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Poor RF Range


Ben Sim
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I'm working with a rented setup from a colleague which should (and used to) have a fine range - but I have a really poor range and just can't find the solution. He couldn't help me  on the phone neither so I try to find more ideas...

Setup:

- Scorpio

- SL6

- 1 Wisycom MCR42, 2 Lectro SCr

- short (1m) antenna cable

- 1 Wisycom LFA active antenna, gain set to 1dB as I run a short cable only

- 1 Wisycom round antenna (ADB2-ADN)

 

I use the filter of the wisycom antenna and have the SL6 filter to wideband.

I'm in different blocks (A and C, wisy is wideband anyway). All Compat Modes, Companders, etc. in transmitters and recievers are set correct. All on 50mW. I scan for free frequencies and use FreqFinder to coordinate them. All good.

 

What else could be the problem that I loose signal on a talents transmitter after 10m???

Boom transmission is fine of course.

Yes, there are a lot of walkies and video transmission around - but still, the range is far to short and shorter than the system should appear.

 

Thank you guys!

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Can you do a scan with RF Explorer? To see what else there might be out there that maybe your receivers are not seeing. Do scans in other parts of the set too, other than right next to your cart.
 

What are you settings in FreqFinder? Perhaps it got accidentally set too loose. 

 

3 hours ago, Ben Sim said:

- short (1m) antenna cable

 

That is kinda short, I'd want another couple of feet at least? So we can get the antennas above people's heads if we want to. 

 

3 hours ago, Ben Sim said:

- 1 Wisycom LFA active antenna, gain set to 1dB as I run a short cable only

Honestly you shouldn't have to have this setup with 1dB, I might in your shoes even run it at slightly negative dB.

 

3 hours ago, Ben Sim said:

- 1 Wisycom round antenna (ADB2-ADN)


Couldn't you get two sharfins? Or do you need one to be omni? 

 

Quote

Yes, there are a lot of walkies and video transmission around

Are the hits matching up when walkie talkies are keying on the A band receiver and not the C band receiver? (it might be, is my possible guess)

If so, swap out the SRc A1 for a SRc C1, then you can also run a tighter filter before your receivers. 

 

If you can't swap out the SRc, at least use the top end of the A1, not at the lower end of A1. (if you think the issues are coming from the walkie talkies)

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8 hours ago, IronFilm said:

Can you do a scan with RF Explorer? To see what else there might be out there that maybe your receivers are not seeing. Do scans in other parts of the set too, other than right next to your cart.

Yes - it looks similar to my receivers scan - and my chosen freqs are good there too.

 

8 hours ago, IronFilm said:

What are you settings in FreqFinder? Perhaps it got accidentally set too loose.

 

They are set to the most conservative settings.

 

8 hours ago, IronFilm said:

That is kinda short, I'd want another couple of feet at least? So we can get the antennas above people's heads if we want to.

 

They are around 2,5m actually - I wrote this topic this morning pretty hectic that's why I wrote 1m...

 

8 hours ago, IronFilm said:

Honestly you shouldn't have to have this setup with 1dB, I might in your shoes even run it at slightly negative dB.

 

Tried that, didn't change anything.

 

8 hours ago, IronFilm said:


Couldn't you get two sharfins? Or do you need one to be omni? 

 

 I would prefer 2 sharks too, but I can't change that now.

 

8 hours ago, IronFilm said:

 

Are the hits matching up when walkie talkies are keying on the A band receiver and not the C band receiver? (it might be, is my possible guess)

If so, swap out the SRc A1 for a SRc C1, then you can also run a tighter filter before your receivers. 

 

If you can't swap out the SRc, at least use the top end of the A1, not at the lower end of A1. (if you think the issues are coming from the walkie talkies)

 

As I have a poor range testing it at home too, I think the walkies are not the main problem - but maybe just increasing it.

 

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I would start by switching all antennas to whips, see if that's any better. It's possible that one or more of the RF cables are in bad condition.

 

I've also seen a "bad" video cable (BNC) spray stray RF into the air and ruin the airwaves in general. Check any cables attached to the camera(s)

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1 hour ago, jason porter said:

I would start by switching all antennas to whips, see if that's any better. It's possible that one or more of the RF cables are in bad condition.

 

+1

I've painful experiences with bad antenna cables and SMA Whips which obviously looked like in perfect condition.

Could be some issue with the SL6 antenna distribution, some loosened connection inside or so.

 

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Contact cleaner zero residue the pins and connections. Use a small wood tooth pick to gently remove any oxidation. 
 

What does your RF finder show your wireless transmission levels at? When you click the TX on and off is the TX putting out a full level peak into the RFinder? Or is it only putting out a little bit. 

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On 9/15/2022 at 11:04 AM, IronFilm said:

Honestly you shouldn't have to have this setup with 1dB, I might in your shoes even run it at slightly negative dB.

Why would you run slithly negative? To prevent overload?

On 9/15/2022 at 7:41 PM, jason porter said:

I would start by switching all antennas to whips, see if that's any better. It's possible that one or more of the RF cables are in bad condition.

 

I've also seen a "bad" video cable (BNC) spray stray RF into the air and ruin the airwaves in general. Check any cables attached to the camera(s)

I checked every cable now and also switched to whips. It's not better with the whips. It's not that big difference than I expected it though.

I also tried another antenna modules instead of the SL6 - the A10 rack and a Audio Wireless DADM226 . Not better, not worse.

 

On 9/15/2022 at 10:20 PM, Dalton Patterson said:

What does your RF finder show your wireless transmission levels at? When you click the TX on and off is the TX putting out a full level peak into the RFinder? Or is it only putting out a little bit. 

 

RF Explorer shows a full level peak close to my transmitter - as does the scan in the RF scan of the SL6 too.

Though I'm surprised again how fast the level goes down when I place the transmitter like in working conditions: onto a person, maybe even close to the skin e.g. on the ankle and then I'm in the next room. It's not even 20dB over the noise floor anymore (around -87 or -90dB while noise floor is around -101dB)...

 

But: I'd think the level on the SL6 should be better than on the RF Explorer, as RF Explorers antenna is weaker then the Shark Fin, right?

 

I also compared the Lectro SSM and the Wisy MTP41 (both on 50mW) - not a big difference either....

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19 hours ago, BAB414 said:

When you hit your receivers, you want to be at -6 to -2 to prevent overload. -6 is an acceptable amount of loss to work with.

 

What kind of dB are we talking about here? And is there a way to messure / see at what level I'm at?

 

I like the dBμV scale of the Wisys to show me the RF level they're recieving - but they go from 0 to 70dB, different scale.

Is there a way to know more exactly the RF level at the Lectro reciever, too? How much dB does each of the 6 bars for the RF indication of the Lectro mean?

 

 

 

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Hey Ben,

 

I'm sure there is a device that can measure it but I've never heard of it. You can do the math yourself though.

I recommend anyone who works with wireless audio to check out the full video here from Lectro. Here's where they begin to talk about RF gain structure: 

 

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Thanks for the video. Very good. I knew about overload but not that detailed. 

But, in the end there are a lot of people out there using passive sharks on short cables into the receiver / SL6. Regarding to that video they would all run at some plus dB into the receiver assuming around +4dB for the antenna  but almost no lost due to short cables, correct?


so would that mean it’s either better to use longer cables (not really) or only fins that have the option to use negative gain??

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You're overthinking it at that point. Any professional receiver will handle the signal from passive shark fins fine provided the transmitters are a reasonable distance away.

 

i.e. Double the distance and you get 1/4th the power. 

 

As noted, where you can get into trouble is if signal amplification is added if not needed. 

 

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What area are you working in?

On the theory of controlling for RF overload:

Many in Atlanta have found the current UHF spectrum to be FAR more energy-dense than several years ago. Some early wide-band designs like the SRc are notorious for being a bit tippy around overload thresholds, and your RF chain is being served by two active stages before the SRc. If either of these is being exposed to enough RF to begin building up distortion energy in the chain, it can become a compounding problem, once energy gets to the non-linear point.

Distortion products of intermodulation rise 3dB for every 1dB of signal rise, but in most cases, the levels  of intermod distortion fall below our noise floor, and go unnoticed. At high amplitudes nearing the IP3 of any stage (active antennas, distribution amplifiers, receiver front ends), though, distortion products can quickly transition from negligible to interfering, to unworkable. Better designed, higher quality active stages in manufacturers' designs, and better controlled signal paths in our systems play a large part in how robust our systems are to common (and uncommon) levels of RF energy.

I took a Venue VRT system outside once and was amazed how much attenuation I could apply at our Wisycomm Antenna controller before the Venue would have less max range. -18dB or more. The sensitivity of our receivers is rarely the weakest link. If your RF path is high quality, and you're not in the middle of nowhere, too little overall energy has a FAR lower chance of giving your RF chain problems than too much energy, SNR being equal.

First, make sure your distro amp and antennas and cables aren't somehow bad, and swap out some known good or brand new parts, and try your receivers out of the distro with just the antennas.

Then, try attenuation of your system at max attenuation, and take your signals to the max range before dropout. Raise the gain of your system, and note whatever happens to the max range. Best if you do this in a known spot that's given you trouble before.

Are your antenna patterns exposed to any nearby RF from your own sends, or digital equipment? Make space and note if there's any significant difference. Try with RX and TX but your recording system off. Perhaps bad wiring or bad power setup is a source of RF woes. RF explorer is a good way to move an antenna around your system and identify RF troublemakers.

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I'm shooting in Berlin right now.

Usually it's OK to find free frequencies here. RX Explorer shows level around -100, -105 on my chosen freqs.

 

Cables are fine. My own sends are around 2 meters away from the antennas.

I had time to do another test last weekend at home and also yesterday on set: it worked fine, I had a range of about 40m without any problems.

 

But it's not solved either: the day before, interior, I was fighting again - just in the next room with open doors.

 

It seems to me that as soon as I don't have a direct line of sight anymore and when the actors / TXs (usually mounted on the ankle) are surrounded by the camera and operators the range breaks down extremely - and way too much as it should.

I checked the camera and monitors with the RF explorer but couldn't find any extreme RF noise there. Their teradek are in the 5Ghz range. Overall noise in my freq area rises just a tiny bit when I check them with the RF explorer.

Also: I'm the second mixer on this show, the other collegue shooting with the same team and camera gear until 2 weeks ago was in the same block (A1) also with lectros and he didn't have any problems.

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assuming your system is working fine, its either something where you are working that is messing things up, but my guess would be to think about your receive antenna placement.

 

are they close to the set and above head height? i stopped mounting the receive antennas on my cart a few rebuilds ago to give me more options of where i could set myself up to be out the way and still be able to keep my antennas close to where they need to be.

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The antennas are above head height (around 2.5m / depending on the ceiling height interior of course). I have extension cables and a tripod to place the antennas closer to set than my cart in case it's neccesary. But I still think it shouldn't be neccesary to do that when my cart is already just around the corner. As it's very hectic job with a somehow chaotic DOP I try to set up the antennas away from the cart only if I have to - to be faster in moving and more flexible. But yes, it seems the way I have to finish this job now (only 4 days left anyway).

 

Thanks for all the ideas and tips.

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Without rereading through the replies, I don’t think you’ve mentioned trying the SL6 on a different filter. It appears you have Lectro SRC in A1 and C1. So have you tried the SL6 filter set to 470-700 instead of the “wideband” setting? 
 

For example, If you have a scene where you only use C1, set the SL6 filter to 580-700.
 

The SL6 filter really matters and makes a huge difference. 
 

Please report back. 
Thanks 
 

 

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  • 4 weeks later...

Hey Peter,

sorry for the very late response...

 

The SL-6 filter did not change anything. I tried all settings also in combination with or without fitlering at the Wisycom LFA antenna.

 

We did another test now after the shoot and of course everything seems fine.

 

On the last day of the last job there was another situation where I had trouble being just in the next room - as soon as cameras and so on entered the set. So I'm quite sure there was something (probably the Teradek) causing my trouble. But still, doesn't feel good like that.

 

 

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