[Elecraft] KX3 - Roofing filters

[Wayne Burdick]

Pierre,

I think what you were hearing was low-level transmit phase noise. The  
KX3 has very low phase noise, but with the two radios on the same band  
and only 40 feet apart, during quiet conditions, the TX phase noise  
floor could be above MDS. Roofing filters won't help with this, but  
the KX3's new noise-reduction feature would (coming soon).

Of course if you hear each other's VFOs at close proximity even in RX  
mode, you can turn on RX ISO (isolation amp). Adds 10-15 mA to current  
drain but drops the VFO leakage by some 70 dB+.

73,
Wayne
N6KR

On Jul 23, 2012, at 7:34 PM, Pierre wrote:

> Hello to all.
>
> Maybe that I don't understand the real utility of the roofing filter  
> but I observed this. Last saturday, we were on a SOTA summit using  
> two KX3s about 40 feet appart transmitting CW at 5 W. And even with   
> the roofing filters on, we heard each other's sending as a diffuse  
> noise. I know that changion RX shift to 8 disable the roofing  
> filters, but we were not using that shift.
>
> So, am I missing something about the use of these filters? Are they  
> designed for operations with operators near each other like SOTA  
> activation on a crowded summit ?
>
> 73, de VE2PID KX3 S/N 190
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