Altair's N4YWK Microwave Radio Projects

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N4YWK's Microwave Radio Page

Microwave Ham Bands

1.2 Ghz - my repeater, links, and beacon , plus see my ludicrous physiognamy on FM TV...
2.4 Ghz - an EASY band for homebrew, tons of hot technology new parts cheap or free!
10 GHz - that ain't so high...voice, video, beacons. Get cheap surplus modules and parts.

Why Microwave?
There are lots of reasons to do microwave; to develop rf technique, to learn, to contest, but my favorite is that its just plain fun. Certainly, I admire SSB/CW horizontally polarized ultra high performance microwave equipment, but we the Great Unwashed masses of FM and vertical polarization have just as much fun as anybody, and for less cost.

Microwave Projects

How would you like a 10 GHz voice transmitter that will talk to Gunnplexers, which has 20 memories, 2 VFOs, DTMF dialler and many features, all in a no-tweek design you can build in a weekend, and for just $15 ! Just use your UHF walkie talkie with this simple waveguide comb generator.

The infamous HawgPlexer Kit allows you to turn one of those ubiquitous 10 GHz motion The original HawgPlexer used an audio amp kit from Radio Shack which has now been discontinued, but nearly any small audio amp which has a microphone input and a speaker output will work just as well. The LM386 and the LM1872 are common audio amp chips, just hook 'em up like the data sheet says, add the circuit shown to the left, and voila ! Your HawgPlexer is complete !
To tune, hook the HawgPlexer output to the Gunn diode of any homodyne Gunnplexer, hook the mixer diode of the Gunnplexer to a scanner set to 30 MHz WBFM. Adjust the HawgPlexer tuning to get the normal Gunn voltage (usually +8 or +9 V ) on your Gunn diode. Set an RF generator, the one above works great, on 10,250 MHz as a known frequency, and tune the Gunnplexer's tuning screw until you hear the static get quiet. Now when you speak into the mic, you will hear yourself in the scanner. If the generator is FM modulated, you will hear its modulation at the same time. See also Theory of Operation, Tuneup and Checkout procedures
Your HawgPlexer can be used with a horn or small dish antenna for a hundred miles or more if you truly have line of sight. The tuning control will allow fine adjustment of the frequency in the field. I recommend you set the screw on your gunnplexer to receive a known generator, then only use the voltage tuning in the field.

How about a 10 GHz scanner receiver which receives AM, FM, WBFM, SSB, CW and has 200 memories ! You guessed it, just use your old scanner with this 10 GHz converter!

Here's a low power video transceiver for 2.4 GHz, built with cheap FCC Part 15 mmic devices from Tri-Quint.

CHEEP 'N EZ 2400 MHz transmitter, up to 4 W output all mode ! Convert surplus 2 GHz ITT terrestrial microwave links to 2.4 GHz. Diagram and Instructions

The HAWG EXTENDER frequency range extender for spectrum analyzers, from the brilliant and loquacious KIP ! This single transistor external mixer circuit uses the LO output of HP and similar spectrum analyzers to mix incoming signals down to the bandwidth of the analyzer.
In this picture of the Hawg SHF converter, the collector/output is to the left and the base/input is to the right. The emitter is plugged into the L.O. output of the 8558.
It uses an MRF941 ( or other SHF transistor). The resistors on Kip's are 75 ohms since he has a 75 ohm analyzer.
Quote of the Day:
Shorter leads would be better.... ( Kip )

Hawg Extender schematic diagram and theory of operation. In the words of Kip himself :
The L.O. on the analyzer tunes from 2.055 GHz ( 0 MHz on display ) to 3.555 GHz ( 1500 MHz displayed ). If the L.O. output is used as the input to a mixer and the mixer output is fed to the analyzer R.F. input and the signals are on the "high side of the L.O., then displayed 0 MHz = 2.055 GHz, Then at 1500 MHz, the L.O. is at 3.555 GHz and the received signal is at 5.055 GHz. The tuning range is 3 GHz. so a dispersion of 5 MHz per division is really 10 MHz per division. The signals are normal, that is a higher frequency reads higher on the dial. The received frequency is (2.055 + 2xdial reading).
This can work to much higher frequencies with a mixer that operates there. The second harmonic of the L.O. tunes from 4.11 to 7.11 GHz and the receiver range is 4.11 to 8.61 GHz. Likewise, the 3 rd harmonic is 6.165 to 10.665 GHz and the tuning range is 6.165 to 12.165 GHz. You can measure frequencies at 10 GHz quite accurately, to a few megaherz, and much, much better if the analyzer has a counter, or a reference is used.
The circuit is exceedingly simple...3 components on a BNC. I used a MRF-941 (8 GHz Si transistor as the mixer.) The emitter connects to the L.O. output, the base is grounded through a 75 ohm (or 50 ohm) resistor. The collector is grounded through a 75 ohm ( or 50 ohm) resistor. The collector is connected to the analyzer RF input through 50 or 75 ohm (depends on analyzer input Z ( Mine is 75 ohms...I think yours is 50 ohms)). No other power is required, the L.O. is the power source. The base is the signal input.
Probably a GaAs transistor would be better for 10 GHz use, but it's an easy way to look at the 2.4 and 3.3 GHz bands. Since the input is not tuned, It can have all kinds of spurs..so you have to keep track of where you're looking. I found the spurs to be quite low, relative to the main signal. The second harmonic of the wavecom at 4.86 GHz. seemed acceptably low ~-50 dB. Any good SHF microwave transistor should work OK. Note that for the Nth harmonic of the L.O. the dispersion is (N+1) times the dial setting.
Have FUN!!! I'll try mine on 10 Ghz soon, just to see if it'll pick up anything!

Design of 1.2 GHz link exciter board which is a drop-in replacement for the exciter board in a GE Master II radio. I made it as a demo for a multisite remote receiver repeater system. The C.A.R.E.S. system has not grown into 1.2 GHz as planned, but I keep the link board around just to show how it can be done. Uses a fixed-modulus PLL from Plessey and a crystal near 5 MHz to lock its vco near 1280 MHz. The circuit board artwork was done with Windows Paintbrush.

Efficient 1.2 GHz and 2.4 GHz dish antenna feeds. Most consumer TV satellite dishes have an f/D ratio which is inefficient with ordinary feed horns. The proper feed used with them is the Chaparral type, notoriously hard to build unless a machine shop is available. This design is easy to build with hand tools and is a near-perfect match for that old TV dish in the backyard. Since I built this one, I hung up all my yagis and loopers in the basement! Here is photo and design .

L-band NBFM repeater on 1291.4 MHz, just an old Icom repeater.

L-band NBFM beacon on 1296 MHz. Design is based on a weak signal source by Down East Microwave which has been modified for NBFM. It is followed by a 1 W hybrid "brick" amplifier and modulated and controlled by a BasicStamp from Parallax.

X-band beacon on 10250 MHz. Experiments with harmonic multipliers, Gunnplexers, active temperature stabilization and injection locking. The object is to create a stable on-air frequency reference. Most promising avenue so far is injecting a CW signal into the detector port of a Gunnplexer and letting the detector act as a harmonic multiplier to create a crystal stable injection locking signal which will capture and hold the free running Gunn Oscillator. I have already demonstrated the injection locking and capture. More work to be done.

Its Easy to Get Started !

Read the Microwave Handbook from the RSGB.
What's all this Gunnplexer stuff? Gunnplexer FAQ.
Start cheap and easy with the HawgPlexer 10 GHz transceiver.
Proposed Atlanta area 10 GHz bandplan.

Future Projects
Some of these may not ever be finished, but then again, the previous list has a few which seemed at first unlikely to survive.

Conversion of DSS or European Ku-band LNBs to block converter for 10 GHz ham band.
An electrostatic-focus 1 watt TWT amplifier for 10 GHz.
Design of a home built Free Electron Maser type microwave source, tuneable from 100 GHz to 500 GHz.

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	How would you like a 10 GHz voice transmitter that will talk to Gunnplexers, which has 20 memories, 2 VFOs, DTMF dialler and many features, all in a no-tweek design you can build in a weekend, and for just $15 ! Just use your UHF walkie talkie with this simple waveguide comb generator.
	The infamous HawgPlexer Kit allows you to turn one of those ubiquitous 10 GHz motion The original HawgPlexer used an audio amp kit from Radio Shack which has now been discontinued, but nearly any small audio amp which has a microphone input and a speaker output will work just as well. The LM386 and the LM1872 are common audio amp chips, just hook 'em up like the data sheet says, add the circuit shown to the left, and voila ! Your HawgPlexer is complete ! To tune, hook the HawgPlexer output to the Gunn diode of any homodyne Gunnplexer, hook the mixer diode of the Gunnplexer to a scanner set to 30 MHz WBFM. Adjust the HawgPlexer tuning to get the normal Gunn voltage (usually +8 or +9 V ) on your Gunn diode. Set an RF generator, the one above works great, on 10,250 MHz as a known frequency, and tune the Gunnplexer's tuning screw until you hear the static get quiet. Now when you speak into the mic, you will hear yourself in the scanner. If the generator is FM modulated, you will hear its modulation at the same time. See also Theory of Operation, Tuneup and Checkout procedures Your HawgPlexer can be used with a horn or small dish antenna for a hundred miles or more if you truly have line of sight. The tuning control will allow fine adjustment of the frequency in the field. I recommend you set the screw on your gunnplexer to receive a known generator, then only use the voltage tuning in the field.
	How about a 10 GHz scanner receiver which receives AM, FM, WBFM, SSB, CW and has 200 memories ! You guessed it, just use your old scanner with this 10 GHz converter!
	Here's a low power video transceiver for 2.4 GHz, built with cheap FCC Part 15 mmic devices from Tri-Quint.
	CHEEP 'N EZ 2400 MHz transmitter, up to 4 W output all mode ! Convert surplus 2 GHz ITT terrestrial microwave links to 2.4 GHz. Diagram and Instructions
	The HAWG EXTENDER frequency range extender for spectrum analyzers, from the brilliant and loquacious KIP ! This single transistor external mixer circuit uses the LO output of HP and similar spectrum analyzers to mix incoming signals down to the bandwidth of the analyzer. In this picture of the Hawg SHF converter, the collector/output is to the left and the base/input is to the right. The emitter is plugged into the L.O. output of the 8558. It uses an MRF941 ( or other SHF transistor). The resistors on Kip's are 75 ohms since he has a 75 ohm analyzer. Quote of the Day: Shorter leads would be better.... ( Kip )
	Hawg Extender schematic diagram and theory of operation. In the words of Kip himself : The L.O. on the analyzer tunes from 2.055 GHz ( 0 MHz on display ) to 3.555 GHz ( 1500 MHz displayed ). If the L.O. output is used as the input to a mixer and the mixer output is fed to the analyzer R.F. input and the signals are on the "high side of the L.O., then displayed 0 MHz = 2.055 GHz, Then at 1500 MHz, the L.O. is at 3.555 GHz and the received signal is at 5.055 GHz. The tuning range is 3 GHz. so a dispersion of 5 MHz per division is really 10 MHz per division. The signals are normal, that is a higher frequency reads higher on the dial. The received frequency is (2.055 + 2xdial reading). This can work to much higher frequencies with a mixer that operates there. The second harmonic of the L.O. tunes from 4.11 to 7.11 GHz and the receiver range is 4.11 to 8.61 GHz. Likewise, the 3 rd harmonic is 6.165 to 10.665 GHz and the tuning range is 6.165 to 12.165 GHz. You can measure frequencies at 10 GHz quite accurately, to a few megaherz, and much, much better if the analyzer has a counter, or a reference is used. The circuit is exceedingly simple...3 components on a BNC. I used a MRF-941 (8 GHz Si transistor as the mixer.) The emitter connects to the L.O. output, the base is grounded through a 75 ohm (or 50 ohm) resistor. The collector is grounded through a 75 ohm ( or 50 ohm) resistor. The collector is connected to the analyzer RF input through 50 or 75 ohm (depends on analyzer input Z ( Mine is 75 ohms...I think yours is 50 ohms)). No other power is required, the L.O. is the power source. The base is the signal input. Probably a GaAs transistor would be better for 10 GHz use, but it's an easy way to look at the 2.4 and 3.3 GHz bands. Since the input is not tuned, It can have all kinds of spurs..so you have to keep track of where you're looking. I found the spurs to be quite low, relative to the main signal. The second harmonic of the wavecom at 4.86 GHz. seemed acceptably low ~-50 dB. Any good SHF microwave transistor should work OK. Note that for the Nth harmonic of the L.O. the dispersion is (N+1) times the dial setting. Have FUN!!! I'll try mine on 10 Ghz soon, just to see if it'll pick up anything!
	Design of 1.2 GHz link exciter board which is a drop-in replacement for the exciter board in a GE Master II radio. I made it as a demo for a multisite remote receiver repeater system. The C.A.R.E.S. system has not grown into 1.2 GHz as planned, but I keep the link board around just to show how it can be done. Uses a fixed-modulus PLL from Plessey and a crystal near 5 MHz to lock its vco near 1280 MHz. The circuit board artwork was done with Windows Paintbrush.
	Efficient 1.2 GHz and 2.4 GHz dish antenna feeds. Most consumer TV satellite dishes have an f/D ratio which is inefficient with ordinary feed horns. The proper feed used with them is the Chaparral type, notoriously hard to build unless a machine shop is available. This design is easy to build with hand tools and is a near-perfect match for that old TV dish in the backyard. Since I built this one, I hung up all my yagis and loopers in the basement! Here is photo and design .
	L-band NBFM repeater on 1291.4 MHz, just an old Icom repeater.
	L-band NBFM beacon on 1296 MHz. Design is based on a weak signal source by Down East Microwave which has been modified for NBFM. It is followed by a 1 W hybrid "brick" amplifier and modulated and controlled by a BasicStamp from Parallax.
	X-band beacon on 10250 MHz. Experiments with harmonic multipliers, Gunnplexers, active temperature stabilization and injection locking. The object is to create a stable on-air frequency reference. Most promising avenue so far is injecting a CW signal into the detector port of a Gunnplexer and letting the detector act as a harmonic multiplier to create a crystal stable injection locking signal which will capture and hold the free running Gunn Oscillator. I have already demonstrated the injection locking and capture. More work to be done.