[Amps] Best source for Gigavac GH-1 ?

[Jim W7RY]

I know all of this Paul. I was asking Jim, W8ZR  what his compelling 
reason was for relay sequencing was.

Thanks
73
Jim W7RY



On 11/11/2013 4:12 AM, Paul Christensen wrote:
>> Can you tell me why sequencing is a requirement? I have found that 
>> the RF never flows (6 ms after the tranciever control circuts 
>> energise)until way after the relays and cathode bias has switched 
>> which as you have pointed out is  3-4 ms.
>
> Sequencing is mostly a non-issue when using recently manufactured 
> transceivers.  Almost all of them will delay RF by at least 8 ms. 
> after the transceiver's PTT line goes low.  They will also allow 
> enough time for RF to decay before reversing the sequence.  Apart from 
> any changes in delay by mode, the time from PTT activation to RF 
> shouldn't change.  As both of you point out, there's generally ample 
> time for bias de/activation and for the waveform to ramp up/down in CW 
> mode.
>
> I think sequencing is more of an important issue with some older 
> transceivers - like a KWM-380 I once owned, or where classic separates 
> are used into an amp.  In addition to sequencing, I think it's a good 
> idea to include RF sensing at the amplifier input.  In the presence of 
> any input RF, the amplifier's T/R should be inhibited from R=>T or 
> back from T=>R until the RF envelope decays to near zero.  Even 
> without sequencing, that one feature alone will prevent relay 
> hot-switching accidents.
>
> Consider a case where a multi-transceiver station controller is used 
> and a transmitter is keyed at 100W while maybe adjusting a tuner.  
> Then, you accidentally go to the transceiver controller while the rig 
> is still in transmit and select the hot transceiver into the amp and 
> the amp immediately keys with RF.  Since the transceiver is already 
> generating RF and the rig's key line is low, the amp will hot-switch 
> when the PTT line is quickly routed to the amp from the controller 
> accessory.  RF input sensing at the amp would prevent this accidental 
> form of hot-switching and save the amp's relays.
>
> Paul, W9AC
>
>
>
>
>
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