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Dave Williams

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About Dave Williams

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  • Location
    Melbourne, Australia
  • Interested in Sound for Picture
    Yes
  • About
    I'm a bit of a jack of all trades (master of some?) who has wide and varied interests in all things audio (and some things not).

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  1. Dave Williams

    Zaxcom TRXCL3

    I wonder if it's possible to get stereo transmission with ZHD modulation? (Or rather 2 x mono I suppose). And presumably that would mean mono only reception with a RX200 if using ZHD?
  2. Dave Williams

    Sound Noob looking for recommendations! (And hello!)

    How did you end up going with this? I did live sound production and some install work for years before I got into production audio. Happy to answer questions and provide some direction if you like.
  3. Dave Williams

    Zaxcom's new High Density wireless

    Excellent! That's a fairly minor caveat to worry about Thanks for all the info folks! Very exciting times, can't wait!
  4. Dave Williams

    Zaxcom's new High Density wireless

    Hi Rado, just to confirm; that will be a firmware update that will allow dual mode ZHD reception on the likes of QRX200 and the QRX212 modules? Oh and if so, is there a known timeline for its availability? I'm poised to start getting finance sorted for a wireless upgrade, but wanted to wait and see if I'd need to hold off for a new QRX model to come out. Cheers!
  5. Dave Williams

    External antenna for Sennheiser G2

    Hi Mingo, that sounds like a connection issue to me, I had some similar problems when the pin of the SMA connector on one of my homemade whips wasn't protruding enough (but if it works on the RX, then the antenna is probably fine). Also carefully check that there are no loose connections or shorts in the TX; I accidentally created a tiny solder bridge to the little horseshoe shaped pad when I was modifying mine and this killed the RF entirely. I haven't modified my TXs as the stock antenna is softer than my 'memory wire' ones, and I didn't want to risk it being uncomfortable for talent. Yep, so long as the sleeve of the SMA connector has a connection to the case (ground) you can run an extension of any length (subject to cable losses of a couple of dB per metre) to a dipole or LPDA, or helical etc... You could also incorporate it into a RF management / amplification system. If anyone is interested in how to calculate the various lengths for antennas themselves, it uses my favourite formula that is also used in acoustics calculations: ƒ=v÷λ Where ƒ is frequency in Hz, v is velocity (speed of light in particular medium) in m/s, and λ is wavelength in metres. Rearranged as λ=v÷ƒ we can calculate a single wavelength, and from that 1/2 or 1/4 wave whips and dipoles etc... If you want to get super finicky the velocity factor (speed of light for) of copper is something like 0.95 so this will change the dimensions slightly - Speed of light in a vacuum is 299,792,458 m/s. So the speed that waves propagate in copper is 299792458 x 0.95 = 284,802,835 m/s. So for example, my G3s sit in the 'B' range 626 - 668MHz so to create an antenna that is most resonant in the centre of that band (647MHz) the calculation is a follows: λ = 284,802,835 ÷ 647,000,000 = 0.44m So a 1/4 wave whip antenna is 0.44 ÷ 4 = 0.11m or 11cm so a 1/2 wave dipole is just two elements that are each 11cm long. However! It's important to note the relative weighting of this information. Yes these are technically the 'correct' values, but will there be a noticeable or even measurable impact if you're a few mm out? Very unlikely. There are way too many other variables at work in a real-world situation.
  6. Dave Williams

    External antenna for Sennheiser G2

    Yep I used heat shrink tubing, which actually ended up slipping off the wire, so I ended up using a cigarette lighter flame and some hot-glue sticks to pre-coat the wire in a thin layer of hot glue so that when the heat-shrink shrunk it also bonded onto the wire really well. You can get commercial glue lined heat shrink but it's considerably more expensive. Yes! By grounding the shield / sleeve of the second SMA to the case (any piece of copper or similar wire should do) you do allow the possibility of a remote dipole antenna. A whip is (kind of) the top half a dipole anyway with the metal enclosure being the other half. (Sort of anyway, haha... 'ground plane' or 'counterpoise' are probably more appropriate terms to use). It's super easy to make a simple (albeit missing a balun) dipole from just coax cable. There's various examples on this forum and out in youtube land. I also have made up a prototype that adapts a regular whip into a sleeve balun dipole design over on the DIY part of the forum if you wanna check it out. I haven't really had a chance to do many tests with it yet though...
  7. Dave Williams

    External antenna for Sennheiser G2

    Hi Astro. I ordered mine from eBay - http://www.ebay.com.au/itm/120476274177?_trksid=p2057872.m2749.l2649&ssPageName=STRK%3AMEBIDX%3AIT Just be aware that it won't tin if you try to solder it directly. I found that crimp connections worked ok, but ended up filling the little SMA centre pin receptacle with solder and then inserting the wire. So while it's not a properly soldered joint it was a reasonably strong mechanical connection (perhaps as the solder cools it contracts around the wire a little?), and you can also give the pin an extra bit of a crimp for good measure. It also pays to be aware of the difference between super-elastic wire (which is the one you want) and memory wire, which will bend quite easily but only springs back to it's original shape if heated to above a certain temperature. Cheers! Dave.
  8. Dave Williams

    Dave's DIY Dipole 'dapter - and other RF thoughts and questions

    Yes this was one of the many examples that I took as inspiration thanks! Do you have some sort of balun or choke in there to help keep RF off the outside of the coax? Although for reception it possibly doesn't make enough of a difference to care about... It was never really the original intention to attach mine to a harness (just a happy coincidence that it works), and also as a glasses wearer, I guess I'm accustomed to the extra eye protection so danger to eyes didn't really occur to me at all! (Good thinking though!) I did also find that when attaching high up on my harness it actually angles backwards a bit so was away from my face / eyes, even when turning my head. Also it only takes a few seconds to unscrew the whip if it's in the way when not shooting.
  9. Hi folks! I'm a bit of a hardcore lurker here, and while I read much, I post little. I'd first like to commend everyone for maintaining such a fantastic community and resource for soundies everywhere! I've learnt (and continue to learn) so much from here. One thing that someone said (can't remember who) but it really stuck with me, was that in this day and age a good production mixer needs to be as knowledgable as possible about RF, and so I've been researching as much as possible and trying to come up with ways to improve my professional practice. One day soon I'll own a full Zaxcom rig to go with my Nomad, but for the time being I'm trying to hone my skills, and get the most out of what I have (G3s). I think one of the most important purchases to further this ethos was an RF explorer, which immediately gave me invaluable real-time feedback on what was happening in the spectrum nearby. I also use the FreqFinder app to help coordinate frequencies and avoid intermodulation issues, and finally have been modding my G3s with SMA connectors to use external antennas / distribution (details are in the topic about this also in the DIY group). I also purchased a bunch of Nitinol super-elastic wire and SMA male crimp connectors and have been making my own whips. So finally to the dipole adapter! I was thinking for a long time about a versatile and easily made dipole antenna (plenty of people make them quickly and easily from coax), but I wanted it to be relatively sturdy as well as compact, and I also wanted to try and have some sort of integrated Balun. I finally discovered the sleeve dipole (which uses a 1/4 wavelength sleeve around the feeder coax as both the lower half of the dipole and also acts as an integrated balun of sorts). So with a few plumbing fittings, some copper pipe and end caps and couple of SMA connecters the 4D mk1 was born! (Dave's DIY Dipole 'dapter). Key points: # - I wanted something that could be mounted almost anywhere easily so there is a 1/4" 20 mounting point epoxy'd into the bottom which fits a squillion different common mounting thingies (pic below shows it attached to a little ball head and 1/3" thread adapter on to a mic stand). # - I made it so that it is an adapter not a complete dipole - you simply screw a whip on the top and suddenly you have a dipole! I've yet to discover the effect of 'tuning' a dipole with only one half of it changing length though... However the parts are so cheap that having several for different 'blocks' would be no trouble - and maybe the thickness of the sleeve half of the dipole would increase the bandwidth a bit? # - It is also pretty easy to attach to a harness (as shown) and the top whip sits above the shoulder for a good LOS to the TXs if they are behind. Finally, I also have heaps of questions and ideas about RF and antennas that I'd like to discuss and share so perhaps this topic could also be a place where people can talk about the sort of things that aren't normally found in HAM radio texts? Cheers!
  10. Dave Williams

    External antenna for Sennheiser G2

    I had a look and that seems pretty handy to have something that will work with all Sennheiser systems, but I get the impression it will be pretty pricey. However I'm pretty sold on the Zaxcoms, especially as I already have a Nomad 12, so will be able to take full advantage of the various extra functions Oh and the wideband won't hurt either! I got a whole bunch of connectors and RF cable (RG316) fairly cheaply off ebay. Also got some nitinol super-elastic wire to make whips with. For example - http://www.ebay.com.au/itm/191686834380?_trksid=p2060353.m2749.l2649&ssPageName=STRK%3AMEBIDX%3AIT I got those particular connectors to make my dipole adapter (details coming to DIY section soon), but the other bulkhead ones I got for the G3s were too long so I modified these other ones by cutting off the sleeve part, grinding the hex down to fit and using hot glue to hold the coax cable core which was crimped and soldered to the centre pin. Note the gap / void where I put the second SMA. I reckon that's probably where the IEM volume control would go if this receiver had been born an IEM.
  11. Dave Williams

    External antenna for Sennheiser G2

    Hi Dan, I have been experimenting with this exact thing of late (trying to wring every last bit of value out of the G3s before I get a loan for some Zaxcoms). I haven't had a chance to do more than a cursory test, but it doesn't seem any worse than its unmodified sibling at least... One interesting thing I've noticed is that the 'B' antenna seems to have a lower level input indicated on the RF meter and drops out sooner. This was true even with it still using the audio cable shield as the antenna (having removed the stock antenna). If you're thinking of doing this yourself, be aware that the G3 case is not designed to fit most SMA bulkhead connectors, so some modification (grinding down to fit) may be required. I'll be doing a new post sometime soon outlining my process for this along with some DIY memory-wire whip and dipole-adapter antennas. Cheers!
  12. Dave Williams

    DIY battery eliminator for sennheiser G3/2

    This seems like the best place to post this little bit of show and tell! Recently finished making my first G3 battery eliminator for in-bag use. It uses three Traco TMR 1210 DC converters (isolated), and locking toggle switches, and locking DC plug/jacks; all protected by a 2.5A poly fuse. The belt clip comes from an old tape measure I had lying around. It was quite a tight fit and fiddly to get it all in the enclosure, but I'm quite happy with the results
  13. Dave Williams

    Mounting Camera Hops

    Hi folks. Here is a couple of pics from a low-budget short that I worked on a few weeks ago. I was itching to try out the new ERX on the Scarlet, and it seemed to perform flawlessly sending both timecode and audio via a DIY cable to camera I was trying to think of ways to attach it to the camera, and ended up buying a Manfrotto Nano Clamp, cheap little articulated arm, and a tripod adapter for an iPhone. With an additional rubber band for some extra security it wasn't going anywhere. This also allowed easy access to the battery compartment. (Not that this was required however; my 2700mAh rechargeables were still metering at 4/5 after a 10hr day!) I am completely in love with this clamp / arm combination. It can clamp to just about anything and I even use it in my car to hold my phone in an easy-to-see-google-maps-way. The arm came with a cold shoe adapter and various extra adapter bits. I can even use an extra 1/4 to 1/3 inch male thread adapter to attach a mic clip for quick and easy mic mounting options. Already planning a better set of cables / adapters to run the audio and timecode out of the ERX. Unthreaded mini-jack is so tenuous... Regards.
  14. Dave Williams

    Lithium Polymer batteries

    Thanks for the tips and experience Joel! I've always been an enthusiastic solderer so that sounds like it wouldn't be too trouble. I'm also planning to wire up my own power distro system, but it will be a while until I populate my bag with some QRXs, so have plenty of time to think about how I'm going to wrangle it all. -- Yeah cheers Vincent, I was also thinking of sourcing (or modifying) a compact and light v-lock adapter in the event that the D-Tap was acting up, or if borrowing one from camera dept... Regards. Dave.
  15. Dave Williams

    Lithium Polymer batteries

    Thanks for the heads-up Johnpaul! Those DCU95s seem to be a good 10% cheaper per Wh, and slightly better weight to power ratio as well (and better volume to power ratio). I was basing my single-large-battery-weight-ratio thoughts on an assumption that I would be carrying a spare with me anyway, but of course there's always safety (redundancy) in numbers Any luck with the search John Leonard? Regards. Dave.
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