Topband: Front End Filters

[Raoul Coetzee]

surely it is important to have the correct loading on the crystal,  just connecting a crystal in the antenna path is not so good?It seems good loading is around 1-3k.
Merry Christmas to all.Raoul ZS1C 



      From: K1FZ-Bruce <k1fz at myfairpoint.net>
 To: topband at contesting.com; Dave <rfsales at freng.com> 
 Sent: Saturday, December 24, 2016 7:48 AM
 Subject: Topband: Front End Filters
   
 
The one they are  developing for marketing 'can' have 1 KHZ segment 
crystals channels.. 
 
I would encourage anyone to insert a single crystal in their receiver 
antenna input to see the
difference before considering a purchase.  (Careful not to transmit 
into the experiement)
40 meters is a good test  band as usually has many signals after dark.. 
 
73
Bruce-k1fz
 
 

On Fri, 23 Dec 2016 17:56:07 -0700, Dave  wrote:

      About 15 years ago I built a switchable front end crystal filter, I was
going to market it but it was too expensive for the Ham market. It covers
1800 to 1850 in 5kHz segments with a slight overlap so that there are no
gaps, each section is a half lattice, the insertion loss is about 6dB but
that isn't a problem because I always have about -15dB of attenuation in the
receive path input. Nose bandwidth is 5kHz and about 8kHz at -20dB. Lack of
noise blanker performance is not a problem because big signals make the
blanker useless anyway. I used it during contests when my rig was an IC781,
since changing to a more modern rig, an IC7851, the filter provides no
significant improvement. For working DX on a crowded band it is useful if
your rig does not have a good roofing filter. 

HNY /MX

Dave AA0RS

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