[Premium-Rx] Siemens CHR 531

[IPAssets]

Folks
 
Interesting what a single Ebay posting of an OK receiver not often seen  will generate re discussions. 
There is also a much better rig for sale on the great equalizer, a Plessey 2282, fyi. (And it ain't mine)
 
John England

Gary Geissinger <ggeissinger at digitalglobe.com> wrote:
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     
 
 


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-----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
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