Monday, December 31, 2018

Moving the 2-M EME Antennas to Vertical Polarization

Horizontal Polarity for 13 Months
For the last 13 months I have operated 2-M EME with antennas that were fixed in horizontal polarization.  My two 13-element LFA InnovAntennas have been mounted "side-by-side" in a horizontal arrangement (see photo at left - click on any photo to see it larger.)  In an effort to see if I can expand the number of stations I have been able to work and maybe work a few New Ones, I decided to re-mount the antennas in Vertical Polarization.  Other EME stations I have talked with here in the U.S. tell me that they work more stations with Vertical Polarization than they do with Horizontal.  In that 13 months of operating with Horizontal Polarization, here are my 2-M EME totals as of November 26, 2018:

Antennas Are Down
   259 EME QSO's
   232 Initials (New Stations)
   185 Grids

   58 DXCC Countries Worked / 53 Confirmed

   U.S. States on 2-M
   44 Worked / 44 Confirmed
(not all via EME)

So, on 27-December-2018, with the help of my grandsons, Owen and Grant, we took down the two 13-element InnovAntenna yagis.  I then began the work of re-configuring the antennas so that they can be mounted in Vertical Polarization.

On 30-December-2018 the temperature was up to 49° F with a little sunshine so I proceeded with adapting the antennas for vertical mounting. This required removing and reinstalling the mounting bracket after rotating it 90°, doing the same for the truss mounting bracket, drilling two holes in each antenna for the truss cables to attach to the boom, and sealing the original holes in the boom.  I decided to locate the new holes for the truss wires 1-inch further away from the center of the antenna to not weaken the boom at that point.  Then, Scotch® Super 88 electrical tape was used to seal the old holes.

Cross Boom Mounting
Rotated for Vertical Mounting
Care was taken to make sure the truss cable was as far from the vertical elements as possible.  I achieved a spacing of 2-inches.  The truss cables are non-conductive but I wanted to avoid any close proximity to prevent transfer of rain/snow/ice and "critter" construction projects (spider webs.)  I also made sure that the antennas remained "in-phase" with each other (both antennas have the same side of the driven element in the same position.)  That is, the side of the driven element that is connected to the center conductor of the coax is pointing down on both antennas.  Both could have been pointing up but that's just how it worked out.  Care was also taken to make sure the mounting bracket for each antenna was positioned at the same point on both antennas. Finally, I drilled a 1/8-inch hole in the bottom rear corner of the driven element (which is constructed of tubing) to allow any condensation to drain out.

When the antennas were in horizontal polarization, the mounting brackets had the antennas sitting on top of the fiberglass cross boom.  I decided this time to allow the antennas to "hang" from the cross boom by the U-bolts when mounted in vertical polarization.  It may not make any difference but I thought it would make it easier for me to install the antennas with the nuts for the U-bolts now on the underside of the bracket.

The above work (including acquiring and replacing all tools) took four hours.  At this point all I need to do is to adjust the turnbuckles on the truss cables to bring the antenna boom into a horizontal position.  I also plan to construct two trusses for the cross boom in order to reduce the "droop" which has crept into the fiberglass cross boom.  That will be covered in my next Post.

Mounting Antenna
Adjusting Truss Turnbuckle
On Sunday morning, January 6, 2019, my grandsons, Owen and Grant, came to my QTH to help put up the antennas.  The temperature reached 50° and was partly sunny.  A very good January day.  First we mounted the antennas one at a time on a Workmate® "Portable Folding Work Support " in the vertical position.  Then, as you can see in the photo at the left, we adjusted the turnbuckles on the support truss so that the antennas were supported enough to keep the boom straight.  And added a Zip Tie to prevent the turnbuckles from loosening.

Once we had the first antenna complete, Owen and Grant installed it on the fiberglass Cross Boom.  In the photo at the right you can see them installing the second antenna on the Cross Boom.  We took care to make sure that the antennas remained "in-phase" with each other when we mounted the second antenna.

The difficult part was to tighten down the second antenna so that it remained parallel to the first antenna.  This took several tries until we all figured out how much we had to "over-compensate" when beginning to tighten the U-bolts.  Once we got that down, we quickly had the two antennas parallel.  The total time to do all of the work today was only 2 hours.  And, the thing I learned from when Tim, K8RRT, and I installed the antennas the first time in Horizontal polarization, was that having TWO people mounting the antenna makes it MUCH easier!  Also, using a small electric drill with the proper deep socket was a BIG improvement over just using a manual ratchet!

Once the antennas were installed, Owen adjusted the inclinometer so that it read the actual elevation (as measured by a digital level on the boom of one antenna.)  I was anxious at that point to raise the antennas to their final operating position until Grant pointed out that I had not connected the feedlines to the power divider!  DUH!  I'm sure glad these boys are understanding what we are doing so that they can keep old Grandpa straight!

Antennas are now Vertically Polarized
As you can see in the last photo, the left-hand antenna has just a little too much tension in the truss for the rear portion of the antenna.  When the grandsons are here later this week (when they are out of school), we will tweak that.  Also, I have completed the trusses for the fiberglass cross boom and maybe we can install them at that time.  That should (hopefully) eliminate the droop in the cross boom.

As I mentioned above, once I have installed the trusses for the cross boom, I will Post that info (with pictures) to this Blog.  Until then, I'm very anxious to try out the antennas in Vertical Polarization to see if I can work stations who I was not able to work when the antennas were Horizontally Polarized.  Moon conditions are not very favorable for the next two weeks but January 20-24 looks like some REALLY good moon conditions so you can bet I'll be in the operating seat whenever the moon is up on those days!

Saturday, December 29, 2018

Acquiring Equipment for Cross-Polarization Operation

My future plans for EME call for me to install cross-polarized antennas so that I will be able to change my antenna polarity at will.  That way I can transmit in either vertical or horizontal polarization and also receive the same way.  No longer will I be "locked out" of making a QSO because of polarity differences between my station and the station I want to work.

IQ+ Dual RX Radio
This switchable Dual-Polarity is a pretty big improvement for me.  But, there is another level of improvement beyond just being able to switch between Horizontal (H) and Vertical (V) polarization. This is call Adaptive Polarization.  It requires a good deal more hardware and software but does an amazing thing.  It combines the Receive signals from the H and V antennas, computes the vector angle of polarization and then peaks the output according to that polarity.  This completely eliminates polarity loss.

The first piece of hardware to accomplish this is the IQ+ from HB9DRI and his company, LinkRF.  This is essentially two receivers in one box with inputs for the H and V antennas.  The two receivers are "locked" together with the same Local Oscillator (LO) so that the output from each have the same amplitude and phase of the original signal.  These outputs supply the I and Q (quadrature) signals which are samples of the same signal taken 90 degrees out of phase. 

Those I and Q signals are fed into the UADC4 (Universal Analog to Digital Converter) and then into the software.  The UADC4 is another product of LinkRF.  It replaces the PC audio cards traditionally used to interface between radios and computers.  However, the UADC4 is MUCH better than even the best PC audio card.  With the proper hardware ahead of it, the improvement can reach as much as 15 dB better performance yielding dramatic improvements in the noise floor!  (Click on images to see them larger.)

The software that does the amazing job of combining the H and V signals is called Linrad and is the creation of SM5BSZ.  Originally it was written in Linux but it is now available for Windows.  The output data stream from Linrad is sent to K1JT's Map65 software and this program provides a waterfall showing all signals in a 192 kHz passband, a WSJT type control panel for transmitting and decoding messages, plus lists of all the stations copied in the entire passband!  WHEW!

As the first step toward configuring my EME station to do all this, I have placed my order for a UADC4 and for the IQ+ revC (modified to work with the UADC4.)  I had previously pre-ordered the UADC4 some 13 months ago but it has taken this long to move the product from initial prototypes to final production.  My IQ+ and UADC4 are scheduled to be shipped about the end of January 2019.  So now I need to get the XP antennas ordered, built and installed.  Let the fun begin!