[Elecraft] P3 vs SDR-IQ

[John Kramer]

I think I know what Joe is getting at….and I agree with him, if I understand him correctly. When he refers to “noise floor” 
he means that he loses averaging when he tunes, resulting in the crazy spectrum display (what Joe refers to as noise).

I haven’t seen or used a P3, but I bought my first Elecraft products 3 weeks ago - a KX3 and PX3. If the P3 behaves in the 
same manner as the PX3 then I can see what Joe is complaining about. Right out the box my PX3 had this frustrating
feature of losing averaging the moment you spun the VFO on the KX3. I pointed this out to a local KX3/PX3 owner, and
he told me to download the latest firmware which allows you to select “fixed mode” or “fixed track”. I downloaded the 
firmware. YES, it kinda fixes the problem….you can now tune the radio and KEEP the averaging….but the problem is
that now your receive filter goes down the display as you tune. This is better than the previous method, however
you now have your receive filter heavily offset from the centre of the display. You might tune down the band, with your
RX filter at the bottom of the scale, and you are now unable to see much below, but you can see a huge chunk of 
the band above you.

I bought the KX3 and PX3 for portable ops. My main rigs for the past 5 years are Flex rigs. I have the 5000/3000/1500
and will be getting a 6500 soon as my shack rigs. With these rigs and PSDR, your RX filter REMAINS CENTRED and when 
you tune around the band, you DON’T LOSE your averaging. This is how I like it to be, and if Elecraft can achieve this 
in a firmware update, I would be very happy.

73
John, ZS5J





On 31 Jul 2015, at 2:56 AM, Eric Swartz - WA6HHQ, Elecraft <eric at elecraft.com> wrote:

Hi Joe - Do you have signal averaging turned on to reduce the noise floor? If you do, it has to stop averaging when the freq is being changed while tuning, temporarily raising the noise floor slightly. It then re-starts multi-pass averaging once you stop tuning. This is normal for signal averaging. I run with averaging set =2 or 3 passes. When I tune I barely notice a small increase in the noise floor.

If you have a lot of local pulse noise, you might want to turn on the P3s NB function to help.

If Averaging is turned off, I can't think of a normal scenario where the noise floor would go up when tuning the band. It certainly does not here.

Anyone else have any ideas?

73,

Eric
/elecraft.com/