[Hallicrafters] SX-42 alignment

[Ed Gable]

Hi Steve:  Yes, these dummy antennas can (depending on
your signal generator) be pretty important.  Those older
radios, unlike today's standard 50 ohm systems, were
designed for use with a "typical" higher impedance doublet
or single wire when you put that little link in place.  The
RF amplifier expects to "see" that source impedance and
when you align the rcvr the alignment is based on that
typical source impedance which is simulated by the dummy
antenna.

Good luck with your project.  73,  

Ed Gable  k2mp
see www.antiquewireless.org

Stephen Victor wrote:
> 
> The SX-42 manual lists a dummy antenna as being needed
> for alignment.  (200 MMF capacitor in series with a 20
> uh RF choke shunted by a 400 MMF copacitor in series
> with 300 ohm resistor, and one 300 ohm carbon resistor
> for bands 5 and 6).
> Is this REALLY NECESSARY?  Can someone explain why a
> dummy antenna would be needed for aligning a receiver?
> Many thanks and 73
> Steve WA2DTW
> struggling with SX-42 restoration
> 
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