Message-ID: <5C3E5B42.6010604@posteo.de>
Date: Tue, 15 Jan 2019 23:14:26 +0100
From: DK7FC <selberdenken@posteo.de>
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To: rsgb_lf_group@blacksheep.org
References: <b3cd7690-f503-354d-b8e3-923eb3c6a97d@n1bug.com> <176712857.20190115154229@gmail.com> <f534bd00-09fc-5f79-48a9-051d555cc398@n1bug.com>
In-Reply-To: <f534bd00-09fc-5f79-48a9-051d555cc398@n1bug.com>
Subject: Re: LF: JT9-10 vs JT9-5 test ends with smoke :)
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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
>>>        
>