[Lowfer] Re: Filters recommendations: IC-R75A

[lowfer@mailman.qth.net]

might be Big Hairy Monsters 
Damn Steve  !!   your not talking about me  ??

HAR (G)

Bob  K3DJC



On Wed, 05 Mar 2003 09:18:39 -0500 Steve Dove <dsp@hifidelity.com>
writes:
> Hi Denis,
> 
> Well, the 9MHz/455kHz thing is the old one of you get what you pay 
> for ;  the shape 
> factor of the lower frequency filters is superior.  That said, a 
> 455kHz CW filter without a 
> corresponding 9Mhz one is a system-architectural disaster waiting to 
> happen  -  ideally the 
> selectivity should be as close to the front of the receiver as 
> possible, else the pre-filter 
> stages crash and burn inder the onslaught of signals that the filter 
> should be getting rid of.
> 
> In the context of present-day QRSS operation, one could very well 
> get by with no 
> additional filter just by closing down the bandwidth using the pair 
> of stock SSB filters with 
> dual-BPF ;  this'd get down to maybe a kHz or so bandwidth.  This 
> does leave one wide 
> open for later on when there might be Big Hairy Monsters in the 
> shape of close-by freshly-
> minted 136kHz licensees.  A couple of years ago, we used to have a 
> problem with CFH, 
> a 10kW or so military station on 137kHz near Halifax NS which 
> without decent filtering 
> wiped out the band.
> 
> So, what is decent filtering?  If you want as a start just one 
> decent general purpose aural-
> CW / QRSS filter, I'd look at either the Icom IC-232 (9MHz, 350Hz) 
> which is a nicer filter 
> with better shape factor than their older 500/250Hz filters, or 
> alternatively the 
> International Radio 9MHz/400Hz filter.  The IR filters on the whole 
> are better and 
> cheaper than the YaeComWood ones, their only drawback (at least for 
> the 9MHz filters) 
> is that they are physically much larger, don't just plug in, and 
> need wiring in and tucking 
> away somewhere in the radio.  This last matter isn't a problem in 
> the R-75, where there's 
> room for a marching brass band.
> 
> Later on, an additional IR 455kHz/400Hz or 250Hz filter would give 
> adequate enough 
> selectivity for any reasonable person.  Unreasonable people like me 
> do stupid stuff like 
> have IR 455kHz/125Hz filters, to limited additional benefit.
> 
> http://www.qth.com/inrad/
> 
> for International Radio.  Say Hi to George.
> 
>         73,
> 
>                 Steve        W3EEE
> 
> 
> 
> 
> 
> 
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> 

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