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" <[email protected]>
To: <[email protected]>
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: [email protected]
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
----------------------------------------------------------------------
--------
[email protected]
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 [email protected]:
> 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:
[email protected] ; [email protected] >
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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