On 6/10/2018 10:27 AM, Jim Thomson wrote:
## Seems to me MFJ supplied a HP filter when using the MFJ-259B, to kill
anything < 1.8 mhz.
Jim VE7RF
IIRC, what MFJ supplied was a tunable NOTCH filter, which might work OK
in situations where there is only one station that is strong
enough to upset the MFJ-259B. Of course you can't calibrate out
the filter, so it could degrade measurement accuracy. Far from a panacea.
My QTH is 6 miles from a 50 KW station on 1140 kHz. My 259B
is useless on 160 meters and marginal on 80 meters. I vaguely
remember the 259B getting messed up by a channel 3 TV station
that is 8 miles from me running 100 KW. I don't have the MFJ notch filter.
I recently got a Rig Expert AA-55 and it is unaffected by AM BCB QRM and
works perfectly on my 160 meter vertical with no help from
external filtering. It has many other advantages over the 259B.
One thing you have to be careful about is to always use a DC
block between the Rig Expert and the antenna. (You can calibrate out
the DC block). Otherwise, static DC voltage could blow out the front
end. I'm guessing that that is the likely reason why your Rig Expert
failed.
Rick N6RK
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