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Lectrosonics RX/TX problem


Sebastian Vronski

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Hi guys ,

I just completed a 3 day shoot and had crazy problems with my Lectrosonics SM Dual RX and Lectrosonics SMDB/E01 TX's.

 

I've had them for a while now and never encountered this problem before. Any help would be appreciated.

 

So basically the receiver was going nuts and kept switching the antenna phase indicator up and down causing all sorts of clicks and dropouts etc. When I had time I scanned for clear freqs but it would still do this on both receivers. Also the RF level was very erratic, constantly moving up and down. I checked and replaced all antennas and also checked the compatibily mode and set the freqs way apart but the problem remained. Also, whenever the signal settled down for a bit the audio quality was very hissy or even kinda muffled. The shoot was outside and it got quite windy sometimes but I used this equipment on 10 shoots so far and never had a problem like this. Is the receiver up for repair or is there anything else that I can try? I never fiddled around with the receiver as I never really needed to so I'm not sure what could have changed......?

 

Any ideas?

 

Thanks

 

 

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Hi guys ,

I just completed a 3 day shoot and had crazy problems with my Lectrosonics SM Dual RX and Lectrosonics SMDB/E01 TX's.

I've had them for a while now and never encountered this problem before. Any help would be appreciated.

So basically the receiver was going nuts and kept switching the antenna phase indicator up and down causing all sorts of clicks and dropouts etc. When I had time I scanned for clear freqs but it would still do this on both receivers. Also the RF level was very erratic, constantly moving up and down. I checked and replaced all antennas and also checked the compatibily mode and set the freqs way apart but the problem remained. Also, whenever the signal settled down for a bit the audio quality was very hissy or even kinda muffled. The shoot was outside and it got quite windy sometimes but I used this equipment on 10 shoots so far and never had a problem like this. Is the receiver up for repair or is there anything else that I can try? I never fiddled around with the receiver as I never really needed to so I'm not sure what could have changed......?

Any ideas?

Thanks

Is the dual rx you refer to a SR? You've written SM rx?

If its a SR, you must follow the SR rules.

Frequency 1 MUST be lower than frequency 2.

The 2 freqs also have to be spaced a certain MHz apart (can't remember the exact figure).

It's in the manual.

Regards

Peter Mega

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Is the dual rx you refer to a SR? You've written SM rx?

If its a SR, you must follow the SR rules.

Frequency 1 MUST be lower than frequency 2.

The 2 freqs also have to be spaced a certain MHz apart (can't remember the exact figure).

It's in the manual.

Regards

Peter Mega

Sorry ....yes it's SR. I know the rules that you have to set them at least 600kHz apart but I didn't make it clear that I was only using one TX at a time and I only switched to the other one when I came to this problem. I have the same exact problem with the other one:

antenna phase idicator goes nuts and RF level is very erratic causing all sorts of dropouts.

Cheers

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Hi Sebastian,

Sure sounds like interference. If the RF level is dancing around, turning off the transmitter should still show about the same amount of RF from the interferer. Since two transmitters show the same symptoms, they are probably innocent. It could be a messed up receiver.

 

Since this has interference symptoms and is happening on two channels, I would remove the SR from the bag and run it by itself, some distance away from the set just as a test.  If it calms down, there is some device on set radiating garbage in the area. Changing frequencies by 6 MHz or so will eliminate TV stations as the problem. A second receiver on the same frequency and in the same location would also test if it is interference or a bad receiver.

 

As I remember, the 744 radiates RF even when turned off. The internal clock continues to run.

Best,
Larry F
Lectro

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" Maybe take the 744 out of the bag and test, just to rule out RF spray from the 744 being your issue " or as Larry suggested, take the RX away from the bag, and maybe even from the set for a test.
But then you'd have to take your battery distribution system out, try and pull out all the cables from the rats nest buried deep in your bag. IMO much easier to remove the 744T and keep the Rx and battery distribution contained nicely in the bag.
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  • 5 months later...

Hello,

Thought that maybe was better to revive an old post that somehow is related to my problem.

I'm running a Rx UCR 201 (blk22) in the bag along with 2 Lma Txs hops on the other side of the bag (blk 21). And I'm experiencing the same problems on the UCR 201. Recording on a DR-680. I have used the same equipment before with no issues. I will try tomorrow to place the Rx on a pouch attach to my harness, however, I'm not 100% sure that the Lma Txs are the problem....

Any suggestions will be greatly appreciated.

Thanks!

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If you are using the same RX and TX's in your bag, are they on the same freq's you normally use? If not, it may be a co-ordination problem. If they are, it could be a location issue. If you have a strong enough outside interference mixing with the RF that is already present in the bag, all bets are off. It could be generating spurs on frequencies that are driving your RX crazy.

 

The first thing I would do is make sure the freq's  are co-ordinated. If they are, I would turn off the LMa TX's, one at a time. If the problem goes away, I would suspect some outside interference at the location your are at. If it is still there, then I would turn off the

DR-680. Hopefully by this time, the problem will have gone away. If not, do a RF scan, looking for possible interference on or very near the freq you are using. Lastly, if the problem is still there, it may be in the 201, or even the TX being used with the 201. It could be that the RF output power in the TX has dropped quite a bit.

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Hey guys,

Thanks a lot for the quick reply!

Today I tried placing the Rx on my harness pouch and it seemed to help. I will keep troubleshooting once I get back home this weekend.

BTW, how much range should i be getting out of my UCR 201 & 200C set?

Right now I'm getting about 100feet tops. Is that reasonable?

Thanks again for your helpfull responses!

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BTW, how much range should i be getting out of my UCR 201 & 200C set? Right now I'm getting about 100feet tops. Is that reasonable?

 

So much depends on RF conditions, actors' clothing, receiver antenna position and so on... it's hard to say. But I think 100 feet is pretty reasonable. 

 

Worst case, you can always move the receiver closer to the actor(s) and just run line audio out and into your mixer. I've had occasions years ago where we had to run the receiver's antenna about 15-20 feet from the actor because of unavoidable conditions, like metal walls and chain-link fences (plus RFI from power lines and other kinds of hash). As Larry F has often said, putting a transmitter around a big bag of water (which is pretty much what the human body is) is not exactly optimum placement for good RF. But it's what we have to work with.

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Thanks Marc for the informative reply!...( you too senator, I guess there's always a place for the "it depends")

Good idea to place the receiver close from the source and then run line audio out...this will work well in a control environment. I do mostly doco stuff so I guess I'll have to deal with the 100f (which is good enough).

Thanks for you help!

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