[Elecraft] KX1 - very quiet on 30m and 20m

[Don Wilhelm]

Bob,

OK, I finished the KX1 up to the point where I am able to give you some 
numbers.
With a 50 uV input at 7040 from my XG2 signal generator, I find 0.866 
volts measured across the AF Gain control (control set to maximum) with 
a high impedance load at the headphone jack.  If I plug in headphones 
(Sony MDR series), the voltage drops to 0.836 volts.
Of course, the AGC should be active which will keep the voltage down a 
bit.  The KX1 has the KXB3080 option installed, and the receiver front 
end is a little more sensitive than either the original KX1 or with the 
KXB30 installed.

With a 1 uV input, I read 38 to 40 mV at the same point - AGC should not 
be as active at that level.

The voltage readings were obtained with a Fluke True RMS reading DMM.

73,
Don W3FPR

Don Wilhelm wrote:
> Bob,
>
> I can't give you a measurement number right away, I do not have a 
> working KX1 here at the moment, but that value may be possible tomorrow 
> or Friday.
> If you do not hear quite a loud signal with the 50 uV output from the 
> XG2 (or XG1  with a 20 meter crystal) - with the RF Gain at full 
> clockwise and the AF Gain between 25 and 35% of rotation, then there is 
> something wrong.
>
> How is the transmit power output?  If that is OK, then the low pass 
> filter is likely OK, and you might want to look at T2.
>
> The KX1 audio is not super strong, and having good volume does depend on 
> using sensitive headphones.  If your headphones do not have an 
> sensitivity rating greater than 108 dB/mW, then your headphones may be 
> the major problem, see the KX1 manual page 62.
>
> 73,
> Don W3FPR
>
> Bob Jones wrote:
>   
>> I've just completed a KX1 build with the 80/30m option and auto atu.
>>
>> It works on all bands but 30m and 20m require the volume control to be fully clockwise and even then it's quiet. I've carried out the recommended checks and everything appears to be fine.
>>
>> Having read the previous posts on 'low audio' there's an element of subjectivity regarding what this means.
>>
>> Does anyone know of a definitive measurement I can make to see if this radio is working as well as it should?
>>
>> For example, I have the XG1 and can inject a 14.060 MHz signal at 1 microvolt or 50 microvolts. With the bandwidth set to maximum, what level of signal should I expect on the input or output of the audio amplifier, or at any other point in the circuit? 
>>
>> Any advice gratefully received.
>>
>> Bob, G3YIQ
>>
>>
>>
>>       
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