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565michookup [2021/07/16 21:41] pa1ap |
565michookup [2021/07/17 12:30] pa1ap |
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| John / N0KHQ | John / N0KHQ | ||
| - | -- July 16 2021 -- | ||
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| - | In case RF feedback keeps poking around despite the correct cabling as described above you might need to focus on RF proximity and how to route that somewhere else. | ||
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| - | But first how to diagnose if RF feedback is occuring. | ||
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| - | 1. Turn down power to 5 watts | ||
| - | 2. Turn down hw mic gain to 0 | ||
| - | 3. Turn down mic gain while transmitting and talking until the ALC led stopped following your voice. | ||
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| - | At the point the ALC led stopped following your voice you know you need to set the mic gain higher in order to activat the ALC. Turn up the mic gain a little to activate the ALC led at your voice. | ||
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| - | The ALC led is very fast and will blink at each peak while talking. | ||
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| - | Once you found the correct mic gain level you should not need to change the mic level anymore. Running low or high power should not need a change in mic gain. Period. | ||
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| - | Here is the symptom which occurs when you have RF feedback; the moment you increase RF power and you notice the ALC led does not follow your voice like it did at low power your likely having RF feedback. | ||
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| - | The confusing part is that due to the sdr process and the associated delay between your speech and the actually tx signal you won't notice it right away. Often the start of the transmission is good and than in a few seconds it starts becoming more difficult to activate the ALC led. Turning up the mic gain might feel like the solution but be aware your not amplifying your voice but most likely RF feedback. The result is less optimal voice quality. | ||
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| - | Two reasons for the misunderstanding; | ||
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| - | 1- the ALC led is connected to the forward voltage and follows the actual tx signal. | ||
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| - | 2- your voice is being processed by the DSP and hence there is a delay. | ||
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| - | You cannot compare your actual voice peaks with the tx signal. There are not in sync. | ||
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| - | When you run low power and the ALC led is blinking at the correct pace with your voice all is well. When you increase your output power and the ALC led is slowly declining it's blinking rate it's not good. | ||
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| - | Anothe way to test RF feedback is to set the mic gain as suggested above and in addition enable speech processor at 9. Yes that's the highest level. When RF feedback is lurking around you won't need much audio to get the speech processor going nuts on RF feedback. In my case I could not run speech processor at level higher than 3 without spontaneous max output without speaking. | ||
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| - | I recommend testing your setup using the simple steps as described above. | ||
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| - | For me the remedy was the following; | ||
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| - | I am using an inverted V which is about 5 meters above my shack. I have opted for a 450 ohm balanced feedline connected to a true balanced tuner right on top of the Orion. | ||
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| - | Here is what happens. The inverted V is not balanced despite same length for each leg. It's suboptimal dues to it's surrounding. This means the | ||
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| - | Regards Onno pa1ap | ||
