Cable Attenuation Question

[W8JITom at aol.com]

In a message dated 96-09-14 19:24:27 EDT, you write:

>loss with the formula  dB = 10(log PO/PI).  Record this value as a reference
>so that some day when the cable is down and about to go up again you can see
>if the cable is still as good as when you bought it.  (allow .1 dB for the
>connectors at each end or .2 dB total).

Hi,

I keep seeing this thing about connector loss everywhere I look. It's become
accepted as fact in our community, but it's folklore. Here's an example
why....

With .1 dB loss per connector, power loss in a PL-259 SO-239 combo would be
about 35 watts at 1500 watts. Loss is concentrated in the center pin and
dielectric of the SO-239 section, in an area less than one half inch long.
The PL-259 section has almost no loss or impedance bump when properly
installed. 

35 watts of connector heat (with a 1500 watt transmitter), when concentrated
in the inside of the SO-239, would quickly make the connector so hot it would
be untouchable. In a few minutes melt the solder connection and dielectric.
If you doubt this, turn on a 35 watt lamp for a few minutes and touch the
glass. Now imagine how hot the galss woud be if it was all within a quarter
inch of the filament.

At 30 MHz, the loss of a 239-259 combo is totally unimportant. One foot of
9913 cable has much more loss.

73 Tom

>From km9p at contesting.com (Bill Fisher, KM9P)  Sun Sep 15 22:53:02 1996
From: km9p at contesting.com (Bill Fisher, KM9P) (Bill Fisher, KM9P)
Date: Sun, 15 Sep 1996 17:53:02 -0400 (EDT)
Subject: CAUTION: FCC ON-LINE AND CREDIT CARDS
Message-ID: <199609152153.RAA02966 at paris.akorn.net>

At 09:04 AM 9/15/96 -0400, you wrote:

>Data security on the Internet is somewhere between zero and nil. 

Not that this has anything to do with contesting, but this is simply not
true.  You have more chance of getting it stolen talking on your cordless phone.

73


Bill, KM9P
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>From km9p at contesting.com (Bill Fisher, KM9P)  Sun Sep 15 22:59:11 1996
From: km9p at contesting.com (Bill Fisher, KM9P) (Bill Fisher, KM9P)
Date: Sun, 15 Sep 1996 17:59:11 -0400 (EDT)
Subject: 80M Wire 4-square owners?
Message-ID: <199609152159.RAA03024 at paris.akorn.net>


I've definately got the room for an elevated 4-square made of wire.  I have
heard from others that there are all kinds of different variations of this
antenna.  ON4UN's is a sloping arrangement.  This would work great for me,
but I believe I can get all of the vertial elements, exactly vertical.  I
have heard of others using less than optimal arrangements... but I would
like to hear from you regarding the systems performance.

For the record... I'm currently using a delta loop fed at the center/top at
105'.  My station is on a very quick sloping hill.  Drops about 250' in all
directions.  I'm sure the delta loop is working well, but would like to
think a 4-square would be an improvement.

73

Bill
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| Contesting Online... The ultimate           |
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