Radio Interference

[Tom Elliott]

To one and all,
You guys are great! Thanks!
Just spent about two hours in the local BJ wholesale store.
I think maybe I found an $100 solution (I will still have to add XLR mixer and mikes for complete solution) in the form or an emergency 12volt (rechargable) with two ac outlets and two cigarette outlets. All self contained and according to the specs it looks like it will power the small monitor, the GL2, and the mixing board: $89.99. Since BJs have a generous return policy I think I will give it a test by plugging everything in and see just how long it takes to run down.
ALSO since these lawyers hate hot lights (the GL2 does have good WB) I think I will also test flourescent flood for shadow fill. I can put gels over the bulb and since it burns cool the gels should last.
Ah me, these independent film makers ....
Also I plan to go to an RV Camper store here south of Miami to see what they have for independent power solutions that are light.
The above thing at BJs was much lighter that going the car battery route and then still haveing to get a trickle charger and outlet adapters. Oh the thing also as a meter, of sorts, to let you know just how much power is left.
I feel much better now. But, boy oh boy, it was was major mental pain and suffering at the start of yesterdays assignment.
Yours,
Tom

[Stephanie Wilson]

Originally Posted by Steve House

You can make a video isolation transformer that MIGHT work with a pair of 300 ohm to 75 ohm transformers connected back to back. Get one of those little thingys (another technical term) designed to match a 300 twin-lead TV antenna cable to a "F" connector input, looks like a squareish piece of plastic with a couple of screws on one side and a push-on coaxial connector on the other. Here's a picture of one:

- http://www.eenid.us/200-510.html

Get a second that does the reverse, looks like a liitle barrel with an "F" conntector on one end and a 300 ohm twin lead pigtail on the other. Another pitcher:

- http://www.eenid.us/200-500.html.

Connect them back to back with the spade lugs on one to the screws on the other. Instant 75 ohm ground isolation transformer for less than $5.00.

I read your post to my satellite truck engineer friend today. He totally agreed with everything you suggested about making a video isolation transformer AND also included the following, "this guy knows what he's talking about - watch for his posts and you'll probably learn alot." Just thought you might like a little positive feedback on your obviously stellar knowledge. Thank you so much for helping to enlighten us all.

Stephanie

[Steve House]

Originally Posted by Stephanie Wilson

I read your post to my satellite truck engineer friend today. He totally agreed with everything you suggested about making a video isolation transformer AND also included the following, "this guy knows what he's talking about - watch for his posts and you'll probably learn alot." Just thought you might like a little positive feedback on your obviously stellar knowledge. Thank you so much for helping to enlighten us all.

Stephanie

Thanks for the accolades! I have to admit I can't claim credit for that isolation transformer idea - I borrowed it from the pages of one of Jay Rose's excellent books on audio production. My talent lies more into the direction of having a good memory <grin>.

[Jay Massengill]

Stephanie, you are foolishly risking lives when you defeat the safety ground in an electrical system. I know that un-grounding adapters are used all the time, but it's a stupid practice that has gotten people killed in the past and will get people killed in the future.
It's my recommendation that defeating the safety ground never be done, but instead use an isolation transformer like the Ebtech Hum Eliminator for audio that I listed in my first post, or the Jensen isolation transformer for video that I listed in my second post. (Which oddly enough performs the same function as the isolation transformer you so highly praised.)
These isolation transformers are called "hum-buckers", so I don't understand your point #2 unless you are mistakenly calling an un-grounding adapter a "hum-bucker". It's the un-grounding adapter that I said wouldn't necessarily have been successful. An isolation transformer or transformers would more likely have been successful as I stated originally and as your engineer friend agrees.

[Jay Massengill]

In addition, the Marshall monitors of that size all use un-grounded power supplies to begin with, so using an un-grounding adapter would definitely be of no help in this particular situation since none of the equipment in question is making a ground connection.

[Tom Elliott]

In regards to my Marshal video monitor:
I use the three to two adapter not so much as to avoid the hum but rather to use it because the Marshal transformer male plug fits very tight in the adaptor and it inturn can have the prongs spread to form a tighter fit into a wall plug, otherwise the transformer just falls out of the wall plug. I have also got short (about 5 inches) grounded extension cords made for transformers if one is using a power strip that does not have the plugs far enough a part.
I think I have my CFO (lovely wife) convinced that it would be wise to get the portable power gizmo from BJs and do a test with all equipment plugged in to see just how long the power will last. If it can't do the job (I mean this is not filming "War and Peace" then I will just have to bit the bullett and get a bunch of batteries for each piece of equipment and change them out just like the one hour tapes of the GL2. I hope that the BJ thing will work. It could solve a lot of problems.
Yours,
Tom

[Jay Massengill]

That's not a problem using the adapter in that manner, because you aren't breaking a ground connection.
I do the same as you with the extension cords. I have several 6-foot grounded cords with 3 outlets on the end. If at least one of the transformers is unpolarized and therefore can be physically reversed, then I can plug in 3 transformers on one socket and put them further away from my audio cables (since the transformers themselves can generate substantial hum).

[Stephanie Wilson]

Originally Posted by Jay Massengill

Stephanie, you are foolishly risking lives when you defeat the safety ground in an electrical system. I know that un-grounding adapters are used all the time, but it's a stupid practice that has gotten people killed in the past and will get people killed in the future.
It's my recommendation that defeating the safety ground never be done, but instead use an isolation transformer like the Ebtech Hum Eliminator for audio that I listed in my first post, or the Jensen isolation transformer for video that I listed in my second post. (Which oddly enough performs the same function as the isolation transformer you so highly praised.)
These isolation transformers are called "hum-buckers", so I don't understand your point #2 unless you are mistakenly calling an un-grounding adapter a "hum-bucker". It's the un-grounding adapter that I said wouldn't necessarily have been successful. An isolation transformer or transformers would more likely have been successful as I stated originally and as your engineer friend agrees.

Okay,

Here's the deal.
The safest way to deal with electricity is to have NO ground at all.
According to my engineer friend a hum-bucker is NOT the same thing as an isolation transformer.
BTW: it's called a ground lifter, not an "un-grounding" adaptor and I know what they are.

[Steve House]

Originally Posted by Stephanie Wilson

Okay,

Here's the deal.
The safest way to deal with electricity is to have NO ground at all.
...

An old Navy radioman once told me "Always keep one hand stuffed in your back pocket!"

[Jay Massengill]

Unfortunately there's no way to achieve not having any ground at all. That's the whole point!!! If you want to provide the path to ground through your own body, or the body of someone on your crew, then be my guest...
I'll send my condolences.
Your engineer friend is simply incorrect. Humbuckers, which you first mentioned not me, use isolation transformers in their construction.
And it's not called a "ground-lifter" either, it's designed to CREATE a connection to ground when you plug into a power outlet that's only equipped with hot and neutral lines and a grounded box. You're misusing it when you don't connect the ground lug. I was simply referring to it by how you were misusing it.
I stand by everything I've said here and will stake my 20 years of professional experience in video and audio production as well as studio system engineering on it.
You're simply flat out wrong in recommending on a public forum to use an adapter to defeat the safety ground on equipment that is wired that way.
Okay, that's the real deal.

[Tom Elliott]

Gee Wizz guys, I was just trying to eliminate the Cuban radio station from my tapes .... and I think that the only sure fire way is to for me and my small productions is to go 100% battery.
And I think that one of the reasons that the majors lug those semi-truck generators is for that exact reason .... eliminate all electrical interferance from the sound tracks, plus reducing electrocution of the grips that handle the lights, though one can still get zapped by the gerators if not hooked up properly.
Yours,
Tom

[Greg Boston]

Okay folks. This thread needs to end now. The 'tone' is getting above the threshold of DV-INFO's policies. There are merits to all of the above responses to the original post (mine included). I have a strong 25 yr + background in RF energy and electronics in general. This is not meant to toot my own horn as much as to say I understand both sides of the issue.

Any information or advice received on a public forum should be treated with caution because it comes with no guarantees or accountability. Use at your own risk should be the mantra of all public internet forums.

Thank you,

-gb-

[Boyd Ostroff]

I have to agree with Greg in this regard. This thread is now closed. We certainly appreciate everyone's input, but the discussion must remain on the professional and not the personal level. I've edited out a couple posts which crossed this line...