[Premium-Rx] Siemens CHR 531

[Michael O'Beirne]

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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