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From: Lawrence Galea <9h9mhrlaw@gmail.com>
Date: Sat, 30 Jul 2016 18:24:15 +0200
Message-ID: <CAFDVXLm5jjZ+Y_9URVV=ZBMZ8LonbBv56nRAvZ=kQQ5yGWVzOg@mail.gmail.com>
To: rsgb_lf_group@blacksheep.org
Subject: Re: LF: AW: My active whip antenna has gone noisy and insensitive
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Status: O

Did you consider whether you or anyone in your neighbourhood have
installed any PV panels recently?
Regards
Lawrence

On 7/30/16, Hans Joachim Brandt <hajo.brandt.dj1zb@t-online.de> wrote:
> Dear Chris,
>
> I am using an active antenna using an operational amplifier OP27; the
> circuit had been published in the german CQ-DL May 2007. This circuit is
> employing two protection diodes 1N4148 at the positive gate input (both
> cathodes in direction to the plus voltage). Additionally a series resistor
> of 47 ohms maximum has been used between the active antenna area and the IC
> positive input and another resistor of 12 kOhm between the positive input
> and a blocking capacitor (at this capacitor the DC voltage is half the
> total
> supply of 12 volts. The negative input of this IC is connected to the IC
> output by an 1kOhms resistor. Until today I have never encountered any
> damage of the IC or its input gate. I guess such a gate protection should
> be
> included into every active antenna circuit. Another advantage of using such
> an operating amplifier is a supply current of just 10 mA! Sorry to say that
> for the moment, due to a change of the computer, I do not have a circuit
> copy available for this active antenna.
>
> HW?
>
> 73 Ha-Jo, DJ1ZB
>
>
> -----Ursprüngliche Nachricht-----
> Von: owner-rsgb_lf_group@blacksheep.org
> [mailto:owner-rsgb_lf_group@blacksheep.org] Im Auftrag von Chris Wilson
> Gesendet: Samstag, 30. Juli 2016 15:13
> An: rsgb_lf_group@blacksheep.org
> Betreff: LF: My active whip antenna has gone noisy and insensitive
>
> 30 July 2016
>
>
> I have a a clone PA0RDT active mini whip antenna atop a wind up mast that
> used to work well, but has recently become insensitive and very noisy. I
> will pull it down later and first check the co ax. If I remove its in shack
> power source the noise stops though, and I have tried it on a battery in
> case the PSU had gone noisy, but no difference in noise on battery power is
> seen. The circuit is at http://dl1dbc.net/SAQ/Mwhip/pa0rdt-Mini-Whip.pdf
> Can
> anyone say if the front end FET may have gone faulty, or what to check
> please? Thanks!
>
>
>
> --
>
>
> Best regards,
>  Chris  2E0ILY                           mailto:chris@chriswilson.tv
>
>  My        part        time        LF        grabber       is       at
>  http://www.chriswilson.tv/grabber.html
>
>
>
>