QRZ! Ham Radio 4/QRZ Ham Radio Callsign Database - Volume 4.iso/digests/digital/940292.txt

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

Date: Fri,  2 Sep 94 04:30:17 PDT
From: Ham-Digital Mailing List and Newsgroup <[e-mail]>
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Subject: Ham-Digital Digest V94 #292
To: Ham-Digital


Ham-Digital Digest          Fri,  2 Sep 94       Volume 94 : Issue  292

Today's Topics:
            9600 baud using Kenwood TM201 & TM401 (2 msgs)
                         Jnos and PK232MBX ?
                  TAPR2 TNC Mods; Bit Regeneration?
                   wanted: tnc firmware with netrom

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We trust that readers are intelligent enough to realize that all text
herein consists of personal comments and does not represent the official
policies or positions of any party.  Your mileage may vary.  So there.
----------------------------------------------------------------------

Date: 31 Aug 94 00:03:00 GMT
From: tulane!darwin.sura.net!wa4mei!totrbbs![e-mail]
Subject: 9600 baud using Kenwood TM201 & TM401
To: [e-mail]

-> Steve,
->
-> I have the 201/401 pair sitting in my storage cabinet collecting dust
-> and I  would like to put them to use. I would appreicate if you would
-> eMail me or post the mod information that you currently have. I would
-> like to at least do the  receive mod so I can monitor the 9600 baud
-> activity around the valley.
-> Please keep me on your eMail list, if and when you resolve the
-> transmit issue. I will do the same on this end, if I find out any
-> other information.
-> Thanks & 73s,
-> Tom WB7ASR

Tom,
Welllll, I guess you're a glutton for punishment. <g> RXA is available
at the junction of D4 and R29 in the IF section. I used Radio Shack
10/26 AWG shielded audio cable, and made the connection on the solder
side of the board. I found a ground close by on the board and soldered
the shield to that. As I recall, I didn't use a resistor between the
modem and the radio, because the signal level was about right for the
TAPR 9600 modem. You may need some level compensation; a 2 to 10K
resistor will do the job. If the level is too high, the modem is swamped
and loses sensitivity.

On the TXA side, I interface 9600 transmit audio at R90. which is on the
audio side of the varactor, isolated by a polarized capacitor. (which is
good) I used a 2k resistor in series between the modem and the insertion
point.

Again, this is the interface info for a Kenwood TM401. IT IS NOT TOTALLY
SUCCESSFULL. Long packets will be distorted by this transmit interface.

I've been quite impressed my James Miller's helpful attitude, and expect
to hear  from him soon. Will let you know what I get from him ASAP. I
would appreciate the same in return, if anything turns up.

Regards,
Steve Diggs, KB4ZTN
[e-mail]

----
Top Of The Rock BBS - Lilburn, GA         SYSOP: Steve Diggs
UUCP: totrbbs.atl.ga.us               Snailmail: 4181 Wash Lee Ct.
Phone: [phone]                           Lilburn, GA 30247-7407

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

Date: 1 Sep 1994 04:34:41 GMT
From: ihnp4.ucsd.edu!agate!darkstar.UCSC.EDU!news.hal.COM!olivea!koriel!newsworthy.West.Sun.COM!abyss.West.Sun.COM![e-mail]
Subject: 9600 baud using Kenwood TM201 & TM401
To: [e-mail]

In article [e-mail],  [e-mail] (Larry Rappaport) writes:
>[e-mail] (Steve Diggs)  writes:
>
>> I haven't given up completely. James Miller, G3RUH, has agreed to look
>> at the schematics of this rig with ideas on ANY POSSIBLE way to make the
>> rig work. Possibilities are to lengthen the RC time constant in the
>> PLL's feedback curcuit, or perhaps modulate the master reference
>> oscillator of the PLL, along with the Varactor. (To prevent the PLL from
>> detecting a frequency drift) James just sent me a confirming note on
>> 8/28 acknowledging receipt of the info package, and his intent to shart
>> on the project in the near future.
>
>I would definitely try first to lengthen the RC time constant in the PLL
>feedback circuit, since that might be the easiest to do.

You gotta be really careful when you start dinking with the PLL loop filter.
There are usually multiple time constants of interest.  It is a really good
idea to first measure the VCO gain over several band segments (since the gain
of most VCOs isn't exactly linear with respect to frequency), determine the
phase comparator gain and the loop filter characteristics.  Then, calculate
the loop frequency and phase response.

Make sure that your modifications to the PLL loop filter do not make the
PLL unstable or increase the reference frequency sideband amplitude.  Also,
some loop filters have an interaction between the corner frequency and
damping factor; by the time you get a low enough corner frequency, the loop
will tend to ring at a very low frequency.  Also, the lower the loop filter
corner frequency, the longer it takes the loop to lock up, though some
filters have diodes inserted in a cheap adaptive filter scheme.

By the way, MX*COM publishes a very nice databook, which includes charts of
BER vs low frequency response of transmitter and receiver.  They recommend
very highly using "two point modulation", in other words, modulate the
VCO and the PLL reference.  By modulating the reference, the loop regains
good low frequency (even DC) response.

A previous poster suggested that the longer the packet, the more the PLL
could adjust out the packet.  This is not accurate; the reality is the
PLL always is damping out low frequency modulation of the VCO.  This has
a negative effect on the bit error rate (BER), such that longer frames
are pretty much certain to have an error while the shorter frames
squeak past.

---
 * Dana H. Myers KK6JQ, DoD#: j    | Views expressed here are    *
 * [phone]         | mine and do not necessarily    *
 * [e-mail]    | reflect those of my employer    *
 * "Sir, over there.... is that a man?"                         *

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

Date: Wed, 31 Aug 1994 17:05:49 GMT
From: psinntp!arrl.org![e-mail]
Subject: Jnos and PK232MBX ?
To: [e-mail]

In a rec.radio.amateur.digital.misc article, Daniel Curry ([e-mail]) recently wrote:
-> I have an AEA PK-232 that was upgraded to a PK-232MBX. I'd like
->to use this for 2 meter tcp/ip. The question is do I need to have a
->battery install in the PK-232? The reason for the question is that when I
->purchased the PK-232 the manual stated don't put batteries in. With the
->upgrade kit it came with a NiCd battery. I haven't installed the NiCd.

  I run my AEA PK-232MBX on TCP/IP 24 hours and it has the battery in it.
Don't see how it could hurt...

  GL, OM!

--
 ================== FROM ====================================================
 Brian Battles, WS1O                  Features Editor, QST Magazine, ARRL HQ
 Internet: [e-mail]                 Newington, CT USA
 Voice     203-666-1541

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

Date: 31 Aug 1994 16:28:36 -0400
From: agate!darkstar.UCSC.EDU!news.hal.COM!olivea!charnel.ecst.csuchico.edu!nic-nac.CSU.net!usc!elroy.jpl.nasa.gov!swrinde!gatech!udel!news.sprintlink.net!redstone.interpath.net!mercury.interpath.@
Subject: TAPR2 TNC Mods; Bit Regeneration?
To: [e-mail]

'I'm in the process of building and installing a 1200 baud bit
regenerating full duplex packet repeater for the PacketCluster
group in this area. (Yes I know you can repeat 1200 baud fairly
reliably through a standard voice repeater, and we are already
up and running in that mode with DCD control of the repeaters's
PTT.  For a number of reasons we will be changing over to  bit
regeneration.)

It's been a real struggle finding info on how to modify a TAPR
-2 clone TNC (MFJ-1270) for bit regeneration repeater operation.
So far I've not found an already engineered solution.

Heres what I have found:

1) Discussions via Internet with several who had done bit
regeneration modifications to non-TAPR 2 TNCs did not apply
to TAPR-2  clone TNCs because the Txdata and Rxdata switching is
different.

2) I was told that the TAPR journals had several articles on
1200 baud bit regeneration mods for TAPR-2 clones. I purchased all
of the TAPR back issues. Almost nothing regarding the subject
was contained within them. Lot's of mention by people using
packet rengerating repeaters (mostly 9600 baud) or advocating
the use of them, but nothing in the way of how to mod a TAPR-2
TNC for 1200 baud bit regeration.

3) Someone told me PacComm sold an EPROM for TAPR-2 TNCs that
turned the TNC into a 1200 baud bit regenerator including a FIFO
elastic buffer. After four phone calls to TAPR no one there has
yet to FAX me specs on this EPROM. Although they say they have
it ($30.00 each), I have been unable to get anyone there to
give me me ANY technical description of it. I don't know if
it reallly exists or whether it works only with their hardware,
etc.


So can you point me toward  a solution or share details on how
you have modified a TAPR-2 for this purpose ?



Mike Wood            Internet: [e-mail]
The Signal Group     Amateur Radio: NT4O
P.O. Box 1979     ***Avoid company disclaimers by owning the company ***
Wake Forest, NC 27588

Phone: [phone]       Fax: [phone]

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

Date: 31 Aug 1994 20:44:48 +0200
From: ihnp4.ucsd.edu!ucsnews!newshub.sdsu.edu!nic-nac.CSU.net!usc!howland.reston.ans.net!EU.net!sun4nl!news.nic.surfnet.nl!tuegate.tue.nl!news.iaehv.nl!news.iaehv.nl![e-mail].
Subject: wanted: tnc firmware with netrom
To: [e-mail]

Hello packeteers,

I am looking for firmware for my tnc2. It should have netrom capabilities. I
currently have tapr 1.1.8 and wa8ded 2.6 and nord><link 2.3c.

My local bbs has no others.

Is there any ftp site or other medium that has rom images online???
Newer versions of tapr wa8ded and nord><link are also welcome.
by the way nord><link2.3c supports dama.

greetings   jan verhoeven   [e-mail]

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End of Ham-Digital Digest V94 #292
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