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Tripp Lite Isobar - the missing specs

May 28, 2009
Decades ago I used these surge protector / rfi filters, and picked a few up recently again. But noticed the front panels no longer have the specs printed on them, so this might help especially from the RF filtering standpoint.

Tripp Lite Isobar - the World's Most Trusted Surge Protector | Tripp Lite

Each outlet *pair* (one outlet on top of the other) is isolated from each other pair. And, the rf filtering is in series with each pair, so the further away you go from the first outlet pair closest to the ac plug, the more the filtering.

The first pair closest to the plug used to be listed as 50db attenuation. The second 75db. The 3rd pair 100db and so on. But what is the major LOW frequency? 1 mhz - right in the middle more or less of the AM Broadcast band. I normally plug in my radio into the last outlet for the most filtering.

They also incorporate a VHF filter as well, but I don't know what the center frequency for that is.

What I do know is that at my place, the AM BCB (and 160m amateur) is a total mess without it. All my house wiring acts like an antenna, and dutifully puts it out over my coax lines in the common-mode. The Tripp-Lite helps a great deal. Yet still I have to use ferrite chokes, but one step at a time. At least the Tripp-Lite brings back some sanity.

Of course there is surge protection all over the place too.

For some who power their radios (not just amateur / swl stuff, but general purpose radios, desk clock-radio's etc with wallwarts, in some cases yes, the wall warts may be noisy - but what is noisier still is the whole house acting like an antenna through the wall wart. The Tripp-Lite might alleviate the problem, or at least get it low enough to a point where simple ferrite choking of the lead to the radio might actually work.


Premium Subscriber
Mar 12, 2018
Tampa, Florida
For power line carried RF interference I suggest an active UPS (dual conversion) unit. These isolate the mains power from equipment completely. Tripp-Lite has a series of them that are RF clean. I use them both at home and at the office, I operate low bands from my office since I have the real estate there to have full size dipoles (including 160 meters). Expensive units but well worth it.
May 28, 2009
That's definitely a great option.

What I found out, and why the Isobars are growing like potato-chips around the house, is that most of my noise is not coming from direct radiation from the devices themselves, but from the junk they are pumping back INTO the powerline, and with my poor ground, right up the coax braid - virtually placing the noisy device inches away from the antenna even if it is far away in the garage. Hence all my ferrite choking and whatnot for the antennas.

Sure enough, if I climb on top of the device with a portable radio, I do hear some radiated noise, but backing away from it it gets much cleaner much faster when an Isobar is used for the device.

In other words, sensitive radios like the CCrane's were typically near unusable indoors - even on batteries - or had very tight positioning. With the isobars preventing junk from getting into my house wiring, I am no longer inside an rf-noise cage, and the CCrane's are even usable indoors.

But yeah, there IS some direct-radiated junk that I can't escape - but now snap on chokes and whatnot seem much more effective from power-cord radiation itself.

It was a revelation from which direction most of the junk was coming from, and how much those devices pumped back into the line.
May 28, 2009
Give an Isobar to a friendly neighbor?

Might be a possibility - where they may not take kindly to the idea of you modifying their stuff, going nuts with ferrites and so forth all over their massive entertainment system ...

They may not understand or care about radio filtering, but perhaps receiving a nice "surge-protector" as a gift is something they may actually be willing to install. It's worth a shot anyway...