[Boatanchors] Low Pass Filter Issues

[Glen Zook]

Depending on the model of the HF low pass filter the
cutoff is going to be between around 35 MHz and for
the Drake high pass filters is 52 MHz.  Everything
above that frequency is attenuated by at least 40 dB
if not more.

That is what the low pass filter is supposed to do,
attenuate frequencies above the cut off frequency. 
Thus it definitely does matter and an HF low pass
filter is not going to work on a 2 meter transmitter.

Most filters for VHF are not low pass filters but are
of a bandpass design.  That is they attenuate
frequencies both above and below the desired
frequency.  However, a "true" lowpass filter that was
designed for 2 meters would allow anything below 148
MHz to pass.  But, again, most VHF filters are
bandpass and not lowpass.

Glen, K9STH


--- "Duane Fischer, W8DBF" <dfischer at usol.com> wrote:

Today I listened as several Hams in a local ham supply
store argued about low pass filters. It was for a two
meter VHF transceiver. One insisted the filter had to
be for VHF use only and would severely inhibit a HF
rig from transmitting. Or the converse, that a low
pass filter for a HF rig would severely inhibit a VHF
rig from transmitting. Another said the same low pass
filter would work on either a HF or VHF rig. What
exactly is the truth here? 	


=====
Glen, K9STH

Web sites

http://home.comcast.net/~k9sth
http://home.comcast.net/~zcomco


		
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