Press etal,
Some time ago I measured various coax lines on a Hewlett Packard 8753
Network analyzer. This instrument is very accurate up through 3 GHz. Here
are my measured values of insertion loss at 28-30 MHz per 100 feet.
Type IL in dB (per 100 feet at 28-30 MHz):
RG58: 1.9
RG8U: 1.1
Foam (Columbia) RG8U: 1.0
RG213: 1.1
RG214: 1.15
Belden 9913: 0.84
LMR400: 0.7
1/2" Alumifoam: 0.3
7/8" Alumifoam: 0.25
I've also observed that the VSWR (and therefore the impedance) on a 100
foot length of 9913 wasn't constant, and from my recollection, had bumps
in the region of 135 MHZ. I have not seen this problem on the LMR400 (even
up through 1 gHz!) so I immediately switched to the later and have never
been sorry. From these data and the cost for semiflexible coax, I'd opt for
the LMR400!
BTW, although I haven't been following this thread very closely, it seems
to me that the addition of a drip loop at the end of a long downward run of
coax would surely cut down on the moisture running over the connector (thus
decreasing the chance of water ingress).
73,
Joe, W1JR
At 02:19 PM 12/20/2001 -0600, n4kg@juno.com wrote:
>--------- Forwarded message ----------
>From: n8ug@juno.com
>To: n4kg@juno.com
To: <towertalk@contesting.com>
>Date: Thu, 20 Dec 2001
>Subject: Re: [TowerTalk] Cable Loss Comparison (Was 9913 reliability)
>
>Hi Tom
>
>The data are right in the ballpark for all but the 213 - no real 213
>is gonna show better than 1.3db/100ft - so "very interesting indeed!"
>
>Press N8UG
>
>(I have the MIME problem on my LT and can't post on TT
>unless I figure out how to change it - no time to fiddle!)
>
>On Thu, 20 Dec 2001 12:26:47 -0600 n4kg@juno.com writes:
> >
> > Thanks for posting your measurements Tony.
> >
> > I converted your percentages to dB total and dB/100 ft
> > as shown in the following table. For your 220 ft runs,
> > it looks like there is little benefit to using 9913 over
> > RG213 and little benefit in using 7/8 inch hardline over
> > 1/2 inch hardline. The 1/2 inch hardline offers 1 dB
> > less loss than 220 ft RG213. Very interesting result.
> >
> > Tom N4KG
> >
> > Cable (avg 220 ft) dB loss dB/100 ft at 10M
> >
> > 7/8" hardline - 88% 0.555 0.25
> > 1/2" hardline - 82% 0.86 0.39
> > 9913 - 68% 1.675 0.76
> > RG-213 - 65%. 1.87 0.85
> >
> >
> > On Thu, 20 Dec 2001 "N2TK" <t.kazmakites@verizon.net> writes:
> >
> > Just had tilted over the tower to replace some antennas. Checked
> > the coax for loss. Measured the power going into the coax and
> > measured the power at the end of the coax at 28.0 MHz with
> > a dummy load on the coax. Used the same watt meter for both.
> > The length of the coaxes is about 210 - 230'.
> >
> > Here is the loss as a percentage of power out/power in.
> > By the way, I cut off the end of one of the 9913 runs at the house
> > (lowest point of run) to see if any discoloration of the copper.
> > There was none. This coax has been up for 8 years.
>
> > > 7/8" Prodelin hardline - 88%
> > > 1/2" Prodelin hardline - 82% - 2 runs measured the same
> > > 9913 - 68% - 2 runs measured the same
> > > RG-213 - 65%.
> > >
> > > The measurements are approximate and were done to just check to
> > make sure the coax didn't have a problem.
> > >
> > > Tony (N2TK)
>
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