Re: [Elecraft] Re: Problems with K3 KXV3 IF Output Level?
Hi All, I have just connected my TT RX 320 to the IF port on my K3, and there seems to be plenty of signal available. With the K3 on 7030 kHz I could tune the RX320 right through the 41 m broadcast band. The only pecularity is that the RX 320 needs to be tuned lf to go hf and vice versa and usb needs to be selected on 40m ssb to resolve the signals. I also tried WinRad on the 320's IF and got a panoramic display working, only 24 kHz wide though. Regards Tim gm4lmh ___ Elecraft mailing list Post to: Elecraft@mailman.qth.net You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com
[Elecraft] Re: Problems with K3 KXV3 IF Output Level?
...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 ___ Elecraft mailing list Post to: Elecraft@mailman.qth.net You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com
Re: [Elecraft] Re: Problems with K3 KXV3 IF Output Level?
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. As I understand it, there's something like a 15 dB difference between the signal level at the antenna input port and the IF sample out. I'll have a better feel for this when my K3 arrives (ordered in May 2007; has been waiting for the 2nd receiver, maybe shipped in August 2008), but I've had reported to me a couple of measurements in that range. The J310 used to provide the K3's IF sample has a voltage divider on the input that knocks down the signal level from the sample point. In addition, the J310 in source follower mode has an output impedance in the 100-200 ohm range, depending on idle bias current. (Output impedance is 1/gm and gm varies with bias/idle current.) Thus, if connected to a 50 ohm device, such as a spectrum analyzer or a receiver, there's an additional loss in the 10 dB range. 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 Z1-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 ___ Elecraft mailing list Post to: Elecraft@mailman.qth.net You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com ___ Elecraft mailing list Post to: Elecraft@mailman.qth.net You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com
Re: [Elecraft] Re: Problems with K3 KXV3 IF Output Level?
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 Z1-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 ___ Elecraft mailing list Post to: Elecraft@mailman.qth.net You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com
