[hpsdr] preselectors

[Henry Vredegoor]

Hi All,
 
What would be the advantages/disadvantages of having the preselector
switched by relays or some sort of semiconductor switches?
(Besides the obvious ones like e.g. mechanical size, power handling,
switch-over times to name a few)
 
??
 
Henry.
 

-----Original Message-----
From: hpsdr-bounces at hpsdr.org [mailto:hpsdr-bounces at hpsdr.org] On Behalf Of
FRANCIS CARCIA
Sent: maandag 12 maart 2007 14:43
To: hpsdr at hpsdr.org
Subject: [hpsdr] preselectors


Hi all,
I looked at the schematic of my Cubic prepost selector and it is quite
complicated. It has an 8035 processor to select the relays controlling
Silver mica caps and 3/4 inch square package adjustable inductors. The board
is about 10 by 12 inches packed with 1/4 crystal can relays and control
parts. This is well above the scope of out board profile. 
A good preselector to check out is the Cubic R3030. You can download the
manual from bama or premium RX. It uses pin diodes for higher bands and
relays for low. Also has a CP640 grounded gate fet amplifier. The R3030 MDS
is about -136 dBM.
I think it has about 10 filters to cover 15 KHz to 30 mhz. It takes 4 bits
to a local decoder to select the correct filter.  The can inductors could be
replaced with torroids. The L vales are on the schematic. The board is about
4 by 6 inches.  fc

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