Re: LF: Ra 1792

[Marco Bruno <IK1ODO@spin-it.com>]

At 19.25 04/06/2005, Mal wrote:
> Hi
> All
> I had a conversation recently with a person that owns a ra 1792. His is
> one of the earlier models and has Collins mechanical filters, whereas the
> later models had xtal filters. He thinks the earlier models were better
> because of the Collins filters.
> This info might be of interest to those interested in these receivers. He
> indicated that the price of these receivers would not be more than £400.
>  
> 73 de Mal/G3KEV
>  

AFAIK no particular differencies between Collins mechanical and ITT or
STC xtal filters, except that the Collins ones identify older radios.
Form factor and IF leakage are very similar; Collins filters tend to
degrade 'cause of elastomeric supports of the nickel magnetostrictive
wire  decompose with time, and xtal filters degrade showing
different ageing of the various crystals inside. So they alter the filter
shape. But those are extemes, the great majority of 455 kHz IF filters
that I found are (very) fine.

My radio has a (quite rare) 100 Hz xtal filter centered at 455 kHz in BW
position 5. I always used it to decode narrow band emissions, and
programmed other filter/BFO settings to do band watching in various
modes. Very useful... that way in LF one seldom uses the tuning know,
tuning beeing done by FFT setting and/or radio memory recall. Try doing
that with a commercial radio with analog BFO and non locked
oscillators... a matter of taste, of course :-)

73 de Marco IK1ODO