Topband: Detuning Relay Flyback Diode

Brad Denison brad.denison at
Sat Dec 23 12:24:02 EST 2017


Yes the end intent is to have the K3 key both an amp and the detuning
circuit.  Would you happen to have an example of the series diode circuit
you are referring to?  Seems better to implement this vs. creating relay


Brad W1NT <>

On Sat, Dec 23, 2017 at 11:05 AM, Tim Shoppa <tshoppa at> wrote:

> Whether a flyback diode is needed depends on what is driving the relay and
> whether it needs snubbing.
> Adding a flyback diode substantially lengthens the time it takes a relay
> to open, which may or may not be an issue. What was a 6ms relay will become
> several times longer on open. There are better snubbing networks to use if
> you are time sensitive.
> If the radio is keying both the detuning relay and an amp, you want to use
> some series diodes to prevent sneak paths between amp key voltage and your
> detuning relay voltage. These isolation diodes do not add any delays.
> Tim N3QE
> On Sat, Dec 23, 2017 at 10:51 AM, Brad Denison <brad.denison at>
> wrote:
>> I have a couple of 6ms 12V Kilovac relays wired up as a detuning circuit
>> during RX.  One question comes up before implementation regarding flyback
>> diodes - would they be needed?  Seeking opinions on this question.  The
>> relays are powered during TX and not powered for RX direct keyed by the
>> radio with no sequencer.
>> Thanks,
>> Brad W1NT <>
>> _________________
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