14
Speaker Output
The KX3’s PHONES socket is a stereo 3.5mm type. If your vehicle has a 3.5mm AUX input, you can buy a
patch cable to bring the KX3’s PHONES audio to your car’s audio system. Elecraft sells a nice right‐angle
3.5mm cable for this purpose, and they also have a kit of four cables available for a complete PC‐sound
and control connection (SKUs E980230 and KX3‐PCKT, respectively). The Elecraft cables work very well
for KX3 mobile sound connections because of the right‐angle connector at the KX3. They’re high quality
cables, not generally what you would find at Radio Shack, Best Buy, or Target.
It’s best to isolate the KX3 output with a 1:1 600ohm or lower transformer. This will help prevent audio
artifacts from being heard at high volume, and avoids ground loops (Pin 1 problems).
If your vehicle doesn’t have an AUX audio input, there are kits available for retrofitting older car audio.
Most of these use the CD Changer input. If you want separate powered speakers, there are dozens of
choices but make sure you can fit them in the interior, and that they’re securely mounted.
Antenna Installation
Figures 9 and 10, on the next page, show one possibility for a mobile HF antenna. I’m using this on my
Honda Civic regularly. The antenna shown in Figure 9 shows a Hustler single‐bander for 40m, using the
short 22” mast and a base spring at the resonator mount point. This is an inexpensive type of mobile
antenna, and not incredibly efficient, but it does work. I’ve had 60 or 70 SSB contacts while mobile, and
about 200 CW contacts while stationary using the Hustler as shown.
The tripod mount configuration shown in Figures 9 and 10 is extremely robust. The main mount and
feed point is at the rear lip of the trunk lid. Two Comet RS480 5/8” trunk mounts are used at the
forward lip for longitudinal and lateral stability. I’ve been able to use the largest Hustler resonators, and
even a home‐brew 100W resonator that I hand‐built for a 5 MHz MARS frequency. The two forward legs
of the tripod are made of 3/8” fiberglass rod acquired from Granger. The mast brackets are made from
scrap aluminum found around my shop. Level adjustment is via the two 3/8‐24 coupling nuts near the
front attach points. Metal and fiberglass are held together at both ends of each forward leg, using two‐
part epoxy. Heat shrink tubing is used to hide the ugly part of each metal‐fiberglass junction.
Hints:
‐ If you’re stationary, lay out a couple of quarter wave radials and attach them to the vehicle
chassis. Fan them out to the sides from the rear of the vehicle. This really helps with efficiency
and gets a bigger signal on the air. QRP mobile isn’t really a good combination with small
antennas and no substantial counterpoise. The vehicle chassis doesn’t really help much as a
counterpoise, unless the vehicle is RV‐sized. Putting out radials will always improve your
radiated signal.
‐ Use higher power levels. The KXPA100/KXAT100 will help with this.
‐ The part of the antenna mount that is mechanically attached to the vehicle should be electrically
grounded to a hard point on the vehicle’s body. Don’t depend on a trunk lid, and its attachment
via hinges to the rear deck, to be a reliable ground. Use some coax braid from the mount base
and route it along the trunk frame using cable ties as needed. There’s usually a good attach
point right on the body metal near the inner part of the trunk hinge. If you examine Figure 6
closely, there is a good hard attach point shown at the far right.
