24 GHz signal source

This is a 24GHz signal source (estimated 100mW out) used for testing.  It can also be used with a harmonic mixer for 47 GHz.

The design comprises of a brick oscillator tuned to 12.096GHz.  I am using a crystal oscillator
running at 96MHz for reference.  Note this oscillator has a heater for stability - plans are to
replace with a Direct Frequency Synthesis source fed by a 10MHz oscillator.

The Brick feeds a X2 multiplier (surplus) to generate 24.192GHz.  The assembly runs
off 24 Volts and uses regulators to supply voltage to the reference LO, Brick, and multiplier.

The multiplier is attached to an isolator and a WR42 output.

Now, for 47GHz, the output can be fed to a harmonic mixer - in this case, the homebrew
mixer I made from soldering chip diodes to the SMA connector discussed in an earlier
post.  This mixer acts as a half frequency harmonic mixer with a high side 1296 IF to
reach 47.088 GHz    (2x24192) yields 48.384 GHz -1.296 GHz = 47.088 GHz

This text mixer has only been tested in the shack but has detected signals from
a 47G signal source to confirm operation.

One option for this assembly was to include a PIC keyer to provide CW keying
for a beacon although this modification has not been pursued.  The keyer would
make/break the voltage line to the multiplier for keying.

47 GHz Part 2 - work in progress

I decided to modularize the TX and RX components of the 47 GHz transverter.  That way I can test different configurations.  The design will comprise of the TX and RX each feeding a dish mounted on a frame.  This eliminates the need for a waveguide switch.  The dishes will be mounted side by side on a frame - this will be covered in a separate post.
This particular project is for a receive downconverter.

The key component of the downconverter is a Scientific Atlanta receive mixer assembly I purchased at Microwave Update.  The assembly consists of a waveguide isolator on the mixer input.  The mixer is a harmonic type mixer and has an LO input in the 12 GHz range.  The IF output is ~1GHz.  A CTI brick oscillator feeds an amplifier which amplifies the LO to the mixer.  The output of the mixer feeds a ~1GHz post amp.  As you can see the LO is attenuated.  The brick oscillator is actually made for the 11GHz band but I adjusted the cavity to 12GHz.  I have a surplus 100mhz phase locked oscillator (another surplus
item from MUD).  This oscillator requires a 10 MHz input.  The mixer is a Ku type mixer made for 35 GHz but feeding with 12 GHz, I did pick off a signal around 912MHz indicating an LO of 48GHz high side when detecting a test signal at 47088 MHz.  I have not confirmed the conversion characteristics of the mixer working in this configuration (I dont have the equipment to do that) so that will have to be done at a conference where test equipment is available.  I originally had this built on a bread board but am now packaging in an enclosure.  The input will be via WR28 waveguide with a square flange.  I still need to integrate the 100 MHz PLL and 10 MHz oscillator and also a second low noise post IF amp in the 900-1000MHz range.

47 GHz Part 1.....

This transverter is built mainly from surplus components.  It is a fixed frequency TX, tunable RX down converter.

The bottom half of the transverter is the TX chain.  A microwave brick oscillator running at 15GHz feeds an amplifier (blue rectangle in the middle).  The LO is attenuated and fed to the amp which is keyed on/off for CW.  The output of the amp feeds a 3x multiplier that has a claimed gain of 10 dBm out!  This output feeds an isolator and a manual waveguide switch (WR28) for T/R.  The output is a small test horn.

The upper part of the transverter is a Phillips 39ghz down converter which is capable of downconverting the 47 GHz signal with an IF of 10.368 GHz.  This downconverter feeds a 10G post amp which then would
be connected to a 10GHz transverter/2nd IF.

The front panel has a manual T/R switch to apply voltage to either the RX or TX chain.  A spot
button is provided that will apply power to the TX chain AND RX chain to allow finding the transmit signal while tuning the IF.  This transmitter is CW only

Beneath the chassis contains two brick oscillators for the RX and TX chain:

This transverter requires 12v and -20v (positive ground).  It is somewhat portable but
does require an outboard 10GHz rig for the 2nd IF.
My goal is to build a more optimized transverter - this unit will still be used as a back up
and as a test platform.

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

Microwave Harmonic Signal Source

I decided to document my various microwave and millimeter wave projects and activity.  In optical astronomy, a new telescope will capture its 'first light'.  For uWave and mmWave, the first signal is captured by a new transverter to confirm the receive portion is working.  So, it makes sense that the first entry is my weak signal source used for testing my transverters.  It is based on a surplus Qualcomm phase locked oscillator board that is modified to generate a signal at 1152MHz.  This signal is applied to a diode which generates harmonics for the ham microwave bands starting at 2.3 ghz and up.  This particular board is described in great detail at the San Bernardino Microwave Society website (http://www.ham-radio.com/sbms/) under the link for the San Diego Microwave Society projects.  This is a very useful item and it does allow me to do a quick field test on the receive portion of my system.  Future entries will detail some of my new projects (and some old as well).  This is all to get ready for the up coming microwave operating season in the spring and summer including the 10ghz and up contest in August and September.

In the photo, the PLL chip is in the lower left corner.  The modifications included lifting programming pins, soldering new connections, and adding a capacitor to get the PLL to lock at 1152 MHz. The transmit signal path follows the left side of the board where MMIC chips amplify the PLL output to just around +10 dBM.  That output is fed to an SMA connector in the upper right which as a very tiny surface mount diode soldered to the connector.  The harmonics are of sufficient strength up to 10GHz although I have not heard any at 24GHz - possibly I need to increase the drive power to the diode to generate a signal up there.