Great camera makes crummy radio

egearbox

egearbox

Member
I ran out and bought the original DVX-100 when it first came out, and just seriously started using it recently. When I plugged in a flat-panel TV to use as a monitor, and a shotgun mic into the XLR connector, I started picking up a local AM radio station in my headphones. That was bad enough, but the interference actually shows up in the recorded audio as well. (It's an AM station at 1580 KHz).

I've managed to do the following troubleshooting:
External mic connected with no monitor is OK.
Monitor connected with no external mic is OK.
External mic connected and S-Video cable unplugged from monitor (but still in camera) is OK. This last one tells me it's not the cables (I think).

I've tried a couple of TVs and the problem seems common to both of them. I'm guessing it's because most things you plug into a TV don't care if stray signals bounce back up to them (for example, a DVD player).

Does anybody know of a line filter or something similar (or some other simple / inexpensive solution) to stop the monitor from feeding signals back into the camera? Right now, instead of a great camcorder, all I've got is a crummy radio.....
 
Welcome to DVXuser!
I love your topic headline. :grin:

Tough call...
Some places are notorious for picking up stray signals in wiring, and through devices. There's a few powerfull radio stations around here that bleed into everythign from the phone lines to radio mics!

Is the TV also plugged into anythign else? For exmple into a Cable-TV cable? This may be allowing signals to ride in from outside along the ground line. This can especially be a problem if the tv is a cheap one that isn't grounded. - If it has a 2 prong power cable that can cause trouble.
Stray signals can ride in along the 'ground' of the video cable from the TV to the camera and then out along the 'ground' of the mic cable. This can result in a ghost signal returning from the mic along a 'hot' signal line.

The first thing to try is a "Hum eliminator" (AKA: Isolation transformer) which seperates the ground of once device to another. My recomendation would be to put it on the video line between the Camera and TV.
There's a nice selection at B&H: http://www.bhphotovideo.com/bnh/controller/home?O=breadCrumb&A=search&Q=&ci=2135
Even though it's an audio issue, my guess would be that you need to isolate the video line. This unit would be worth a try: http://www.bhphotovideo.com/bnh/controller/home?O=productlist&A=details&Q=&sku=192393&is=REG&addedTroughType=categoryNavigation

Don't forget to try unplugging other cables from the TV(s) first!

..Or you could try your luck using a radio mic, but i'm not sure it would help.

Good luck!

- Mikko
 
You must mean KDAY in Los Angeles...I used to live near them, and they get into everything!

Try calling the engineer of the station and ask him what they recommend...the get a lot of calls about this, or did years ago when I lived nearby. Every telephone and audio system within miles has problems with their over-modulated signal. They run 50,000 watts, if it's the one I'm thinking of. Of course, if you shoot somewhere miles away, it shouldn't be a problem.

Off the top of my head, I'm thinking a tiny .001 capacitor soldered onto the hot wire to ground on the XLR cable near the camera will probably fix it. A capacitor like this will short out the radio frequencies but not the audio you want. Or even a more expensive cable may be all that's needed. (better shielding)
 
Thanks for the feedback! (No pun intended.) B&H is one of my favorite stores, I even checked them for solutions before but looked under audio instead of video. Thanks for the tip!

I'm actually in Phoenix, not LA. The local station is KMIK, a Radio Disney affiliate. So, if you don't mind a steady diet of inane chatter and teen pop on your audio track, I guess it might not be that bad. :)

The capacitor sounds like it might also do the trick, although it's been a lot of years since I did any component-level soldering. (How many? Don't ask.)

I've also got emails into the Panasonic support group and Audio-Technica (maker of the microphone I'm using) to see if they have any ideas! I'll post any information I get back on the board here; I'm sure I'm not the only one to ever have this problem.

Thanks again!:Drogar-BigGrin(DBG)
 
Looks like the FCC just generally allows illegal overmodulation on that frequency in other places than LA...here, it's in Spanish...anyway, the RF is getting into your system but you might do as I said, cut it off at the last point where the shielding is likely to be better from there on, at the camera. For more ideas, you might even talk to a techie at the phone company, they have to deal with this all the time.
 
Problem is solved

Problem is solved

Thought I would let everyone know that one of the video filters from B&H Photo Video solved the interference problem with the AM radio station. It's worth noting that I NEVER heard back from Panasonic and the microphone maker couldn't help, so this forum really was a lifesaver. Special thanks to everyone who responded.

Tom
 
Excellent :thumbsup:
Good to hear you got it fixed, thanks for reporting back with your results too (other's take note!)

- Mikko
 
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