[Premium-Rx] RF-590 VLF sensitivity improvement

[John USA]

Hi folks,

Frank Carcia mentioned my emi screening materials...which worked great, by 
the way.  First do a close probe of the rx with the antenna input 
terminated...you can use a spectrum analyzer, which gives freq specific 
results or a scope which just shows you levels.  The probe can be tow or 3 
1" diameter wire loops on a coax test lead--alligator clips are helpful.

Not only does stuff pour out of display openings, but heypad penetrations, 
headphone jacks (when headphones are plugged in), bad top/bottom 
cover-to-chassis contact, etc.  I originally used 350 x 350 (per inch) 
stainless steel mesh for my displays, which worked very well but has a very 
slight issue with being baclit (it's shiney).  I since found a one time 
source of equally fine (or very close) blackened mesh which did away with 
the backlighting issue.  I have not been able to find the black again...the 
original 350 x 350 comes from McMaster Carr and costs about $40 last year 
prices, for 1 square foot, which, if you're careful, does about 12 displays.

Things like keypad openings, I have sealed with copper foil...the foil I 
used was from a anti-slug garden kit, but there are tons of other household 
and garden products that have copper foil.  The 590 rx that started this 
thread sounds not-so-bad compared to my Cubic 3030's that were about S-9 at 
fundamental.  Of course the frequency content and intensity of the digital 
crud changes with display content.

I'll wish you good luck if you embark on such a project--feel free to ask 
questions.  And if anyone finds a viable source of the black mesh, please 
let me know.

regards

John Collins
________________
----- Original Message ----- 
From: "Carcia, Francis A HS" <francis.carcia at hs.utc.com>
To: <premium-rx at ml.skirrow.org>
Sent: Friday, February 24, 2006 1:36 PM
Subject: RE: [Premium-Rx] RF-590 VLF sensitivity improvement


>
> We had a sales guy come in from Chromerics who turned me on to some
> interesting display filters. I got enough to do my R2307 and a RA6830.
> It does block a little light but it is flat. You might check their web 
> site
> and see if you can get some. All displays have update rates or scan rates.
> LEDs pull some current so as the buss moves from led to led slugs of 
> current
> produce noise. John Collins also found some fine screen to do his 3030.
> I find the quality of coax has a lot to do with leakage. fc
> -----Original Message-----
> From: premium-rx-bounces at ml.skirrow.org
> [mailto:premium-rx-bounces at ml.skirrow.org] On Behalf Of
> ToddRoberts2001 at aol.com
> Sent: Friday, February 24, 2006 3:39 PM
> To: premium-rx at ml.skirrow.org
> Subject: Re: [Premium-Rx] RF-590 VLF sensitivity improvement
>
> After some careful listening today I noticed the RF-590 does have some
> fluorescent display noise at about 15.6KHz with a rough audible broad 3rd
> harmonic
> around 46-47KHz and this can drift in frequency a bit. The fundamental at
> 15.6KHz is audible even with the antenna disconnected, I would say about 
> an
> S-1
> signal level. Interesting that this fluorescent display noise frequency is
> very
> close to the standard horiz. osc frequencies used in standard TV sets. 
> Using
> an
> outboard upconverter with a 4MHz LO the noise can be just about eliminated
> with the receiver tuned to 4015.6KHz and using shielded antenna 
> connections
> to
> an outside antenna. Display noise on VLF would still be a problem if using 
> a
>
> loop antenna or any antenna in close proximity to the receiver though. 73
> Todd
> WD4NGG
>
> _______________________________________________
>
> Premium-Rx Mailing List
> To Post: premium-rx at ml.skirrow.org
> For Info: http://ml.islandnet.com/mailman/listinfo/premium-rx
> Visit the Website: http://kahuna.sdsu.edu/~mechtron/PremRxPage/
>
> _______________________________________________
>
> Premium-Rx Mailing List
> To Post: premium-rx at ml.skirrow.org
> For Info: http://ml.islandnet.com/mailman/listinfo/premium-rx
> Visit the Website: http://kahuna.sdsu.edu/~mechtron/PremRxPage/
>
>