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 <[email protected]> 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: [email protected]
> [mailto:[email protected]] Im Auftrag von Chris Wilson
> Gesendet: Samstag, 30. Juli 2016 15:13
> An: [email protected]
> 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:[email protected]
>
> My part time LF grabber is at
> http://www.chriswilson.tv/grabber.html
>
>
>
>
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