Topband: MFJ 1025

[W2pm at aol.com]

In a message dated 1/8/2007 3:48:07 PM Eastern Standard Time, tod at k0to.us  
writes:

The  MFJ-1025 does not have an internal preamp. 

Some radios, in particular  the FT1000MP series, provide an RF OUT and an RF
IN jack on the back of the  radio. The RF IN jack can be selected from the
from panel and is used with  beverages, K9AY loops, Pennants, EWE's and the
like. 

The RF OUT  jack connects the transmitting antenna to this output when the
radio is  receiving. This permits one to use the transmitting antenna to
connect to  the AUX or the MAIN input of the MFJ . Now you can use an
external antenna  for listening or you can use it for providing a sense
antenna input  (connected to AUX) or you can use the TX antenna as a sense
antenna to  remove signals and/or noise (or add signal) to the RX antenna .
This is  discussed on the ON4UN book.



Sorry - I misstated the preamp issue - it does have a jumper.   However, Im 
not sure the preamp has a separate gain control.  I have an  ANC4 which also 
has a preamp for the noise but it is not very useful as I find  it necessary to 
be able to twidle the noise preamp level.  Note that  because of a BCB band 
filter in the 1025/6 the noise input is subject to a  degree of loss -- 
modifications for this are on W8JI's site (I think). Another  very useful mod is to 
put in relays to allow reversing the noise input with the  main input.. Ive not 
done the latter mod but I have experimented in manually  reversing the noise 
and main antennas (not for transmit of course) and find  better null 
possibilities that way but I think those could be matched by bigger  and better noise 
antennas.  73 Pete W2PM