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Re: [Amps] Input relay for QSK amp

To: Bob Maser <>
Subject: Re: [Amps] Input relay for QSK amp
From: MU 4CX250B <>
Date: Sat, 8 Dec 2018 18:37:57 +0100
List-post: <>
Years ago, I bought a lifetime supply of RJ1As for my own projects,
and have tested roughly two dozen on my homebrew relay tester. The
RJ1As typically close in about 2msec, with the fastest closing I
measured at 1.2msec. Their opening time is typically about 500uSecs.
None of them show any contact bounce. Other vacuum relays, e.g., RF1D,
RJ1. GC1, etc., are more like you remember.

Here's a link to a 2015 QSK article I wrote for QST,
that goes into detail on amp relay timing issues, including the
crucial need to avoid hot-switching. Doing so is more complicated than
merely choosing a slow input relay, or slowing down the input relay
transistor driver with an RC circuit. Many purported "QSK" designs
ignore these other considerations.
Jim w8zr

 from my iPhone

> On Dec 7, 2018, at 8:16 PM, Bob Maser <> wrote:
> I must be old school.  The input relays need to be slower than the output
> relay.
> Seems to me that a RJ-1 takes 8ms to close and stop bouncing around. I have
> always
> used a P&B miniature open frame DPDT for that purpose.  The output of the
> amp needs
> to be closed before the input turns on.
> Bob
>> On Fri, Dec 7, 2018 at 9:39 PM Jim <> wrote:
>> Those relays that Rich (and I ) used are mostly unavailable. I used to
>> buy them 100s at a time. No more of them can be had.
>> Most of what you find on eBay are seconds and most don't work. Or they
>> are re-labeled counterfeits.
>> Thanks
>> 73
>> Jim W7RY
>>> On 12/4/2018 4:03 PM, Alek Petkovic wrote:
>>> G'day Vic.
>>> The Matsushita/Panasonic relay that Rich Measures used in his QSK
>>> circuit, published at, is still available on Ebay. I bought
>>> 10 of them a couple of years ago
>>> Otherwise, Jim, W7RY, uses a small relay in his QSK kit. He laso deals
>>> on Ebay.
>>> 73, Alek.
>>> VK6APK
>>>> On 4/12/2018 6:21 PM, Victor Rosenthal 4X6GP wrote:
>>>> I'm trying to choose a relay to use as the input relay in a QSK amp.
>>>> I have been very satisfied with the Jennings RJ1-A as an output
>>>> relay. The input relay in this circuit needs to be DPDT, or I'd just
>>>> use two similar vacuum relays.
>>>> Here are my needs:
>>>> 1. DPDT.
>>>> 2. 12 or 24v coil.
>>>> 3. Operate/release time, including bounce <= 4 ms. Faster is better.
>>>> 4. Should carry 100w RF in 50 ohm system. Not expected to make/break
>>>> live circuit.
>>>> 5. Must have low resistance for low-level signals (receive path).
>>>> 6. Must have long life >= (10 x 10**6 operations)
>>>> 7. Must not be insanely expensive, and available from Mouser or RS.
>>>> I found this relay:
>>>> <
>>>> But maybe there's a better choice? I'm overwhelmed by the number and
>>>> varieties of relays in the catalog.
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