Don't stop that blog on SDR!
Its great and I look forward to reading it ever since I discovered it.
I am 81 years old and been in sdr since the SDR 1000. I don't pretend to be very proficient at either
the electronics or the DSP or the computer part of the systems but it is such a wonderful learning experience that I look forward to any explanations. Yours are especially clean and clear.
To me this is totally cool, and I hope if I make it to 81 I'm still digging my SDR!
He says he like my personal touch even my prejudice against the K-3!! Actually even though I am a little harsh on the K-3, what I actually find distasteful is how quickly the backbone of radio in general is being replaced with SDR on every front and how little most hams have been instructed in this technology. I'm cynical and I think it is conspiratorial between the manufacturers and the magazines especially ARRL. How is it our "national organ" has done such a dismal job of educating us? How is it things like this only get covered in QEX, or by some gun slinger with a blog?
When I read the reviews of SDR in QST the reviewers clearly are novices in the land of SDR. Just the way they couch their criticisms make it clear they really don't quite understand what the hell they are talking about. I'm sure in the analysis of radios like they K-3 they are hip deep in experience but not when it comes to SDR. SDR demonstrates a whole different skill set. (that is what this blog has been devoted to, trying to expose the skill set of the SDR)
If you look at this one pic
It begs the question, if a ham over in Russia can make this pic why is it the ARRL failed to generate this same pic? All they had to do was mover the 2 signals INSIDE the roofing filter. This is the thing that I find disturbing, not whether the K-3 is a good radio or not. The K-3 is clearly a very strong radio BUT.... and the fact that the BUT is treated like the crazy aunt in the attic to me is disturbing. here is another pic:
This is shot of the LP-PAN with and without the K-3's IF connected. Note how the K-3 adds 15dB of phase noise to to the signal, and note how clean the LP-PAN (which when run along with PowerSDR constitutes a complete SDR receiver around the IF frequency) is about 15dB better on its own. Another crazy aunt in the attic? Here is a quote from Larry N8LP's site regarding the quality of his LP-PAN
I wanted to make sure that the K3 was the limiting factor when used with LP-PAN, at least up to the maximum signal level of LP-PAN, which is +2dBm (S9+75dB). Above that level, the combination of the K3 roofing filters and hardware AGC add another 30dB of dynamic range under most conditions, making it the best rig on the market in that regard. Luckily, the user will likely never see a signal that large, and the +2dBm maximum signal handling of LP-PAN will not be taxed unless you are in a multi-multi contest station or in Europe next to a large broadcasting station.
As you can see in the top picture for the standalone LP-PAN, IMD DR is about 90dB, with no extraneous distortion products. Quite amazing for this bandwidth, and comparable to some of the best rigs on the market, including the K3.
Note the user will likely never see a signal that large!! I have a car that will do 155mph. I will likely NEVER see an occasion to go 155mph. I have that car because I wanted that car, not because I NEED that car. The last line tells the story. If you add up a loaded K3 its around 4800 bux. Larry's 200 buck converter box PLUS POWER SDR is comparable. Just let that permeate your old cerebral sauce pan for a second!! Now Larry's radio only receives on the IF frequency so to be sure it is not stand alone, but still the statement is remarkable.
The limiting factor of this system is the K3, not the little "LP-PAN plus PowerSDR" receiver. Note the LP-PAN on its own is nothing with out PowerSDR or another software back end. The new F3K will similarly be this good (actually probably a little better in terms of performance), comparable to the K-3 and the F3K is a full featured 100W radio with built in antenna tuner, FOR 1600 BUX and needs no additional filters or anything else!!!! Hello Hello anybody out there? This is where ham radio is going. It has to go there. There are very few circumstances where you would ever need more radio than this for most hams. Like Larry says, maybe multi multi on a desert island or parked next to a foreign broadcaster in EU. I have corresponded with Flexers over in EU and none of them have complained about the IM response of the RX to me.
So what does this say about prejudice? Here are the facts, and you can draw your own conclusion. If you add up the cost of the K-3 fully loaded with filters, antenna tuner, bandpass filters, I/O board, Second RX, and the LP-PAN plus sound card, it comes to about $4800. I have discussed this with K-3 afficianodos before. People start subtracting things to try and get the price down, like well you don't NEED all the filters, you dont NEED the ant tuner, you dont NEED the high accuracy oscillator, you dont NEED the transverter I/O board. OK I will subtract the ant tuner that leaves $4470. Right now you can buys a F5K for 2520 on sale with second RX for 3220. Why do I include all that other stuff, because that is the apples to apples comparison. ALL THAT OTHER STUFF is already in the F5K. In fact the oscilator in the 5K is 0.5ppm not 1ppm, and the 5K has a more versitile and effective antenna switching setup. So again what does that say about prejudice? Here are the facts you can draw you own conclusion.
This is where ham radio is headed for no other reason than economics. Ham radio went the way of transeivers 40 years ago because of economics. You got a lot more for a lot cheaper from a Kenwood that you could get from owning a seperate TX RX combo. The same thing will drive SDR. You get a heck of a lot more bang for the buck, period. You can buy a heck of a nice beam or the better part of a nice amplifier for $1250. A new AL-80B goes for $1449. So there are the facts. You pays your money and gets your deserts. At some point you have to ask yourself is that extra couple dB dynamic range really worth $1250?
just ask yourself these questions and check the ( ) if they are true:
I don't live next to a SWBC station ( )
I don't plan on running multi multi on a deserted island any time soon ( )
I might like to buy a linear amp or beam, or take the wife on a vacation with the 1250 bux I save ( )