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PA2AGA > HDDIG 08.08.00 12:12l 217 Lines 7467 Bytes #999 (0) @ EU
BID : HD_2000_213B
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Subj: HamDigitalDigest 2000/213B
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From: PA2AGA@PI8HGL.#ZH1.NLD.EU
To : HDDIG@EU
Date: Mon, 07 Aug 00 23:46:51 MET
Message-Id: <hd_2000_213B>
From: pa2aga@pe1mvx.ampr.org
To: hd_broadcast@pa2aga.ampr.org
X-BBS-Msg-Type: B
>multipath will take out the whole signal tens or hundreds of times
>each second, so with sufficient interleaving and ECC, the burst errors
>may be converted to random errors and reconstructed using the ECC.
>However, if the mobile stops due to a traffic jam or traffic light, it
>most probably will stop at a signal null and no communication is
>possible, until the mobile moves some centimeters :-).
We have done some mobile work (digital voice), and the multipath
problems aren't horrible, even on 222 MHz, until you stop. As you
say, you always seem to stop in the null. Of course digital voice
is quite tolerant of bit errors, unlike data transmissions.
Gary
Gary Coffman KE4ZV | You make it |mail to ke4zv@bellsouth.net
534 Shannon Way | We break it |
Lawrenceville, GA | Guaranteed |
------------------------------
Date: Mon, 07 Aug 2000 00:21:36 +0300
From: Paul Keinanen <keinanen@sci.fi>
Subject: 56Kb Packet Radio Modem
On Sun, 06 Aug 2000 14:15:45 -0400, Gary Coffman <ke4zv@bellsouth.net>
wrote:
>We have done some mobile work (digital voice), and the multipath
>problems aren't horrible, even on 222 MHz, until you stop. As you
>say, you always seem to stop in the null. Of course digital voice
>is quite tolerant of bit errors, unlike data transmissions.
IIRC "Microwave mobile communications" by Jakes even derives a formula
for the probability of stopping at the null :-).
While this old book (1974) is severely outdated when talking about
communication systems, the UHF/microwave non-LOS propagation part is
very interesting even today.
Paul OH3LWR
------------------------------
Date: Mon, 07 Aug 2000 00:21:34 +0300
From: Paul Keinanen <keinanen@sci.fi>
Subject: 56Kb Packet Radio Modem
On Sun, 06 Aug 2000 13:54:32 -0400, Gary Coffman <ke4zv@bellsouth.net>
wrote:
>The WA4DSY RF modem requires a signal strength of about -110 dBm
>to maintain a 1 in 1E6 bit error rate. But that's the signal strength at the
>modem's 29 MHz input. The transverter ahead of it may have gain, as
>may the antenna, so the off air field strength may be considerably lower.
>(Typically with our setups about -140 dBm is the point where bit errors
>exceed 1 in 1E6.)
Are you sure about your sensitivity measurements ?
After all, we are talking about terrestrial links and you will have
the warm earth in the receiver antenna lower sidelobe, so maybe a 300
K antenna temperature is a reasonable quesstimate for VHF/UHF. This
corresponds to -174 dBm/Hz noise density and with a bandwidth of
larger than 10 kHz, the noise power would be stronger than -134 dBm
and you need some positive SNR, so the signal has to be in the -120 ..
130 dBm range even with noiseless front end. Even if you have 30 dB of
transverter gain ahead of your 29 MHz system, I do not think you can
get much better sensitivity than the -110 dBm level.
Of course, things get different if you are receiving the data from a
high orbit satellite in the microwave band, when you can have the
system noise temperature below 300 K.
Paul OH3LWR
------------------------------
Date: 07 Aug 2000 01:17:08 GMT
From: w3nj@aol.com (W3NJ)
Subject: Looking for Nico Palermo -YAM author
..not having much luck with direct email. Need to know if he received my
money
order
Tnx es 73
de Bruce - W3NJ
------------------------------
Date: Sun, 06 Aug 2000 21:00:52 GMT
From: kf4sir@earthlink.net (Dale Coleman)
Subject: Next Saturday PSK31 relay experiment
Hi all, next Saturday (Aug 12,00) KF4SIR (QTH Orlando) will be running
a relay experiment to see if PSK31 can be used to send e-mail
messages.
Will be running contest style auto CQ on 14090Mz + 1500Hz starting at
8:00AM EST until 11:00 AM EST. Will try and run second session from
8:00 PM until 11:00 PM EST. Will also be trying QPSK for the last hour
in the first session and the first hour in the second session.
UTC times and more information available at:
http://psk31relay.net
Please stop by if you can and be part of this interesting experiment.
Will only need to copy one short message - should take less then 1
minute.
Thanks, Dale
------------------------------
Date: Sun, 6 Aug 2000 18:22:11 -0600
From: "DBell" <dbell@allwest.net>
Subject: Palm Pilot, Email, Packet?
I am not "seasoned" with packet radio or the soldering iron but wonder if
the following can be done with simplicity:
Dad (newly licensed) goes RVing across the US from time to time. Can he use
packet radio connected with a palm pilot to send messages from varying
locations to my email address? (His location changes every 1 - 3 days and it
would be nice to keep in touch and know where he is.)
Is there a way that I could email (I'm not set up on packet yet) messages
back to him that could be held at a BBS where he could pick them up via
packet? Could he somehow connect by packet to the same BBS to receive any
messages?
For this to work it needs to be kept relatively simple. If it became
complicated Dad probably wouldn't want to be bothered by it.
I hope that this is being done already. Wouldn't it be wonderful to be on
the road, pull into a place, fire up the radio and send off a quick packet
message that you have arrived safe, how your day went, and where you expect
to be tomorrow. Then with a minimum of packet commands receive any messages
from home.
If you can give me direction or advice in this regard I would greatly
appreciate it.
Thanks in advance,
David Bell (KC7CNA)
------------------------------
Date: Sun, 06 Aug 2000 12:49:45 -0500
From: Ed McGinley <alco-ge@swbell.net>
Subject: Palm Pilot, Email, Packet?
there was an article on how to do this in either QST or CQ within the last
year. Some one could search the indexes for the article. It dealt with using
a
palm pilot and a TNC with a mobile radio.
I will look to see if I can find the article.
Ed
DBell wrote:
> I am not "seasoned" with packet radio or the soldering iron but wonder if
> the following can be done with simplicity:
>
> Dad (newly licensed) goes RVing across the US from time to time. Can he use
> packet radio connected with a palm pilot to send messages from varying
> locations to my email address? (His location changes every 1 - 3 days and it
> would be nice to keep in touch and know where he is.)
>
> Is there a way that I could email (I'm not set up on packet yet) messages
> back to him that could be held at a BBS where he could pick them up via
> packet? Could he somehow connect by packet to the same BBS to receive any
> messages?
>
> For this to work it needs to be kept relatively simple. If it became
> complicated Dad probably wouldn't want to be bothered by it.
>
> I hope that this is being done already. Wouldn't it be wonderful to be on
> the road, pull into a place, fire up the radio and send off a quick packet
> message that you have arrived safe, how your day went, and where you expect
> to be tomorrow. Then with a minimum of packet commands receive any messages
> from home.
>
> If you can give me direction or advice in this regard I would greatly
> appreciate it.
>
> Thanks in advance,
>
> David Bell (KC7CNA)
------------------------------
Date: Sun, 6 Aug 2000 14:59:10 +0100
From: Bob Sayers <bob.sayers@zetnet.co.uk>
Subject: Vote Green Party
To be continued in digest: hd_2000_213C
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