Monday, May 25, 2009

6 Meter Opening to Mid-West




Nice opening tonight on 6 Meters into the Mid-West. While Minnesota was a regular here last year, most of the stations on tonight were new to me. Picked up new grids in EN11, EN43, EN23, DN96, EN16, and EN08.

Grid square total up to an even 150 grids worked in just a little over one year on 6 Meters.

Best contact of the night goes to KD0GWB, John Wicklund of Horace, ND in EN16. John is just ten years old and licensed in March. Fine Business operator, sounding like an old pro on 6 Meters. When I told him that I'd send him a card, he said that he didn't have any printed yet but would "make one" for me! Wow! That's the amateur spirit!

Welcome to the Magic Band, John...and also to a magical hobby. Everyone look for John on the band, and make him feel welcome.

Great night, lots of fun to hear the band open again.

73,

DE N1LF, Les

Thursday, May 14, 2009

Improving the Signal to Noise Ratio (AKA Before & After)



At the suggestion of Jordan Arndt, VE6ZT I spent most of last evening removing my 222, 432, and 1.2ghz Yagis from my indoor, attic mounted "stack". The cluttered stack is pictured above. After completing that task, I relocated the 3 Element 6 Meter beam to the top of the mast which places it at about 22 feet above "true ground".

More importantly, it moved it a good 11 feet or so from the AC wiring and other cables that run along the attic floor.

The 2 Meter 7 Element Yagi remained it's it's location on the stack, about five feet above the wiring, and 16 feet above "true ground".

Prior to relocating the antennas, I did basic noise floor plots for both antennas using the WSJT software. Tuned to 50.125mhz and 144.200mhz, I adjusted the software for a 0 db noise level at an azimuth reading of 00. I then moved the antennas through each 10 degrees of azimuth and plotted the noise level for each one.

As you can see from the "before" numbers on both bands, noise floor levels would rise to as high as 11db on 6 Meters in some directions, and 7db on 2 Meters. Noise floor levels this high made it impossible to do any "weak signal" work in these directions. 6 Meter Meteor Scatter was very difficult, though e-skip work was certainly possible. Last season saw 149 grids worked on the Magic Band.

With the antennas removed and the 6 Meter beam relocated, I repeated the noise floor mapping without adjusting any settings. The readings were taken approximately 2 hours apart. In an indoor environment, the clock can be a major factor in regards to noise. As neighbors switch off appliances, TV's and other devices, the noise floor can change significantly in some directions.

But even allowing for that, these readings were taken at approximately 9:30PM local time, and as you can see from the plots, the results were impressive on both bands. Six showed the most improvement, as much as 20db better in some directions.

2 Meters did not benefit as much, but improvements of over 4db were noted there as well. For an installation like mine, that's a huge improvement!

I allowed WSJT to run overnight on 50.260 with the beam pointed out West. When I checked this morning just prior to 10am, I had captured three complete QSO's from Texas stations. That's a big improvement over any other unattended recording that I've tried in the past.

Bill Olson, K1DY also suggested adding additional ferritte cores to the feedlines of the 6 Meter antenna, which I did while it was on the ground. Jordan has suggested that using a balanced "T" match feed might help to reduce noise pickup as well. I'll likely try replacing the 6 Meter beam with an M2 CM3 when the budget will allow. For now, the additional ferritte chokes should keep feedline radiation and noise pickup to a minimum.

The plan now is to play with the antennas at length and see what the improvement translates to in terms of real world improvements. One thing I immediately noticed is that my lowest noise floor on 2 Meters is now at 40 degrees azimuth. It was almost due North, so most of my SSB and CW grids have been worked in that direction. The lower noise at 40 degrees opens up the Carolinas and there VHF population to me. Very excited about that.

The other antennas will be added to the rover package, and I'll pursue most of my other band work strictly during major contests. As Jordan pointed out, I wasn't gaining grids on those bands at home anyway, and having the antennas up there only served to degrade performance on the "work horse" bands of 6 & 2 Meters.

I can't thank Jordan & Bill enough for all the advice. Everyone on the VHF Reflectors has been helpful too.

Here are the "before and after" noise floor plots:

SIX METER NOISE PLOT FOR WSJT 50.125 (Before & After)

36 0db -13db
35 1db -13db
34 1db -13db
33 1db -14db
32 2db -12db
31 2.5db -9db
30 4db -8db
29 5db -8db
28 6db -4db
27 8db -2db
26 10db 0db
25 10db 1db
24 11db 2db
23 11db 4db
22 10db 4db
21 10db 4db
20 8db 4db
19 7db 3db
18 7db 2db
17 8db 0db
16 9db -2db
15 8db -4db
14 8db -4db
13 8db -4db
12 8db -5db
11 8db -7db
10 8db -7db
9 10db -8db
8 11db -7db
7 11db -7db
6 11db -8db
5 11db -8db
4 11db -9db
3 10d -10db
2 8db -11db
1 3db -12db
0 3db -12db

2 Meter Relative Noise Floor Readings.
Icom IC-746 Pro. Pre-Amp off. S Meter set to "5" to avoid AGC "OFF" AGC Setting. WSJT calibrated to read "O" db at heading 00. Freq=144.200mhz

"After" readings are after the removal of 222, 432, and 1.2ghz antennas on May 13, 2009. 6 Meter 3 element beam moved to top of stack, approx. 22 feet above true ground.


AZIMUTH READING

00 0db -2db
01 2db -2db
02 4db -3db
03 4db -6db
04 5db -6db
05 5db -1db
06 4db 0db
07 4db 0db
08 4db 0db
09 3db -2db
10 3db -3db
11 3.5db -4db
12 4db -4db
13 6db -4db
14 6db -1db
15 6db 0db
16 5db 0db
17 4db 0db
18 3db 0db
19 3db 0db
20 4db 0db
21 6db 2db
22 6db 3db
23 7db 3db
24 6db 3db
25 5db 3db
26 4db 2db
27 2db 1db
28 2db 1db
29 2db 1db
30 2db 0db
31 1db -1db
32 0db -2db
33 0db -2db
34 0db -2db
35 0db -2db
36 0db -2db

Tuesday, May 12, 2009

T-Match Vs. Gamma Feed




A noted VHF man suggested today that I might try swapping my MFJ 3 element beam for 6 Meters with it's Gamma match for another with a balanced or "T" match feed system.

His logic is that the gamma match does not isolate the feedline from the antenna and that noise may be traveling along my hardline to the antenna. While I've added ferrite chokes at the feed point, this might be a valid way to reduce noise pickup a bit more.

The pattern of the antenna might also benefit which would help decrease noise pick up off the back side of the beam. I'm considering the M2 6M3 pictured above as a replacement.

He also suggested that removing the antennas for 222, 432, and 1.2ghz from the stack and increasing the spacing between the 2 Meter and 6 Meter antennas might yield improvement. Since I've worked very few new ones from these antennas anyway, that may have a lot of merit too. These antennas could be committed to rover/portable operation.

That would give me fewer bands from the home station, but might improve performance and reduce noise on the two most popular bands.

Much to consider. Comments, anyone?

Flagg Mountain, Dipoles, and Frustration


Weeks have passed now without a single new grid being worked on VHF or higher. This is due to a number of factors:

  • Limited Operating Time. Perhaps the biggest reason of all. Just haven't had time to be at the radio. Responsibilities at work, home, and serving as Section Emergency Coordinator for ARES take their toll. Missed a nice tropo opening on 2 Meters for instance.
  • Finances. IRS tax bill and other expenses related to the sale of my business meant selling my Icom 910-H. I'm making due with an Icom 746 Pro and Yaesu FT-857D. It's also limited my ability to try new things to improve the station.
  • Truck Lease. I'm blessed with a company truck but the lease is running out on May 25th. We're purchasing a new truck, which means rebuilding a portable VHF station in the next few weeks prior to the June contests.
  • Location, Location, Location. The noise floor in my HOA neighborhood continues to rise as more homes are built. 6 Meters on the attic antenna is almost unusable for anything other than e-skip. WJST modes from that antenna are usually impossible due to the noise floor.
But I'm not quitting now. Time to change my strategy and see if I can improve the grid totals that way.

One option I'm seriously considering is operating from a portable location during the June Contest. As long as it's within a 100km radius of my home QTH, I could still count any new grids worked towards VUCC. One location that we scouted last week is in Coosa County, AL called Flagg Mountain. It's at 1,140 feet and it's the highest Southern peak in the state.

I'm hoping that it would give me more access to much needed grids in Florida and into Georgia. Other options included Cheaha Mountain in East Central Alabama, which is the state's highest peak. The issue here in the South is getting above the tree line for a clear view. Almost impossible to acheive 360 degree views here. But I'm checking out several sites in the next two weeks.

Another option I'm experimenting with tonight is "temporary" antennas on push up masts. I plan to deploy a 6 Meter Hamstick Dipole along with an Arrow Antenna 4 Element beam tonight to test how it works. I'll set this up in my drive way after dark with a short run of coax back to the station. I can compare the noise plots with ones I've already done on 6 and 2 with the indoor antennas.

To give you an idea, my noise floor will vary as much as 11db in some directions on 6 Meters, and as much as 8db on 2 Meters. This limits my operating directions for weak signal work.

I'm hoping that moving the antennas away from my own home will reduce the noise, and getting them clear of the roofing materials will boost signal levels a bit. If it works, I'll try it again with a 7 element 2 Meter beam and a PAR Moxon antenna for 6 Meters. This "temporary antenna" set up may become a mainstay of my operation on the low bands.

222 and 432 grid chasing may be relegated to portable hilltop operations.

I hate to admit defeat, but my patience for indoor operations is lagging. Portable operation seems to be the best bet. The Flagg Mountain Tower, pictured above, is privately owned by a group that is restoring the tower and some cabins at the site. Access to the summitt is possible, but it requires a million dollar liability insurance policy and a lot of pre-planning.

We'll just have to see if that's in the cards for June or not. VUCC on VHF from indoor antennas is certainly possible. I've worked 149 grids on 6 Meters is less than a year. 91 Confirmed.

Two Meter has yielded 40 Grids worked, with 20+ confirmed. 222 and 432 in the teens. A great e-skip opening on 2 Meters could double those totals in an afternoon, but that doesn't happen very often.

The noise floor limits my "secret weapon" of Meteor Scatter via WSJT to a just a few directions. Limited participation hurts even more. Time to change the game.

Another option that I'm kicking around is EME. Currently running 200watts on two meters into a 7 element beam. 1/2 hardline and an SSB Electronics pre-amp. In theory, it's good enough to work several of the big gun eme stations. But it remains to be seen what the actual effect of the roofting materials are, even in favored directions.

Plus I know almost nothing about EME, so the learning curve is steep for an operator with limited time to devote to the effort. Anyone know a good EME mentor or one of the Big Gun stations who might be up for the challenge of working EME on Indoor Antennas?