[TenTec] RFI Issues

Tue May 22 16:30:11 PDT 2012

And add another 2 cents to the collection
to underscore what is being suggested ...

This "Oh, I always unplug and disconnect"
so don't have to do anything is going to
bite you someday, when you least expect it.

It's simply a question of when for many,
especially in areas where summer storms
may show up with little or no notice here
in the mid-South, your mileage may vary.

With multiple antennas,rotors,TX and RX 
arrays, all with control lines and coaxes 
there is a point where disconnecting each 
and every connection becomes unreasonable.

My towers are higher than most of the local 
trees and are located in the open really. I
have learned the hard way that is not always
a good thing without the proper protection.

I went through what Cecil describes in 1995
and the reality of being canceled by my long
time insurance company made me learn how to 
do this right to be covered again, and for a
long three years, it was at a very high rate.

The key is getting and keeping everything at
the same potential. That was the message over
and over again with some of the local engineers
that keep the radio/TV stations on the air here.

The other point they made, do NOT allow any form
of a sneak path. In other words don't do this to
the 95% point, because that 5% will undo all the
good of the 95% was protecting. Cover your bases.

Case in point, one of the local packet-cluster
stations kept having damage, after damage. He
grounded the shields on the main tower, bypass
on control lines, and so on. Still the damage
continued. I stopped by one afternoon and we
were taking a closer look and under his deck
area, I noticed all the "ham" stuff was going
to one SPG/ground rod and then several feet
away was all the house/cable/tele to another
SPG/ground rod and so I suggested that "SPG"
meant exactly that SINGLE POINT GROUND. 

A 3" copper strap was run at ground level 
between the two individual SPG/ground rods
with the proper connections and no more of 
the repeat damages has been reported. Mnn.

Polyphaser has a book, QST has had articles
by R. Brock, and W8JI's site. There are many
reliable resources to review and do this 
right BEFORE you have to rebuilt it all.

73 de Billy, AA4NU

-----Original Message-----
>From: d.e.warnick at comcast.net
>Sent: May 22, 2012 9:20 AM
>To: Discussion of Ten-Tec Equipment <tentec at contesting.com>
>Subject: Re: [TenTec] RFI Issues
>
>
>
>The tower itself should be well grounded. The following url 
>
>
>
>http://www.3starinc.com/rohn_r-bgk2ggx_tower_base_ground_kit.html 
>
>
>
>shows Rohn's suggestion with excellent information. Their kit lists at $170 & you should use 1 per tower leg. I found them last year at Hill Radio for less than half that cost when I put up 100' of Rohn 55. 
>
>http://www.hillradio.net/ 
>
>  The kit includes 1 10' ground rod & 30 ' of cable with clamps. You should use at least 1 or 2 more ground rods on each cable running radially from the tower. ( I couldn't go 30' in the one direction so that cable makes a big sweeping turn.) The rod & connection are buried. Use lots of anti-corrosion compound . I like the marine-grade stuff sold for antenna assembly. I also sleeve the connection with a piece of 4" or 5" PVC about a foot long. Slot it to pass the cables, set it down over the rod & connection. Then put an end cap on it at ground level. When you do your annual tower inspection, it's a simple matter to remove the cap (I didn't say glue it on - Hi), loosen, re-apply anti corrosion compound & retighten the connection. The clamps included in the above kit are excellent. I shudder when I see ground wire clamped to a tower with a hose clamp. 
>
>See Jim Brown & others information for bonding all this to all other grounds. 
>
>Thanks for the bandwidth 
>
>73 
>
>Dave 
>
>WA3F 
>
>
>
>----- Original Message -----
>
>
>From: "chacuff" <chacuff at cableone.net> 
>To: "Discussion of Ten-Tec Equipment" <tentec at contesting.com> 
>Sent: Tuesday, May 22, 2012 9:13:32 AM 
>Subject: Re: [TenTec] RFI Issues 
>
>Just my 2 cents worth.... 
>
>Your grounding work shouldn't start just outside the wall from the radio 
>gear...it really should start at the tower and be an antenna/tower grounding 
>"System" designed to stop/minimize the lightning impulse at its source as 
>you work back towards the station. 
>
>A single rod lightning protection system is of little protection because 
>much like Bob has pointed out the resistances involved between the multiple 
>ground points there is also resistance between a single point of ground and 
>earth.  If the ground resistance was measured at the single rod it would 
>probably be measured as several hundred ohms.  If your station lightning 
>protection ground was measured at that level and subjected to several 
>thousand amps of instantanous current simple ohms law will tell you what 
>kind of voltage potential you can expect on the chassis of equipment...and 
>that gets dumped onto the electrical system of your shack/house.  Lots of 
>damage. 
>
>The lightning protection grounding has to be approached as a system.  The 
>ground rods can be looked at like resistors...put more in parallel and you 
>bring the total system resistance down.  That's done by driving multiple 
>rods at 2 times there length apart and bonding them together with large 
>gauge wire, preferrably bare.  The Cellular industry uses #2 bare solid (not 
>stranded) wire welded to the ground rods.  It's not unusual to have a dozen 
>or more rods driven to get the system resistance down to 5 ohms or 
>less...the lower the better. 
>
>The tower should be tied to this ground "System" and all feedlines should 
>have ground kits installed on them which ties the shield to the ground 
>system.  Each feedline and rotor cable should have an inline commercial 
>protection block...ie Polyphaser or ICE connected and tied to a common point 
>with a low impedance path to the ground "System".  Finally all this should 
>be tied to your house electrical panel at the point where your meter can is 
>located which should be where the small ground rod the electrican drove and 
>tied to the house panel. 
>
>As you can see this can get expensive (and complicated) but so can loosing 
>all your nice gear and a bunch of stuff in the house that's not related to 
>the ham shack.  It can come to 10s of thousands of dollars easily....all in 
>a millisecond.  Been there and done that.  Hope to not have to deal with it 
>again. 
>
>Again just my 2 cents worth... 
>
>Cecil 
>K5DL 
>----- Original Message ----- 
>From: "Bob McGraw - K4TAX" <RMcGraw at Blomand.net> 
>To: "Jim WA9YSD" <wa9ysd at yahoo.com>; "Discussion of Ten-Tec Equipment" 
><tentec at contesting.com> 
>Sent: Tuesday, May 22, 2012 7:30 AM 
>Subject: Re: [TenTec] RFI Issues 
>
>
>> 
>> 
>> Here's where I view that people get in trouble.  They drive a ground or 
>> two 
>> and connect it to their radio or station equipment.  They plug the radio 
>> in 
>> the wall plug which has neutral and ground.  Neutral and ground are 
>> connected at the breaker panel for the house per NEC.  The ground at the 
>> breaker panel is attached to a driven ground outside, again per NEC.  A 
>> lightning storm approaches and they disconnect their antennas.  A nearby 
>> strike, meaning up to 5 miles away, causes the two or more ground points 
>> to 
>> have different voltage potentials as they are separated by some distance 
>> of 
>> a few feet to several hundred feet.  There is resistance in the earth 
>> between the ground points thus with current flowing through the earth 
>> there 
>> is a difference in voltage between the two or more grounds.  Now, what's 
>> connected between the two ground points?  The radio and station equipment. 
>> Therefore, even when antennas are disconnected and the radio is turned off 
>> there is a path through the ground and neutral back through the radio or 
>> station equipment.  It spells failure and we often hear........"but my 
>> radio 
>> was grounded, my antennas were disconnected and the radio was turned off". 
>> 
>> The point is the fact that ALL grounds must be bonded together and 
>> preferably outside of the structure.  This includes a hard electrical 
>> connection back to the AC mains ground point. 
>> 
>> 73 
>> Bob, K4TAX 
>> 
>> 
>> 
>> 
>> ----- Original Message ----- 
>> From: "Jim WA9YSD" <wa9ysd at yahoo.com> 
>> To: "TenTec .com" <tentec at contesting.com> 
>> Sent: Tuesday, May 22, 2012 12:52 AM 
>> Subject: Re: [TenTec] RFI Issues 
>> 
>> 
>> Sorry Jim 
>> 
>> When the FCC had checked out my installation cause of an RFI issue, they 
>> found that I had a bad solder joint on my shielded ground and fixed it for 
>> me. All was well. If the the shielded ground was BS they would have told 
>> me 
>> and not fix it? 
>> 
>> Tying station ground to electrical ground low impedance please describe. 
>> 
>> Existing wiring. The 2 grounds were separated at time of inspection was in 
>> code then but is not in code now, residential wiring does not have to be 
>> upgraded unless there was remodeling, house was sold, and the sort, so 
>> then 
>> it needs to be brought up to code at that time. 
>> 
>> Stay on course, fight a good fight, and keep the faith. Jim K9TF/WA9YSD 
>> _______________________________________________ 
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>> 
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