trouble passing power

[thom]

http://www.tvfool.com/?option=com_wr...990027c93c8ecd

So, I have one of these for lightning protection:
http://www.amazon.com/TII-Broadband-.../dp/B00737FWLK

I've spent half the morning on the roof and off the roof trying to figure out why my new PA-19 amp was cutting my signal in half. It looks like power (or enough power) to the amp does not want to pass through the surge protector. If I pull it out of the loop and replace it with a simple connector, I see the boost I would expect from the amp. If this is expected behavior, what's the proper way to get lightning protection and still have power pass to the amp?

Many thanks.

[GroundUrMast]

If you are trying to add protection for your TV tuner, the surge protector needs to be on the TV side of the power insertion block.

If you are trying to add protection for the preamp, the surge protector needs to be installed between the antenna and preamp input.

In either case the surge protector needs to be connected to the electrical service ground by way of a #10 AWG or heavier copper wire. AND, the surge protector is not a substitute for grounding the mast or coax shield prior to the cable entering the building.

re. Grounding:

My stock answer is, Grounding the mast and coax shield are prudent and relatively inexpensive steps that limit the buildup of static-electricity which can damage the tuner. When done correctly, grounding can also reduce the risk caused by a nearby lighting strike.

http://forum.tvfool.com/showthread.php?t=901

Grounding in a basic system is a two step process:

1) Connect a #10 gauge copper wire to the antenna mast. A bronze ground clamp such as the Halex #36020 is well suited for this application. Run the wire directly to the electrical service ground. Avoid sharp bends in the wire. (If the ground wire between the service panel and ground rod is accessible, an Intersystem Bonding Termination devise can be placed onto the ground wire without cutting or disconnecting it. This provides a means to connect the #10 mast ground wire to the existing ground wire close to the ground rod outside the building. If possible, avoid running the new ground wire inside the building, energy from static or electrical storms is best directed to ground before it has any path into the building. The mast ground wire can be bare or insulated, your choice.)

2) Run the coax from the antenna to a location close to the electrical service ground. Install a ground block and with another peice of #10 wire, connect it to the electrical service ground at the same point you connected the mast ground.

I don't recommend short-cuts such as driving a new ground rod that is not connected to the existing electrical service ground. An isolated ground rod often has a high resistance that provides very limited ground connection. The goal is to connect to the same ground system that protects the rest of the home.

Surge protectors located inside outlet strips at the TV, computer or similar devises are worth consideration. A surge protector with a high joule rating is able to absorb more fault energy than a unit with a lower joule rating. Some surge protection units include phone jacks and F-connectors to enable protection of a phone line, coax cable and the power cable(s). However, in the case of an outdoor mounted antenna, this type of protection should not be considered a 'first-line of defense'.

[westom]

Originally Posted by thom

If this is expected behavior, what's the proper way to get lightning protection and still have power pass to the amp?

If a protector was on the roof, then it was not doing protection. Any protector that will absorb surge energy is a scam. If that protector would stop or absorb a surge, then tiny RF signals are also blocked or absorbed.

Protection was never about a protector. Energy gets absorbed by earth. An antenna lead must drop down to the building's single point earth ground. Make a low impedance connection (ie 'less than 10 feet') to that ground before rising back up to enter the building. GroundUrMast describes it as a ground block in his point 2).

A wire properly earthed means hundreds of thousands of joules dissipate harmlessly in earth. In most cases, a wire is the best protector. One from the TV mast as short as possible to an earth ground rod. Another from the coax where it enter the building.

In rarer cases, some will make that same connection to earth via a protector similar to what you have. That protector has a ground lug for the 10 AWG (or thicker) wire. To dissipate hundreds of thousands of joules in earth. Not inside any protector.

All protectors also create dB losses. How much? Less dB (signal) losses typically mean a more expensive unit. How many dBs does your protector claim diminish a signal at 1.5 Ghz? An industry benchmark is Polyphaser. Compare those numbers for their equivalent product. dB loss numbers increase for each higher TV channel (frequency). Better protectors have a lower dB loss for each frequency.

BTW, earth a 'whole house' protector on AC mains. Earthed also low impedance (ie 'less than 10 feet') to the same earth ground rod. Otherwise the TV remains at same risk - remains unprotected.

[thom]

Thanks to you both for prompt and detailed responses. We rarely get thunderstorms here, but no sooner had I disconnected the combo surge protector and ground block, and large thunderheads started piling up in the East and moving West.

GUM: The mast is grounded, but I'll need to swap in a new shield ground block to replace the existing combo shield block/surge protector (they're fused together).

westom: from the product description: "Device uses gas tube overvoltage technology to shunt surges to ground, when device is properly installed." So there's nothing much different from this and the way an ordinary shield block will behave? (lol, except maybe $10). I hadn't noticed any significant attenuation on unamplified signals prior to this, but that's just ad hoc observation, not instrumentation. The fact it won't pass power in the reverse direction makes it useless for my current build, though. Is this the kind of Polyphaser device you're thinking of (http://www.theantennafarm.com/catalo...oducts_id=1933)?

However, if that's just an inline piece with no ground, what's to stop all the energy from arcing the gap? Or is it simply enough resistance to persuade the energy to take the mast/shield ground route?

thanks again.

[westom]

Originally Posted by thom

westom: from the product description: "Device uses gas tube overvoltage technology to shunt surges to ground, when device is properly installed." So there's nothing much different from this and the way an ordinary shield block will behave? ...
The fact it won't pass power in the reverse direction makes it useless for my current build, though.

I am confused by these statements. No protector works by blocking or stoping a surge. In fact, that blocking or stopping is impossible. The protector should work in either direction. To a signal, a protector should look just like a coax wire.

View these spec numbers. Is your existing 'problem' similar to these specs?
http://www.protectiongroup.com/Surge...e-Protector-(1)

View the wire from antenna mast to ground. That is also what any protector does. No protector works by absorbing or blocking a surge (which is why protectors adjacent to appliances also claim no such protection). A protector only does what that wire does. Obviously, if the coax center conductor is earthed, then no signals will flow. So a protector connects that center conductor to earth - and still have TV signals.

Some protectors make that connection with significant losses. Others do it with minimal losses. 'Lower loss' protectors also are rated at higher frequencies - ie 3 Ghz and 7 Ghz.

But again, no protector does protection. The connection to and quality of earth ground determines protection.

[GroundUrMast]

All of the 'surge protector' devices use some type of component that will conduct current if the voltage reaches a specific level. Varistors and gas tubes being the most common components used in these designs. Varistors and gas tubes are limited as to how much current they can carry without failure. They also conduct to a very limited degree, before the 'on voltage' is reached, so they can and do cause some signal loss. As you have experienced, the voltage from the preamp power supply is enough to 'turn on' the varistor or gas tube in your 'protector'. When that occurs, the RF loss through the device goes way up.

In a coaxial surge protector application, the varistor or gas tube is connected to the center conductor and shield so that the voltage between the center conductor and shield will be limited to no more than the 'on voltage' rating of the 'protecting device'. If the fault current is too great or continues for too long, the varistor / gas tube will fail. If the 'protecting device' fails 'open', the 'protector device' is no longer able to limit voltage or current.

A coax grounding block makes no direct connection to the center conductor. It's intended to provide a secure and substantial connection to the shield only. When installed, the center conductor of the coax may be indirectly connected through the balun or similar component.

As I've already said, protectors that attempt to limit voltage between the center conductor and ground may be nice additions to the system, but they do not replace the two basic grounding tasks of mast and shield... outside the building.

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