Denwood Radio

Denwood Radio

Wild West Waiuku on 88.0 MHz FM

What is Denwood Radio?

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 non-elevated 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.

Station Details

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 very good specifications.

        The CZERF CZE-7C Stereo FM transmitter

The transmitter FM synthesizer and multiplex stereo generator uses the Rohm BH1415F device. The power amplifier is a Mitsubishi RD06HVF1 MOSFET.

A half-wave vertical dipole, fitted with a 1:1 ferrite balun, and fed by 10m of low-loss coaxial cable. The elements are 6mm Aluminium split tubing, enclosed in 20mm PVC conduit for stability and weather-proofing. The antenna height is only about 4m AGL, which purposely limits the range. In the picture to the right, the item in the brighter area is the FM antenna.

Operating Frequency
88.0 MHz.

Operating Schedule
The station usually operates continuously, day and night. The station does not operate when I'm away from home. 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.

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. You can just see the base of the antenna at the back of the transmitter. 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.

Two small electret microphones are attached to the top of the computer monitor, to provide stereo audio for live transmission. The desk microphone below the monitor is an electret type mono microphone used for recording announcements. For lowest background noise, the transmitter (which includes a fan) needs to be turned off while announcements are recorded!

The modest Denwood Radio Studio
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
  • Digital music library of about 3200 tracks     - - -     that's about a month of music at four hours per day!

    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 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 the classical music. Some of the music is quite obscure.

    The Library contains 3300 tracks, in over 400 folders (representing nearly 500 different artists). The total Library size is currently 21GB, and growing. There is (almost) no rock, and definitely no grunge, rap or reggae! I enjoy singers who can sing, with 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 are ruthlessly culled as part of ongoing library assessment.

    Since the Library is digital, most of the tracks include meta data, such as artist, album, track number, genre, year, and even a thumb-nail picture of the record cover! Not that the listener gets to see those things. They do however appear in the Library and play list editor, so assist with, and add 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. 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!

  • Copyright Murray Greenman 1997-2016. All rights reserved. Contact the author before using any of this material.         V1.1, 21 Nov 2016.