one would think so, however, there are a lot of other devices that produce noise that can be mixed down into the HF bands (either by interstage mixing or inter mod).. a low pass filter is still useful for reducing that incidental noise to acceptable levels. Also, when it comes to a phone patch, those are still useful (as cell phones don't work in all places).

I read this somewhere: "don't forget what you already know".

-eric

On Jan 31, 2014, at 11:31 PM, Howard Kaufman wrote:

> With modern radios and modern television, their is little need for a low 
> pass filter.
> If you are going to use one, it should be as close to the transmit output as 
> possible.  With so few stations transmitting from channels 2 through 6, and 
> the modern rigs having both auto tune and internal tuner features, I think 
> the low pass filter has gone the way of the phone patch, and the plate 
> modulator.
> 
> 
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