Jeff DePolo wrote:
I have had
the opposite experience with the two most recent Micor UHF stations I
put on-line. Both have a peak very near to 400 Hz, and roll
off several
dB/octave above that. Setting for 3 in/3 out @ 1KHz, I get
abt 4 out @
400 hz, and abt, oh, 1.5 or so at 3K.
Anyone else noticed a peak around 400 Hz on a UHF Micor station?
You're probably seeing the peak in the PL filter's response. If you remove
the PL filter and config the A/S board for carrier squelch operation, you'll
probably see relatively flat response up to about 2.5 kHz where the
"splatter filter" starts to take over.
--- Jeff WN3A
Jeff is right on the nose here....
I have swept the MICOR and MOTRAC PL filters and there is a defined peak
around 400 Hz. It is likely caused by the self resonance of the 6 Henry
chokes and associated support components which create the tuned network
used in the filter. This can be tamed down (filter made to be flatter
in response) to some degree by placing a 220K resistor across the choke(s).
See Here:
http://www.repeater-builder.com/rbtip/plf.html
Kevin Custer
