[Premium-Rx] Marconi LP Filter

[Mark Donaldson]

Just so happens I was sweeping one of these out on my network analyzer a few weeks ago, beware they are designed for a 75 Ohm source impedance and if they look into 50 Ohms the response gets ugly, at least on the higher frequency bandpass filters it does, the low frequency low pass may be more tolerant to load miss-matches. The unit belongs to the receiver portion of a Marconi noise test set used for doing performance measurements in the old analog FDM channel banks, they are available from time to time on Ebay at give away prices and come optioned with a variety of different filters.

	-----Original Message----- 
	From: Richard M. MC Clung [mailto:wa6knw at sbcglobal.net] 
	Sent: Tue 10/7/2003 1:10 PM 
	To: Premium-RX LIST 
	Cc: 
	Subject: [Premium-Rx] Marconi LP Filter
	
	

	I just received a really nice 300KHz LP Filter. It is in a metal case
	that has spring loaded thumb screws to attach it to something else.
	
	It is passive with a BNC chassis connectorfor input and a short cable
	with BNC connector for output on the rear of the chassis and a switch
	to select or bypass the filter on the front panel.
	
	It is 10 inches long X 2 3/4 inches height X 1 5/8 inches wide.
	
	The chassis data is:
	
	MARCONI INSTRUMENTS LTD
	300 KHZ LOW PASS (B) FILTER
	TK 2095
	TYPE NO 52095-014P
	BATCH NO J 173311
	TO CCIR RECOMMENDATION NO 339/1
	
	The PCB data is:
	PM3
	44816-108
	300KHZ LP
	
	I put it on the spectrum analyzer and it is flat from 0 KHz to 300KHz
	with a 2dBm insertation loss is 36dBm down at 308KHz and 50dBm down at
	319KHz.
	
	I'd like to use it ahead of my VLF RCVR's and would like to get any
	documentation on it.
	
	I'd also like to retune it to 500KHz. It has adjustable inductors in
	it.
	
	Anyone ever see one of these or have any doucmentation on it?
	
	RICH  WA6KNW
	
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