[Lowfer] 185.3 party tonight!

Thu, 24 Jan 2002 06:30:12 -0500

Bill

Looks like you guys went a bit wild last night!

To answer your question...What I am saying is that the 2 dB should be considered
a worst case uncertainty. Most measurements should be much better - probably
within a dB. The more diligent you are with the cursor to find a maximum level
on the two signals to be compared the better your measurement. If you gave me
two off the air signals on Argo I wouldn't want to stake my life that my
measurement was any better than 2 dB, although it is quite likely that it would
be.

Again, more study is needed.

Jay Rusgrove, W1VD

"Ashlock,William" wrote:

> WOW, I leave you guys for an hour and now the mail screen is all filled up.
>
> Hi Jay, glad you joined in.
>
> Nice analysis below. So how did you happen to read the WA signal ratio so
> close to the correct value, earlier, if you are seeing a step error of ~2db?
>
> Bill
>
> -----Original Message-----
> From: Jay Rusgrove [mailto:[email protected]]
> Sent: Wednesday, January 23, 2002 9:34 PM
> To: [email protected]
> Subject: Re: [Lowfer] 185.3 party tonight!
>
> Bill and all
>
> Thanks for the invite. I sure hope this isn't a black tie affair! I prefer
> come
> as you are...
>
> Well, until we have Lowfer slow-scan TV you're OK.
>
> Per my earlier e mail I brought some test equipment home to measure the Argo
> "signal strength meter". I used a trusty old L/C HP 652A "audio" generator
> into
> the RF-590 receiver through HP 355C and HP 355D attenuators. Both the signal
> generator and the receiver had extra pads to stabilze any impedance
> variations.
> The output of the generator was 185.300 and after a good warmup the
> frequency
> was pretty stable. The output level is very stable. I centered the signal at
> 800
> Hz and made output steps of 10 dB. Multiple 10 dB steps up and down were
> made
> running Argo in the 10 seconds per dot mode. My sound card (part of the
> limitation in performance I'm sure) is a Sound Blaster Live 5.1.
>
> Results were pretty good - if you are careful with your measuring technique.
> I
> have no idea how the program determines what it displays as a signal level,
> but
> dragging the cursor over a seemingly constant white line yields varying
> signal
> levels of  several dB. By dragging the cursor over an entire section of a
> line
> or character you can easily find a maximum level. When you compare one
> segment
> with others that are stepped up or down by 10 dB using the maximum level
> method
> you can probably be within  2 dB (or better) of the actual step without a
> great
> deal of difficulty. As the signal gets weaker and approaches the background
> noise this figure gets worse. Errors of 3 dB or more are possible. I think
> the
> white specs of background noise add to the weak desired signal to give an
> unexpectedly high reading  - which is to be expected.  All in all, as a
> relative
> indicator,  I would say it is quite useful. Measurements within at least a
> few
> dB should be possible.
>
> More testing is in order.
>
> Jay Rusgrove, W1VD
>
> "Ashlock,William" wrote:
>
> > All,
> >
> > This message is to invite you to all to another rip roaring 185.3 party!
> > John A. will be home (not doing the bar scene like last night), watching
> the
> > e-mail for any glimmer of a TAG capture from a party goer. Bill will be
> here
> > at work finishing up the first build of a new PCB, due tomorrow morning,
> > distracted only by reports of distant captures of his -20.0000db down
> > signal. Dex will be working like crazy thinking up a new prank (since
> Bills
> > retaliation today for his prank last night) .  Mitch will be reconnecting
> to
> > that land line to Boston that allows him to fake the all-day sizzling
> > captures of WA.  Jay will be madly clicking on our ARGO traces to see if
> our
> > ERPs are exceeding the UK 'guidelines'. ....And I know there are many more
> > guys that were onboard last night that should be getting recognition, but
> > I've got to go home for a tasty dinner!
> >
> > Please join in tonight!!
> >
> > Bill
> >
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