On Sun, 3 Nov 2002 16:10:17 -0600
"Max Moon" <maxmoon@umn.edu> wrote:
> Gents,
Grrr... Does that mean that my opinion isn't worth anything to you?
After all, you only asked for "gents" and I don't qualify. Before I get
on to the technical issues I want to say that this is a pet peeve of
mine, and of a number of other female hams I know. Please, this is a
mixed gender group. Don't exclude us, OK?
Oh, and Max, I'm only picking on you because you are the latest example.
It's not just you.
> I've been reading this list for a couple of weeks. Yesterday a Paragon
> was sold here. I didn't know anything about them so I went to the ARRL
> members-only QST Equipment Tests to look for a review. Also, since my
> only basis for comparison is the Corsair I got a few weeks ago (the
> reason I joined the list), it seemed logical to compare their numbers
> so I might have some perspective. I discovered that QST didn't review
> the Corsair I but they had figures for the Corsair II.
Not so. I just went to the ARRL web site (members only section) and I
have the numbers for the Corsair I. I've included them with your other
numbers inline below. It might surprise you to know that the Corsair I
had significantly better receiver performance as tested in the lab than
the Corsair II.
> Then I learned that the Paragon was
> essentially the replacement of the Corsair II so it seemed to be a
> very good comparison.
Not really. The Paragon was general coverage. The Omni V would be the
more direct replacement, although there was a gap between the two
models.
>
> I decided to compare some rcvr performance figures first. I looked at
> minimum discernable signal (MDS, in dBm), blocking dynamic range (BDR,
> in dB), and second-tone third-order intermodulation distortion (IMD,
> in dB). In each case, I checked the figures for 3.5 MHz and 14 MHz.
> Here is what I found.
>
> Corsair II, Aug'87, MDS 127-124, BDR 117-???, IMD 84-80
> Paragon, May'88, MDS 139.5-137, BDR 136.5-136, IMD 101.5-101
Corsair I MDS 131/na, BDR 130/na IMD 93
>
> Although I'm a novice at understanding such figures, it certainly
> looks like the Paragon was an improvement on the Corsair II, besides
> being its replacement.
In theory, yes. In practice, maybe not. There is a lot more to what
makes a receiver listenable and what allows you to pick out weak signals
than can appear in three numbers. Lab tests don't lie, but they don't
tell the whole story.
>
> That was my frame of mind when I looked at other TenTec rig
> performance numbers. Continuing to look at the same figures (MDS, BDR,
> and IMD at 3.5MHz and 14MHz) this is what I found:
>
> Paragon, May'88, MDS 139.5-137, BDR 136.5-136, IMD 101.5-101
> Omni V, Nov'90, MDS 135.0-136, BDR 135.0-135, IMD 95-97
> Omni VI, Jan'93, MDS 133.5-136, BDR 123.5-128, IMD 95-100
> Omni VI+,Nov'97, MDS 135.0-133, BDR 123.0-123, IMD 98-97
> Jupiter, Jun'01, MDS 127.0-135, BDR 113.0-123, IMD 87-85
Let me show you a set of numbers that will startle you. These are for a
modified Argosy, released in 1980
Argosy, MDS na/138.5, BDR na/133, IMD na/98.5
Is the Argosy a better rig than an Omni VI+? I think not, although it
is a very good rig indeed. The reference is at:
http://www.qsl.net/tentec/mods/525mods.htm
>
> Has it been all downhill?
I don't think so. MDS is a measure of receiver sensitivity. The Omni
VI+ may be very slightly less sensitive than the other rigs listed
(except the Jupiter). However, the filtering available, both analog and
digital, and the ability to reduce noise and therefore improve signal to
noise ratio provided by the DSP makes it far more likely that you could
receive a very weak signal on the Omni VI+.
The only fair way to compare rigs is to put the side by side and A/B
switch between a common antenna. The Delta II, which has a very poor
reputation, does incredibly well in such a test on 40m because the
combination of the Jones filter and pass band tuning allow you to
isolate a weak signal next to a strong signal very well and clearly hear
the weak signal. A very good IF DSP rig (i.e.: an Icom 756ProII) can do
better, but most pre-DSP rigs cannot. This is the reason I picked up a
recently offered and very inexpensive Delta II. My Scout moves out to
the car :)
>
> My question to you, should you care to accept it, is: how does your
> hands-on experience of TenTec (and other) rigs compare to such
> numbers, and how much do numbers matter, anyway?
They matter. A glaringly bad number probably indicates a serious defect
in the receiver.
>
> Somebody else (just an e-mail or two previous) asked for a comparison
> J(ignoring cost) between the Jupiter and the Argonaut V. In a way, my
> question is just another version of his. What makes a great rig--in a
> ham's shack, not in the laboratory?
IMHO, it's the ability to hear signals and work them.
72/73,
Caity
KU4QD
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