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PA2AGA > HDDIG 26.07.00 02:09l 177 Lines 7306 Bytes #-9303 (0) @ EU
BID : HD_2000_200E
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From: PA2AGA@PI8HGL.#ZH1.NLD.EU
To : HDDIG@EU
Date: Tue, 25 Jul 00 17:08:52 MET
Message-Id: <hd_2000_200E>
From: pa2aga@pe1mvx.ampr.org
To: hd_broadcast@pa2aga.ampr.org
X-BBS-Msg-Type: B
the common for computer/radio communications. Thus, there is yet another
conductor circumventing the optocoupler and transformer "isolation."
I don't know about you folks, but my interface consists of two shielded
audio cables from Radio Shack. No ground loops, no feedback, no hum. Lab
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: Tue, 25 Jul 2000 00:31:06 GMT
From: Dick Hughes <dhughes33@earthlink.net>
Subject: RigBlaster
I was only responding to your argument that the MFJ switch box and the
RigBlaster are very similar in complexity and therefore should cost
roughly the same. I contend that the RigBlaster is several times more
complex than the MFJ, and that if the MFJ is "worth" $40, then the
RigBlaster is easily "worth" $80 or more. I speak from 30 years of
experience in aerospace and commercial electronic manufacturing,
including cost estimating.
Dick Hughes - W6CCD
On Mon, 24 Jul 2000 16:13:29 -0400, "Rob" <Pse@NoEmail.Com> wrote:
>Dick,
>
>I think you will find that RigBlaster does NOT use a power transformer to
>power the 4N33 opto-isolator. The transformers in RigBlaster are more
>likely audio isolation transformers used to break up any ground loops on the
>audio lines to and from the sound card.
>
>It is my understanding that RIGBLASTER only uses one opto-isolator for the
>PTT keying circuit. Instead of a transistor, an opto-isolator is used.
>Most opto-isolator PTT keying circuits consist of one opto-isolator, one or
>two diodes and one resistor. Not very complicated at all. For an example
>of such a circuit, see www.qsl.net/wm2u
>
>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 cost much more.
>
>73's
>Rob
------------------------------
Date: Mon, 24 Jul 2000 21:15:14 -0400
From: "Bob Lewis" <rlewis@staffnet.com>
Subject: RigBlaster
> 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: Mon, 24 Jul 2000 21:31:25 -0400
From: "Rob" <Pse@NoEmail.Com>
Subject: RigBlaster
I think you are confusing isolation with protection.
Yes, even with optocouplers (or optoisolators) the chassis of the computer
and rig are tied together via the green wire or ground in the AC wires.
But even with this common ground connection via the AC lines, audio
isolation transformers and optocouplers break up the ground loops on the
audio lines and PTT lie and REALLY help prevent hum etc. They do work! A
lot of telephone modem manufacturers use audio isolation transformers to
break up ground loops. Old telephone modems are a great source for audio
isolation transformers if you can't buy new ones locally.
But optocouplers do MORE than just break up ground loops. Optocouplers also
help isolate and PROTECT your computer from any dangerous voltages from the
rig and vice versa due to any malfunctions, short circuits and improper
installation. Audio isolation transformers don't do that. If you really
want to protect your rig and computer, I contend that you should use
optocouplers throughout NOT JUST on the PTT line.
Audio isolation transformers just break up ground loops. Optocouplers break
up ground loops and also help isolate and PROTECT your rig and computer from
dangerous voltages.
By the way you can buy or build a device using optocoupler technology to
completely isolate the RS-232 connection between your computer and your
KACHINA rig.
I have seen posts where HAM's contend that you canot break up ground loops
on the RS-232 line. This is not true. They can be broken up using a series
of optocouplers and op amps. To isolate all the 25 pins in a RS-232 25 pin
connector, the device will use quite a lot of optoisolators. But since most
HAM applications only use 5 or so pins or lines, a simpler device can be
used.
73's
Rob
"George , W5YR" <w5yr@att.net> wrote in message
news:397CE300.D6F928E1@att.net...
> An interesting thought is that despite the optocoupler for the PTT line
> and the isolation transformer in the transmit audio line to the radio mic
> input, the computer chassis is tied directly to a-c protective ground
> through the "green" wire in its power cable, as is the radio. Thus, the
> two chasses are connected despite the presence of the optocoupler and the
> transformer. 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.
>
> The situation is even more interesting when you consider a
> computer-controlled radio like my Kachina. There the RS232 cable to the
> radio runs a wire from computer chassis ground to radio chassis ground as
> the common for computer/radio communications. Thus, there is yet another
> conductor circumventing the optocoupler and transformer "isolation."
>
> I don't know about you folks, but my interface consists of two shielded
> audio cables from Radio Shack. No ground loops, no feedback, no hum. Lab
To be continued in digest: hd_2000_200F
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