Low Pass Filter?
 

Would a passive Low pass filter (1.6 to 30 Mhz), inline with the radio's
antenna, help to reduce RF noise?

It might help some with regard to "intermod" - - that is, higher
frequency signals outside of the shortwave spectrum that are so strong
as to get into your receiver's mixer circuitry and come thru the radio
(that's quite a "loose" explanation). But much of the RF noice we're
bothered with is so broad-banded that it's actually at the frequency
your radio is tuned to. If you filter that out, you'll also filter out
what you're trying to listen to.


bob2 wrote:

Would a passive Low pass filter (1.6 to 30 Mhz), inline with the
radio's antenna, help to reduce RF noise?

(WHOOPS...damned fingers on keyboard) - - I really DO know that "noice"
is spelled "NOISE"!! - - SORRY...Carl S

Carl / W5SU wrote:

It might help some with regard to "intermod" - - that is, higher
frequency signals outside of the shortwave spectrum that are so strong
as to get into your receiver's mixer circuitry and come thru the radio
(that's quite a "loose" explanation). But much of the RF noice we're
bothered with is so broad-banded that it's actually at the frequency
your radio is tuned to. If you filter that out, you'll also filter
out what you're trying to listen to.


bob2 wrote:

Would a passive Low pass filter (1.6 to 30 Mhz), inline with the
radio's antenna, help to reduce RF noise?

"Carl / W5SU" wrote in message
...
(WHOOPS...damned fingers on keyboard) - - I really DO know that "noice"
is spelled "NOISE"!! - - SORRY...Carl S

Carl / W5SU wrote:

It might help some with regard to "intermod" - - that is, higher
frequency signals outside of the shortwave spectrum that are so strong
as to get into your receiver's mixer circuitry and come thru the radio
(that's quite a "loose" explanation). But much of the RF noice we're
bothered with is so broad-banded that it's actually at the frequency
your radio is tuned to. If you filter that out, you'll also filter
out what you're trying to listen to.

Right on the mark Carl. Your best bet would be to try to reduce the noise
coming into the antenna- balancing the feed/ antenna arrangement if needed,
grounding the shield of the coax and perhaps an isolation transformer at the
RX end to prevent common mode noise for riding out to the antenna on the
outside of the shield.

Dale W4OP

BOB2-47,

1. What your are describing is a 'passive' Shortwave Band Pass Filter
with a Low Point of 1.6 MHz and a High Point of 30 MHz.
Works like both a Low Pass Filter and a High Pass Filter.

* Low Pass Filter - Would simply Pass Signals Below 30 MHz for
the Shortwave and AM/MW Bands.
(Eliminating the TV & FM and above type RFI/EMF interference.)

* High Pass Filter - Would simply Pass Signals ABOVE 1.6 MHz for
the Shortwave Bands.
(Eliminating the AM/MW Band and below type RFI/EMF interference.)

Now to Answer Your Question - YES.

PLUS: You should try to Identify and Eliminate any local sources
of RFI/EMF that you can to reduce the Load on your Filter and Help
to Improve the Overall Signal to Noise RF Environment.


2. Here is a Reading List related to RFI/EMF Noise Reduction:

* A Perspective on RFI "Noise" = And How To Find It !
http://groups.yahoo.com/group/SWL-AM...na/message/515

* Finding Solutions for BCB Interference Problems on Shortwave Bands
http://groups.yahoo.com/group/SWL-AM...na/message/284

* How Do I Reduce/Eliminate TV Interference on Shortwave ?
http://groups.yahoo.com/group/SWL-AM...na/message/186

* RFI/EMF Suppression, Reduction and Avoidance
http://groups.yahoo.com/group/SWL-AM...na/message/113

* Grounds & Grounding = Five Topics for your Consideration
http://groups.yahoo.com/group/SWL-AM...na/message/539


iane ~ RHF
..
..
= = = bob2
= = = wrote in message .. .

Would a passive Low pass filter (1.6 to 30 Mhz),
inline with the radio's antenna,
help to reduce RF noise?

..