[OZAPRS] Setting up TT4 Tx on 2m and more! Problem Solved
David and Justine Olsen
davejust at bigpond.net.au
Thu Feb 18 13:34:45 EST 2010
When in doubt, check the baud rate <blush>
David
On 18 Feb 2010, at 12:29, David and Justine Olsen wrote:
> Too late for my hair Ray.
>
> I've moved on to the other part of my project now, and will go back
> over your email when I get back to the TT4 Tx issue.
>
> I've got a tracker to install in my aircraft an 8W unit from Byon.
> I want to set up a portable computer EEPC with TT4 and UIview at
> the gliding club, have a tracker in my glider and have its position
> shown on the EEPC.
>
> I'm running it now and it is being decoded by the TT4 via a Kenwood
> TM201A. I can see the decodes in Hyperterminal, of my tracker and
> other local APRS transmitters when TT4 is in text and when TT4 is
> in KISS mode. In KISS mode the first part of the transmission is
> gibberish in Hyperterminal - no problems.
>
> My problem is how to setup UIView in KISS mode to receive data from
> the TT4. The TT4 is setup in Alpha mode.
>
> As I said, Hyperterminal shows data received via the serial port,
> but I can;t get anything to appear in UIView.
> Can anyone point me to UIview KISS setup for TT4?
>
> Thanks for the audio stuff....I'll file it away for when I get back
> to that part of the project.
>
> David
>
>
>
>
> On 18 Feb 2010, at 12:14, Ray Wells wrote:
>
>> David/All,
>>
>> I'm not suggesting your problem is tone level related but failure
>> to grasp the following is arguably responsible for more TNC decode
>> issues than any other cause.
>>
>> The need for "twist" adjustment depends on the radio hardware
>> involved so a brief discussion is probably in order.
>>
>> The "norm" for an FM/PM radio is to apply 6dB (x2) per octave of
>> preemphasis in the transmitter. For packet, this results in the
>> high tone (2200Hz) having twice (near enough) the deviation as the
>> low tone (1200). In the receiver deemphasis is applied which
>> restores the audio to a "flat" condition, i.e. both tones going to
>> the TNC have the same level.
>>
>> If TNC audio is fed into the microphone socket you can depend on
>> 6dB per octave preemphasis. However, if the TNC audio is fed in
>> further down the tx audio chain, such as the audio injection point
>> for tone signalling, preemphasis will not be applied in the tx and
>> should be applied externally - with twist, in the case of the TT4.
>>
>> Going to the receiver again, if it receives a signal without
>> preemphasis, it will still apply deemphasis (assuming audio is
>> taken after deemphasis), resulting in the high tone being just
>> half the level of the low tone when fed to the TNC. FSK
>> demodulators based on the the exar pair 2206/2211 will not decode
>> if the high tone is lower in amplitude than the low tone, by even
>> a very small amount.
>>
>> If rx audio is taken from the demodulator in the radio, i.e.
>> before deemphasis, the preceding is not a problem because audio
>> that is transmitted "flat" will be decoded "flat".
>>
>> The exar chip set (found in genuine TNC2 TNC's) is not disturbed
>> by high tone being considerably higher in amplitude than the low
>> tone.
>>
>> In summary, every tx should employ preemphasis, regardless of it
>> being generated internally, or externally. That will eliminate any
>> decode problems in TNC's with finicky chip sets because high tone
>> will always be the same level as, or higher than, the low tone
>> coming out of the rx.
>>
>> David, is TXD 60 60mS or 600mS? Although TXD provides time for
>> your tx to stabilise before valid data is sent, it can also have
>> an impact on the remote rx in cases where muted audio is being
>> used for the TNC. There are some very sluggish receivers kicking
>> about and TXD needs to be long enough for that rx to unmute. My
>> Icon handheld scanner is pathetic in this regard, with the mute
>> being so slow that I can miss at least half of the digi beacon,
>> even when I'm at the digi site.
>>
>> Get that CRO working and save your hair, lest you should end up
>> like me :-)
>>
>> Ray vk2tv
>>
>>
>>
>> David and Justine Olsen wrote:
>>>
>>> I am presently running TxD of 60 and TXTWIST of 50. I've tried a
>>> range of TXTWIST but none sound too different
>>> David
>>>
>>> On 18 Feb 2010, at 00:36, Scott Evans wrote:
>>>
>>>>
>>>> ABAUD is just the speed set for serial port 1 ... what TXDELAY
>>>> are you running? because depending on how quick you radio is you
>>>> may need to lengthen the delay a little, also check the TXTWIST
>>>> setting too, this controls the level between the 1200Hz & 2200Hz
>>>> tones.
>>>>
>>>> On Wed, 2010-02-17 at 21:51 +1000, David and Justine Olsen wrote:
>>>>>
>>>>> ABAUD is set to 19200
>>>>>
>>>>>
>>>>> On 17 Feb 2010, at 21:37, Norm, VK3XCI wrote:
>>>>>
>>>>> > Sort of like 9600 baud?
>>>>> >
>>>>> >
>>>>> >
>>>>> >
>>>>> >
>>>>> >
>>>>> >
>>>>> > 73 de Norm, VK3XCI
>>>>> > Mildura, Australia
>>>>> > The Wintersun City
>>>>> > QF15bt.
>>>>> >
>>>>> > David and Justine Olsen wrote:
>>>>> >> I've gone through all of the TT4 audio adjustments as
>>>>> explained in
>>>>> >> the help docs by listening on another set, but still no
>>>>> success being
>>>>> >> received by any digis.
>>>>> >>
>>>>> >> One thing that has me curious, is the the squak from my Tx
>>>>> sounds
>>>>> >> nothing like those from others. The others are a deehdaaah
>>>>> kind of
>>>>> >> sound with two distinctly different tones ate the beginning
>>>>> and end
>>>>> >> tone, whereas mine is a sqaaaark :-) of mixed tones at the
>>>>> same time.
>>>>> >>
>>>>> >> David
>>>>> >>
>>>>> >> VK4MDX
>>>>> >>
>>>>> >> _______________________________________________
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>>>>> >>
>>>>> >>
>>>>> >>
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>>>>> >>
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>>>>
>>>> --
>>>> Scott Evans <scott at vk7hse.hobby-site.org>
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