Fw: [HBR] 160 meters

[waltah at earthlink.net]

Kees ...
> Having the first IF so close in frequency is a problem ...

is right, as usual.   The consequence is you get a lot of direct 
feedthrough at the IF -- 1665 kcs in mine, 1615 in the real HBRs I 
think?   That shows up mainly as a higher noise level.

The cure is a trap tuned to the IF in series with the antenna lead.   
Such a trap would probably improve performance on 80, as well.  
The ideal would be a low inductance-high capacitance trap, very 
high Q coil.  You might lose just a touch of sensitivity at the 
1800kcs end of the band, but that's not much of an issue.   Haven't 
done it yet, but one of these days ...

There's no problem covering the band with the same tuning cap, 
though, because although the frequency is halved, the band is only 
200 kcs wide instead of 500.   If your setup covers all of 80, it will 
also cover all of 160 with the right coils and fixed caps.

Walt 
KJ4KV