Hello Bill,
This might be down the drain
for you, but I only listen to your podcast very few months:
The background hiss you
mentioned in Soldersmoke 148 definitely was a crosstalk from the switching
voltage converters for the CPU in your laptop.
The CPUs these days are
operated with voltages in the .7 V to 2 V range,with currents from
several Amperes up. A high-performance CPU may dissipate150 W which can easily
mean supply currents of 100 A an more. The CPU operating voltage, especially in
a laptop, might change several 100 times a second. I think you can imagine the
rest.
Why is that voltage adaption
so important? This is within your domain: The biggest heat source in digital
electronics these days is charging and discharging capacitors. Unless you use a
resonant circuit (which you cannot do on a chip) you dissipate P = 1/2 C U^2
with every discharge. Yes: Power depends on the square of the supply voltage.
And at a clock frequency in the 2 GHz range you charge and discharge all those
capacitors quite often. Each of these has a capacity in the fF (.001 pF) range,
but you have billions of these...
Over the time you had quite
some complaints about your whistling s. In former times this was definitely
made worse by some technical problems. But this is a problem long gone. An
Soldersmoke 149 I believe the remaining problem simply was the tooth gap you
described a few years back.
BTW: You could easily reduce
the file sizes of your podcasts by at least 50% with a few simple measures:
- You should record the
podcast as you do now, with a 44 or 48 kHz sampling rate, that's fine. I would
even record in wave format.
- Afterwards downsample your
recording to a sampling rate of 12 or 16 kHz. This provides ample audio
bandwidth for this purpose. See e.g.http://forum.audacityteam.org/viewtopic.php?f=28&t=19705
- Then create the MP3 file
with a signal rate of 48 or 64 kbit/s.
BTW: Last weekend at a ham
flea market I got a variable transformer. Now I can try to revitalize my Drake
TR4C that has not seen any electricity for some 30 years. I bought it when I
got my shortwave license in 1975. At that time I lived with my parents. Then I
could operate it during my military service. But after that I got an
electronics engineer and lost all possibilities to erect any kind of SW
antenna. Only three years ago I got my own house near Munich. But I'm hardly at
home and I nearly exclusively operate from my car. I will not try this with any
kind of boatanchor :-)
vy 73
Alexander
DL4NO
------------------------------------
Von: solder smoke
[mailto:soldersmoke@yahoo.com]
Gesendet: Dienstag, 19. März 2013
09:49
An: DL4NOAlexander
Betreff: Re: Soldersmoke 148:
Background Hiss
Thank you Alexander. That is very
useful information. I have switched to a new computer and I think the hiss
problem is gone. The gap in my teeth remains however!
I am thinking about getting a better microphone. Any advice on this?
I am glad to hear that you are back into ham radio. My Elmer (the guy who
helped me get started as a novice) was an immigrant from Germany (Hilmar,
WN2NEC). He was an excellent technician. I still use some of the things he
made for me.
73 Bill
------------------------------------------------
Hello Bill,
about a microphone: Think about a headset, possibly a wireless one. I
would search forums about dictation software for advice.
A headset fixes the position of the microphone relative to your mouth. At
the same time the microphone is near your mouth so any ambient noise is
suppressed. A wireless [Bluetooth] headset would allow you to move around
freely. Unless you come near a larger hard or soft surface or leave the room the
sound should not change much. You could arrange the materials for your next
podcast around the room and move from "chapter" to "chapter". And as the
digitizing happens in the headset all weak analog signals are safe away from
any voltage converters and digital electronics.
I had never left ham radio, I just
reduced and modified my activities. 2m or 70cm FM were always possible. Here in
Germany we have more than 1,000 repeaters. Many of these repeaters have Echolink
capabilities. For the last 15 years I have more or less exclusively worked from
my car while driving. In my car I have a FT-857D. For shortwave I use monoband
antennas on a PL mount at on the roof of my car. For pictures see http://www.dl4no.de/thema/amateur1.htm. The schematic in http://www.dl4no.de/thema/mobil-st.htm shows how I ensure that
my TRX gets its 22 A peak from the 12V outlet in the trunk of my car: I buffer
it with a 1 F capacitor - really 1,000,000 µF! The mean supply current during
SSB transmit is less than 5 A.
A quite important role in my ham life play the local chapters of our
German ham radio society DARC. There are more than 1,000 of them, each with its
own DOK. So wherever my customers are, at least one local ham meeting a month is
not far away. I participate in their activities, give a lecture from time to
time. This is a big help as I mostly work at my customers and these are
scattered all over southern Germany.
Just a short story with some local connection for you: Peter, DL5NC,
spent quite a few years in the Washington, DC area. He has a US call, but please
don't ask. He was born some 50 km from my home town. Formally this area,
Franconia, has been part of Bavaria since 1806. Nevertheless we believe that the
Bavarians have no clue how to brew beer.
One Friday morning (your time) he was on his way into Washington, DC.
Through Echolink he connected to a Munich repeater while I was in the afternoon
rush hour on my way to a beer garden. I told him that this was one of the few
places in Munich where you could get a decent beer. And otherwise I had my own
beer at home imported from Franconia. He threatened to never again talk to me
because of mental cruelty. In the meantime he returned to Germany and got a
neighbor. We drank a few Franconican beers together in the meantime
:-)
vy 73
Alexander
DL4NO
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