Message-ID: <15df1862402.marcocadeddu@tin.it>
Date: Thu, 17 Aug 2017 20:48:06 +0200 (CEST)
From: "marcocadeddu@tin.it" <marcocadeddu@tin.it>
To:  <rsgb_lf_group@blacksheep.org>
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Subject: R: LF: Re: G4HUP aerial current meter
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Hello Thomas,

thank for the link to a nice web page!
Wish to add just a reference to datas reported: it is advisable for a 
proper work of the current transformer that the secundary winding has 
an inductive reactance 6 - 10 times the loading resistance.Just to give 
some figures.. in my case the current transformer has a 1:50 ratio (so 
in the secundary flows a current 1/50 of the antenna current) and it is 
terminated on a 50 ohm resistance.
I used an FT50-43 and 50 turns has an inductance in excess of 1mH that 
at 137 kHz means more than 800 ohm of reactance. In these conditions my 
RF ammeter which is rated for 4A fsd had, up to now, no problem ;-)
The current flowing in the load resistor is 80mA for an RF current of 
4A, and across this resistance will be developed 5V. I use an old 
fashionated OA95 to rectify this.

73, Marco IK1HSS

----Messaggio originale----
Da: Thomas.Rosenkranz.1@gmx.de
Data: 17-ago-2017 11.49
A: <rsgb_lf_group@blacksheep.org>
Ogg: LF: Re: G4HUP aerial current meter

http://dl0rcp.bplaced.de/index.php/themen-raw/mf-lf-equipment-dl3arm-en

73! Thomas

-----Ursprüngliche Nachricht----- 
From: Alan Melia
Sent: Wednesday, August 16, 2017 2:32 PM
To: rsgb_lf_group@blacksheep.org
Subject: Re: LF: RE:G4HUP aerial current meter

Thanks Mike that is very useful after Hugh flagged up the diode 
voltage
problem. It has the added advantage of not being as ragile as a nice
thermocouple meter. You can thus save those for more controll 
conditions of
use in calibration. I imaging the linearity is probably due to the high
voltages induced. I suspect it is not quite so good at 100mA. BUT then 
the
lowest FSD thermocouple meter  have is 350mA FSD.

Thanks to the Group the stock of kits has shrunk quite nicely. I do 
have one
or two more that are not spoken for. :-))

Thanks and Best Wishes
Alan
G3NYK

----- Original Message ----- 
From: "Mike Dennison" <mike.dennison@ntlworld.com>
To: <rsgb_lf_group@blacksheep.org>
Sent: Wednesday, August 16, 2017 12:22 PM
Subject: Re: LF: RE:G4HUP aerial current meter


>I made several modifications to get 5A FSD on my meter. Firstly, I
> used all of the supplied wire to make 17t on the toroid instead of
> the recommended 10t. I changed the input resistors which were getting
> hot with 3A RF. I also added a fixed resistor in series with the
> meter. This of course changed the old 100mA range to something like
> 2A, but it could easily be retained with some slightly more complex
> mods.
>
> I calibrated the HUP meter with a Russian WW2 thermocouple ammeter,
> and found its linearity to be good. A very nice piece of kit.
>
> Mike, G3XDV
> ===========
>
>> Hi Hugh thanks for that.......I dont have a power source at the
>> moment.Yes they would probably just survive 2A but certainly not
>> 10.The solution then is to increase the number of turns on the
>> ferrite. Though I think reducing the load (two 100R in parallel
>> currently :-))  ) would work too. say 2 x 10R ??The original
>> components were designed to get the 100mA range I think. That needs
>> checking against Ian GM3SEK's web site.
>>
>> Alan
>>
>>   ----- Original Message ----- 
>>   From: dhchurch@lineone.net
>>   To: rsgb_lf_group
>>   Sent: Tuesday, August 15, 2017 5:52 PM
>>   Subject: Re: Re: LF: RE:G4HUP aerial current meter
>>
>>
>>   Having just put this meter into use, I must point out that the dc
>>   output from the BAT42 diodes is about 15V for the 1A range so I
>>   would have thought actually potting this down after rectification
>>   with 10A would promptly see off the diodes which, I think, are 
rated
>>   at 30piV.
>>
>>
>>   Hugh, M0DSZ
>>
>> 
----------------------------------------------------------------------
>> --------
>>
>>   dhchurch@lineone.net
>>
>>     From: DK7FC
>>     Date: 2017-08-05 10:46
>>     To: rsgb_lf_group
>>     Subject: Re: LF: RE:G4HUP aerial current meter
>>     Hi Ian,
>>
>>     When the range of a current tranformer should be increased from 
1A
>>     to 10A, the best way is to increase the number of turns of the
>>     secondary winding by a factor 10. This transforms the current 
down
>>     by a factor 10 (not up) in the secondary winding... I*N has the
>>     same value on both sides (ideally/theoretically).
>>
>>     73, Stefan
>>
>>     Am 05.08.2017 11:35, schrieb i.frith@ntlworld.com:
>>     > Hello Allan
>>     >
>>     > I assume the 10A mod is a matter of increasing the series R 
with
>>     the > meter to around 800k? > > I suppose a 3way switch and 
extra
>>     trim pot could be added to preserve > the 1A range too. > > 
Thanks
>>     for the note re-shipping Monday. > > Look forward to getting the
>>     Kit. > > 73 > > Ian G4GIR > > -----Original Message----- From:
>>     Alan Melia > Sent: Friday, August 4, 2017 9:36 PM > To:
>>     rsgb_lf_group@yahoogroups.co.uk ; rsgb_lf_group@blacksheep.org >
>>     Subject: LF: RE:G4HUP aerial current meter > > It has just 
occured
>>     to me that the 1A range may not be high enough for > some > of 
the
>>     LF QRO merchants. There is a simple mod which will extend the >
>>     range > up to 10A though you should be aware the ferrite core 
has
>>     not been > tested at > this level of RF. These cores are used on
>>     mains leads carrying up to > 13A so > I think they will be OK. > 
>
>>     Thank you to those showing interest, there are a few kits still 
>
>>     available. > > Alan > G3NYK > >
>>
>>
>> ---
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>> http://www.avg.com>>
>
>
>