[PCR-1000] PCR-1000 Front end overload

[Martin Francis]

Hi there Mr Grasser,

I looked up the presector at MFJ's web site.   It seems that it only goes 
down to 1.8MHz - great for Hams, less so for NDB / MF DXers.

I found another product by MFJ that looked interesting:
http://www.mfjenterprises.com/products.php?prodid=MFJ-956

If you click on the 'Download the MFJ-956 Manual' link you see a very 
simple circuit diagram - switchable inductor in series with 365pF tuning 
capacitor.

1/(2 * PI * sqrt(L*C))

The inductors for the bottom couple of bands are 2.5mH and 33uH.   Assuming 
a usable tuning range of 40-365pH:

2.5mH gives 166-503KHz.
330uH gives 458-1385KHz

If you wanted to rearrange the formula with a known capacitance of say 1nF, 
for a frequency of 1110KHz... you'd need a bigger brain than I have.   I'm 
hopeless at these things.

Now my question is, if this thing is wired to shunt out the unwanted signal 
(i.e. the shunt goes between antenna and earth), and you add extra 'stages' 
to remove other frequencies, or does the whole thing just turn into one 
almighty mathematical mess?


Any ideas?   Or do I have to build it and try it?

?

Martin Francis <><
=============================================================
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 Location:  Richmond Hill, ON, CANADA / FN03GV
 Antenna:   Twin K9AY 140' loops on 300 feet of coax
 Receiver:  ICOM PCR1000 (2.8KHz filter) + DSP-599ZX
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=============================================================




-----Original Message-----
From:	R. J. Grasser [SMTP:rgrasser at frontiernet.net]
Sent:	Monday, September 06, 2004 5:09 PM
To:	DB Nicholson; Discussion of PCR-1000 by Icom
Subject:	Re: [PCR-1000] PCR-1000 Front end overload

First off ground your radio at the "in ground" side of your water pipe.
Your house wiring, or the power meter may not be anything more than a
"floating ground".

If you have the money, buy an MFJ-1045C active preselector ($67.00 on the
web), as it has a very sharp cutoff notch filter.

We also have a 50 KW station about 7 miles from us, but using the 1045C in
conjunction with my H-800 active antenna (10 Khz to 50 Mhz) from LF
Engineering, and my ST-2 broadband vertical array (30 Mhz to 1.3 Ghz), I 
can
totally eliminate the offending AM station, and its images/harmonics.

RJ (rgrasser at frontiernet.net)

Rochester, NY
----- Original Message -----
From: "DB Nicholson" <d_nicholson at bellsouth.net>
To: <pcr-1000 at mailman.qth.net>
Sent: Monday, September 06, 2004 12:09 PM
Subject: [PCR-1000] PCR-1000 Front end overload


I live less than 3 air miles from a 50kw AM station (WBT - 1110).  Front 
end
overload makes AM band reception useless.  I am using a longwire abt 30'
above ground.  Radio is grounded using the house ground at power meter.
Someone once suggested using an RC filter to shunt 1110 to ground, but I'm
not sure what components to use, etc.  Any help would be appreciated!
TIA,
Dave
Charlotte, NC
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