Instruction manual

Electrical Specifications
Current Drawn from IC-7000 Accessory Jacks: <100 mA.
Antenna Motor Power Feed: 13.8 VDC, Fused @ 3 Amperes (User Supplied)
Screwdriver Antenna Motor Running Current: 2.5 Amperes Maximum
Motor Stall Current Threshold: 3.5 Amperes Maximum (User Settable)
Motor Over Current Threshold: 3.5 Amperes
Nominal Pulse Width on Slow Motor Speed: 50% (User Settable)
Amplifier Control Current: 1 Ampere Maximum and 120 V Maximum
Maximum Number of Resonance Retries after Minimum SWR Found: 3
Maximum Number of Full Range Searches for Resonance: 2
IC-7000 CI-V Address: 70h
RF Bypassing Remotely Controlled Antenna Leads
Remotely controlled HF mobile antennas are very popular. Although they are commonly referred to as Screwdriver
Antennas, there are several different styles to choose from. The traditional screwdriver was conceived by Don
Johnson, W6AAQ, and there have been dozens of copies and variations of the scheme. The majority of them
change over all length as the frequency is varied.
Other designs like the HiQ do not change length. There's one made in Australia which is based loaded, but most
are a variation of center loading.
Controllers also come is different configurations. Some read the SWR from the radio like the TC/SC does, while
others have separate SWR detectors, or count the number of turns using a built-in reed switch. Some are manual,
and some are fully automatic, but none of them are RFI bullet proof!
The one thing all remotely tuned antennas share, is the fact their tuning motor (and reed switch if so equipped) is
operated above RF ground potential. This means there is RF impressed on the control wires anytime transmit
power is applied to the antenna. Whether the antenna is manually, or automatically controlled, some form of an RF
choke needs to be used. In most cases, the choke takes the form of a ferrite bead or toroid.
While controller and antenna manufacturers are very explicit about how these
chokes should be installed, very few of them are installed correctly. Add in a little
insult caused by improper mounting of the antenna in question (typically an
inadequate image plane under the antenna), and RFI problems abound. Let's take a
moment to look at ferrites.
Ferrites are mixtures of iron oxide and one or more metals typically manganese,
nickel, and zinc. Occasionally rare earths such as yttrium and scandium are also
added. They are not always or predominately iron oxide, and may contain “soft
iron” meaning magnetically soft not physically soft. They provide high magnetic
permeability and high resistivity, although some formulations (known as mixes)
are conductive.
Combined with a variety of stabilizers and binders they can be molded to just
about any desired shape, with toroids, bars and beads being the most common ones
encountered by amateurs. By selecting the right mixture of metals, initial permeabilities from 10 to as high as 5000
or more are easily obtained. The temperature coefficient can also be adjusted to meet a specific use.
For example, a mix 31 split bead has an initial permeability (expressed as ui) of 1,500 and a nominal operating
range of .01 to .1 MHz. When placed over a wire where there is RF energy flowing (between one and several
hundred megahertz), it is equivalent to placing an inductor and resistor in series with the wire for RF currents.
Depending on the frequency of the RF energy, the equivalent impedance can be as high as 50 ohms or more, yet
DC current can pass through unrestricted.
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