However, at the freq. range of HF for 213, the loss curve is linear, 1 - 30 MHz
for good quality cables.
Lets start with those questions and I can shed some light
on the matter.
Regards, Steve K1PEK DAVIS RF Co. (and DavisRope LLC, a separate entity for
all kinds/sizes of rope, Made in USA... DavisRopeAndCable.com ( the "cable"
of this co. is metallic cable, not RF cable. for RF items, see DAVISRF.com )
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Subject: TowerTalk Digest, Vol 215, Issue 36
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Message: 1
Date: Sun, 29 Nov 2020 09:58:52 -0800
From: "Jim Thomson" <jim.thom@telus.net>
To: "kj6y--- via TowerTalk" <towertalk@contesting.com>
Subject: [TowerTalk] Understanding Coax Loss Measurements
Message-ID: <887BA95DE5C849978032714E2E54CD0D@DESKTOPSV54DBH>
Content-Type: text/plain; charset="iso-8859-1"
Date: Sat, 28 Nov 2020 11:43:28 +0000 (UTC)
From: Kirk Kleinschmidt <sohosources@yahoo.com>
To: Towertalk Reflector <towertalk@contesting.com>
Subject: [TowerTalk] Understanding Coax Loss Measurements
<Method 2: RF Power meter and TX. Calibrate: Connect TX output to RF power
meter, then through the test length of coaxial cable, then to dummy load.
Carefully set TX output to to 10 W. Swap test cable and power meter, so TX
output now goes to test <length of cable, then to power meter, then to dummy
load. Record power levels of between 7 and 9.1 W with TX power set to same
level as "calibration " run, but with meter now placed after test cable length.
<Testing 100-foot lengths of RG-6, RG-11 and RG-213.
<With the power meter, loss values are RG-6, 3 dB; RG-11, 1.9 dB; RG-213, 2.8 dB
<As you can see, these methods don't line up well.
<Help?
<--Kirk, NT0Z
## How did you manage to arrive at a whopping 2.8 db loss , at 30 mhz,
with 100 feet of RG-213 U ?
The bird wattmeter method at each end of the coax has worked flawlessly for
years. DL at far end of feedline, or ant with 1:1 swr.
## Try it again, but use exactly 100 watts at the near end. You should
measure aprx 77 watts at the far end... at 30 mhz.
Jim VE7RF
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