[Elecraft] KPA500 strange behavior

[Bob McGraw K4TAX]

How are you handling the PTT?   Direct from the KPA-500 to the TS-2000 
via the PA Key on the amp or by the KPA-500 Aux connector pin #10.   
Check cables as one of those commands is being dropped.

Add a ferrite choke on the PTT line if using the PA Key command 
method.    Or, reduce drive power to 5 to 10 watts and see if it 
occurred.  If it doesn't occur at 5 to 10 watts of drive, you can bet it 
is and RFI issue and the ferrite choke may correct it.

73

Bob, K4TAX



On 7/20/2018 8:58 AM, W1IE wrote:
> Good morning,
>
> I have an interesting problem in which I hope the group here has an easy
> solution.
>
> My KPA 500 is hooked to a TS-2000 outputting 20 watts to the KPA500 and
> displays the following abnormalities :
>
> 1. At frequencies between 4581 kc to 4601.6 (we are working on MARS
> frequencies) using USB and a waveform of M110A, the following
> characteristics are observed.
> 2.  The amplifier stops transmitting briefly (less than a blink of an eye)
> and then resumes during a M110A transmission at multiple random times.
> 3. Does not appear to happen when using voice, although some stations on the
> MARS net have mentioned that my transmissions sometimes do drop to very low
> levels.
> 4. This drop out does not occur:
> 	a.  On frequencies outside the range as listed in item #1.
> 	b. If the emission is any other type other than USB/LSB.
> 	c. When I turn off the amplifier and only transmitting using the
> TS2000 at 100watts.
> 5. Occasionally, but not every time when this event occurs I hear a relay
> inside the KPA500 click
> 6. I did the following tests in an attempt to located the problem.
> 	a. The conditions occurs whether I am attached to any one of the
> antennas I have here.
> 	b. It also occurs when a dummy load is attached.
> 	c. It still occurs when I switch out KAT500 antenna tuners (I have
> two of them).
>
>
>
>
> Initially, my thoughts were that the frequency range seems to lie some where
> in the boundary between 3.5 and 5.0 band
>
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