Message-ID: <3D9A092BFA65418DBEE13188A4C58580@gnat>
From: "Alan Melia" <alan.melia@btinternet.com>
To: <rsgb_lf_group@blacksheep.org>
References: <0883B95D3F4D417F975C59A900E1A838@gnat> <alpine.DEB.2.11.1708042259310.734@mailn.lipkowski.org>
Date: Fri, 4 Aug 2017 23:28:47 +0100
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Subject: Re: LF: RE:G4HUP aerial current meter
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Status: RO

Hi Jacek, Yes I have been collecting thermocouple meters for about 60 years. 
The problem with them is they are very fragile. In the UK it is generally 
the case that any  meter offered is usually of 1940s vintage and invariably 
the thermal link is fused. I even played with repairing them but not really 
knowing what the couple was I was not successful. I keep the working ones 
for occasional calibration checks. I even saw no reason why you should not 
be able to shunt them ......but that didnt work too well....probably because 
of the difference between the DC and RF resistances.

The ferrite transformer circuit is very rugged and I have used it over the 
years since toroids became easily available. I remember an RSGB Convention 
about 2002 when Geri brought some 3A meters thermocouple meters (I dont 
remember the origin) over and sold the lot. They may have been from a 
similar source.

It is a bit like the HP and Marconi wattmeters, the thin-film sensors are 
very fragile, and very expensive to repair but you can easily make a unit 
with modern ICs that is almost as good and nowhere near so traumatic it you 
overload it :-))

Best Wishes
Alan
G3NYK


----- Original Message ----- 
From: "Jacek Lipkowski" <sq5bpf@lipkowski.org>
To: <rsgb_lf_group@blacksheep.org>
Sent: Friday, August 04, 2017 10:53 PM
Subject: Re: LF: RE:G4HUP aerial current meter


> On Fri, 4 Aug 2017, Alan Melia wrote:
>
>> It has just occured to me that the 1A range may not be high enough for 
>> some of the LF QRO merchants.
>
> for qro you can buy cheap ex-warsaw pact "antenna equivalent". these are 
> boxes which have an rf thermocouple ammeter (3A or 10A), and RC in series 
> (usually 10ohm and 68pF, which simulates a 4m rod antenna). these were 
> used for silent tuning of transmitters.
>
> description here:
>
> https://klubnl.pl/wpr/en/index.php/2017/08/04/ekwiwalent-anteny-4m/
>
> they do appear from time to time, i got mine for 50zl (abt 12 euro)
>
> VY 73
>
> Jacek / SQ5BPF
>
>