[Premium-Rx] Siemens CHR 531

[Gary Geissinger]

Premium Folks,
 
I tend to agree with Michael about the advantages of the LC pot cores.
My Drake R8B (not exactly a premium rx, but good value for the money)
uses the LC filters and is wonderful.  It will probably stay that way
for a good long time.
 
Unfortunately the old Hammarlund and National receivers aren't as well
fortunate.  Because of the "vacuum state technology", the receivers get
hot and shift the values of the passives in the IF strip over a number
of years.  They get pretty deaf after a while.  The inductors hold ok,
but the capacitors and resistors need to be replaced after 30 or 40
years.  I had an HQ-180 that needed virtually every resistor and
capacitor in the IFs replaced.
 
I suspect that high end units like those from Siemens and R&S hold their
age pretty well.
 
Gary WA0SPM     
 
 

________________________________

This mailbox protected from junk email by MailFrontier Desktop
from MailFrontier, Inc. http://info.mailfrontier.com
<http://info.mailfrontier.com/> 


	-----Original Message-----
	From: premium-rx-bounces at ml.skirrow.org
[mailto:premium-rx-bounces at ml.skirrow.org] On Behalf Of Michael O'Beirne
	Sent: Friday, January 14, 2005 3:42 PM
	To: Premium-Radio
	Subject: [Premium-Rx] Siemens CHR 531
	
	
	Hi everyone,
	 
	I don't know the Siemens CHR 531 but in general terms, 30kHz is
a popular final IF with many German receivers, typically my Siemens E311
from the 1960s (it cost DM15,000 new in those days!!!!) and the R&S test
receiver ESH 3 which requires a second mortgage on the family home to
purchase.
	 
	At this low frequency it is possible to create a good IF
response using just LC pot cores.  A lot of old Drake ham receivers used
50kHz for the final selectivity for this reason.  
	 
	These LC filters have the added advantage that they usually have
very good phase linearity and in consequence they do not ring, unlike
many tight mechanical and crystal filters.  Thus they could be used for
DFing whereas most other filters are useless in that application.
	 
	I believe that Telefunken used to make (and perhaps still make)
excellent mechanical filters at 30kHz.  
	 
	As for the drop in response at MW, this is presumably because a
filter has been interposed in the RF stage to remove the effect of some
crushing MW signals.  A typical example is the Collins KWM380
transceiver. It has a reasonable receiver but it loses sensitivity at
MW.
	 
	I'd stick with the RA6790.
	 
	Regards and 73s
	Michael
	G8MOB

-------------- next part --------------
An HTML attachment was scrubbed...
URL: http://mailman.qth.net/pipermail/premium-rx/attachments/20050114/bb69920e/attachment.htm