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Export Radios, Amps, and the Police?
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There was a real old dude outside my town. He had one of those Maco 300. He was around 2 miles away. That thing destroyed everything around it. I couldn't talk anywhere that thing bled so bad.
Back when I first started becoming serious about the hobby (circa 2000) I put up my first base station. A galaxy 77hl driving a Texas star 500 out through an Antron 99. I knew nothing about clipped limiters/alc, wasn't long before my neighbor told me I was talking through his TV and I was setting off touch lamps in my house or who knows who else's. I did a little reading and immediately saw stories about fcc getting involved.....Scared me enough to do some learning and correcting to my setup before keying it another time.
It's really unfortunate that nearly all the CB amp makers (with rare exceptions) can't be bothered to include a low pass filter on the amp output. Amps in EVERY other radio service include them, and the makers of that equipment would be laughed out of town if they didn't. Yet for some reason nobody building CB amps bothers !
Having a filter would prevent the vast majority of these cases of interference (especially with TV's) from happening in the first place ! Amps are supposed to have them for that reason....they minimize the harmonic radiation that causes interference issues.
Having a filter would prevent the vast majority of these cases of interference (especially with TV's) from happening in the first place ! Amps are supposed to have them for that reason....they minimize the harmonic radiation that causes interference issues.
CB amps are built cheap to maximize the builder's profit. Low pass filters cut into that profit. Since what they're selling is at best gray market merchandise anyways, might as well get the max cash they can.
It's been that way forever, why add extra parts that cost more money.
Some did a better job than others , the best ones cost more because they had decent bias and some filtering on the output.
But most do not want to pay extra for a well built amp when you can get the unbiased minimum parts version that swings your watt meter just as far ( or farther) for 25-30% less.
The original Palamar built 4 transistor solid state amps that actually had complete band pass filter boards in them.
With a band switch that was hooked up and even worked so they were very capable of building them them this way.
85% of the target market back then could care less about band pass filters.
73
Jeff
Varmint amplifiers had a low-pass filter on a small circuit board that was added to the original design. Problem lies with how the amplifier is operated. Driving it too hard produces a lot of harmonic energy, and the low-pass filter would overheat and poof. Removed more than a few smoked filters like this.
Takes more than a filter. Also takes a setup that doesn't produce a lot of harmonics in the first place. The "hot-rod" design of most CB base amplifiers made that kinda tough to do.
73
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thus we got 27.0250,drift to say 26.350 to 27.1850 and we get buckets full of blood. but thats my opinion n observation
The way I understand it a low pass filter does not have anything to do with bleeding channels within its operating range, It is more to stop spurious emissions above 30 mhz.
You are 100% correct. LPF prevents harmonic radiation which causes interference to TV's, other radio services, etc.
Splatter (Bleeding onto other channels) is caused by over-modulation, audio clipping due to cut limiters, and poor amplifier design (especially in tube amps). Usually a combination of those things is at work.
That doesn't surprise me one bit.
luckily I'm in the country, this one sitting covered up for a few years on the Shelf.