yeah, I know this is a 4+ year old post but hopefully someone can benefit from my reply.
any cb radio with a 10d4 filter (99% of the ssb 10.695 I.F staged C.B radios) is gonna be rubbish compared to a 600 buck + real ham radio transceiver even with a stock ssb filter in regards to dynamic range..thats where the sherwood test would "drop your jaw to the floor" and the super duper mod would look silly at the bottom of his list
however
Unless it has a filter cascaded after it (at the price of reduced sensitivity when engaged but that can be a good thing too therefore increasing dynamic range in doing so as well as selectivity)...
Exactly - Except you
can have both at the same time.
Take one of Franklin's 10.695 Channel Guard kits or make your own and remove the stage coupling cap right after the NB and install it there. Instead of setting it up for a zero gain/loss, mod your RF Gain to max, and use the RF gain knob to control the +DC (13.8v) to the circuit. Adjust incoming +DC voltage so that when the RG gain knob is at 12 o'clock, you have zero gain/loss (keep incoming signal low - below AGC turn on). Also, doing it this way, you don't have to re-calibrate your S meter. Keep the NB on. This way, the signal going into the circuit has been "cleaned" up. You may need to change the value of the transistor bias resistor to get a linear response as you increase/decrease +DC to the circuit.
With the RF Gain @ 12 o'clock, you get "normal" max sensitivity and -100dB @ 10 KHz selectivity. Turn the RF Gain CCW and you reduce the sensitivity but increase your selectivity even more. Turn the RF Gain CW and get an increase in sensitivity (past the normal max sensitivity) and still retain very high selectivity.
And yes, you can hear signals that otherwise you wouldn't. Now whether you can get them to hear you is another matter...
.
I usually keep my RF Gain at 12 o'clock but when there is a station that is right in my noise level, I dial it up and pull him out with ease. It has more sensitivity
and selectivity than any of my HF rigs.
Basically, greater dynamic range, increased selectivity, and increased sensitivity (variable, clean, attenuator/preamp) for any radio with a 10.695 I.F. stage.
About the Channel Guard from
www.cbcintl.com:
The CHANNEL GUARD combines 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.
FEATURES: · 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. 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.