Tag Archives: lectrosonics

Repairing a Broken Lectrosonics SMA Elbow Whip Antenna

leamj23The Lectrosonics Elbow, or jointed whip antenna, has been the subject of some concern since their introduction with the SRa and subsequent rise in popularity. The pin in the antenna’s connector has a tendency to become detached internally from the elbow, breaking the connection between receiver and antenna.

Damn it! Another one!

The problem can go unnoticed, because Lectro’s diversity reception receivers have two antennas, and the opposite antenna  keeps the receiver working well most of the time. Eventually, the broken pin falls out, which can take a long time from the initial break. This visual indication is often the user’s only sign that the antenna is broken.  Of course, if the antenna is used on a  transmitter, and the results would be immediately apparent. However, the elbow antenna couldn’t have been intended to work on a transmitter worn by an actor. Why? The elbow exposes the antenna conductor, which can come in contact with the talent’s skin and sweat, severely de-tuning the antenna and possibly reducing range dramatically.  Not to mention, in stabbing into the talent’s backside, or stuffed in a pocket the elbow joint could be subject to subject to enough tourque to break the pin.

Lectrosonics has addressed this issue with testing of their jointed antennas, intentionally applying stress to the structure, and exploring means of strengthening the build. Their last announcement stated that 20 pounds of torque was required to break the connection. Therefore, the only reason they should break is due to abusive treatment. I suggest the break develops over time, as a result of reasonable, regular field use.

Apparently, Lectrosonics and/or their dealers have selectively been providing free-of-charge replacement antennas to those who bring in their broken units. My inquiry to the Lectro home office regarding the 8 or 10 broken units in my possession was met with “warranty limitation” issues. They explained that my antennas were over a year old, and therefore were no longer under warranty. I would have to buy new antennas at about $40 a piece.

After buying replacement whips (and abandoning the elbow antennas entirely), and also being somewhat of a DIY-er, I went about building my own whip antennas, using SMA connectors and steel antenna cable. Success came soon enough, but in toying with my handful of broken Lectrosonics Elbow Antennas, I wondered,  can a repair be possible?

Possibly… Here’s what happened next.

You’ll need to be good a soldering. Also have a small, table top vice. You’ll also need a Dremel tool with a miniscule drill bit (the kind for drilling circuit boards).  A Dremel sanding/cutting disc. A big pair of Vice-Grips. A small allen wrench. Good wire cutters. A means of measuring a few mm accurately. Some thick, solid tinned wire, like from a 1 watt resistor.

Use Thick WIre like from a 1 watt resistor. Don't use thin wire, like from a 1/4 watt resistor

Use Thick WIre like from a 1 watt resistor. Don’t use thin wire, like from a 1/4 watt resistor

Have good eyesight or wear some headworn magnifiers.  You’ll need supply of pins from virgin SMA connectors from the various sources that sell these things. The Chinese ones are pretty cheap, Try www.aliexpress.com. For this project,  all you’ll need are the center pins that are included with the SMAs. For experimentation, I ordered 50 of them, in many different cable-size configurations. Most of the pins are the same from one kind of SMA to another. Use the pins that look like the ones in the photos, below. P1020672

P10206491. Plug in your soldering iron, dummy. P1020651

2.Remove the screw from the broken Lectrosonics antenna and remove the whip. There will be one or two washers in there, and a bunch of dirt and crap to clean. save all of it for reassembly later. P1020652

3. Clamp the SMA screw-on nut in the vice grips like so. Do not over tension, or you’ll squash the damn thing. P1020653

4. Insert an allen wrench (or something)  through the holes for the screw. This gives you some purchase on the center assembly to pull it out of the connector body. P1020654

5. With the vice-grip in one hand and the allen wrench in the other, pull the two pieces apart, like you are un-corking a bottle of wine. Pull!  P1020655

P1020663

My solder is not black, it just looks that way in this pic.

6. Insert the antenna top-piece in the vice, broken-pin-area facing up. ( I call this the spud). Use your Dremel tool with a circuit-board drill bit to create a hole in the top of the spud where the old pin broke off.P1020657 Make it as deep as you can, say 1/8 inch. Steady hands!                                Make sure the hole stays in the center of the spud.  Tin the hole with some solder. Use a little too much solder, its ok. You’ll file off the excess later (below).

7. Remove the top piece from the vice, set aside, and Insert your thick wire (like from the 1 watt resistor) in the vice. Slide the new SMA pin over the wire. Solder the pin to the wire. Make a damn good connection. P1020660

8. Measure at least 10.40 mm from the top of the pin and cut the thick wire at that point. This length may vary, depending on how deep a hole you drilled in the spud previously. Regardless, the tip of the new pin should end up 10.30 mm away from where the old pin broke off the spud. Thats .403 inches.  Cut and trim the thick wire so the pin-tip arrives at this length. File down the cut point to smooth and round, OK?

9. Put your drilled spud back in the vice. Insert the pin/wire combo into the hole in the spud. Again, make sure the distance from the tip of the pin to where the pin broke off is 10.30mm.P1020662

10. Holding the pin up straight in the spud, solder the wire to the spud. Solder gets weaker and shitty-er the longer it stays hot, so quickly solder up a damn good connection between the pin, wire, and spud. The thick wire will add some flexibility, length and integrity to the connection. Test the strength of the solder job, but don’t bend the shit out of it in testing!  The wire will be thick enough to allow you to push top assembly back into the SMA housing, without smashing or bending the wire in the process. P1020664

11. file or grind the excess solder around the joints. Don’t over grind, just make it level with the thickness of the spud. P1020665

P1020668

Dangerously close to drug paraphenalia and jewelry making.

12. Insert your pin assembly into the SMA base and use the Vice -Grip to push it all the way in. There should be a fair amount of resistance from the white plastic surround, which is good. As Batman said to Robin, “Push it all the way in, and don’t let it fall out.”P1020669

P102067113. Make sure the new pin doesn’t protrude from the face of the SMA nut . A little is ok. If the pin protrudes too much, It will run out of receptacle on the receiver. If it came out too long anyway, you can still grind it down level with the SMA nut. If you have to grind it shorter, round it out a little, too, ok? So the pin can “find” its way into the hole. Nuff said.

14 Do a continuity test between the pin and the elbow. Should be a half-ohm or less. No continuity? You fucked up! The solder connections were bad and broke when you pushed the assembly in.

15. Take a big swig of an alcoholic beverage of your choice. (Like I am doing right now). Repeat the process on your other broken Lectrosonics SMA elbow antennas, or just buy new ones. Or ask for a trade-in at LSC, like I heard some have done. I’m not that popular. But I am tenacious.

How long will your repair job last? I don’t know.  Probably as long as the new Lectro units did, maybe longer. Ask about the warranty before you proceed. For fun, educational purposes only.

I would test periodically for continuity between the pin and the elbow.

Coming soon: how I made my own SMA whip antennas

-by Pete Verrando

Video Blow Torch Transmitter Interference for Wireless Microphones

gx-68 wireless video transmitter swamps wireless mics

The GX-68 Swamping Video Transmitter from Canada.

Imagine yourself listening to your favorite music on an Ipod with some really nice headphones. Maybe those Bose Quiet-Comfort 15’s, my fave on airplanes. They really sound great.

Now imagine you’re at a Skrillex show, 1st row, next to a massive stack of loudspeakers, while still listening to your Ipod with those great Bose headphones. What? Can’t hear your Ipod? You might say you’ve been swamped or more technically, de-sensed. Your headphone audio can’t compete with a Skrillex speaker stack. Bass, highs, no matter. Can’t hear a thing. No matter how great those headphones are, Skrillex’s speakers are overwhelming them.

Skrillex is swamping your headphones. The only remedy is physical distance between you and Skrillex.

lectrosonics, scans, wireless microphones, interference

Various Lectro Scans…Top left- pretty swamped! Bottom right- wide open.

The whole hop affair requires robust, expensive wireless audio systems. But, like my Bose headphones, my fine audio receivers had to share 1st row with the blazing Skrillex video flamethrower, and were de-sensing as a result of the powerful RF eminating from said blowtorch. The receivers have a frequency scan function (Lectrosonics UCR411a), and it was showing complete RF obliteration with the video transmitter switched on. A solid black block, floor to ceiling. When a powerful RF transmitter comes shoulder-to-shoulder with an RF receiver, de-sensing happens. The trans RF overwhelms the circuitry in the receiver, regardless of frequency selected. The only cure is distance.

Move the transmitter 3 or 4 feet away, and everything’s OK! But the only place for the video transmitter and my receivers to live were on the side of the camera. So who’s problem is this? Why mine, of course! Camera and director could not work without the little wireless video system.

No problem, the director says! We’ll just go “hard wire” from sound to camera for the entire week. Dark storm clouds formed over my head, images of water skiing behind camera, with an audio-cable tow rope, inside a wrecked-out house. Outside of interviews and other “tame” shoots, the last time I went hard-wire to camera was probably sometime in 1998.

Cameraman: Works great at home, he says. You can take the camera home tonight and “work it out.”

Lectro Lectrosonics scan swamped

Another Swamped scan on a Lectro Receiver

So, my 1st day goes down with the cable tether, as the production was in 1st day freight-train mode, and no down time for a little audio troubleshooting. I trudge the camera home that evening to perform the “prep” that should have happened the day before the shoot. On the bench, I learn that the transmitter is tunable from 512 thru 800 mHz. From the internet I learn about the transmitter, specs & how to set the frequency, as camera dept. hadn’t a clue about their little black box. I try different combinations of transmitter and hop frequencies, looking for those that play well together. No go. The video transmitter swamps everything from Lectro Block 21 thru 26 and beyond, regardless of frequency setting.

I try some surgery on the video transmitter’s antenna, running a tightly looped wire around the antenna and soldering it to the BNC shell. This detuned the antenna to the point where it became a less effective radiator. However, this may make matters worse by raising the vSWR of the antenna, which may cause the transmitter case radiate RF, or even burn out the transmitter.

I finally mount the transmitter way forward on the camera, tucking the antenna under the viewfinder, and set it to 800 mHz (channel 69). I mount the audio receivers at the extreme rear of the camera, using Lectro block 21 (520 mHz). Doing a scan, this gets the swamping down to the 50% point on the scan display.

Using 100mw transmitter hops, I send audio to the camera and walk test it in the backyard. Amazingly, no dropouts or hits! The Lectro wireless are robust enough to deliver clean audio despite 50% RF interference levels on the receivers. This is using UCR411a Receivers. I’m not sure I could have accomplished the same feat with the less-robust Lectro UCR401 receivers, or SRa’s, which are the equivalent of 401’s. Looks like camera’s gonna have to lug around a little extra weight on the side!

Regardless, I keep a minimum distance from the camera throughout the week, to make sure those hops were solid. I also ran 24 bit backup audio files on everything. Camera dept. refused to do a free-run sync of timecode with my recorder, something to do with the antiquated notion that sequentially coded files digitize faster. No argument from me. If they need the backup, hello Plural Eyes.

Lessons learned! Good times!      by Pete Verrando www.txsound.com

 

bountyxmtr2

Car-to-Car with Lectro’s SMV

   Recently, I was on a shoot following bounty hunters around a city every night for about 10 days. Both cars worked together, with two hunters in each. Each car had a camera operator inside,  and both “hunters” were mic’d with Lectro SMV’s , transmitting directly to an SRb 2-channel receiver on the camera. 

    Camera mic was on channel 3/4.  Now the fun part–   a plant mic was placed in the car’s headliner dead center, and fed to an external SMv transmitter on each car. Both SMv’s at 250mw full power, and taking 12 volts  from each car’s cigar lighter. Our follow vehicle had two Lectro SNA-600 dipoles mounted about 12″ above the roof on fiberglass poles, feeding a Venue Field inside the van. The Field received the 4 officer’s wireless, & the two plant mic wireless.  

Rubber band pulls transmit antenna away from car to maximze range. Fixed to glass with heavy-duty Velcro.
Transmitter  then covered in gaff tape 
Follow vehicle SNA-600 antennas fed a Lectrosonics Venue Field inside. 


On the road, the follow vehicle could reliably  hear those plant mics  up to 1/2 mile away from the hunter cars-  sometimes more in the countryside!  In the city, we would routinely loose the cars in traffic, but could usually still hear them.   This made for great follow vehicle IFB, & two clear recorded tracks of car interior when bad guys were loaded in the car. 

-by Pete Verrando

SRa1

Lectrosonics New SRb Receiver Antenna Distro WTF

When Lectrosonics released their SR, a dual channel wireless receiver, sound mixers seized the opportunity to load unprecedented piles of these receivers in their sound bags.  The SR’s original design, however, and a host of RF interference issues from neighboring gear in their “bags”, left sound guys scratching their heads.
These receivers were supposed to be equivalent in performance to Lectro’s 401 receivers. Except they weren’t. And they were even farther away in RF performance from Lectro’s top line 411a.
The SR receivers were less sensitive than the 401’s, meaning reduced working distance from the transmitters. And in UHF, working distance is not a linear thing. One could have excellent reception at 40 feet, then the signal disappears at 42 feet !
Those guys who invested heavily in the first SRa’s (version with removable antennas) were forced to load their packages down with RF amplifiers and gain-based antennas, to overcome the range issue. Basically, they force-fed amplified signals into the SRa’s antenna jacks. Which creates another bunch of problems, but what the hell.
Gavage for the SRa Receiver
Months later, Lectro re-designs the RF board of the SR, bringing the RF performance much closer to the original claims. The SRb was introduced, and Lectro has a very generous upgrade policy for all those hapless mixers who invested heavily in the SRa.
However, now you have guys with piles of antennas, amplifiers, and combiners in their package. And they are chomping at the bit to plug that mess into their SRb’s.
Now, that the SRb is a more sensitive receiver, and I bet it is not going to like all that amplified RF being force-fed into the antenna jacks.  The SRb is a much-improved design, but physics is physics, and receivers will squawk like a goose destined for Foie Gras when fed too much RF.  Wait and see.
-by Pete Verrando