[Elecraft] K3 panadapter choices

[Erik N Basilier]

Thanks, Don for your thoughts.

I am familiar with the relationship between sound card sampling frequency 
and achievable spectrum width, and also with the SoftRock Yahoo group, 
athough it has been a while since I have been there. Sound card choice is 
complicated by the fact that the K3 invites portable operation; if I take a 
sound card dependent approach, I would want it to work with both desktop and 
laptop (as the non-soundcard solutions already do). The desktop currently 
has a Sound Blaster XFi Xtreme Audio, with 24 bit sampling at 96 kHz. This 
may be good enough for me for use at home. I have no spec's for the laptop's 
built-in sound card, but suspect it won't sample above 48 kHz. I know that 
it is susceptible to hash on the audio input when operated with its mains 
power supply operated from a power inverter in the field. A PCMCIA card 
might upgrade the laptop to be on par with the desktop without an extra box, 
but it seems the PCMCIA standard is considered obsolete. I found a PCMCIA 
audio card with good specs that has been recommended on the SoftRock group. 
That card is available used. However, I found a web site that states that it 
won't work with one of the chips in my laptop (and a lot of other laptops). 
The Soundblaster Live is a new one to me. There seems to exist an outboard 
box version of it, which may be attractive for the laptop (except an 
external box is per se unattractive). Whether I add an external or PCMCIA 
card, it seems that I would have to plunk down the money first and then find 
out if it is any better than the laptop's built-in audio w.r.t. the power 
supply hash. Maybe I should just build a filter for the laptop power supply 
first. On the other hand the SDR's that don't need any sound card would 
avoid that whole hassle (assuming they don't have a problem working with 
laptop with some hash on the DC supply).

It is one thing to choose one path to achieve a single goal. It is another 
thing to plan for multiple goals. I would like to be able to have the 
spectral display run simultaneously with digital mode software. "Why do you 
want that", someone objects, "when you already have the waterfall in the 
digital mode software?" I know that, unless operating conditions are very 
benign, I get better digital copy with a narrow filter setting that means no 
other signals than the currently worked station is visible on the waterfall. 
The panoramic display should still be functional under those conditions. I 
know many people love the panoramic aspect of digital mode software because 
it offers so much for so little, but that very fact tends to lead to 
distorted priorities (I am sticking out my neck here!) such as "everyone has 
to run low power and be close to everyone's noise level, so that noone's agc 
affects the noone's wanted signal". No such need once people have real 
panoramic reception with the corresponding frequency resolution (and click 
to tune), and then IF filters can be kept narrow all the time. (This is also 
a virtue of the K3's built-in PSK and RTTY encode/decode, although I don't 
find it useful until PC software supports it so that one can send from the 
keyboard and see more than a few received characters.)

OK I just went off on a tangent. Now back to the subject. An external 
soundcard in combination with the laptop's built-in audio would let me 
operate both digital and panadapter at the same time, albeit at least one of 
the two would have substandard audio with power hash problems. Suppose the 
external soundcard fixes the power hash problem. (I think this to be likely; 
after all the makers of these high performance audio solutions probably 
wouldn't want user complaints due to DC supply hash.) Then I'd want two 
external sound cards if one is needed for panoramic reception. It might be 
more prudent to spread the technology evolution risks by only getting one of 
these, plus an SDR that doesn't need a sound card. Ultimately though, I 
believe that today's hardware seldom breaks, but is very often made obsolete 
by changes in software. (That is one reason I am happy that my radio is able 
to function without a computer!). In the absence of software-free panoramic 
adapters for the K3, we obviously have to accept using computer software. 
Digital modes also require the computer with only a few minor exceptions. 
For contest use we may require the computer for logging. Then we have 
several pieces of software sharing one display (at least in portable 
operation, multiple monitors may be impractical; I do have two monitors on 
my home computer next to the radios). If each program displays a large and 
complex window, it is going to be hard to place the windows so that they 
don't interfere with one another. Thus I am back to the following order of 
priorities: 1. What are the characteristics of the candidate software 
packages, and 2. What hardware is supported by the best software 
combination.

73,
Erik K7TV

----- Original Message ----- 
From: "Don Wilhelm" <w3fpr at embarqmail.com>
To: "K7TV" <ebasilier at cox.net>
Cc: <elecraft at mailman.qth.net>
Sent: Friday, November 14, 2008 5:55 PM
Subject: Re: [Elecraft] K3 panadapter choices


> Eric,
>
> The expensive soundcard is not required to use the K3 IF output 
> effectively.  Yes, the better soundcards will allow you to display 192 kHz 
> of the band centered on the K3 frequency, but how often is that needed? 
> If you can answer "rarely or never", then you can use one of the lesser 
> capability soundcards to display 80 kHz or so.  The Soundblaster Live card 
> is still available at a reasonable price and has a 24 bit ADC with a 
> reasonable noise floor, so the dynamic range should be adequate.
>
> The real answer depends on your wants and needs - if you want to display 
> the maximum slice of the spectrum, then go with the best available, but if 
> your budget must be minded, then there are other alternatives.
>
> Actually, any soundcard will work - the question is just how much dynamic 
> range will you have and how wide a swath of the spectrum will you be able 
> to display.  You may want to look at the Softrock reflector (a Yahoo 
> group) for additional information - but there are a lot of advocates there 
> who strive for the best of the best.
>
> 73,
> Don W3FPR