Wednesday, June 25, 2008

You want to do what?


Ah, what would life be like without the skeptics? Think of all the fun you'd miss out on if you never go to say, "I told you so". Or at least I hope that's how this all turns out.

When I told many VHF guru's of my desire to earn VUCC with nothing but indoor antennas for a location only 400 feet above sea level, the reactions ranged from laughs, and my favorite of all advice, "Move."

Fortunately, there were some who offered encouragement. To their credit, even some of the skeptics said, "It won't work, but if you want to try I'll help you". Then there were the true believers...like Bill Olson, K1DY.

After carefully measuring the space available in my large, open attic, I posted to the VHF E-mail reflector asking about antennas with tight turning radius that might fit my needs. Bill works closely with "Directive Systems" of Maine.

Directive Systems make an innovative line of antennas, specifically designed for VHF rovers, who must keep their booms short if they're to remain "street legal" on the highways. The trick is maximum gain in the shortest possible boom length. Bill suggested modifying these antennas for true "center mount" ignoring the center of gravity and other mechanical considerations that would affect an outdoor mounting.

So far, it's turned out to be the best and most important decision that I've made. Pictured above you can see the entire "Stack" which consists of the following:

  • MFJ 6 Meter Yagi. 3 Elements mounted on the bottom.
  • Directive Systems DS-144RS 6 Elements on 2 Meters. Modified "Rover" antenna.
  • Directive Systems DSFO222-10RS. 10 Elements on 222.
  • Directive Systems DSFO432-15RS. 15 Elements on 432.
  • Directive Systems 2325LY Loop Yagi. 25 Elements on 1.2ghz.
Next up, I added the Icom mast mounted pre-amps to the rotor stack for 2 Meters and 432mhz. A Mirage mast mounted pre-amp was added for 222. I've since found out that the noise figure on the Icom pre-amps is about 1.0db. Not too good, even for a broadband pre-amp. So with Jim Long's help, I'm upgrading these to the Advanced Receiver Research pre-amps.

Specifically, I'm adding the 160 watt RF Sensed, mast mounted GaASFET pre-amps. You can find a lot more information about these amps on this link to their web site, AAR GaAsFET.

The noise figures on these are much lower, around .55db. I did a quick test by installing them in-line near the radio...and they clearly improved the signal to noise ratio on 2 Meters. If you want to use them with some of the satellite rigs like my Icom IC-910H they can even install RF chokes to allow you continue sending 12 vdc up the coax. I opted to "hard key" them from the PTT line instead.
From a design standpoint, a lot of folks might question the considerable expense of this installation. The feedline runs are short, so I could have used Belden 9913, for example. It considerably less expensive, and the losses are not much greater than with the 1/2" hardline. My thought was that the entire installation is already a compromise. In a lot of cases, I'll be working stations who are at or even below the noise floor. If anything, every fraction of a db is more critical for an indoor installation, not less.

The installation has been "completed" to this point for about a month. I finished just in time for Sporadic "E" season on 6 Meters and the June ARRL VHF Contest. Results are pretty good so far. 109 grids worked on 6, along with four countries. 13 grids on 2 Meters, including four of them worked via E-skip. (My most distant contact on 2 Meter SSB has been in DM79 in Colorado), five grids on 432, and five grids on 222.

A lot of even modest stations could beat those numbers in a weekend...so patience is part of the plan. We're headed into the dog-days of summer here in Alabama, which should mean some good Tropo openings. Thus far, it's been mostly backscatter and E-skip. I've yet to be part of a really good tropo opening.

One lesson I learned already. Use CW!! If your code skills aren't up to speed, or don't even exist...you can still take advantage of this mode. Using a soundcard interface like you'd use for PSK-31, you can use software like the amazing, "CW Skimmer" to help you copy callsigns and grid square exchanges.

My code speed is good up to about 15-20wpm...but during a recent e-skip opening on 2 meters, there were five or six stations all sending CW at the same time on 144.200. No way I could copy all those signals by ear at the same time, but CW Skimmer had no problem with it.

Likewise, there are several software programs like CWType that allow you to send flawless Morse Code using only your computer keyboard. The bottom line is that if you need those grids, CW may be the only way to get them.

Another "secret weapon" that I'm just now trying is the amazing WSJT Meteor Scatter and EME modes. This amazing software allows you to work 6 Meter and 2 Meter meteor scatter contacts almost 24 hours a day. And as it turns out, a smaller 2 Meter Yagi might actually be better for this mode than those big boomer, because the wider beamwidth allows you to "see" more of the sky and catch more meteor pings! Score one for the small pistols.

I'll let you know what kind of results i get with WSJT as I gain more experience with it. I think it's the only real option for 2 Meter VUCC that I have. Perhaps even 222!

Just the other day, I received an e-mail from another "true believer", Dan O'Connel, WA7TDZ. Don operated with quads for 6 Meters and 2 Meters in his attic for years, along with a 432 "Quagi" mounted between them! My his estimation he has worked close to 100 grids on 2 Meters, and over 300 grids and 38 countries on 6 Meters! All with indoor, attic mounted homebrew antennas!

So, maybe I'm not crazy after all. Maybe it can be done. I'm still not aware of anyone who claims to have earned VUCC entirely on indoor antennas on any band other than 6 Meters, but that doesn't mean that they aren't out there.

Until receiving Don's e-mail, the "best" grid square totals I'd heard of for 2 Meters with indoor antennas was only 14! Don thinks he worked close to 100, without the benefit of WSJT.

73 DE N1LF









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