False logic? I don't believe it is good design practice to ever allow
an on-line high power amplifier to look into an open circuit, even if
no drive is present. To do so is to invite instability. The output
relay should be sequenced to close (allowing for contact bounce)
before the amp is biased on-line. This means the on-line amplifier
always sees a proper load.
Both of these actions should take place before the input relay is
closed - not for situations when the exciter output is properly
delayed, but for those occasional situations when it is not and RF
arrives at the amp input too soon. Good design practice means
protecting the amplifier circuitry for abnormal situations as well as
normal ones.
73,
Jim w8zr
Sent from my iPhone
> On Dec 8, 2018, at 9:42 PM, Jim <jimw7ry@gmail.com> wrote:
>
> Not necessarily!
>
> Really there no need for a faster input relay or a faster output relay. That
> is all false logic.
>
> I matters NOT which relay closes or opens first... AS LONG AS the RF is not
> sent from the radio BEFORE the relays are closed and ready to take RF.
>
> AND the RF STOPS flowing before the relay DE-energise. That's ALL that is
> needed.
>
> 73
>
> Jim W7RY
>
>
>
>> On 12/7/2018 9:16 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 <jimw7ry@gmail.com
>> <mailto:jimw7ry@gmail.com>> 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 somis.org <http://somis.org>, 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:
>> >>
>> <https://www.mouser.co.il/datasheet/2/418/NG_SS_108-98005_L-1019204.pdf>
>> >> But maybe there's a better choice? I'm overwhelmed by the
>> number and
>> >> varieties of relays in the catalog.
>> >
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>>
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