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[AMPS] TS930s-SB220 Interface

To: <amps@contesting.com>
Subject: [AMPS] TS930s-SB220 Interface
From: measures@vc.net (Rich Measures)
Date: Tue, 2 Dec 97 02:30:58 -0800
>Rich,
>
>I am rapidly getting the feeling that I totally misunderstood what everybody
>meant by "hot switching". I thought it meant that the transceiver was seeing
>undesirable transients because it changed modes - ie receive to transmit -
>before the amp could switch and present the proper load on the transceiver.
>Now I'm getting the feeling that you are referring to opening and closing
>SB220 relay contacts while they are carrying current.
>
>Could you help clear up what you mean by hot switching?
>
Hotswitching usually means that the transceiver begins delivering RF 
before the amplifier relay contacts have closed and stopped bouncing.  
The way to tell if this is the case is to watch the SWR indicator in the 
transceiver.  If the SWR indication briefly spikes upward when the VOX 
trips, or the PTT button is pressed, hotswitching is indicated.  
A better test is to send CW dashes, watch the SWR indicator on the 
transceiver, and vary the speed.   

If RF is on the amplifier relay's contacts during contact-bouncing, rapid 
contact errosion takes place.  

Some modern radios begin producing RF in 5mS.  If the amplifier relay can 
not beat 5mS, it will get beat up.  The circuit shown in Figure 7B on my 
Web site will switch in 2mS or less.  [circuit also in "The Nearly 
Perfect Amplifier", 1-94 *QST*]  
-  -  (note: a Jennings RJ-1A vacuum relay will not switch fast enough to 
beat modern radios unless it is driven with a v-limited {100v - 160v} 
current source instead of a fixed voltage {usu. 26v}  source.) 
Rich...

R. L. Measures, 805-386-3734, AG6K   


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