23CM Portable EME Station Tripod and Rotator Details - Dec 11, 2021

Here are details on the portable 23cm EME station.  I can set this station up in less than 30 minutes.  The PA and feed electronics power supplies are located in boxes at the base of the dish.  Four cables run from the dish to the operating location:

• 25 foot LMR600UF from TX/RX relay at base of dish to IC-9700.  6 watts output from the IC-9700 through the PA delivers 350W at the dish feed (rated to 500W but I don't need it)
• 12V on receive from the M2 antenna sequencer to control the TX/RX relay
• PTT from the M2 sequencer to key the PA
• Yaesu G5500 AZ/EL rotator control cables

The PA is the Gene K7BQ design using the W6PQL 600W pallet.  Paul, W2HRO can provide a 250W circulator that can be placed on the output of the PA to protect from high SWR.  On RX only 12 is present on the PA.

I use the Yaesu G-5500 rotator with USB-232b controller purchased on eBay to control the rotator.

For the past 6 weeks I have been experimenting and tuning.  The station is working very well now.  I can work all stations I can hear and with the 2.4M dish and WD5AGO preamp I am hearing many more stations even in the very high local noise environment at my home location.

Over the last week I have been calibrating my rotator AZ by sun tracking and I believe I am now tracking within 2 degrees during a typical moon pass.  (0 error in EL, 0-2 degrees error in AZ)

I plan to do a three day activation trip to GA, MS, AL to test the 23cm station toward the end of December.  I will post my plan here.

This Summer I am planning a 40 state expedition to activate 23cm.

This is the 2.4M W2HRO dish operational in Tampa, Florida.  The tripod is held firmly to the ground using 3 36 inch long, 1 inch thick circus tent stakes and ratcheting truck cargo tie-downs.

The dish mounting bracket bolts on to a steel pipe running through the G5500 elevation rotator.

The steel pipe is bolted to the moving part of the elevation rotator to prevent any slippage.

When not in use the dish is covered by a 7 foot long patio umbrella bag.

Closeup showing the antenna mounted to the elevation rotator pipe.

The rotator is mounted to a piece of 3/4 inch plywood.

Orange tie-down straps connect to holes in the tripod top.

The tripod legs are 1 inch threaded pipe that screw into threaded floor brackets.

The pipe brackets are through bolted through wedges cut from a 4 inch by 4 inch post.  The angle of the wedge is 25 degrees.  The three wedges are located at 120 degree points around the base.  If you travel you could leave the 48 inch pipes at home and buy them locally at your destination, Lowes, Home Depot.

Closeup shows the four G5500 azimuth rotator bolts that mount to the tripod plate.

I built two tripods for side-by-side dish comparison of the 1.8 and 2.4M dishes

The 2.4M dish needs to be pointed to 2 degrees or better accuracy.  The G5500 rotator is inexpensive and very light weight compared to SPID and other rotators.  It also doesn't have the tracking accuracy of the heavy rotators.

I use the pstrotator program "Antenna Offset" page to provide calibration corrections for azimuth and elevation.  I am not using a counterweight on my dish so there is some "sag" when the dish is at low elevations.

I use Sun noise and track the Sun for several passes during several days and apply calibrations to optimize Sun noise at 10 degree AZ and EL increments.

The top correction table is for AZ.  Each G5500 may have different non-linearities in the potentiometers used to report rotator position.  These can be corrected using the Azimuth Correction Table.  The G5500 should be carefully calibrated first following the instructions in the Yaesu G5500 installation guide.  This will set the full scale rotation limits and the output voltages from the AZ and EL location potentiometers.

Elevation calibration is performed using a digital protractor.  This is very accurate.  I bought the digital protractor below on Amazon.  You can see the name on the front.  For my installation measuring the elevation by placing the protractor at the end of the feed tube gives an elevation measurement 1 degree higher than the actual elevation of the dish.

Placing the protractor on the inside of the dish, at low elevations, shows 1 degree lower elevation that what is shown on the back of the dish.  At elevations above 50 degrees the difference is less than 1 degree.  The feed at the end of the tube droops an additional 1 degree.  I decided to use the measurement inside the dish as the basis.

My WD5AGO preamp is mounted on the feed connected to the RX isolation relay/terminator.  Thin coax is run to the back of the dish where th WD5AGO filter is installed.  12 volt and 28 volt power run to the dish.  I use LMR400UF to connect to the PA.

Photo shows cables run through the dish.  The dish can fold with all of the cables attached.

This is the TX/RX control box.  The LMR600UF cable connects to the bottom of the relay.  The blue cable at the top runs to the RX cable to the dish feed.  The cable at the bottom is the TX line that connects to the PA input.

This box contains the 600W PA.  48V and 12V power input.  Exciter PA input from the TX relay is at the left.  At the right the 250W circulator (intermittent rating) connects to 15 feet of LMR400UF that runs to the dish TX feed.

This box contains the power supplies.  Silver box at top is the Meanwell 3.5KW 220VAC input 48V power supply.  I only use about 1000W of the capacity.  The supply is sized to run two 700 - 800W amps at the same time.  Below is a 3KW 120V to 220V autotransforment with a 12VDC power supply for the PA electronics and PA bias.  The blue supply on the lower right is a 28VDC supply for the RX isolation relay.  There is a 12VDC relay on top of the 28VDC supply that switches the 28VDC to the RX isolation relay at the dish feed during RX.

The 28VDC supply has an "enable" button on it that must be pushed each time the supply is powered on before voltage is output.  This "forces" me to go out to the dish electronics and check everything before the RX relay can be engaged to connect the preamp to the dish.

The station is designed to be "fail-safe".  If any power supply fails, any cable is disconnected, the default configuration is the PA output connected to the dish (always) and the RX isolated.  This "should" prevent preamp failures.

I have two backup preamps in case I manage to damage my primary preamp.

This photo shows the equipment in the station.  The Yaesu controller on top.  The M2 sequencer in the middle and IC-9700 (Bodnar GPS stabilized) on the bottom.  I used to have the Yaesu controller and a PC to track the moon located in the dish-side electronics, however the RAM refresh frequency created powerful interference so the rotator is back in the operating location.  For portable operations this equipment stack sits on the desk on the passenger side of my truck.

This is the updated operating location in the truck.  The laptop now has two extra small screens from "xebec".  This provides the screen space to run two stations at once.  In the photo below I am running 2M and 6M MS at the same time.  The ICOM-705 is used for 6M, 2M, 222, and 432 operations.  I use the IC-9700 for 23cm.  As a backup for the IC-9700 I have a Q5 23cm transverter that can be run using the ICOM-705.

During my trip this Summer I plan to run 23cm at all stops and in addition run 2M, 222 or 70cm EME at the same time using the antenna tripod.