I'm short on technical knowledge compared to most everyone here, but I'm high on curiosity.  I may not be able to explain all of the technical nuances of this, but I wanted to share my new RTL dongle > panadaptor setup in case it encourages someone else to give this a try.

Based on a thread on QRZ's "Homebrew" forum, and an offer in that thread by someone who has done a few of these to help, I reached out to understand what it would take to tap the IF on my Kenwood TS-140S and then use HDSDR, my existing dongle and HRD together.

Basically, once the IF was located before any filters, it was a matter of cutting the wire from the antenna that came with the dongle, and soldering that in place (with a .020 capacitor).  HDSDR has an option for "SDR on IF ouput"; the IF frequency of the radio (40.55 in this case) is input into HDSDR.  With spectrum showing, HDSDR is then connected to HRD to control the radio. A little fine tuning is required to get the indicated frequency to match the actual frequency (first with a coarse adjustment - 499000 Hz in my case), and then with fine adjustments for each mode.  Note that I already had rig control for HRD set up via the optional aftermarket board for this radio, and a serial > USB adapter.  

The result....  click on a signal in HDSDR and the radio tunes. The reverse is true too - tune the radio and the SDR software follows (there are options to change this behavior to suit).  The photo shows 7020 khz through about 7350 khz; I didn't have the spectrum zoomed all the way out.  Zoomed out, I'm seeing from 7000 khz through 9400 khz, based on the sound card on this Mac and my 2400 khz bandwidth choice in HDSDR (really, really small traces on the screen)!  I haven't played with the 3400 khz bandwidth option yet, but will - it didn't work very well when I was using the dongle for VHF/UHF, but it may be different using the radio.  Oh, and the software is Win only - I run Win 7 on my Mac (Bootcamp, not virtualized).

I read other references to doing an IF tap on the interwebs, and there is some discussion about using an amplifier between the tap and the dongle.  In my case, I don't see a need...  There is also a possibility of the signal being attenuated; in my case, the signal seems fine (...in limited testing between last night and this morning) on both the radio and on the computer.  The value of the capacitor plays a large role here.  Max gave us a range to try, and my friend calculated & felt the .020 microfarad capacitor would work well.

A friend helped me with the soldering, and Max, my "virtual Elmer" from Canada, provided me with the details on where to make the tap, the frequency, potential capacitor values and encouragement.  For now, I just ran the wire out the back of the radio.  I may go back and drill a hole / mount an RCA adapter on the back of the radio for a cleaner install.

Very cool !!

I owned several TS-140's and TS-680's and they were very capable rigs.

Bump for elcope.

Since I first wrote this, I went back and mounted an RCA connector in an empty hole on the back of the radio, and connected the IF tap to that.  It's a much cleaner install that way, and obviously the external wire can be plugged / unplugged.  It still works great, and I see no downside.  It has absolutely transformed the way I use my radio in the shack.

I've contemplating doing this on my 857D, but despite finding info about how to do it on the web, I'm not brave enough to do it on a radio that's still under warranty.

ETA:  Here's a video of it working:  

[youtube]https://www.youtube.com/watch?v=L9JtF1WkQtI[/youtube]

Cool,

Thank you.