47 GHz project - Part 0....

One of the first projects above 24 GHz Im tackling is to add some enhancements to my existing gear.  On these bands, you build two complete systems so you have somebody to talk to with the second rig.  My one portable transverter is a DB6NTdesign integrated to a small dish.  I picked this up at a Central States VHF conference a couple years ago second hand and is essentially my 'reference system' for testing my home built gear.

My 'other rig' is made up of surplus parts accumulated over the years.  Of course when testing, there is the need for a way of generating a test signal and some way to hear that signal.  Before I got the DB6NT unit, I built up a simple harmonic mixer based on designs from the San Bernardino Microwave site.  This mixer took less than an hour to build.  It is made up of two diodes soldered antiparallel on an SMA bulk head connector.  The diodes were removed from a 12ghz Qualcomm mixer board.  The LO is applied by the SMA connector.  The IF is picked off by a second piece of hardline soldered to the SMA connector - a tiny piece of wirewrap wire is passed through the connector and soldered to the center pin.  No efforts were made to optimize the mount.  I used a brick oscillator tuned to 12 GHz to pump the diodes with an HT tuned in the 900-1000 MHz band in wide band FM mode for the IF.

This is the SMA bulkhead with the LO input and IF tap.

Back of the SMA bulkhead with the antiparallel diode pair and IF tap.

The HT with the WBFM mode was selected as I only had a gunn oscillator to generate a test signal.  By tuning the gunn, I could hear the 'swoosh' as the signal swept through the pass band.  Later on, I obtained a harmonic multiplier that was cut from a 39GHz down converter.  This block contains a pc board with a diode pair.  Hitting this mult with 100mW will generate a signal at 47GHz.  I have read that these multipliers will generate a signal up to/beyond 80GHz which make them perfect for a CW beacon/transmitter.

Now with these components, I can generate a weak signal and detect it - again, not optimized but the purpose is to have for testing.

I did mount a small horn on the multiplier block and have feed with a Frequency West brick oscillator to generate a signal at 47GHz.  That assembly is in the header photo of this blog.

As far as design philosophy goes, I am considering a fixed frequency CW transmitter (or FM) at ~47088 MHz and a tunable IF.  The reason is I can get a usable signal (0dBm) from a multiplier and not suffer the conversion loss from a bilateral mixer  Of course, this requires two LO sources and a separate TX/RX chain.  For the experiments at 78G and up, I will probably try both the fixed tuned TX rig and tunable IF as well as a bilateral mixer.  Two very good links for designs I am using for guidance is the excellent article from Alan, VK3XPD:
http://vk9na.com/attach/76-122GhzTransverterDesign.pdf
And the excellent article by Wolfgang DD8BD:
http://www.pamicrowaves.nl/website/technica_articles/24-47GHz_Mixer_experiments_by_Wolfgang_DD8BD.pdf
And also the original project by Kerry Banke N6IZW from the SMBS site.
http://www.ham-radio.com/sbms/sd/47ghzndx.htm