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@myfairpoint.net>
To: topband@contesting.com; Dave <rfsales@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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