Icom IC-746, Часто задаваемые вопросы

Страница: 77 / 113

IC-746 FAQ
6.17 How do I get rid of ignition noise?
Someone should write a book on this topic. (Oh wait, someone did, see below) Here are
some of the suggestions that have been made in the past.
•
Clean the battery contacts
•
Run the power leads inside a grounded shield (possibly an old coax braid)
•
Add bypass capacitors to chassis at both ends of each power lead (positive and negative).
•
Ground the tailpipe to chassis
•
Ground the hood to chassis
•
Use higher quality plug wires (Magnecor?)
•
Use better spark plugs (Platinum is better that resistor) (Iridium is even better)
•
Better quality (copper inserts) cap and rotor button
•
New radio suppression condenser at coil
•
Use PI network noise filter at radio power feed
•
Ground the fuel pump and add RF suppression
•
Check the tachometer as a noise source
•
Add RF chokes to remote head cable (not applicable to the IC-746)
•
Put snap-on ferrite beads on the electronic ignition-wiring bundle.
•
Ground engine block to chassis
This problem is not specific to the 746; all radios can be afflicted. Covering this topic
thoroughly is beyond the scope of this FAQ. For more help/information, try the following:
http://www.arrl.org/tis/info/rfiignit.html
http://www.arrl.org/tis/info/pdf/001qex32.pdf
http://www.k2bj.com/Pages/Noise/Intro.htm
http://www.qsl.net/ka6wke/
http://www.realhamradio.com/Ford_F350.htm
or join the "mobile-portable" e-mail list at http://www.qth.net/
It turns out that someone DID write a book on this topic: the "ARRL RFI Book". Chapter 16
is devoted to "Automobiles". Check out the description at:
http://www.arrl.org/catalog/6834/
6.18 How do I adjust or make the NB work better?
The NB is susceptible to both overload and cross modulation from strong nearby signals.
Often, turning off the RF preamp or even turning on the attenuator will improve the
performance. Remember, the IC-746 has plenty of gain to spare.
Page 77 of 113
2003-02-08