[time-nuts] RS 232

Brian Alsop alsopb at nc.rr.com
Sat Jul 27 11:45:13 UTC 2013


There are other timing issues involved too.

Many radios still use relays to switch from transmit to receive. (PIN 
diodes only in the more expensive ones).  The radio receives a key 
closure but delays RF output from 8 to 20 ms or more to allow time for 
relay closure.  This time delay becomes particularly important when one 
is driving a high powered amp (like 1.5 KW).  It heavier relay in them 
need at least 8 to as much as 20ms (even when hot shotted) to go from 
transmit to receive.  Hot switching is to be avoided at all costs. 
Some top of the line amplifiers do use PIN diodes too but they are not 
very tolerant of higher than 2:1 SWR's. In the heat of action it is easy 
to select the wrong antenna or put the amp in a >2:1 SWR situation. 
Their replacement costs are $100 and up and more than one are used.  Yes 
there are protection circuits which help preserve them most of the time. 
  It only takes one bad zap though.

BTW latency/aural feedback issues also affect the acoustic world. 
Performers in locations with echos need to wear an earpiece which 
carries non-echo band music to not get totally confused.  It is an 
interesting phenomena to see a performer go totally flaky because of echos.

Brian

On 7/27/2013 05:05, Didier Juges wrote:
> Most CW operators use "keyers" to generate the dits and dahs precisely. The keyer can be controlled directly by the computer or be a software Meyer or be controlled by an iambic key connected to the computer. A few operators still use straight keys like the J38 or a 'bug' like the Vibroplex. The key is the input method, or the keyboard.
>
> Some software, like the N1MM contest logging software have an embedded software keyer and also support a separate external keyer.
>
> Didier KO4BB
>
> Bob Camp <lists at rtty.us> wrote:
>> Hi
>>
>> ….. but why route the key *through* the computer if you are generating
>> the side tone off of RF…
>>
>> Bob
>>
>> On Jul 26, 2013, at 6:16 PM, Brian Alsop <alsopb at nc.rr.com> wrote:
>>
>>> Actually computers generate probably 98% of the code during so called
>> radio contests.  During a contest weekend it is not at all unusual for
>> individuals to make thousands of contacts.  Computers automate the
>> drudgery of sending your call thousands of times and most exchanges.
>>>
>>> However even during these contests, the manual key has to sometimes
>> be used to provide corrections or handle situations not covered by
>> "canned" messages.
>>>
>>> Because of the tremendous adjacent and even on frequency
>> interference, computers have proved incapable of decoding code with the
>> accuracy and speed of a human in real time.
>>>
>>> Brian
>>>
>>> On 7/26/2013 22:04, Bob Camp wrote:
>>>> Hi
>>>>
>>>> There's also the time honored approach of generating the side tone
>> off of the generated RF. In that case the latency to the transmitter
>> would matter quite a bit. I have no idea *why* you would run the key
>> through a computer in that case ….
>>>>
>>>> Bob
>>>>
>>>> On Jul 26, 2013, at 4:52 PM, Jim Lux <jimlux at earthlink.net> wrote:
>>>>
>>>>> On 7/26/13 12:50 PM, Didier Juges wrote:
>>>>>> There is a difference between managing the latency (as in ensuring
>> that sound and video are synchronized, but latency itself is
>> acceptable) and minimizing the latency as in a Morse code keyer where
>> the operator has to manually control the generation of elements that
>> can be as narrow as 20mS (one dit at 60 words per minute) while getting
>> timely aural feedback. That means you need the sound to start and stop
>> within less than about 5 mS following the key closing and opening.
>>>>>>
>>>>>> It is trivial to do on a microcontroller running at 1MHz but
>> surprisingly harder to do on a 2GHz Windows machine.
>>>>>>
>>>>>> It is not just a matter of time stamping the key closure, you have
>> to get the sound system starting and stopping.
>>>>>>
>>>>>
>>>>> Yep. although, since the propagation path is on the order of 100
>> milliseconds, providing feedback to the user directly from the
>> interface works quite well (e.g. generating tones directly from the
>> keying).
>>>>>
>>>>> The challenge is trying generate the sidetone through Windows.
>> But really, there's no reason why you can't have a "keying box" that
>> provides the direct side tone and sends the events to the host
>> computer.  Then the issue is more about keeping constant latency (or
>> else the CW will be really, really hard to copy)
>>>>>
>>>>> It's not like an extra 10 milliseconds of delay between keying and
>> the emitted RF waveform makes any difference at the other end.
>>>>>
>>>>>
>>>>> _______________________________________________
>>>>> time-nuts mailing list -- time-nuts at febo.com
>>>>> To unsubscribe, go to
>> https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
>>>>> and follow the instructions there.
>>>>
>>>> _______________________________________________
>>>> time-nuts mailing list -- time-nuts at febo.com
>>>> To unsubscribe, go to
>> https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
>>>> and follow the instructions there.
>>>>
>>>>
>>>> -----
>>>> No virus found in this message.
>>>> Checked by AVG - www.avg.com
>>>> Version: 2012.0.2242 / Virus Database: 3209/6023 - Release Date:
>> 07/26/13
>>>>
>>>>
>>>>
>>>
>>>
>>>
>>>
>>> -----
>>> No virus found in this message.
>>> Checked by AVG - www.avg.com
>>> Version: 2012.0.2242 / Virus Database: 3209/6023 - Release Date:
>> 07/26/13
>>>
>>>
>>> _______________________________________________
>>> time-nuts mailing list -- time-nuts at febo.com
>>> To unsubscribe, go to
>> https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
>>> and follow the instructions there.
>>
>> _______________________________________________
>> time-nuts mailing list -- time-nuts at febo.com
>> To unsubscribe, go to
>> https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
>> and follow the instructions there.
>




-----
No virus found in this message.
Checked by AVG - www.avg.com
Version: 2012.0.2242 / Virus Database: 3209/6025 - Release Date: 07/27/13





More information about the Time-nuts_lists.febo.com mailing list