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Announcing Installation of Longwave Products Collins Mechanical Replacement Filters

Dave Curry of Longwave Products has done a fine deed for all R390A enthusiasts by developing a line of replacement mechanical filters specifically designed for the R390A/URR receiver. Reviewed in a recent issue of and now being sold through Electric Radio Magazine, the filter line consists of a 6kc, 2.5 kc and .5 kc bandwidths.

The various filter performance curves can be seen at the Longwave Products WWW Site by clicking here.

What is especially attractive, the filters take advantage of the input and output isolation provided by the chassis of the IF deck. This feature was been incorporated in the Longwave case design by retaining the flange mount of the filter. Shown at the right is a Longwave Products 6 kc filter placed in a scrap IF deck to illustrate the mounting technique. The inputs are at one end of the filter (top) and the outputs are at the opposite end (botton). The filter mounting flange and IF deck chassis provide for near 100% isolation and eliminates coupling of the input and output. Certainly this is a first for an aftermarket filter. The Longwave R390A (and 75A-4) filters are not intended to be a "1 product filts all" design!

In practical use, there are many on air situations where the 4kc filter is too narrow and the 8kc (really an 11) is just too wide. Add to that, the Collins Mechanical filters have a finite life. Like crystals, they reach a point beyond which they stop resonating. Because the 4kc is perhaps the most used, they are experiencing the highest failure rate in the face of a dwidling supply. Installation of the 6kc Longwave filter in the 16kc filter position offers a performance alternative to overusing the stock 4kc filter while still having it available.

Longwave Products and myself, with the cooperation of Electric Radio have established a non-financial relationship which has resulted in my offering the installation of the Longwave Product filters at minimal cost in the receivers which I restore. Additionally, I have developed a technique and variation of aligning the R390A IF deck which will wring maximum performance from both the Longwave Products filter(s) your choose to have installed and the remaining, stock Collins filters.

For those who are willing to patiently wait in line for me to restore your R390A receiver, the filter installation and the proprietary alignment precedure will be another layer of "icing" on your cake." To recognize R390A owners whose receivers I have restored in years past and would like Longwave filters installed, I will be able to accommodate you also.

Interested parties should drop me a note for details.

Page prepared by R. Charles Rippel

E-mail to: Charles Rippel
URL: http://www.R390A.com
Revision: 04 December 24, 2002
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