[Elecraft] K3: pseudo KRX3 "free" via LP-Pan+Power SDR

[Larry Phipps]

I think what Eric is saying is that if you watch PowerSDR and listen to the K3 / KRX3, it will be a super combination. You will be able to see the passbands of both VFO A and VFO B frequencies and tune either one from the K3 or pan display, as long as the sub-receiver is tuned to within +/- 90kHz of the main receiver. 

There are some good reasons why listening to the K3 / KRX3 is desirable, especially for CW (and why the K3 blows the doors off the Flex Radios for CW). The main ones are the latency of the DSP processing in PowerSDR, and the serial interface of the K3. Under extreme contest situations, the added protection of the HAGC will be needed, and on the higher bands (10,6m), the K3 has more usable sensitivity because the transfer loss at the K3 IF output port adds to the NF of the panadapter. And the KRX3 allows cross band listening, more filter slots, etc.

But many non-contesters will find that using the sub receiver in PowerSDR will be a viable option, especially in SSB. PowerSDR is no slouch when it comes to IMD and BDR, and has excellent DSP filtering. Up to about S9 + 65dB (K3 preamp off) the BDR is comparable to the K3 at spacings down to less than 1 kHz. Of course, in both cases transmitter IMD will be a bigger problem than BDR anyway.

Either way, the operational flexibility of the panadapter in split mode is a killer feature. Being able to see holes in a pileup and click on them, or quickly jump to the frequency of the last guy who was answered will be invaluable. When full VFO B support is released in a couple weeks, I'll have some beta testers with KRX3s in hand, and I can get some comparative feedback.

Larry N8LP



Date: Wed, 30 Jul 2008 22:19:10 -0700
From: Brett Howard <brett at livecomputers.com>
Subject: RE: [Elecraft] K3: pseudo KRX3 "free" via LP-Pan+Power SDR
To: n1al at cds1.net
Cc: 'Elecraft Reflector' <elecraft at mailman.qth.net>, "'Eric Swartz -
	WA6HHQ,	Elecraft'" <eric at elecraft.com>
Message-ID: <1217481550.8426.13.camel at lappy>
Content-Type: text/plain

The part that confuses me is the mention that "[PowerSDR] fully
integrates with the KRX3's main and sub RX frequenciy on its panoramic
display".  

Thats what it does now.  But in order for the KRX3 to actually be adding
anything you'd have to be listening to its output with the full K3
filter chain.  Cause you're not going to correct the dynamic range
problems unless you're doing that.  

Then I don't see how it could allow you to be more than 192KHz/2 away
from your main center freq as you'd have to have two sound cards and two
IF outputs in order to pull that off.  I guess I don't really see a
SubRX adding much to the PowerSDR setup unless you use one RX as a
spotter and the other as simply a K3.  I think that 2 K3's would be a
better setup for that.

I see the subRX in the K3 as a way to make the K3 a better unit as a
standalone unit.  Which I think is one thing that the K3 does really
well especially since you can make RTTY/PSK contacts with just a K3
sitting on your desk and nothing else.  You can also run it as a contest
station for both CW and SSB (once the DVR is out).  I find it quite fun
how much one can get done without the need to interface it to a
computer.  Now don't get me wrong I'm a total computer guy and I find it
even cooler that while it does all this stuff to not require you to have
a computer it also makes is SOOO easy to interface to one when you
decide you want to.  

So I guess all in all color me happy yet still confused as to the KRX3
adding much to a powerSDR setup.