[Elecraft] Re: Problems with K3 KXV3 IF Output Level?

[Eric Swartz - WA6HHQ, Elecraft]

Hi Jack,

Lyle was referring to tracking of signal levels (i.e. level changes), 
not absolute gain.

In our case, the IF output was designed specifically for internal use by 
a possible future Elecraft option and fully meets our design needs in 
this area. It has sufficient signal for this use and clearly works with 
other external devices that are designed to handle these levels, as 
noted by Lyle. We were very concerned about having an overly strong IF 
signal inside the K3 and kept this level as low as possible to avoid 
additional RX and TX spur generation inside the radio. Our intent was to 
have it amplified by an external, higher input impedance, amplifier as 
noted in your email.

Regards,
Eric


Jack Smith wrote:
> Lyle:
>
> As we have discussed, the K3 does not follow the normal 
> commercial/military practice of providing a 1:1 relationship between 
> the IF sample and the signal level at the antenna port. Since the K3 
> has a switchable pre-amp, the 1:1  relationship would presumably be 
> with the pre-amp off.
> ......
> Now, a Softrock or Larry's LP-PAN has enough sensitivity to overcome 
> most or all of this loss, but it's still a design error.
>
> (The IF sample can also be amplified by an external amplifier such as 
> my Z10000-U. If configured in high Z input mode, the J310's output 
> impedance becomes a non-issue.)
>
> Jack K8ZOA
> www.cliftonlaboratories.com
>
> Lyle Johnson wrote:
>>> ...There is just no tracking of levels at the I F
>>> out with what is fed into the antenna input of the receiver.
>> If that were true, LP-PAN, SDR-14 and SDR0IQ could not be used as 
>> panadaptors.  But they can and are being used, so one can only 
>> conclude that the output at the IF jack most assuredly follows the 
>> signal at the input.
>>
>> Note that there are a mulititude of signals at the IF output 
>> connector since this is the unfiltered output from the mixer 
>> post-amplifier. These signals must be accounted for in any device 
>> which attaches to the IF output jack.  See < 
>> URL:http://www.telepostinc.com/LP-PAN.html > and scroll about halfway 
>> down the page to "L.O. leakage / isolation:" for details
>>
>> The lower the impedance of the attached load, the lower the gain (or 
>> increased loss) there will be at the IF output.  We're talking 
>> microvolt levels here, not hundreds of millivolts.
>> 73,
>> Lyle KK7P
>>
>