Jim, You're right in principle, of course. The problem is that a
well-designed amplifier relay circuit shouldn't depend on what
transceiver is used. The amplifier itself should be immune to
hot-switching in all situations.
Here's an extreme example. The Flex 6000 series transceivers have a
menu-set delay time adjustable from 0 -1000 mSec, which is the time RF
appears after the amp relay keying line is closed. The default setting
for this delay is zero mSec, which means RF arrives at the amplifier at
the exact same time the amp relay line is closed. A well-designed amp
QSK circuit should ignore that RF and not key up the amplifier at all,
until the Flex delay is adjusted to be long enough for the amp relays to
accommodate it.
Similarly, if a key is closed, for example to allow tuning of the
amplifier, and then the relay keying cable is accidentally pulled loose,
then a proper QSK circuit will keep the amplifier on-line until the RF
disappears, even though the relay cable is disconnected. Keeping the
amplifier on-line so long as RF is present is a key requirement of a
good QSK circuit
Furthermore, for high speed QSK CW operation, the amp has to be fast
enough to transition from receive to transmit and back in a few mSec,
all the time sequencing the relays properly to avoid hot switching.
Doing that involves some circuit complexity that can't be avoided. So,
yes, in principle all that's needed is to keep RF out of the amplifier
until the amp is on-line and ready to receive it, and to hold the amp
on-line until after the RF disappears. It's implementing that
requirement for all possible situations that's the challenge. What on
the surface seems simple, in practice actually involves a bit of circuit
complexity in the QSK design.
73,
Jim W8ZR
On 12/9/2018 7:08 AM, Bob Maser wrote:
I agree with everything you said. The problem with some radios is
they start sending'
RF down the line at the same time they are giving the relays the
energize signal. I have built
some big amplifiers in my day (don't forget the saying that in
California too much power is just
enough) and I always made sure that the output relay was quicker than
the input/bias relay
in fact I usually used open frame P&B for them and RJ2B on the
output. RJ1's just don't
instill confidence HI.
Bob
On Sat, Dec 8, 2018 at 11:49 PM Jim <jimw7ry@gmail.com
<mailto:jimw7ry@gmail.com>> wrote:
Its actually very simple Jim.
Don't send RF until the amplifier is ready. Not doing so, makes the
relays hot switch. It matters not which one is energized before RF is
sent. As long as they both are before RF is sent from the exciter.
Same
on dekey. RF MUST stop flowing from the exciter BEFORE the relays
(either one of them) DE-energize.
Thanks
73
Jim W7RY
On 12/8/2018 11:37 AM, MU 4CX250B wrote:
> Bob,
> 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.
> 73,
> Jim w8zr
>
> from my iPhone
>
>> On Dec 7, 2018, at 8:16 PM, Bob Maser <bob.maser@gmail.com
<mailto:bob.maser@gmail.com>> 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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