[TowerTalk] Total station grounding and ethernet (summary)

[Bob Wanderer]

They may have changed their tune under the new owners, but when PolyPhaser
was still owned by its founder, he refused to make products (including
customs) with RJ11/14/45 because he said these would fuse with a strike.
That's why the products required hard wiring.  Before ruling out PolyPhaser,
check with the factory technical types and see if a custom product meeting
your needs already exists.  That's assuming they still do customs.

The capacitance of their 66 block protectors is listed in their catalog, or
was the last time I was able to get one from them, which was a couple of
years ago.  These would be inappropriate for your needs, but will give you
an idea of the performance of MOV's in this parameter.  These products have
two MOV's with a gas tube across them, if memory serves.

73
Bob AA0CY/3
former PolyPhaser technical consulktant


-----Original Message-----
From: owner-towertalk@contesting.com
[mailto:owner-towertalk@contesting.com]On Behalf Of Pete Soper
Sent: Saturday, June 03, 2000 11:17 AM
To: towertalk@contesting.com
Subject: [TowerTalk] Total station grounding and ethernet (summary)



For running ethernet into my station building I wondered if I could make a
simple surge supressor with MOVs to clamp each of the four twisted pair
conductors of a CAT5 cable run to the single point ground at the cable
entrance into my station.

This wouldn't work as MOVs have enough capacitance to foul up ethernet
according to multiple folks who wrote to me. (If I can find the special
place
where I hid my LC meter I'll report some measurements)

The perfect solution is to run fiber into the station instead of copper.
Transceivers that translate between fiberoptic ethernet and copper are
available and sometimes inexpensive (a quick check of ebay found an
FL to AUI transceiver whose high bid was $9.50).

For twisted pair (i.e. 10baseT) ethernet APC makes the model PNET1
suppressor.
It clamps at 8 volts and protects all eight conductors (and uses RJ45
connectors). Polyphasor also provides some products for twisted pair but
none
seemed to be a match for my application.

As I've already invested in the copper bits and pieces I'll be using one
PNET1
on each end of the CAT5 between my house and the station. The second PNET1
will
be go between the house end of the cable and my firewall box, saving me a
hub
(which I was going to put in between so the hub would take the zaps and
hopefully spare the firewall).

The APC info on the PNET1 and the vendor where I ordered a pair for $39.94
shipped are here:

	http://www.apcc.com/products/protectnet/pnet1.cfm

	http://www.onvia.com/streetprices/home/index.cfm

(There were no comments about fusing or specifics about how much of an
impedance
bump 10baseT can tolerate.)

Thanks for the help!

Pete
KS4XG

PS This didn't go through on Friday because of the lack of a reply-to field
matching the one I used for subscription. Gotta remember that majordomo
looks
at "reply-to" instead of "from" so you can post from multiple places.


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