SICK OF CHANNEL BLEEDOVER INTERFERENCE?
The Answer — the CHANNEL GUARD.
A unique active IF filter that wipes out CB's most annoying problem once and for all.
Fits all PLL or crystal CB transceivers that use a 455 KHz, 7.8 MHz, or 10.695 MHz IF
frequency.* Installs in minutes with common tools and no special knowledge. Works on AM, FM, or SSB.
CB is popular. Maybe even too popular. Either the skip cycle is in, with great DX to crowd
every channel, and all the Hams converting CBs to 10 Meters. Or the skip is dead, so every local guy in town
seems to be busy talking to his neighbor at the same time as you. Many stations are overpowered and overmodulated,
and are guaranteed to make your operating miserable with splatter and bleedover. Fed up with hearing the guy down
the street ten channels away? The CHANNEL GUARD will stop him
There are two CHANNEL GUARD IF filters to fit nearly all
the most popular crystal and PLL type radios:
1) The 455 KHz version replaces the existing Murata ceramic filter. Just unsolder the
old filter, install the CHANNEL GUARD
leads in the empty INPUT/OUTPUT/GROUND holes, and connect to +8-13 VDC. You are
2) The high-frequency versions are specially designed for SSB rigs. Simply remove the
correct IF coupling capacitor, install the INPUT/OUTPUT leads and GROUND, and connect to +8-13 VDC. Detailed
installation instructions included for both types.
Using the same idea as our popular 455 KHz CHANNEL GUARD, the SSB filters combine an
IF amplifier stage with two high-Q crystal elements. You install it at an early IF signal point, before the signal
branches off to the separate AM, FM, or SSB detectors. The result — razor-sharp selectivity in every mode. Since
the "Q" (Selectivity Factor) of a crystal is many times higher than the normal tuned IF transformers, the strength
of interfering signals even slightly off the center IF frequency drop off very quickly. Bleedover is greatly
reduced. See the Graph below.
· Provides up to 100 dB adjacent-channel rejection. This is
much better than the majority of CB transceivers, which typically specify only –40 to –60 dB. A factor of
"100 dB" means that any signal outside the normal 10 KHz CB channel spacing is reduced in strength by a factor
of 10 billion from channel center. Turn your ordinary rig into a hot performer!
· No reduction in receiver sensitivity. In fact, the
CHANNEL GUARD adds one
stage of amplification at the most critical point—right in between IF filtering stages. You may even hear
those weak signals that you missed before.
REACT monitor needs one to eliminate Channel 9 bleedover.
Quality components used. Each CHANNEL GUARD is hand-made and
thoroughly checked against a powerful 30,000 µV modulated test signal. You get a 1-Year Warranty when
properly installed. Just solder it in and forget it!
*NOTE: Most CBs use the IF frequencies shown above. The dual-conversion SSB rigs
with a 455 KHz IF use that only for AM or FM; otherwise nearly all SSB types are 7.8 MHz or 10.695 MHz. The AM-only
or AM/FM-only radios almost always use a 455 KHz IF. If in doubt, send us a large stamped SASE with
the exact model and we can advise you what to order.
CBC INTERNATIONAL, P.O. BOX 1898, MONTEREY CA 93942 U.S.A.
TEL/FAX: 888-I-FIX-CBs (1-888-434-9227), (831) 333-1800