No insult intended - It was a legit question based on what I had been
exposed to so far.
As a side note, I am looking for a service monitor. I also need some
sort of two-tone source & if the sound card is good enough for a
beginner, thats what I am going to use.
73 de Martin
Jeff Blaine AC0C wrote:
> There are 2 ways to look at this. If you look at it from a "is this
> the official lab-standard proper way" standpoint, it comes up a
> loser. I'm not suggesting it is.
> And If you look at it from a "is it a step in the right direction" and
> "can it be done by average joe ham for a few bucks" and get somewhat
> interesting results - the answer is yes.
> If guys want to keep peppering me with the details of proper IMD
> measurement, we can do that - but it's a sidebar to my key point. I
> get it. This is not a proper Grandberg setup. So for all those guys
> who are reading this or are sending me little off line mail about "IMD
> measurements 101," give me a break. You are missing the point.
> Better the guy use a ruler to measure things than none at all. If one
> headlight burns out in my car, I don't turn them both off because "if
> it's not perfect, then it's not worth doing." There is no point to
> debate that a ruler is not as good as a caliper and my mailbox is
> filled with guys making that comment. Even if the ruler is a gross
> approximation, the simple effort of looking at it raises awareness in
> an area of the hobby that as far as I can tell, gets damn near zero
> attention. Well unless someone mentions certain down-under amp
> suppliers, anyway.
> Is better to have some newbie cranking away on his amp or his rig
> without any thought at all to the stuff going out his pipe - than it
> is to have him use less than perfect test setups? Not here, at least
> here in the fly over country of KS.
> But then again, I've got a lot of inbox nonsense suggesting I don't
> know what I'm talking about. Maybe that is the case...
> From: "Martin Flynn" <firstname.lastname@example.org>
> Sent: Sunday, May 23, 2010 3:06 PM
> To: "Jeff Blaine AC0C" <email@example.com>
> Cc: <firstname.lastname@example.org>
> Subject: Re: [Amps] How to read the 3-500Z spec sheet?
>> Is using a sound card good enough? One of my elmers <sk> had a
>> dedicated two channel audio generator for testing.
>> Motorola published a white paper by Helge Granberg on IMD
>> measurements: http://w4neq.com/pdf/ssb_im.pdf
>> Jeff Blaine AC0C wrote:
>>> Of course, a real IMD test requires a 2 -tone source and you can
>>> download those applications on the web free of charge. A good quick
>>> and dirty solution is to switch your digi mode application over to
>>> PSK. In fact, if it were up to me, it would be a legal requirement
>>> for all PSK ops to have station monitors of this type when running
>>> PSK. Lot of misinformation and nonsense in that community among the
>>> rookie ops.
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