Matthew Steel

Well, well, well. Anyone care to guess what showed up in the database yesterday?

If there is one coming - and I expect there is eventually - it hasn't passed FCC testing yet. I don't see any new Lectrosonics authorizations in the FCC ID database (https://www.fcc.gov/oet/ea/fccid) since January 2019, except for the 940MHz variants and the DPR/DPRA.

I expect you have already tried a different frequency, but in case you haven't, I have noted a few times that two transmitters on the same frequency will create interference that could be described as a squeal. I can't remember if it was with our Lectros or other brands though.

Looks like we have a couple of winners...https://www.lectrosonics.com/lectrosonics-introduces-the-dchr-miniature-stereo-digital-receiver.html

940MHz SMWB and 940MHz SMDWB were certified in July. Have they been announced?

If she is that good, then it makes the audio mixer/editor's job easy. If she's not, then there is still the possibility of a lot of tedious editing to get all the audio lined up to the picture....

Also places like Tai Audio, Trew Audio, Location Sound will either consign or outright purchase gear. I'm not sure whether they are still accepting 600MHz stuff, but I still see it listed at least some of those places.

I have run Wireless Designer over LAN using a Raspberry Pi. The USB in the Venue Racks uses a standard FTDI USB/serial chip. So it "is" a USB serial port. The Linux USB/serial driver, on the other hand, does not recognize the USB VID/PID combination. I had to write a udev rule to tell the kernel to use the standard FTDI driver. Once you have the driver set up and you have the Venue working as a usb/serial device, you can use a program called ser2net to present it as a TCP device. Wireless Designer can then connect to it over the network without any additional hardware. I have not used this combination extensively - I would like to do so but I need another application to share the Venues and have not yet written the component to allow that.

If it's not a DPR(A) digital plug-on transmitter with recording capability, then I have no idea what it it is.

Pretty cool for a 14 year old product. My first thought was that it was new today, but alas. So far I see no new unbelievably cool products announced today. @LarryF @Gordonmoore1? And, sorry in advance for potentially derailing the thread....

If you are wanting to check a stereo mix for phase compatibility, etc. then a simple mono sum capability should be sufficient and you would not need a separate speaker. This is a standard capability for most live and studio mixers I have used. The essence is that the monitor controller (or section on whatever mixer) sums L and R and applies the sum to both speakers whenever the mono function is engaged. So you have a mono mix, but it is coming out of two speakers and you get a "phantom center" image. I have never used the Big Knob but it has a mono button and I would expect that it has this capability.

First computer I remember using was a Timex Sinclair 1000. My dad bought it on clearance at K-Mart. It lived on our dining room table for a while until my mom got sick of that. The computer then moved to the room I shared with my brother and essentially became our toy. I believe my dad rigged it up with a second memory expansion module for 32k of RAM. My dad then proceeded to get a Kaypro which (unlike the Timex Sinclair 1000) could easily do real work.

Thanks very much @LarryF for your comments. I will try not to be a worry wart. On the receiver side it (almost) impossible for talent to get within 10 feet of any of our antennas, and anyway the multicouplers are all Lectrosonics VRMWB either in a short chain or fed from a UMC16b. On the transmitter side it sounds like we should be fine under almost all circumstances. We are not operating out of a bag. In the theater-like scenarios where we see our largest channel counts it does seem like there is a chance talent could get that close. I will have to keep that in mind then. Thanks again for sharing your knowledge. Most of the information I have found on this topic gets to the point of saying "you need to use coordination software" but to get past that point it seems to be a lot harder to find specific recommendations about what settings are most important and how to most reliably get the channel counts higher.

I have encountered a situation in my RF coordination that seems just at the edge of my knowledge and I'm hoping some of the Lectrosonics RF gurus that frequent the forum can chime in on whether I'm understanding the situation correctly. And whether I should be concerned. I'll try to be succinct but this might be a bit long, sorry. What sparked the question is this: I use Shure's Wireless Workbench software to calculate coordinated frequency sets for the various wireless systems used on our campus. A portion of that equipment is Lectrosonics, and I can connect to that equipment for monitoring with Lectrosonics' Wireless Designer software. I ran into a situation where the Lectrosonics software is complaining about frequencies that the Shure software says is fine. The specific complaint Lectrosonics Wireless Designer has is: "The System at 475.300 MHz is subject to interference from 3rd Order IMD at 475.175 MHz caused by the mixing of carriers from transmitters at 532.700 and 590.225 MHz. The offending carriers do not all fall within the passband of the affected receiver." On the other hand, the Shure software is not complaining. Both programs are configured to flag 2Tx 3rd Order intermod products that fall within 149kHz of carriers - and I can do the math myself to see that this potential intermod product fails to meet the spec. So I am wondering why Shure Wireless Workbench would not flag it. The only reason I can come up with why the Shure Wireless Workbench software might not be flagging this as a problem is that it has a "Filter Selectivity" parameter (which I have left set to its default of +-50MHz outside the tuning range of the receiver). It seems that the Shure software is predicting that the 532.700 and 590.225 carriers will be filtered out by the receiver front end before they can intermodulate and create a problem. This seems to be the basic idea of the Lectrosonics software's message about the carriers not falling within the passband of the receiver. But that's not the only way this intermod product can be a problem, is it? For example couldn't it be created by transmitters in close proximity to each other or by strong signals in a multicoupler upstream of the receiver? Am I being paranoid or should I legitimately distrust the Shure software because of this?

Others have answered but here is one more personal experience to add to the pot. I once ran a musical theater show where I used a single pair of SNA600 antennas to feed 38 UHF receivers spanning blocks 470-26. In that case I believe the SNA600s were fully extended so the block 24-26 stuff was outside the frequency range Larry mentioned. It still performed flawlessly.

Seems like they solved this issue shortly after dinosaurs roamed the earth so if it got unsolved in a new model then somebody dropped the ball... https://www.lectrosonics.com/Support/component/com_fsf/Itemid,714/tag,Wireless, 48, phantom power, damage, receiver/view,faq/

Might be worth a call to Lectro to see what their current wiring recommendations are. I found this note in my files (I know this is a different mic, but the principle of different opinions on wiring is a valid possibility): Sept 16, 2011 Talked with Rene (ext 171) at Lectrosonics because Countryman E6 mics were noisy on new UM400a transmitters. He said that the documents on the web showed the wiring recommended by Countryman, but that there in the Lectrosonics shop they prefer a different wiring: TA5F Wire Pin 1 Shield Pin 2 Jump to 4 Pin 3 White (or green, as in the 10/2016 mics) Pin 4 Jump to 2 Pin 5 Not connected This wiring has been tested and seems to work nicely on the following transmitters: M185 UM200c SMa UM400a (sound much improved over factory wiring) [And today I can also add LMb to that list]

I have done some tests on used batteries like that. I put them in an SMa transmitter and logged the battery voltage on a Venue rack until the transmitter died. If memory serves, the battery indicators in both the SMa and Venue seemed to be based entirely on battery voltage. I was not able to come up with any consistent relationship between initial battery voltage and life expectancy. Here is the graph. Vertical scale is battery voltage. Horizontal is minutes. For reference we usually got 4-4.5 hours (so 240-300 minutes) on a brand new lithium in the SMa. My rule of thumb is that if you get a "good" reading for the first 5 minutes then the battery is not dead and you will get "some" use out of the battery - but don't count on any specific amount.

I have heard of times with today's small transmitters where the transmitter itself has been hidden in the hair. This may have been in more forgiving theater situations though...

This paper was helpful to me and addresses (at least to a small degree) the long run/short run nature of the question: http://audiosystemsgroup.com/Which_Coax_for_Wireless_Mics.pdf In short, the loss from mismatch is a one-time loss, where cable loss accumulates over distance. Thus, for short runs the mismatch loss is more significant (but still quite small). But for long runs, definitely the cable loss far outweighs the mismatch loss.

Not sure if this is Larry's tumbleweed, but there is an FCC certification for the DPR: * Tunes anywhere in TV channels 14-36 - i.e. any legal TV frequencies. * Size and weight of the HMa so probably plug-on. * 50mw and 25mw power settings. Also there is a unit called the DBu that is digital encrypted wireless in the LT form factor. It might already be released because it was certified in 2017. It doesn't seem well advertised but the manual is out there if you search.

Just for the record, I just paced it off and we're more in the range of 110-170 feet. Considerably closer than my mental estimate.

We have a couple of things going for us as far as channel count - we are indoors, in a building that uses a wire mesh as a base for plaster. Also, we are in a small/medium city and so the TV stations are not totally crammed in. We routinely operate at 200-250 feet between transmitter and antenna but not much farther. I use Wireless Workbench for coordination. I found the WW default settings for Lectrosonics gear to be a bit too conservative and so I messed around with Wireless Designer to see what intermod spacings it uses, then I set up custom device profiles from that info. And, it helps that of the 49 channels there were 38 UHF and 11 VHF. Personally I think the diversity has more to do with the VHF noiseups than anything. And the fact that these are 30 year old units, some of which have never been sent back for a tuneup ever. I doubt the 50mW had as much to do with it since some of our UHF were also 50mW. Although we had 100mW stuff for that show it was our older 600mHz stuff, and with the 600MHz transition I have moved to 50mW or less across the board. This is mainly because I don't believe we meet all the FCC requirements for part 74 licensing and I prefer us to be compliant. As far as the LMb battery doors, I think it was confined to a small number of transmitters, possibly even only one. I was able to adjust catch for the door a bit tighter. We'll see how things go after that.

Thanks Larry! I'll have to put a wideband multicoupler on my list of possible improvements, since one of our buildings has 5 inline Venues at this point. Thankfully we haven't seen any reception issues so far. In fact our last show was our biggest ever and we had an even longer antenna chain without troubles: SNA600 -> VRWBL -> VRWBL -> VRWBM -> VRWBM -> UMC16 25/26->(VRWBM, UMC200D, UMC200D). The show had 49 transmitters (all Lectrosonics) and the only transmitter issues were a few noiseups on the ancient VHFs and a couple of LMb battery doors coming open.

This topic has raised a couple of questions in my mind: * There seems to be conflicting specs on the bandwidth of the SNA600. I have seen the 30MHz figure, but I have also seen the figure of VSWR <= 2:1 over a 100MHz range, and the comment that the SNA600 fully extended will operate satisfactorily from 440MHz to 600MHz. Does it come down to how we define bandwidth in a particular case? For instance I wonder if the 30MHz spec is -3dB where the 2:1 VSWR might correspond more with -6dB? (and VSWR is a spec more suited to transmitting anyway, correct?) * My personal experience includes feeding block 26 receivers with a pair of SNA600's fully extended with no problems, so I'm doubtful they would offer much protection from new 600MHz cellular interference. In this particular case it was also at the end of a long chain - (2) VRWB Lo, (2-3) VRWB Mid, a two-block UMC16 and a two-block UMC200d with the block 26 receiver in it. * And, would there be any benefit in converting a "chain" of VRWB into a "star" configuration where each VRWB is fed from a wideband UMC16a? It seems there might be slightly S/N for the downstream receivers but I'm not sure whether it would matter real world.