Denwood Radio is a Low Power FM (LPFM) station which meets the requirements of the NZ Radio Spectrum Management General User Radio Licence for Low Power FM Broadcasting.
Denwood Radio is primarily designed for personal use, not for wide broadcasting, or even community broadcasting. It runs very low power, using a height-restricted antenna, in order to keep the useful range down to a few hundred metres.
The station studio and transmitter are located in the Hamilton Estate, in Waiuku, on the west coast about 50km south of Auckland city.
Transmitter
CZERF CZE-7C self-contained solid state unit. The transmitter is rated at 7W output, and is operating on the low power setting at 400mW. This is less than the maximum permitted by the LPFM GURL. The transmitter operates in Stereo, and has reasonably good specifications:
- Total Harmonic Distortion typ 0.1%
- Channel Separation typ 40dB
- Frequency Response 20 Hz - 15 kHz
The transmitter FM synthesizer and multiplex stereo generator uses the Rohm BH1415F device. The power amplifier is a Mitsubishi RD06HVF1 MOSFET.
The CZERF CZE-7C Stereo FM transmitter
Antenna
A half-wave vertical dipole, fitted with a 1:1 ferrite balun, and fed by 14m of low-loss coaxial cable. The antenna is home-made, with elements of 6mm Aluminium split tubing, enclosed in 20mm PVC conduit for stability and weather-proofing. The antenna is mounted on a 'hockey stick' (barge mount), so the height is only about 4.5 metres above ground level, a strategy to purposely limit the range. In the picture to the right, the the antenna is the white T-shaped vertical device with an L-shaped mount. The knob on the top of the support pole is a GPS antenna.Operating Frequency
88.0 MHz.Operating Schedule
The station usually operates approximately 7am to 11pm, but not every day. Operation is mostly in fully automatic mode: music and a few announcements.Listening Range
Approximately 300m radius from the station for ultimate signal-to-noise ratio in stereo. It is useable around the Hamilton Estate, and using a good receiver and antenna, in some places up to 1km away. Approaching Waiuku by car from Auckland or Pukekohe, you can receive the station as soon as you enter the 70km/hr zone.Studio Equipment
The station equipment has been chosen to provide very high quality stereo audio, using digital technology as much as possible. The transmission has very low distortion, and very high signal to noise ratio. The program is sent to the transmitter digitally via USB. Conversion to analogue to operate the transmitter is achieved using a very high-specification Hi-Fi digital to analogue converter connected directly to the transmitter. The microphone preamp, transmitter and DAC are DC operated to minimize noise and hum. No clipping or compression is used.In the picture below, the transmitter is at the top of the stack of 'things' on the left. Below the transmitter is the 24-bit Audio D-A Converter, and below that a cardboard box containing a 12V 5A industrial supply which operates the DAC and transmitter. At the bottom is the Dell computer which runs the automated station. To the right of the computer on the desk is the 1TB hard drive which contains the music archive.
The desk microphone below the monitor is an electret type mono microphone used for recording and making live announcements. For lowest background noise, the transmitter (which includes a fan) needs to be turned off while announcements are recorded!
The modest Denwood Radio StudioTransmissions are monitored using a Sony ST-JX2L FM receiver, which operates a home-made stereo Deviation Meter which uses a Vacuum Fluorescent display for good peak response. The deviation meter is calibrated so that transmitter audio level can be set accurately. The transmitted audio can also be monitored via the Deviation Meter.
Equipment Summary
FX-Audio DAC-X6 24-bit 192 kHz D-A converter ZaraStudio ZaraRadio V1.6.2 (Free Edition) Dell Optiplex 475 computer running Win7 Pro Mixer is simply the one provided by Windows Home-made stereo microphone preamp Stereo electret (condenser) microphones Mono electret desk microphone Monitor headphones are Audio-Technica ATH-M50x Sony ST-JX2L station monitor receiver with home-made stereo deviation meter Digital music library of about 2600 tracks - - - that's about a week's continuous music! 
Program Content
The station operates in fully-automatic mode, playing continuous music without announcement, except for very brief station announcements repeated every hour to meet licence requirements. There is no advertising. Music selection operates in random mode, which means that, although the Library is sorted into folders by artist name, and then sometimes by album, you don't hear all tracks from an album consecutively. This technique has the unfortunate side effect that multi-track music such as concertos and symphonies are played one track at a time - you might not hear the next movement for several days!The music transmitted is the stuff I like to hear. It is a mixture of mostly 50s to 90s pop, folk, classical and jazz, with some newer stuff. There is very little instrumental music other than some classical music and jazz tracks. Some of the music is quite obscure. When did you last listen to Chet Baker, Django Reinhardt, Laura Pausini or Blossom Dearie? Many hours of effort has gone into music selection, which is an ongoing and enjoyable task.
The Library contains 2600 tracks, in 350 folders (representing more than 500 different artists). The total Library size is currently 14GB, and growing. There is (almost) no rock, and definitely no grunge, rap or reggae! I enjoy singers who can sing, with undistorted backing that complements rather than drowns the singer! The aim is to provide clarity of voice, instrumentation and overall music quality, above all. Distorted or faulty tracks have no place in the library.
Since the Library is digital, almost all tracks include meta data, such as artist, album, track number, genre, year, and even a thumb-nail picture of the record cover! The Library is also sorted into folders alphabetically by artist name, and is fully backed up on a network drive. Not that the listener gets to see those things. This information does however appear in the Library and play list editor, so assists with, and adds pleasure to selecting tracks to play. As time goes by I will add to the Library and remove or re-record tracks I'm not so happy with. I'd be pleased to hear any suggestions for the Library.
Example of playlist with meta data and album art (Winamp)If you hear a track that you like, and perhaps can guess the name or artist, send me an email and I will look it up for you. I can search the Library by both artist and track name, and with some effort can probably find the track even if you only know a few words. Better still, tell me exactly WHEN you heard the track so I can look it up in the station log. My email address is listed at the bottom of the page. I'd be pleased to hear any suggestions for the Library, and if you have CDs to share, even better!
