[Elecraft] [Elecraft_K3] Re: KSYN3A FAQ

[Wayne Burdick]

On Feb 13, 2015, at 11:58 AM, "'Joe Subich, W4TV' lists at subich.com [Elecraft_K3]" <Elecraft_K3 at yahoogroups.com> wrote:

> 
> Wayne,
> 
> >> A: With preamp OFF, we measured about -125 dBm at 475 kHz and -90
> >> dBm at 250 kHz. We have not measured MDS below 250 kHz, but the
> >> receiver will gradually become less sensitive as you go lower in
> >> frequency due to band-pass filter rolloff (in the KBPF3, which is
> >> required for operation below 160 meters).
> 
> Would it make sense to update the KBPF3 to replace (or convert) the
> 0.5 - 2 MHz BPF to a 2 MHz LPF? Perhaps by removing L1/L2, changing
> L4/L5 to 2.0 uH, removing C6 and connecting a new inductor (~10 uH) 
> between pins 2/7 of K2?


This is certainly not necessary for use of the 600-meter band, or even for listening to beacons in the 300-kHz range, which I've been doing lately. If you were really determined to improve MDS below 250 kHz, you could do this. I would start thinking about the lower-frequency limitations of the PIN diodes with large signals.

73,
Wayne
N6KR