Topband
[Top] [All Lists]

Re: Topband: New MFJ 259C available

To: "Paul Christensen" <w9ac@arrl.net>, "topband" <topband@contesting.com>
Subject: Re: Topband: New MFJ 259C available
From: "Tom W8JI" <w8ji@w8ji.com>
Reply-to: Tom W8JI <w8ji@w8ji.com>
Date: Wed, 5 Mar 2014 14:54:14 -0500
List-post: <topband@contesting.com">mailto:topband@contesting.com>
Hi Paul,

Reading the link, it looks like there are very few analyzers that use receivers, either superheterodyne or direct conversion. The AA-54 is in the class of broadband detectors, which are all sensitive to external RF.

http://www.rigexpert.com/index?s=articles&f=aas

Scrolling down the page to near the bottom, we find the superheterodyne or direct conversion frequency selective types. This is the mistake I think MFJ made, not doing a selective detector. The single overwhelming problem is external voltage.

73 Tom



.


----- Original Message ----- From: "Paul Christensen" <w9ac@arrl.net>
To: "topband" <topband@contesting.com>
Sent: Wednesday, March 05, 2014 2:03 PM
Subject: Re: Topband: New MFJ 259C available


Where is a selectivity spec or a description??

73 Tom

Tom,

Apart from the N2PK analyzer, I don't know any published selectivity spec. The detector minimum res. bandwidth of the N2PK unit is 7 Hz and produces +4dBm into 50 ohms.

FWIW, RigExpert put together a comparison of analyzers based on measurement topology. For sure, it's a biased piece -- especially when the MFJ product is discussed. So, keep that in mind.

http://www.rigexpert.com/index?s=articles&f=aas

The plot below shows how well the N2PK analyzer can selectivly ignore a large multi-volt base voltage from three nearby AMBC stations located 2 miles to the south. Two of the AM stations are Non-D in the daytime. One is 15KW, the other is 5KW. Note that the T is resonated to 1420 kHz, right where the stations transmit (look for 1320, 1460, and 1530 kHz). The attached plot shows total RF immunity on the X trace. On the R trace, small "blips" do show - each representing the local AMBC stations. However, even these can be easily ime-averaged away in the software.

http://72.52.250.47/images/N4NN.jpg

Paul, W9AC
_________________
Topband Reflector Archives - http://www.contesting.com/_topband


-----
No virus found in this message.
Checked by AVG - www.avg.com
Version: 2014.0.4259 / Virus Database: 3705/7155 - Release Date: 03/05/14


_________________
Topband Reflector Archives - http://www.contesting.com/_topband

<Prev in Thread] Current Thread [Next in Thread>