Low Pass Filter Advantage

[slowmover]

Cleaner is Meaner

A couple of videos (Scott’s Radio) covering the advantages of using Low Pass Filtration where an inexpensive outboard amp is used with a system. Inexpensive as it lacks RF filtration.

Second video features the MORGAN 411cb Bypass Filter.

One will hear that an LPF is not needed now that TV is a digital signal.

My experience is that the proliferation of dirt cheap low quality electronics makes some areas astonishingly noisy (BPF helps) and that spurious emissions means you’ll possibly cause interference yourself (LPF the actual minimum).

Worth examining.

The clean, quiet radio gets responses.
That’s STRONGLY a goal.

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[RFI-EMI-GUY]

That specific Morgan BandPass filter will also improve the receiver performance as all superhet receivers have some degree of out of band spurious responses which can degrade the on channel desired signal performance.

 

[merlin]

Most quality radios meet FCC specs for harmonic emissions and a low pass filter won't do much.
Adding a cheap power amplifier, those lack post filtering so a LPF really should be used.
TVI makes no difference with ATSC, a strong signal will still overload TV front ends.

 

[slowmover]

What one doesn’t at first realize in having installed 411cb or similar is that those on the other end are impressed by the increased quiet out of which one’s voice arises. You’ll get compliments.

Overcoming the deficiencies of the other mans typically poor rig.

These compliments are because their attention was heightened. This is crucial, IMO, in having “radio” (the communication art) operate best.

A BPF isn’t cheap. It doesn’t seem to quieten things that greatly. Until you get the TX feedback that twins the RX component. This has been true for me with “old tech” GALAXY 959, or with NRC QT60; even if less with the latter.

As I don’t operate except on 11M, a BPF has been a good choice. I’d call it optional. For me that’s been a mandatory option.

I also run a feedpoint choke at the antenna and a coax filter at the transceiver. “Overkill”, maybe.


My experience is that a cool head and a great radio rig becomes its own coordination point on which other men are relying as we identify, define, and solve what’s needed with a problem still underway up ahead.

So, there’s consideration of one’s neighbors at home or on the road, there’s cutting RX noise, and there’s less confusion from my TX when men are taking adrenaline hits at 68-MPH. And I’m nailing info points needed (state, road, direction, mile marker; etc).

Just remember that by loading up the coax it means more expense, more potential trouble points, and increased maintenance. No free lunch.

Need spares. Need tools. Onboard. Dedicated.

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[kc2asb]

Most quality radios meet FCC specs for harmonic emissions and a low pass filter won't do much.
Adding a cheap power amplifier, those lack post filtering so a LPF really should be used.
TVI makes no difference with ATSC, a strong signal will still overload TV front ends.

Often times the fault lies with the TV itself. Ditto for other home entertainment equipment. 35 years ago, I was coming over my neighbor's TV (even when it was off!) despite using an FCC type accepted radios (Cobra 142GTL / Realistic TRC-30A), running legal power, good coax, etc.

Nothing cured the problem. I was in high school at the time and did not have the budget to pay for a cable TV subscription for the neighbor.

 

[slowmover]

AKA

Making Toasters Talk!
circa 1990

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[jcrmadden]

Circuitry explained

 

[prcguy]

Circuitry explained

That explains some audio band pass filters, not RF.

 

[jcrmadden]

That explains some audio band pass filters, not RF.

Yeah yeah... I uh, I knew that...