SD-330:The Diamond SD-330 is a remotely controlled mobile antenna that can be fitted to the car in minutes using a magnetic mount such as the Watson W-300S triple magnetic mount.
(Do not use a single leg magnetic mount as the capacity to earth will not be enough below 14MHz and unless stationary, will not provide adequate adhesion.
The antenna comprises a base-loaded electronically tuned “screwdriver” antenna with a flexible whip mounted on a spring coil.
The total height is 1.7m approx. depending on frequency. From the antenna is a detachable DC cable with a total length of approx. 22ft (5m) of DC feed cable.
This includes a short detachable length at the car end which comprises a remote up/down press button unit and a cigar plug. The current drawn is just 100 mA.
Tuning is achieved by pressing either the up or down button and listening for the signals to peak in strength.
This is very noticeable and gets you very close to minimum VSWR. Any fine up / down adjustments can be carried out with the radio’s VSWR meter.
The antenna has a large diameter base coil and can be tuned to any frequency in the range of 3.5 – 30MHz.
To change the frequency, first tune the antenna to maximum noise on the receiver, then start transmitting at low power (10W) and tune in to get the best SWR. With a good counterweight an SWR equal to or better than 2:1 is possible.
Tuning requires max.50 seconds from 3 to 30 MHz or 20 seconds from 7 to 30 MHz.
Bands: 3.5 – 30MHz
Power Supply voltage & current: DC 12v 100mA
Max Power Rating: 200W (SSB)
Height: Approx. 66″ (28 MHz)
Approx. 73″ (3.5 MHz)
Type: 1/4l center loading
VSWR: Less than 2.0 / Impedance: 50Ω
Up-Down time: Approx. 50 sec. (3.5-30Mhz )
Approx 20 sec. (7-30MHz)
NOTE: The SD330 uses the car body for its ground. The bracket and the car body need to be well grounded.