QRZ! Ham Radio 4/QRZ Ham Radio Callsign Database - Volume 4.iso/digests/tcp/940221.txt

Internet Message Format | 1994-11-13 | 10KB

Date: Thu,  6 Oct 94 04:30:02 PDT
From: Advanced Amateur Radio Networking Group <[e-mail]>
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Subject: TCP-Group Digest V94 #221
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TCP-Group Digest            Thu,  6 Oct 94       Volume 94 : Issue  221

Today's Topics:
                   antenna switching time (2 msgs)
                        radio switching times
               WG7J, Author of JNOS (forward) (2 msgs)

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policies or positions of any party.  Your mileage may vary.  So there.
----------------------------------------------------------------------

Date: Wed, 5 Oct 1994 06:02:33 -0700
From: [e-mail] (Dana Myers)
Subject: antenna switching time

> Date: Tue, 4 Oct 1994 10:00:11 -0600 (MDT)
> From: Klarsen <[e-mail]>

>     Been reading how guys are trying the 9600 baud modems at 19,200
> baud and now are looking at switching times. About time too. I have a x1j
> node that is using a Motorola Railroad Micor radio (we got 100's of these
> at $25). It is on 145.070 MHz and is a 1200 baud Tiny-2 tnc. I
> experimented with the tx delay and found that this radio takes about 0.4
> seconds to go from receive to transmit!

How did you measure this?  By changing TXDelay up and down during a
connection to some other radio?

My experience with Micors in general is that they switch pretty quickly;
I have a 110W VHF High-band radio in service that happily works with a
TXDelay of 100mS.  Remember, the TXDelay allows time for both (a) the
transmitter to start transmitting and (b) the receiver on the other end
to start receiving.  If the remote receiver is using squelch, the time
required to break squelch can be quite long, greater than 250mS, depending
on the radio.

My empirical tests of the Micor was against a remote station using
open-squelch DCD.  As I said, 100mS of delay was plenty.

>     At 1200 baud .4 seconds is not a real problem, but is an
> agrivation that makes you want to put in an electronic switch. But not
> quite. When you get to 9600 baud you begin to see the problems. I have
> just mounted a Comet 145.07 and 445.01 MHz antenna that will have a Tekk
> radio with a tx delay of .02 seconds running  9600 baud and it's tnc will
> be connected to the older 145.07 1200 baud system. At some later time I
> plan to make the the 145.07 system run at 9600 baud.

Are you *sure* the problem is the T/R switch in the Micor?  I've never
looked at the railroad Micors; is there something special about the T/R
switch that isn't in the conventional Micors?

On another note, VHF High-band Micors are generally phase modulated.  This
tends to present an issue for 9600 baud operation; you really need to have
a direct FM radio.  You can make high-band Micor do direct FM; you either
install a complete Micor repeater exciter and 4 pin channel elements (also
found in the DVP Micors, but these are pretty rare) or you install a 4 pin
element in a PM exciter, disable the PM modulator, and wire the modulation
to the "fourth" pin of the element.  The receiver IF also may need some
attention, too.

>     Now that .4 second looks HUGE! It takes 1 full packet time to
> switch that old radio. So something new must be invented, or a new way to
> use the radio so it isn't a problem. The only thing that comes to mind is
> a duplex radio that has no antenna switch and the transniter is just left
> on until packets stop coming.

Since I've looked at several Micors, and none of them had excessive
T/R delays, I'd suggest you have a look and understand why you're seeing
this 400mS T/R time.  It could be your remote receiver is very slow; it
also could be some artifact of how the Micor is set up.  It should be
possible to get this radio to perform much better.

Dana
KK6JQ

------------------------------

Date: Thu, 06 Oct 94 14:06:55 +0900
From: Ryuji Suzuki -- JF7WEX <[e-mail]>
Subject: antenna switching time

 |Date: Tue, 4 Oct 1994 10:00:11 -0600 (MDT)
 |From: Klarsen <[e-mail]>
 |Subject: antenna switching time

 |    Now that .4 second looks HUGE! It takes 1 full packet time to
 |switch that old radio. So something new must be invented, or a new way to
 |use the radio so it isn't a problem. The only thing that comes to mind is
 |a duplex radio that has no antenna switch and the transniter is just left
 |on until packets stop coming.
 |
 |    Do you have any ideas or tried solutions?

I also think that full-duplex is effective for data to be transmitted
with high bit rate, but its application for practical connections
except for point-to-point ones would be rather hard.

Delay to responce in magnetic relays or other switching devices must
not dominate the delay time to transmit. Typical set/reset time for
magnetic relays ranges from a few milliseconds(for signal) to twenty
milliseconds(for large power). I think elements that affect the delay
time are time constants in DC power lines or bias circuits, oscillator
startup time, and PLL lock-in time.
--
Ryuji Suzuki  JF7WEX

------------------------------

Date: Wed, 5 Oct 1994 07:31:13 -0800 (PDT)
From: Glenn Elmore <[e-mail]>
Subject: radio switching times

Karl k5di wrote:

>     At 1200 baud .4 seconds is not a real problem, but is an
> agrivation that makes you want to put in an electronic switch. But not
> quite. When you get to 9600 baud you begin to see the problems. I have
> just mounted a Comet 145.07 and 445.01 MHz antenna that will have a Tekk
> radio with a tx delay of .02 seconds running  9600 baud and it's tnc will
> be connected to the older 145.07 1200 baud system. At some later time I
> plan to make the the 145.07 system run at 9600 baud.
>
>     Now that .4 second looks HUGE! It takes 1 full packet time to
> switch that old radio. So something new must be invented, or a new way to
> use the radio so it isn't a problem. The only thing that comes to mind is
> a duplex radio that has no antenna switch and the transniter is just left
> on until packets stop coming.
>
>     Do you have any ideas or tried solutions?
>

I don't know about the Motorola but I think you may be in trouble with
20 milliseconds on the Tekk radio.  I see this after measuring and
taking notes on only one Tekk KS960 which was fresh from Tekk a few days
ago.  I hope to clean up my notes and post them.
  What I found was that the Tekk receiver was very slow in recovering
after the radio transmits.  While it can go from assertion of PTT to
full power in a millisecond or so, getting the receiver back to full
sensitivity after letting go of PTT takes about 40 milliseconds.  I ax25
connected two Tekks back-back with a single TAPR Modem/TNC2 and verified
that things broke at 20 ms TxDelay.  They still worked at TxDelay=30 ms
but that was with very strong signals.

  I don't yet even have a schmatic of the radio so can't determine who
the culprit is, whether supply switching, saturation of an amplifier
stage or something else.  All I know at the moment is that the RSSI line
doesn't find full signal for a long time after negating PTT.
There may be a reasonable fix for this problem.

  I don't believe that duplex is necessary for fast turnaround times.
The highspeed radios we are running are presently being used with 1 ms
txdelays but this is only because that's the smallest value the PI2 card
drivers presently allow. The radios work fine at 50 microseconds and
are not FDX. They use PIN switches for T/R and I took only a little extra
care in how things were switched inside the radio. No crystal oscillators
have to start up when things are switched and time constants associated
with filtering are kept to reasonable values. It's not useful to "filter
the heck out of it" to make things perform cleanly and quickly. You may have
seen my original estimates that the radios are fast enough and sensitive
enough to copy their own *packets* by aircraft-bounce with the planes at
5-10 miles distance using only an 8' or so antenna.
  Certainly we don't need packet radar for most amateur networking but
making fast non-FDX radios isn't all that difficult.


Glenn Elmore n6gn

amateur IP:    [e-mail]
Internet:    [e-mail]

------------------------------

Date: Thu, 6 Oct 1994 09:44:32 +0900
From: Isao SEKI <[e-mail]>
Subject: WG7J, Author of JNOS (forward)

Hello group,

This is a forwarding message, original by JF1LZQ Yutaka Sakurai.

Isao, JM1WBB

--- forwarding message
This is just FYI.

I suppose that many of you would know the JNOS, another TCP/IP software
for packet radio which includes "Converse" as well as RBBS gateway feature.

Johan. K. Reinalda (WG7J), the author of JNOS, is living in Miyazaki Japan now.
He has just joined PRUG-net and his email address is

[e-mail]

The kban.prug.or.jp is connected with PRUG-net backbone by UUCP.

The PRUG-net is Japan's AMPR network which is build not only with packet
radio TCP/IP but also ISDN as well as leased line. PRUG-net backbone is
connected to the INTERNET through the comercial internet provider by IP.

* PRUG : Packet Radio User's Group
--- end of message

------------------------------

Date: Wed, 5 Oct 1994 17:36:28 -1000 (HST)
From: Antonio Querubin <[e-mail]>
Subject: WG7J, Author of JNOS (forward)

So when will the Japan AMPRnet join the other 'connected' AMPR nets?

Antonio Querubin
[e-mail] / [e-mail]

------------------------------

Date: Wed,  5 OCT 94 14:17:08
From: [e-mail]

SUBSCRIBE TCP-GROUP BOB ANDERSONR AA7TR

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End of TCP-Group Digest V94 #221
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