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PA2AGA > HDDIG 05.12.99 11:16l 189 Lines 7422 Bytes #-9661 (0) @ EU
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Date: Sat, 04 Dec 99 23:33:58 MET
Message-Id: <hd_99_304C>
From: pa2aga
To: hd_broadcast@pa2aga
Subject: HamDigitalDigest 99/304C
X-BBS-Msg-Type: B
> <http://pgp5.ai.mit.edu:11371/pks/lookup?op=vindex&search=0xEDECB44F>
> Key ID: 0xEDECB44F
> This key is RSA, NOT Diffie-Hellman !!
>.
------------------------------
Date: Wed, 24 Nov 1999 22:56:15 +0000
From: Roger Barker <roger@peaksys.co.uk>
Subject: Best Windows Terminal Program for WA8DED TNCS
In article <84U_3.193227$5r2.446546@tor-nn1.netcom.ca>, Rob
<NoEmail@NoWay.com> writes
>Hi Roger,
>
>I am not that famiuliar with TF2.7b. But is it a KISS to WA8DED emulator??
>If so, I assume the TNC must be in KISS mode (ie the WA8DED host mode
>supported by the TNC is not used)
TF firmware is a super-set of WA8DED. WinPack in "TF2.7b" host mode will
detect that it is in fact talking to WA8DED and modify its behaviour
accordingly.
--
Roger Barker, G4IDE roger@peaksys.co.uk
Boston, UK http://www.packetradio.org.uk
>.
------------------------------
Date: 25 Nov 1999 03:08:04 GMT
From: johnl84238@aol.com (JOHNL84238)
Subject: Computer RF noise in HF SSB
In addition to the steps you have taken, maybe you should be looking at the
power supply to the radio. Many manufacturers
(Alinco et al) leave out RF bypass caps
on the A/C input line. These caps, referred to as Y-caps are to bypass RF
interference form each side of the A/C line to ground.
Check to see if the power supply to the Xcvr has RF bypassing on the A/C
input.
I have found that adding RF bypassing helps a lot....especially for RF coming
in through the power supply.
-JL
>.
------------------------------
Date: Sat, 27 Nov 1999 06:09:06 -0500
From: Robert Cook <captcook@mindspring.com>
Subject: Computer RF noise in HF SSB
Gary,
Hello and thanks for your thoughtful and comprehensive input and suggestions.
I will
look it over more thoroughly and get to work on the various elements.
Bob K9KKY
Gary Coffman wrote:
> On Wed, 24 Nov 1999 07:02:00 -0500, Robert Cook <captcook@mindspring.com>
wrote:
> >There is a law which manufacturers of electronic devices and electronic
> >devices must be in compliance with. The law requires that any electronic
> >device may not cause interference to other devices or services. It is
> >FCC Rule Part 15.
>
> Do realize that the unit only has to comply with the emission limits for a
> Class B computing device. It is not required to generate no RFI at all.
> That compliance level may still leave you with *substantial* interference to
> a nearby sensitive SW receiver, though it should provide protection for
> reception of a strong nearby broadcast signal on an ordinary consumer
> broadcast receiver. So the computer may be in compliance with the law
> and still cause you severe interference.
>
> You have to take steps on your own to resolve the problem below the
> Class B level. The FCC has a booklet which offers a number of suggestions
> on how to do that. Better, the ARRL publishes an RFI handbook with a
> number of good suggestions on how to solve this sort of problem.
>
> In any RFI situation, the solution generally involves improving shielding
> and filtering of the source of the emission, and relocation of antennas
> and feedlines to minimize pickup by the radio set suffering the
interference.
> (Improvement of the shielding and filtering of the radio may be required
too.
> You want the radio to respond only to signals entering via the antenna
> input connector.)
>
> Since your problem seems to be primarily related to the switching power
> supply, you should attack that problem first. A brute force line filter
attached
> directly to the power input of the switching supply would the be first line
of
> attack. A combination of a common mode choke and RF bypass capacitors
> should sharply reduce conducted noise from the switching supply.
>
> You may also want to power the computer from a different branch circuit
> than the one powering your radio. (The radio power supply may need a better
> line filter too.) To solve conducted interference problems, multiple lines
of
> attack are often required. Not only do you need to limit the energy getting
out
> of the source, you also need to limit the energy getting in to the
destination.
>
> (Watch out for multiple ground paths too. Grounding conductors often
> serve to conduct noise from one piece of equipment to another. Single
> point grounding practices should be used. Actual Earth grounds are
> generally worthless. Earth is not a noise sink, it is typically a noise
> source.)
>
> Now solving the display radiation problem may be harder. With radiated
> interference, filters are of little use. You have to shield the radiation
source.
> This is difficult with displays, since you also still have to be able to see
> them. Wire mesh can be effective, but it must totally enclose the source
> of radiation or it will not work. RF radiation can escape via poorly bonded
> seams, via openings in the shielding, or via wiring passing through the
> shielding. Shielding must be *tight* to be effective.
>
> The radio may need improved shielding too. It should not respond to signals
> which aren't picked up by the antenna. If you disconnect the antenna, *no*
> interference should be heard. If you still hear interference with the
antenna
> disconnected, you need to work on the shielding of the radio.
>
> Getting your antenna well away from the source of radiation is also helpful.
> The inverse square law comes to your aid here, attenuating the noise in
> proportion to the square of increasing distance. Outside antennas are
> obviously preferred. You do have to guard against system imbalances.
>
> The interference can travel up the outside of coax as a common mode
> signal to the antenna, then travel down the inside of the coax to the
> receiver. This negates the inverse square benefit you'd normally have
> by locating the antenna far from the source of interference. The solution
> to this is to suppress common mode currents by the use of a current balun
> (choke balun) in the feedline to choke off RF currents on the outside
> of the coax.
>
> Completely solving computer RFI problems is often difficult. There are
> a number of things you have to do correctly. Neglecting any one of them
> may negate the benefits of other changes you may have made.
>
> Gary
> Gary Coffman KE4ZV | You make it |mail to ke4zv@bellsouth.net
> 534 Shannon Way | We break it |
> Lawrenceville, GA | Guaranteed |
>.
------------------------------
Date: Fri, 26 Nov 1999 19:48:20 -0500
From: Gary Coffman <ke4zv@bellsouth.net>
Subject: Digital Modes, What a mess
On Mon, 8 Nov 1999 08:36:53 -0600, "Gilbert Baron" <xzs1947@us.ibm.com> wrote:
>That is not at all true. FCC will mandate a single standard and then all
>will follow it, no choice, and I think it is already done so you won't see
>all these modes for long.
No, the FCC didn't do that. The FCC approved the Grand Alliance system which
uses a common modulation method, 8VSB, and a common overall transmission
baud, but several different video/audio standards (scan rates and types, color
To be continued in digest: hd_99_304D
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