By trying to keep this thread focused and on topic it seems that I did just the opposite. Unintended consequences?
I am going to have to think about this.
Neil
we had two choices with this thread:
1) Talk about the legality of the ground lead issue.
2) Go off-topic.
Over the years posting here at the world's main Part 15 website, something has nagged in the background of the experience.
I have noticed a continuing effort to "keep threads on topic".
And in my until now unexpressed thoughts I have wondered how that could be either possible or realistic.
Thing is, the topic of low power radio has many dimensions.
Talk about a particular antenna tuner, the ATU for example, and someone reasonably refers to the rules or certification that applies, someone else makes a comment about the general subject of dealing with government rules, someone else is reminded of an incident when a similar rule experience happened to him, and we have basically webbed.
This is the web, you know, and webs are like nets in the sea. They capture all kinds of fish, boots and artifacts from the deep.
It can't be controlled.
The description of the RS grounding block does not state that it provides transient protection, the ability to shunt spikes appearing on the center conductor to ground. I would ask RS to verify that.
The protector Rich has offered is designed to not only ground the shield but shunt transients to ground, a much better device.
Does anyone have one for the ATU? There may be an RF choke on the ground lug already..
There is no choke in the line to the ground terminal of the ATU. There is a toroid input transformer to which the coax connects but the coax shield and ground terminal are common.
The manufacturer has cautioned that connecting to the ground terminal will affect compliance. However, they maintain that the coax was accepted as part of the system and does not affect compliance.
"The description of the RS grounding block does not state that it provides transient protection, the ability to shunt spikes appearing on the center conductor to ground. I would ask RS to verify that.
Many things need to be clarified and verified by RS about that entire system..beings we cannot get that from the OET database.
But let's take some basic elementary common sense here. Two other units incorporate spike/lighting protection. The ATU does not.
The original intent of the other two devices are for actual broadcasting, where the systems could be set up in an elevated situation, like an apartment building or top of building.
The ATU unit's original intent was to sell houses, where there is a short stick holding up a for sale sign out in the front yard. The certification description clearly says "real estate transmitter", which also applies to the iAM unit since it is using that same certification of the TH, and both use the same ATU with that same certification.
It would seem the ATU was intended to be mounted pretty darn close to the ground, even the manual shows a picture of that ATU mounted to the side of a house..not up on a pole.
Basic elementary physics has proven and shown the higher something conductive is in the air, the more chance static will build up and lighting strike.
Ever been told that if your out on a golf course to get the heck out during a lightning storm? Why is that?
Because your out in the open and most likely the tallest object there and stand a very good chance in getting struck by lightning..which has happened and been documented BTW.
Running a ground wire from the ground slug on the ATU when it is mounted on the ground or on a short stick such as a for sale sign post probably won't bring any issues regarding compliance. Elevated it's best to just leave that ground slug unconnected and rely on the coax shield to carry any static buildup to ground via the power supply ground...won't mention about lightning cause a lightning strike will vaporize that coax and entire system in a blink of a flash unless that strike as a heavier path to ground..via that ground slug on the ATU.
But at that point we get into the blah blah about compliance. I remind again, although I suggested it months ago and was ignored, the RF choke will work, regardless if it is a tuned circuit or simple toroid choke or spark ball/plug system, there is still that long ground line that obviously tagged another installation as beyond 3 meters.
So here is probably the biggest conundrum mix mash bash ever to exist in Part 15..and probably will remain so until that particular parameter is clarified and verified by the OET and FCC.
You do need a ground for safety reasons. There is no argument about that. You want the whole setup to be fully compliant, no argument there. You want maximum coverage, fantastic and all that.
Unfortunately it is not I or anyone else who created the conundrum regarding grounding issues and long leads etc etc. However no matter how hard you try, or wish it to be ignored, or attempt at preventing it's factual linkage to discussion of that ATU or ANY OTHER antenna system under 15.219, well your only kidding yourselves as those regulations and adherence to them are like links in a chain and a fact of life. You cannot separate the two and it wont be when an inspecting agent comes along.
Now let's take that ATU to another level from the manufacturing point.
Given it's actual intent as described in the OET certification paper, and the pictorial evidence shown in the manual, if RS thought that thing was going to be mounted up on high support structures, wouldn't they have incorporated surge/static/lightning protection to begin with....like those other two units did..aka Rangemaster and Procaster.
I wish there was someone who did have one of these installed in an elevated situation and got hit by lightning and was around to tell us about the fantastic light flash vaporizing display along that thin coax line and into the studio!
"There is a toroid input transformer to which the coax connects but the coax shield and ground terminal are common."
Both ends are isolated with a toroid. Look at the schematics. The output of the TH transmitter feeds BOTH internal and external ATU systems via a toroid..ie before either of them. The ATU has one too, as well as identical ferrite rod tuned coils driven by a hand turned knob, just like the ferrite rod tuned coils in the transmitter which is driven by a geared reduced motor assembly. The only common connection between them is that ground via the coax and any static or lightning on that thin coax dumps into your studio and through the transmitter enclosure to that tiny power plug on the back and through the thin ground wire inside the power cable to the outlet ground and through the woods and over the hills and to the breaker box and finally hitting a REAL ground at the service entry point. Heck of a long pathway..isn't it!
I believe that in a normal as intended setup..ie real estate for sale sign setup, there isn't any big worry about static buildup or lightning hits or sky falling or cats living with dogs. That TH/iAM and ATU were designed for "radio for dummies" aspect in ease of setup and operation, not actual tinkerers and hobby types who understand the need for such things as static/lightning paths and discharge methods or with the ability to add such devices to things without them. I seriously doubt a real estate agent trying to sell a house is thinking about all these things and just wants to get the message out about the house being sold.
But take that thing outside of its original intent and mount it up high, yep it's vaporization light show for sure...and damned if you hook up a ground..damned if you don't.
So which way did he go...is it up or down, left or right, forward or backwards.
It's your call.
RFB