I’ve just made a new addition to my self-made power distribution system- a small voltmeter (the display with the numbers on the left, by the recorder).  This allows me to see exactly how much battery power I have left  They’re available from a number of sellers in China on ebay

I just soldered the red and green wires (+ power and voltage reading point) to the positive pin and black to 0V) on my power distribution box and it all works

Here’s the distribution box and battery:

It’s essentially a load of locking DC connectors wired in parallel


Radio microphone comparisons

I’ve done a comparison of the various models of (reasonably) high end radio microphones available in the UK which will work with DC powering.  As a number of them work with 2 transmitters to 1 receiver, I’ve also made a cost comparison (most competetive I could find, including VAT) of 2 sets and put in the weight of the transmitters.

Transmission systems:

Analogue: Up until recently all radio microphones were analogue.  They use a compander circuit which compressed the audio signal on transmission and expands it in at the receiver.  The circuits need to be compatible on each end to match

Digital Hybrid:  Here a digital signal processor at both ends of the system looks at the incoming analogue signal coming in an compares it to a predictor algorithm, and sends any difference from this to the receiver as an analogue signal which will recreate the original.  They can also program in different compander algorithms, which can mean the receivers can work with other equipment.  The conversion and processing adds some latency (time in ms)

Digital:   With ‘pure’ digital systems, the signal is converted into a digital signal and compressed using a high-speed codec (like mp3 but faster to read/write and maybe better quality) before transmission.  This means they don’t use a compander at all and there are less analogue to digital conversions than with hybrid systems.  The conversion processes also add latency


This effectively means that the receiver has two goes at picking up the signal and picks the strongest, however the point where this happens depends on the receiver design (all receivers here have diversity in some form).  “True” diversity requires two separate receiver circuits, whereas antenna diversity switches between the signals from the two antennae.  In analogue systems it is often audible when switching between antennae, although I’m not certain with digital systems.  Also only two systems have true diversity in a dual channel receiver (4 receiver circuits), the Wisycom and Audio ltd EN2.


Although UK Channel 38, which we’re all supposed to be using next year is only 8MHz from 606-614Mhz, if you’re doing any work abroad or getting site-specific licenses you may have to be more flexible (or if things like ‘white-space’ devices start popping up).  The Wisycom, Sennheiser and  Audio Wireless systems have larger bandwidths (at a cost)


Some of the systems have methods of remotely monitoring and/or controlling the receivers, and a number of them require buying a separate add-on or device.  Both digital systems will allow full control of transmitters from the receiver and the Sony system will allow you to name transmitters. The other systems require things like infra-red remote controls (which may not penetrate costume).  The Lectrosonics system uses audio tones through the attached microphone.


A few of the digital systems will allow digital output to recorders/cameras which have it, which can free up some more channels and reduce conversion processes.  Only the Sony system has word clock, so can be used in multiple instances in a system without sample rate converters.


One of the main differences between the Zaxcom system and the others is that it can do some things which would require additional hardware.  The transmitters also act as 2.4GHz receivers so talkback and timecode transmission can be used with them if the receiver has the IFB option (or from a Zaxcom recorder).  Finally, some of the transmitters have recording facilities (for backup purposes) and will transmit in stereo.

Also, finally- if you are buying radio mics in the UK, make sure they’re Channel 38 compatible (606-614MHz), the current band, Channel 69 (854-863MHz) is probably going to be sold to mobile phone companies after the olympics.  Also the (otherwise lovely looking) Lectrosonics D4 isn’t available here as it uses a current GSM mobile band, so it won’t work.

System (RX/TX) Transmission system Diversity RX weight Dimensions (mm) Bandwidth (CH38) Remote Output RX cost TX cost Price: 2xTX+2xRX Notes
Lectrosonics SR / SMB Digital Hybrid
Antenna (1ch true) 195g 68x89x18 25.5MHz All with RM (£462). Or phone app (£30) Analogue £1,650.00 £1,170.00 £3,990.00 Compatible with Senn HiDyn+, Shure, Audio ltd tx. Scan function
Lectrosonics UCR411a  / SMB Digital Hybrid
True (1ch) 330g 82x120x31 25.5MHz All with RM (£462). Or phone app (£30) Analogue £1,250 £1,170.00 £4,840.00 Compatible with Senn HiDyn+, Shure, Audio ltd tx. Scan function. Front end tracking
Zaxcom QRX100 / TRX900LT Digital (3.6ms) Antenna
(1ch true)
170g 83x133x32 30MHz All + IFB/TC – IFB board
needed £590 (2.4GHz)
Analogue+ AES £1692
(£2282 w/IFB)
£1,149.60 £3990 / £4580 Stereo transmission. IFB allows
2 way audio, TC, recording option on TX. Camera link TX. Scan
Wisycom MCR42 / MTP30 Analogue with digital expander
TRUE (2ch) 180g 68x115x18 240MHz All (IR), (battery on emulations) Analogue+ AES £2,548.00 £1,978.00 £6,504.00 Compatible with Senn HiDyn+, HDX, Audio ltd  and most other analogue systems. Scan. 10mW circulator on TX. Moveable filters
Sony DWR-S02D / DWT-B01 Digital
Antenna 280g 88x119x31.3 72MHz
/ 66MHz (tx)
All + metadata (2.4GHz) Analogue + AES
(+Word Clock)
£1,901.33 £1,278.84 £4,457.00 USB keyboard input. 7V power only. Scan, full remote control of TX from RX. TX power goes down to 1mW
Audio Ltd EN2 Analogue TRUE (2ch) 196g 63x139x20 24MHz Analogue whole kit £2,753.00 LCD on side. Scan. mini TX avalable
Sennheiser EK3241B / SK5212-II Analogue True (1ch) 200g (x2) 74x120x28 36MHz RX,
184MHz TX
Battery (RF) Analogue £1277 (x2) £1,996.00 £6,546.00 RX can be reprogrammed within a 240MHz block. 10mW circulator on TX
Micron SDR550 / TX700 Analogue True (1ch) 200g (x2) 63x121x22 32MHz Analogue £1618 (x2) whole kit £3,236.00 no LCD display, New tiny TX
Audio limited DX2040 / miniTX Analogue True (1ch) 250g (x2) 64x147x20 24MHz All on separate IR device Analogue £1716 (x2) £960.00 £5,352.00 display on switchIR only (£50). Scan on palmpilot only. TX is Tiny
Audio Wireless Analogue True (1ch) 200g (x2) 62x114x20 32/64/120MHz Analogue £1275/£1700
/£2150 (x2)
whole kit £2750/£3400
LCD on side


I’m really excited about a job I’ve got coming up, I’m off to France for a week to follow Team Strakka around for the Le Mans 24 hour.  Not only is it going to be taxing on me, especially for the race- but also for powering my kit.  So far I’ve managed to get by on AA batteries (bulk bought duracell procell from ebay or Kingsland waste market in Dalston), but it’s really not going to be practical for a week.

First of all I’ve found a way of getting a bit more from the AA’s- you can buy chargers which will get a few more goes out of alkaline batteries.  I’ve just had a couple of these arrive and they’ve got some of the spent batteries in them at the moment.  Both the mixer and recorder seem to give up when they get down to around 1.3V.  They’ll still be useful for the radio mics and as a backup.

For a while I’ve used a cheapo chinese Li-Ion 12v battery “6800mAh” designed for CCTV (with a polarity reverse cable) which’ll get a couple of hours out of the recorder. I think the 6800mAh quoted might be for something like 5V though (or just lies).  The connector is jut a 2.1mm barrel connector though so I really don’t trust it.

From having a look at what was available my choices were:

7.2V DVcam batteries- small, long lasting (although the equipment may drain more at a lower voltage, depending on the regulator), locking connector. Reasonable price

9V/12V consumer DVD player/CCTV batteries.  Cheap. Non Locking connector

Professional 14.4V NP1/V lock/gold mount etc. Big. Locking connectors.  Expensive

Unfortunately 7.2V wasn’t enough to power my recorder (even though it only gets 6V on AA’s), so that was out.  The consumer stuff would involve risky connectors and look cheap so I’ll see if I can do pro stuff.

I also found a full length NP1 doesn’t fit in my bag (I’ve got a couple of old ones).  The V-lock batteries etc were even more expensive and wider so that may not have been an option either.

Fortunately Hawk-Woods make a ‘Stubby’ NP1 style battery, the NP35 which will fit.  Shopped round a bit and got them for £70 each.  However they’re Li-Ion and my (broken) NP1 charger only recharges Ni-Cd and NIMH.

So, new charger.  They can get really expensive (up to £700…and they just recharge batteries?!?). Got a no-name chinese one off ebay (*hope it works*) for £80 which will recharge 4 batteries after just missing out on a 2nd hand PAG.

Finally to hook it up to my kit.  I’ve just bought a Hawk-woods NP1  shoe (rather than the full regulated distro) and I’m going to sort out a custom cable for it.