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PA2AGA > HDDIG 26.07.00 02:42l 198 Lines 7340 Bytes #-9303 (0) @ EU
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Sent: 000725/1805 @:PI8HGL.#ZH1.NLD.EU #:64456 $:HD_2000_200F
From: PA2AGA@PI8HGL.#ZH1.NLD.EU
To : HDDIG@EU
Date: Tue, 25 Jul 00 17:08:53 MET
Message-Id: <hd_2000_200F>
From: pa2aga@pe1mvx.ampr.org
To: hd_broadcast@pa2aga.ampr.org
X-BBS-Msg-Type: B
> tests on the Kachina in PSK31 mode, with a separate station in the shack,
> shows that the third-order IMD component is 35 to 38 db down. That is on
> the air, not into a dummy.
>
> 72/73, George W5YR - the Yellow Rose of Texas
> Fairview, TX 30 mi NE Dallas in Collin county QRP-L 1373
> Amateur Radio W5YR, in the 54th year and it just keeps getting better!
> R/C since 1964 - AMA 98452 RVing since 1972 Kachina #91900556
> (12/99)
>
>
> Rob wrote:
> >
> > Yes, RIGBLASTER uses one opto-isolator on the RS232 line to key the
rig's
> > PTT line. Not a big deal at all.
> >
> > Instead of using a transistor, you use a opto-isolator to key the PTT
line.
> > The circuit is simply a 4N33 opto-isolator, one or two diodes, and one
> > resistor. It provides better isolation and costs only a dollar or so
more
> > than the transistor keying circuit. See www.qsl.net/wm2u for a simple
> > circuit.
> >
> > BUT RigblASTER does NOT use any opto-isolators on the audio lines
between
> > the sound card and rig. I think you will find that RigBlaster simply
uses
> > audio isolation transformers. Audio isolation transformers will work
fine
> > but do not provide the same level of isolation and protection as
> > opto-isolators. For the price of a RigBlaster, you would have thought
that
> > opto-isolators would have been used throughout. It would not have cost
much
> > more.
> >
> > 73's
> > Rob
------------------------------
Date: Mon, 24 Jul 2000 22:05:25 -0400
From: "Rob" <Pse@NoEmail.Com>
Subject: RigBlaster
Well, I do not think that most transmit problems are caused by RFI. Just
listen on the ham bands. Hum due to ground loop problems is very common on
the ham bands. But you typically cannot hear the hum unless the signal is
very strong.
I once had a ground loop problem with a MIC. I only found out about it when
a local station noticed the problem. When I switched the mic, the hum was
gone. When I listened VERY carefully to the transmit audio monitor, I could
hear a VERY LOW hum when using this problem mic. You must listen carefully.
I found a problem with the mic wiring. I fixed the wiring and the hum
disappeared.
Some Hams do not even realise that they have a ground loop problem. They
never even listen to the transmit audio (or even the receive audio) when
using the digital modes. If they never listen CAREFULLY, they will never
know unless someone tells them -- typically another local station.
For many digital modes, you can still be copied (but usually not as well) by
another station if you have a ground loop problem. The DSP based filters
used by most sound card programs typically filter out the hum.
The same thing typically happens when you use a mic with ground loop
problems. Most Hams can still copy your audio but not as well. Sometimes
only local stations can hear the hum in your mic's audio. e.g. I operated
most of a contest with this problem mic and made lots of contacts. No one
ever complained about the hum until a LOCAL station heard my signal. DX
stations could not hear the hum even when I asked for a audio quality
report!
I have not heard many stations complain about RFI problems when using a
computer's sound card as the modem. This can be partly explained by the
presence of RFI bypass capacitors INSIDE the VAST majority of rigs. In most
cases, you really do not need RFI bypass capacitors and other RFI prevention
measures inside a sound card interface device UNLESS you are using one of
the FEW rigs that do not have RFI bypass capacitors inside.
73's
Rob
"Bob Lewis" <rlewis@staffnet.com> wrote in message
news:xL5f5.172$1N5.55@newsfeed.slurp.net...
> > Some folks have had to resort to two-prong a-c adapters to
> > break up this common connection when operating PSK31 and
> > other digital modes involving the computer.
>
> This is a very risky thing to do. If something shorts in the power
> supply on the computer you may have 120 volt difference between the
> rig chassis and the computer chassis. I'd sure look for a safer
> solution to a ground loop problem.
>
> I'm not sure where all this ground loop problem comes from anyway.
> Perhaps some of what is thought to be a ground loop is actually RFI
> caused by having RF on the radio chassis. I've interfaced a lot of
> stuff (sound cards, packet boards, TNCs, etc) to various rigs over the
> years without any ground isolation and never had a ground loop
> problem.
>
>
>
------------------------------
Date: Tue, 25 Jul 2000 02:43:33 GMT
From: "George , W5YR" <w5yr@att.net>
Subject: RigBlaster
That "some folks" certainly wasn't me, Bob! That is one of the last
things I would ever do.
I think this whole "ground loop" thing has been blown way out of
proportion.
72/73, George W5YR - the Yellow Rose of Texas
Fairview, TX 30 mi NE Dallas in Collin county QRP-L 1373
Amateur Radio W5YR, in the 54th year and it just keeps getting better!
R/C since 1964 - AMA 98452 RVing since 1972 Kachina #91900556
(12/99)
Bob Lewis wrote:
>
> > Some folks have had to resort to two-prong a-c adapters to
> > break up this common connection when operating PSK31 and
> > other digital modes involving the computer.
>
> This is a very risky thing to do. If something shorts in the power
> supply on the computer you may have 120 volt difference between the
> rig chassis and the computer chassis. I'd sure look for a safer
> solution to a ground loop problem.
>
> I'm not sure where all this ground loop problem comes from anyway.
> Perhaps some of what is thought to be a ground loop is actually RFI
> caused by having RF on the radio chassis. I've interfaced a lot of
> stuff (sound cards, packet boards, TNCs, etc) to various rigs over the
> years without any ground isolation and never had a ground loop
> problem.
------------------------------
Date: Tue, 25 Jul 2000 07:25:53 GMT
From: nomail@rob.knoware.nl (Rob Janssen)
Subject: RigBlaster
George , W5YR <w5yr@att.net> wrote:
>That "some folks" certainly wasn't me, Bob! That is one of the last
>things I would ever do.
>I think this whole "ground loop" thing has been blown way out of
>proportion.
The fact that you apparently are lucky and don't see the problem in your
own shack does not mean the problem does not exist!
It depends on details that are difficult to predict and prevent. You may
have big problems when you install a different antenna or upgrade your
computer.
Rob
--
+----------------------------------+--------------------------------------+
| Rob Janssen pe1chl@amsat.org | WWW: http://www.knoware.nl/users/rob |
| AMPRnet: rob@pe1chl.ampr.org | AX.25 BBS: PE1CHL@PI8WNO.#UTR.NLD.EU |
+----------------------------------+--------------------------------------+
------------------------------
Date: Tue, 25 Jul 2000 09:13:57 GMT
From: nomail@rob.knoware.nl (Rob Janssen)
Subject: RigBlaster
Bob Lewis <rlewis@staffnet.com> wrote:
>> Personally, I would have liked to have seen opto-isolators used
>> NOT ONLY on the PTT keying line BUT ALSO on BOTH of
>> the audio lines to and from the sound card. It would have not
To be continued in digest: hd_2000_200G
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