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Anyone find RF Hash/interference with SD 633?


Freeheel

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On 10/30/2020 at 12:25 PM, codyman said:

The only time I've had trouble in the A1 band (anything outside of A1 these days in LA is pretty useless ever since the recent repack), it has usually been because of a walkie transmitting near while I'm in the 4xxmhz frequencies.  Speaking of repack, I think everything technically finished in July this year while we were all quarantining so maybe things that used to be clear aren't anymore for you?  Also, looks like you have a lot of Public Safety channels in the A1 range.  You're not transmitting in that range are you?

Screen Shot 2020-10-30 at 9.23.43 AM.png

Where did you get this chart? If I had to only go with the small bands that are "Available for Wireless Mics" I wouldn't have much of anything. Yes, I do at times transmit in or near the public safety stuff, though I try not to go so low. Still, seems like there's not a lot of clean stuff...anywhere. You're probably right about the repack.

 

On 10/30/2020 at 1:22 PM, LarryF said:

Hi Ben,

With the good separation you have, I don't think the SD products are the problem. Those problems were common with bag setups where the SD was close to the receivers.

 

If you haven't already, do an RF scan with the Venue to make sure you have a clean RF spot for your selected frequencies.

 

Also try one transmitter on at a time just in case multiple transmitter are causing intermod. The proper selection of transmitter frquencies will dodge this problem

 

If the signal falls to 60% and it is interference, it must be very strong with the interference overloading the RF inputs, which is hard to do. You need to do some methodical, logical trouble shooting. Start by turning off those things that might be causing interference such as the SD's. Keep turning things off until the problem goes away. If it doesn't, move 100's of feet away from any video transmitters, walkies, controllers or any other thing using RF on set. You can also simulate this by setting up your sound rig at home and see if the problem exists. That will tell you if it is location specific. This may be the most important thing to try.

 

Check out your antenna system by getting rid of it temporarily. Put simple whip antennas on your Venue with the Venue out in the open and see if it now works properly. If it does, your problem may be as simple as bad cables. 

 

Basically, all the trouble shooting here is eliminate and simplify. If this doesn't resolve anything then it may be time to substitute a different receiver to see if the problem is in the Venue.

Best Regards,

Larry Fisher 

 

 

 

Yesterday I tried scanning with my recorders on and off and saw very little (if any) difference. However, I put some 470-614 filters in and started to find a few areas with seemingly no noise floor and experienced no issues.

 

Sometimes I'll run 100 feet of Ultraflex 240 to active antennas and still have similar issues I described earlier so I don't think it's the passive fins or the 10 foot cable.

 

Obviously, there are always Walkies, Iris transmitters, teradeks, follow focus and HMEs in addition to shooting on a stage near 5 other shows so it very well might not be a problem with the gear at all. Just congestion. Still, I'd like to increase performance and the filters seem to be a good start.

On 10/30/2020 at 1:23 PM, Philip Perkins said:

The 744 is a sprayer for sure: I ended up putting some of that RF filter cloth between the 744 and my RX in the pouch of a PortaBrace bag.  That and the slight increase in distance caused by all the layers of the bag+pouch fabric made it workable, but there is still some spray noticeable when the 744 is powered up.   I have not noticed spray in my 6xx machines, and they live in similar proximity to the RX in their bags.

Thanks Philip. I just bought some of the cloth. Is it supposed to act as a barrier between the receivers and the RF Sprayer or should you just wrap the culprit device in it? Or just the receivers?

 

On 10/30/2020 at 2:05 PM, karlw said:

In addition to Larry's recommendations, I will suggest looking at some band filtering and possibly attenuation. The ALP690 antenna offers both. With your ALP620s and short cables, you are likely pulling in more RF than you really need, which raises the noise floor and can increase intermods in the receiver. By putting a bandpass filter at "6" on the antennas (470-608) and then bringing down the gain by say 3dB (set the gain to -3), you will see your noise floor go down and also you'll reduce the possibility of strong out-of-band signals desensitizing your receivers. 

Thanks Karl - Just ordered x2 -3dB attenuators.

 

Moving forward, I'll have the attenuators and filters in line. If I'm still having problems, I'll try to separate the 664/744 about an inch away from the Venue2 and put the RF cloth in. Thanks everyone for your help.

On 10/30/2020 at 1:22 PM, LarryF said:

Hi Ben,

With the good separation you have, I don't think the SD products are the problem. Those problems were common with bag setups where the SD was close to the receivers.

 

If you haven't already, do an RF scan with the Venue to make sure you have a clean RF spot for your selected frequencies.

 

Also try one transmitter on at a time just in case multiple transmitter are causing intermod. The proper selection of transmitter frquencies will dodge this problem

 

If the signal falls to 60% and it is interference, it must be very strong with the interference overloading the RF inputs, which is hard to do. You need to do some methodical, logical trouble shooting. Start by turning off those things that might be causing interference such as the SD's. Keep turning things off until the problem goes away. If it doesn't, move 100's of feet away from any video transmitters, walkies, controllers or any other thing using RF on set. You can also simulate this by setting up your sound rig at home and see if the problem exists. That will tell you if it is location specific. This may be the most important thing to try.

 

Check out your antenna system by getting rid of it temporarily. Put simple whip antennas on your Venue with the Venue out in the open and see if it now works properly. If it does, your problem may be as simple as bad cables. 

 

Basically, all the trouble shooting here is eliminate and simplify. If this doesn't resolve anything then it may be time to substitute a different receiver to see if the problem is in the Venue.

Best Regards,

Larry Fisher 

 

 

 

Even with the antennas remoted, can the SD RF spray still mess with the Venue2 if it's touching or right next to it?

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2 minutes ago, BAB414 said:

Where did you get this chart? If I had to only go with the small bands that are "Available for Wireless Mics" I wouldn't have much of anything. Yes, I do at times transmit in or near the public safety stuff, though I try not to go so low. Still, seems like there's not a lot of clean stuff...anywhere. You're probably right about the repack.

There's an excel spreadsheet on Lectro's main site with various cities in the US and the frequencies that *should* be available: https://www.lectrosonics.com/images/FCC-documents/City_by_City.xlsx

The repack really screwed over a lot of us unfortunately.  Block 19 (and some of 20) has been pretty much the only reliable spectrum left here in LA and even that stuff has Public Safety on it you can't use.  If you do use spectrum in the public safety channels, you will lose that battle as their transmitters will absolutely blast you off the air.

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3 minutes ago, codyman said:

There's an excel spreadsheet on Lectro's main site with various cities in the US and the frequencies that *should* be available: https://www.lectrosonics.com/images/FCC-documents/City_by_City.xlsx

The repack really screwed over a lot of us unfortunately.  Block 19 (and some of 20) has been pretty much the only reliable spectrum left here in LA and even that stuff has Public Safety on it you can't use.  If you do use spectrum in the public safety channels, you will lose that battle as their transmitters will absolutely blast you off the air.

Thanks for this. Very good to know. NYC is super tricky.

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23 hours ago, Freeheel said:

Fun to see this thread again 7 years later!   I will confirm Philip's confirmation on the 744 being quite a nasty sprayer of RF when in a bag, and it was a big part of my push to quickly get a 633 seven years ago once I determined it didn't have the same problem.  As Larry stated, the separation you have with your antennas should make the spray of the 744 pretty negligible.  It generally only took a few inches of spacing to knock down the spurious spray enough to stop worrying about it.  Hard to do in a bag, but not an issue  with a 10 ft antenna. 

 

Cheers,

Brent Calkin

Yeah, I'm just wondering if the proximity of the 744 to the Venue2 itself might be causing problems. The 744 is on top of the 664, which is on top of the Venue.

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2 hours ago, Nicolas said:

Hi guys

 

I made this two years ago when I noticed something strange happening with my radios. I didn't went any further with the problem because I am with the 888 now and the interferences are close to none. 

 

Best regards

Nicolas

SRC-A1_Scan_633.pdf 5.17 MB · 4 downloads

Thanks for sharing. That is wild. Never seen the pyramid before. Do you happen to know if the SRb's are as susceptible?

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