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Asunto: Psk31 Digest V1 #243
Fecha: sßbado 27 de noviembre de 1999 4:36
Psk31 Digest Saturday, November 27 1999 Volume 01 : Number 243
In this issue:
Re: [psk31] DC isolation between sound card and rig
[psk31] Re: [Logger] Re: DC isolation between sound card and rig
Re: [psk31] PSK31SBW and IBM THINKPAD 701C
Re: [psk31] DC isolation between sound card and rig++
Re: [psk31] PSK31SBW and IBM THINKPAD 701C
Re: [psk31] PSK31SBW and IBM THINKPAD 701C
Re: [psk31] PSK31SBW and IBM THINKPAD 701C
[psk31] Ground loops
Re: [psk31] Ground loops
[psk31] Emailing QSL's
[psk31] interface
See the end of the digest for information about psk31-digest
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Date: Thu, 25 Nov 1999 21:09:13 -0700
From: "Gary McDuffie, Sr." <mcduffie@scottsbluff.net>
Subject: Re: [psk31] DC isolation between sound card and rig
On Thu, 25 Nov 1999 20:43:20 -0500, Charles Greene wrote:
> If you want to order from Mouser or www.Radioshack.com,
> let me know, and I'll give you some part numbers. Any 1:1 or a 1:3
> should work, even though it's not so small.
The two RS xfmrs I got are about the size of your thumbnail and maybe a
half inch thick.
gm
- --
------------------------------
Date: Fri, 26 Nov 1999 00:39:26 -0600
From: Martin <rutherford.ulea@mcleodusa.net>
Subject: [psk31] Re: [Logger] Re: DC isolation between sound card and rig
HUH? Jim, a lot of folks ARE using 1:1 audio transformers just for DC
isolation. I found that the line output on my old Sound Blaster 16 card
was a close enough match to the "modulation input" on the ACC jack of my
Icom 706MKII. At first, I didn't use any transformers, and I had a hum
in my transmit audio. This was most apparent on 2m FM. I used a couple
of audio transformers that I had on hand. They are either 10:1, or
20:1, I cannot remember which. On the laptop that I use now, I use the
mic input, and the headphone output. I still use the same cable to the
Acc jack. I don't want to use vox, as I don't like the idea of Windows
sounds accidentally going out on the air. I suppose that you could use
a different ratio to do impedance matching depending on the situation.
Cul8r
Martin Campbell rutherford.ulea@mcleodusa.net KB0HAE
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------------------------------
Date: Fri, 26 Nov 1999 00:53:49 -0600
From: Martin <rutherford.ulea@mcleodusa.net>
Subject: Re: [psk31] PSK31SBW and IBM THINKPAD 701C
Hi Charles. The problem you had is known to Recording professionals as
a "ground loop". The cause of the hum is that the chassis "grounds" of
the radio and computer are not quite the same. Even connecting the 2
together with a large ground strap sometimes will not cure the problem.
It is better to isolate the 2 devices, thus the audio transformers.
- --
Cul8r
Martin Campbell rutherford.ulea@mcleodusa.net KB0HAE
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------------------------------
Date: Fri, 26 Nov 1999 07:56:39 -0000
From: "emi2" <emi2@worldnet.fr>
Subject: Re: [psk31] DC isolation between sound card and rig++
Peter Jackson wrote :
>On one of the websites they recomend Radio
> Shack ones but here in our town there equivalent Tandy's are as >much use
as a chocolate frog! Maplins don't have anything like a 1:1 > ratio
transformer.
You may find a large choice of 1:1 line transformers at Radiospares
1. Newport Components NM600 RS Code 178-9754
2. Bourns SM-LP 5001 (SMT Type for flat mounting) RS 218-9880
3. Bourns LM-NP-1001 RS 174-0620
Pls note that the Code nrs are taken out of my
French catalogue. In the UK they muight bear a different number.
Of course the cheapest solution is to take the transformer out of an old
telephone receiver. You probably have one laying around somewhere.
>using 6N137 opto isolators, I wonder if they would work with audio?
No. You have an LED at the input which means that half of the sinewave of
your audio signal would be clipped off.
The transformer is still the best solution.
Ezio M. Insinna - F5MWA France
------------------------------
Date: Fri, 26 Nov 1999 08:08:09 -0500
From: Charles Greene <cgreene@loa.com>
Subject: Re: [psk31] PSK31SBW and IBM THINKPAD 701C
At 12:53 AM 11/26/99 -0600, Martin wrote:
>Hi Charles. The problem you had is known to Recording professionals as
>a "ground loop". The cause of the hum is that the chassis "grounds" of
>the radio and computer are not quite the same. Even connecting the 2
>together with a large ground strap sometimes will not cure the problem.
>It is better to isolate the 2 devices, thus the audio transformers.
Tnx, Martin,
I suspected as much, and the isolation transformers do work.
It is impossible to keep from connecting the grounds at one
place or another, as there are the PTT ground connection, the AF
input and the AF output ground connections.
____________
Try PSK31. Check: http://aintel.bi.ehu.es/psk31.html
and May 99 QST. K2 S/N 462.
Chas, W1CG
Rhode Island TCPIP Address Coordinator
w1cg@arrl.net
_____________
------------------------------
Date: Fri, 26 Nov 1999 11:26:25 -0600
From: Martin <rutherford.ulea@mcleodusa.net>
Subject: Re: [psk31] PSK31SBW and IBM THINKPAD 701C
Hi Charles. You can avoid a common ground connection in the keying
circuit if you use a relay...Some folks have successfully done this. I
use a home brewed switch box, and key the rig manually. Why? Well my
com port is in use by other devices, and I don't like the idea of using
vox as windows sounds can accidentally key the rig, and go out on the
air. Also, someone has used the IR port on a laptop to use the rig
control functions, as well as keying the rig. There is a circuit you
have to build for this, but it is not too complicated.
- --
Cul8r
Martin Campbell rutherford.ulea@mcleodusa.net KB0HAE
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------------------------------
Date: Fri, 26 Nov 1999 11:41:14 -0600
From: Martin <rutherford.ulea@mcleodusa.net>
Subject: Re: [psk31] PSK31SBW and IBM THINKPAD 701C
Hi Michel. How are you adjusting the output? Are you using the
computer's volume control, or the windows volume control? If you double
click on the speaker icon in your system tray (the little box that shows
the time in the lower right corner of the screen) you will get a set of
controls that can be adjusted. If the Wave slider is at or near the
bottom, try setting it up about half way. Also make sure that the mute
box for the wave control does not have a check in it.
- - -
Cul8r
Martin Campbell rutherford.ulea@mcleodusa.net KB0HAE
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------------------------------
Date: Fri, 26 Nov 1999 16:02:04 -0600
From: Elaine and Ronald Waxman <erwax@interaccess.com>
Subject: [psk31] Ground loops
Ground loops are a result of having the grounds of two or
more pieces of equipment connected together at more than
one point. When there are two ground connections the
grounds form a loop which is the equivalent of a single
turn transformer. Flux threading through this "loop"
induces a current in the ground wires which produces the
noise. Generally, the ground loop picks up flux from the
power system and the most noticeable effect is at the
power line frequency and/or a multiple of this frequency.
Using transformer to uncouple the grounds between the
signal ports greatly suppress this noise. Appreciable
unwanted signal can also occur at RF frequencies.
Your ground system should be "star" connected, each
chassis connected to a common ground point through a
single piece of wire. This point is usually through the AC
power connection.
73
de W9KNB
Ron
------------------------------
Date: Fri, 26 Nov 1999 17:25:12 -0700
From: "Gary McDuffie, Sr." <mcduffie@scottsbluff.net>
Subject: Re: [psk31] Ground loops
On Fri, 26 Nov 1999 16:02:04 -0600, Elaine and Ronald Waxman wrote:
> When there are two ground connections the
> grounds form a loop which is the equivalent of a single
> turn transformer. Flux threading through this "loop"
> induces a current in the ground wires which produces the
> noise.
I'll have to disagree with you on this. I won't say it isn't possible,
but that isn't the commonly known reason for ground loop problems. The
hum created by ground loops is caused by a difference in potential
between the two ends of the ground wire (usually the shield in a case
like an audio cable). The difference in potential can be caused by
leakage from internal circuits (bypass caps, etc) and/or different earth
grounds being used.
One way to get around this is to only connect the shield on one end.
You can't always do that in an unbalanced system, so the way around it
is to use a transformer. A transformer allows a "full circuit" on both
ends without having the two grounds connected together.
> Using transformer to uncouple the grounds between the
> signal ports greatly suppress this noise. Appreciable
> unwanted signal can also occur at RF frequencies.
> Your ground system should be "star" connected, each
> chassis connected to a common ground point through a
> single piece of wire.
> This point is usually through the AC
> power connection.
No. Your ground should be a real earth ground. Your words about single
point are good, but it shouldn't be the AC power connection.
Gary
- --
------------------------------
Date: Fri, 26 Nov 1999 18:46:47 -0600
From: "Pete Francescon" <PFrancescon@worldnet.att.net>
Subject: [psk31] Emailing QSL's
Hi,
Yesterday I met my new friend Pavel - OK1MPD on 10 meter PSK31. He was kind
enough to send his QSL to me by email. His is the first I have received by
email, but it makes perfect sense; "Digital Hams" sending QSL's via the
internet!
I would like to return Pavel's QSL the same way. Can any tell me if you can
download a QSL card program off the internet that will make a QSL card to
either send by email or print on the printer? Thank you.
And don't forget PSK on the low bands - 30, 40, 80, and 160 meters during
these long nights in the north!
Best 73's and Happy Holidays,
Pete WB4YDY
WB4YDY@arrl.net
------------------------------
Date: Fri, 26 Nov 1999 20:57:09 -0500
From: Francis Flynn <fflynn@together.net>
Subject: [psk31] interface
This is what I use for an interface:
http://homepages.together.net/~fflynn/psk31.html
As for DC islolation, the sound card is designed to run a speaker
directly,
so there should be no DC voltage at it's output. If there is, I would
suggest
a new sound card :)
73 de
Fran km1z
------------------------------
End of Psk31 Digest V1 #243
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