222 Night on Tuesday & an Antenna problem


David Olean
 

For quite a while, I was having a weird problem with my 222 antenna.  While operating on the activity nights, I finally convinced myself of some strange performance with my array pattern. I asked WA1T to put on a low power signal so I could measure my pattern. Sure enough, I was seeing two main lobes on either side of my boresight direction and separated by about 18 degrees.  This was a terrible situation. I came back to the VHF shack on Sunday in an effort to start some tests to determine what was wrong. WA1T's test signal verified that I had a long standing problem.

On Sunday, I did listen in on KA6U/ Idaho on 222 and heard Peter along with W7MEM, Idaho,  N1AV in Arizona, and W6TCP in California. KA6U went past his operating time to leave the site, so finished working N1AV for a new state and then tore down and headed for Washington state in a hurry I hung around and worked W7MEM and N1AV and then  went QRT and started work on checking the antenna.  VSWR in the shack looked a bit poor and not normal. I went to the top of the tower at 100 ft and started checking each of the four antennas with my antenna analyzer. All of the antennas checked OK, but the four, when connected to the power divider did not look good at all. I disconnected one feedline from the PD, and saw very little change in VSWR at the power divider feedpoint! This is not good. I wondered if maybe a connector pin had broken inside the PD. Knowing that each antenna was good I took the power divider down off the tower to check it back at home with four good 50 ohm loads. Imagine my surprise when the two feedpoints on one side of the 1/2 wave divider showed no difference when 50 ohm loads were screwed onto the connectors. When I popped off the metal plug from the end of the power divider, I was greeted by some water flowing out. It was at that point that I discovered a tiny weep hole that was located on the top side of the power divider. No wonder there was water in the divider. When I added elevation to the system last summer, I had turned the power divider over to make routing cables easier, and that change put the small weep hole up on top. I never noticed it. It filled with enough water to drown one end of the divider.

I cleaned out the power divider with pure alcohol and then dried it all out so that there was no observable resistive leakage due to water inside.  I epoxied the weep hole and then put an aluminum plug in the end of the square tube. It looked like the water in the power divider was enough to disconnect one of the antennas and make it appear to not be there. I am not sure how it produced two main lobes.  I have seen a similar situation on 1296 with a quad looper array producing a strange pattern due to unequal power distribution.  Maybe someone can enlighten me.

Next time, I hope I remember when I drill a weep hole!!

This morning, I replaced the power divider and checked the pattern. It looks normal and everything is very close to the boresight headings now. Checking a pattern with a weak and fluttery beacon is difficult, but I am not seeing two main lobes, just one big lobe and two much smaller side lobes.  Now to try it on tropo scatter & EME again.

Tuesday evening is 222 Night again, and I will be on 222.100 starting at about 22:30 UT.  It will be a great way for me to check out the antenna performance. So, if you have any 222 MHz gear, please plan to be on the SSB/CW part of the band after dinner. Activity can be quite good, and stations in Connecticut or New York can work 15-20 contacts in the evening.  We are always looking for new blood, and I always try a longish sked well beyond my range just to see if something can be heard. To date, this plan has not resulted in a contact, but the summer is just getting started! Stations in Ohio or Indiana are way beyond my range as is North Carolina.  Just the thing to try on a Tuesday night! KE8FD in Ohio is 625 miles from me and a great distance to try a sked. Remember, folks that the worst thing that can happen when you try is that you won't make the contact. You will have fun trying. It also spurs you on to improve things in your station.  I have a big reel of new large LDF-7 coax all set up on a home brew reel holder, so I can swap out my ailing 222 MHz feedline to get a lower VSWR. The new coax will be about the last thing I can try other than moving to a high mountain with a better takeoff angle!

CU on 222!

Dave K1WHS

Join 222Activity@groups.io to automatically receive all group messages.