| Author |
Message |
    
James L. Stuart
| | Posted on Sunday, March 17, 2002 - 10:36 am: | 
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I have two older linears but they do not have a SSB Delay option. Will they still operate on SSB or do I need one with the delay. Whats the delay do for a person? |
ChillyDog
| | Posted on Sunday, March 17, 2002 - 1:58 pm: |
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James,
SSB delay is used on amplifiers with a RF triggered transmit/receive relay to allow the amp to stay in the transmit mode between spoken syllables during SSB transmission.
With an AM signal the radio carrier provides signal to switch the amp to, and keep the amp in, transmit. Since SSB has no carrier, without SSB delay the amp would "chatter", in other words, switch between transmit and receive when talking on SSB. SSB delay holds the transmit relay on long enough to stay in transmit mode.
It's not too difficult to modify most amps to increase the relay hold time; usually it's just a matter of increasing the value of a capacitor. With only a little more effort a switch can be added to allow the original delay for AM while providing the longer delay for SSB.
Here's the real issue; what is the amp biasing? If it is an AM only amp it may be biased at class C, which is not acceptable for SSB. (Actually, it's not acceptable for AM, either, but that's another issue!) You can add a SSB delay to an amp, but without the correct biasing it's not ready for SSB use.
Bob |
bruce
| | Posted on Sunday, March 17, 2002 - 3:37 pm: |
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no you don't to get delay increase the time delay in the tr relay |
bruce
| | Posted on Sunday, March 17, 2002 - 8:16 pm: |
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class c is only good for FM or CW .... my kinda amp |
Taz
| | Posted on Sunday, March 17, 2002 - 9:16 pm: |
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I like to use ab1 class for am |
bruce
| | Posted on Sunday, March 17, 2002 - 10:44 pm: |
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good choice taz less output but cleaner there are a lot of shadie amps out there not only cb ones |
Taz
| | Posted on Sunday, March 17, 2002 - 11:44 pm: |
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weathe its less output i dont care they run excellent and if there is less output just buy a bigger amp to make up for it! |
409
| | Posted on Monday, March 18, 2002 - 1:57 am: |
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James, the delay in linear amps are due to the relay driver having a electrolytic cap. switched into the circuit causing a slower decay rate for the driver. Some tube linears hold the voltage on the driver tube grid or cathode, depending on how it's biased,and solid state ones just keep the transistor from switching off too soon by holding the voltage on the base. It all depends on how you want to do it. |
ChillyDog
| | Posted on Monday, March 18, 2002 - 9:03 am: |
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Taz
You're right. You'll get better overall performance with AB on AM. When properly driven, AB results in less spurious in-band products (less splatter) and better harmonic performance. A little less efficency but the 5% or 10% increase in current is well worth the improved performance!
Bob |
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