KX3 Tech Question

[Jim Brown-10]

While setting up for a grid expedition next weekend, I fear that W6GJB
and I may have blown up the front end of my KX3 -- transmitted 1kW FT8
into a Yagi within 100 ft of the antenna connected to the KX3. Prior to
that, I had a screen full of JA decodes on 6M, but after, I had none.

Returning from FD, I put the KX3 into an old HP generator of unknown
calibration, and, for comparison, also fed the RX in of my K3. 50uv at
50.09 MHz gave S9 on the K3, but only S5 on the KX3 with the preamp off
and 5 dB over S9 with the preamp on.

I can clearly hear the preamp turning on and I could hear -143 dBm (the
lowest level to which I can set the generator).

So, the question is, is this "normal?"  Is it possible that a protection
diode has fried? This is major physical effort for the four guys
carrying a complete station up a 3 mile trail that gains 1,000 ft, so I
want to make certain that they're taking a good radio. :)

73, Jim K9YC

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[wayne burdick]

Jim,

S9 (or S9+5) is in the right ballpark with a 50 uV signal. This applies to the preamp-on case for all of our rigs.

Also, if you can hear a -143 dBm signal, you’re doing just fine :)  

I suspect there’s some other reason for the loss of decodes on 6 m. Make sure you weren’t in SPLIT, didn’t turn off the preamp, didn’t turn on the attenuator, and had RF GAIN set to -0 dB. Also set COR LVL to the default (0.1 W, or +20 dBm).

Note that the KX2 and KX3 both have high-signal protective features born and bred during close-quarters HF Pack operation. Depending on the offending signal levels, they will automatically turn off the preamp, turn on the attenuator, turn off an IF gain stage, or even open all of the LPFs. We’ve tested these features by injecting levels up to 10 W directly into the antenna jack.

73,
Wayne
N6KR

> On Jun 24, 2018, at 4:53 PM, Jim Brown <[hidden email]> wrote:
>
> While setting up for a grid expedition next weekend, I fear that W6GJB and I may have blown up the front end of my KX3 -- transmitted 1kW FT8 into a Yagi within 100 ft of the antenna connected to the KX3. Prior to that, I had a screen full of JA decodes on 6M, but after, I had none.
>
> Returning from FD, I put the KX3 into an old HP generator of unknown calibration, and, for comparison, also fed the RX in of my K3. 50uv at 50.09 MHz gave S9 on the K3, but only S5 on the KX3 with the preamp off and 5 dB over S9 with the preamp on.
>
> I can clearly hear the preamp turning on and I could hear -143 dBm (the lowest level to which I can set the generator).
>
> So, the question is, is this "normal?"  Is it possible that a protection diode has fried? This is major physical effort for the four guys carrying a complete station up a 3 mile trail that gains 1,000 ft, so I want to make certain that they're taking a good radio. :)
>
> 73, Jim K9YC
>
> ______________________________________________________________
> Elecraft mailing list
> Home: http://mailman.qth.net/mailman/listinfo/elecraft
> Help: http://mailman.qth.net/mmfaq.htm
> Post: mailto:[hidden email]
>
> This list hosted by: http://www.qsl.net
> Please help support this email list: http://www.qsl.net/donate.html
> Message delivered to [hidden email]

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[Jim Brown-10]

Thanks, Wayne.

73, Jim

On 6/24/2018 5:06 PM, Wayne Burdick wrote:
> S9 (or S9+5) is in the right ballpark with a 50 uV signal. This applies to the preamp-on case for all of our rigs.
>
> Also, if you can hear a -143 dBm signal, you’re doing just fine:)  


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