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LF: Re: Elad FDM-DUO on LF

To: rsgb_lf_group <[email protected]>, "[email protected]" <[email protected]>
Subject: LF: Re: Elad FDM-DUO on LF
From: Andy Talbot <[email protected]>
Date: Wed, 21 Nov 2018 16:42:45 +0000
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I got an answer from the design team at Elad, including a circuit of the receiver front end, and it looks safe enough.

On receiver a PE4283 solid state relay places a short circuit across the transformer feeding the A/D chip.   There is also a BAR66 clamp diode at this point, clamping to ~ 1.2V pk-pk max.  The BAR66 is a  high peak current surge protection device with maximum 1.8 ohm forward resistance at 100MHz, 5mA

If using the Rx-2 ant input, there is an additional BAR66 on this.

I'd still be happier seeing circuitry that specifically opens the Rx path to the A/D when on transmit, but those clamps and the switched short look good enough. (And the fact teh BAR device is rated to 100MHz suggests its OK for protection at high VHF back-leakage too).

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