Re: LF: JT9-10 vs JT9-5 test ends with smoke :)

[N1BUG <paul@n1bug.com>]

Hi Stefan,

Thanks for the ideas. Yes, it makes sense to monitor the system for
changes and shut down if any are detected. I guess you want no
antenna on that RX, or at least very small antenna. :-) I will add
this to my list of things to study.

Imagine what could have happened if this failure occurred at a time
when I was not checking every few minutes. Hmm...

73,
Paul



On 1/15/19 5:14 PM, DK7FC wrote:
> Hi Paul,
> 
> For VLF i use a protection circuit that monitors the antenna current. If 
> it suddenly or slowly drops, the transmission is interrupted. This help 
> to prevent smoking coils. In principle you just need an RX that converts 
> to audio and ten feed this into SpecLab. There you directly calibrate 
> the level into Ampere and produce a nice antenna current plot. You will 
> see which drift and changes are normal and then you can decide at which 
> level you interprete it as a fault. My circuit needs just 1 second to 
> stop transmitting after the level has been crossed.
> Maybe worth to consider?
> 
> 73, Stefan
> 
> PS: Another technique may be without software: Measure the current of 
> the PA (DC, input) and the antenna current. Then, compare these two 
> voltages. If a certain ratio is lost, then stop TXing. There you don't 
> even need a receiver and complex measurements.
> 
> Am 15.01.2019 22:56, schrieb N1BUG:
>> Eventually I will rebuild it perfect... although I would prefer to
>> start over with a new coil as this one requires too much
>> maintenance. Right now I don't have the luxury of time for any of
>> that. It's solar minimum and I need this thing working. :)
>>
>> I don't trust the inner coil form for HV now, too much carbon:
>>
>> http://www.n1bug.com/vario-fail-2-1200.jpg
>>
>> So that'll have to get replaced. I will make the connections
>> differently this time!
>>
>> 73,
>> Paul
>>
>>
>>
>> On 1/15/19 10:42 AM, Chris Wilson wrote:
>>    
>>>
>>> Hello N1BUG,
>>>
>>> I  too  have had issues with bolted connections to the variometer. Not
>>> an  expensive  fix  so  long as you don't mind a few battle scars, but
>>> knowing  you,  you  probably  want it cosmetically perfect again ;) LF
>>> without smoke is QRP...
>>>
>>> Tuesday, January 15, 2019, 2:50:18 PM, you wrote:
>>>
>>>      
>>>> Thanks to all who monitored and provided reports on this latest test
>>>> of slow JT9 modes.
>>>>        
>>>      
>>>> The test ended suddenly around dawn this morning. Here is the reason:
>>>>        
>>>      
>>>> http://www.n1bug.com/vario-fail-1-1200.jpg
>>>>        
>>>      
>>>> It's the inner coil from the 2200m loading coil / variometer:
>>>>        
>>>      
>>>> http://www.n1bug.com/vario-fail-0-1200.jpg
>>>>        
>>>      
>>>> I had hoped to be on looking for QSOs tonight, but obviously that is
>>>> not going to be possible. I do not know when I will be QRV again.
>>>>        
>>>      
>>>> I have a very busy day today, so the final report on the JT9 test
>>>> might not be ready until tomorrow.
>>>>        
>>>      
>>>> 73,
>>>> Paul N1BUG