Recently the VHF Contesting E-Mail List has had some interesting discussions about "compact beams" for indoor attic installations. While I think the Directive Systems "Rover" beams are a great solution, some other interesting ideas have also been kicked around.
Even if you're not interested in "contesting", this list is still a great place to learn a lot about VHF in general. Here's the information:
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Today, there was a post from James Duffey, KK6MC which offered a number of suggestions that might be useful for those contemplating operation with indoor antennas. With his permission, I'm going to reprint that post below.
One of the ideas that he mentions is to install longer, fixed antennas pointed towards population centers to supplement shorter antennas on rotors. This really intrigues me! My attic had only two locations that were suitable for the installation of rotors and antennas. The largest of these contains my "stack", and I've just about maxed out the length of antennas that can fit that space.
I went so far as to have an architect help me decide where I could safely move structural supports to give me more space. But the attic contains other voids which could offer very long booms a home, only they couldn't rotate. Hmmm.... That really has the wheels turning.
As compared to amplifiers and hardline, antenna gain is the cheapest way to get a bigger signal. Especially on 2 Meters and 432, I could really benefit from longer antennas. The trick now is to figure out which directions and available, and which would do me the most good.
My goal wouldn't be higher contest scores, but more grids.
Here are Jame's suggestions, which I think all have a lot of merit.
A Moxon rectangle as a simple to build with proven performance 6M
beam. It can be built simply from materials obtained at your local
hardware or building supply store:
< http://www.n2mh.net/moxon.htm >
If you have room to swing the Cushcraft A270-10s you will have room
For 144 MHz, 222MHz, and 432 MHz, the WA5VJB Cheap Yagis are easy to
build, have good patterns and gain for their length.
< http://www.wa5vjb.com/yagi-pdf/cheapyagi.pdf >
To see how you can put two of these on a single beam, look here:
< http://www.wa5vjb.com/references/Cheap%20Antennas-LEOs.pdf >
There are various sizes so that you can pick the one you that will fit
in your attic.
These beams can all be stacked. You can go lower in stacking distance
than is usually suggested. If you don't have much space, two feet is
OK on 2M above the 6M beam and a foot above that for 432. The pattern
will start to deteriorate, but the SWR and gain will not change much.
You will have to accept compromises.
You don't need to stack the beams so that they are all parallel. You
can put the boom of the 2M and 432 MHz beams parallel to the elements
of the 6M beam for instance. This is less than optimum in terms of
passing stations from one band to another, but it can get you a bit
You also don't need to swing the beams a full 360 either. You can make
the Moxon so that it is reversible; see Cebik's page for details on
this. You can also build beams for the higher bands this way, put the
beams back to back with a common reflector and then switch the feeders
from one driven element to another to change the direction.
Depending on the shape of your attic, You may also consider multiple
antennas pointing in different directions. For contests, it may be
usseful to have long boom antennas pointing towards population
centers, even if they can't be rotated.
Some thoughts, I hope that you find them useful. Go ahead and try
things, it is better to get on the air with a sib optimal antenna than
waiting until you get the "best" solution. With an antenna up and
installed, you can operate and see where your problem areas are, then
pay attention to improving those. - Duffey
Cedar Crest NM
Thursday, June 26, 2008
Soldiers and law enforcement types refer to "situational awareness" as being keenly aware of the environment that you're operating in. Alert to possible opportunities to gain a tactical advantage.
If you're operating with indoor antennas, it becomes even more vital. Fortunately, there are lots of ways to get this vital "intel".
The best way is also the easiest...use your ears. Park your radios on the weak signal calling frequencies when you're working in the shack. 50.125mhz for six meters, 144.200mhz for 2 Meters, 222.100 for the 222 band, 432.100 for 70cm, and 1296.100 for 1.2ghz. All in USB mode. Obviously, you're listening for CQ's...but also other subtle "cues".
For example "Sporadic E" has a bubbling sound that is very different from other types of noise. You'll usually hear this on six meters and 2 meters just prior to an opening. Sometimes you may hear it, and the opening will never come, but often it will.
You may also want to program in the National Weather Service NOAA Weather Radio frequencies. They're in FM mode, and spread out over seven channels:
|162.400 ||162.425 ||162.450 ||162.475 ||162.500 ||162.525 ||162.550|
I made a simple chart that noted each of the four major beam headings, North, South, East & West, and listed which stations I could usually receive under "normal" conditions. Depending on the direction, I average about five channels out of seven. Those with outdoor and larger beams will likely get stations on all seven frequencies.
During enhanced conditions, tropo, and rarely even Sporadic E events, you'll suddenly have new stations dominating the frequency or two stations competing for the FM Capture Effect! This is a sure sign that 2 Meter is open! Get on 144.200 and make some noise!
Here in Central Alabama, it's easy to tell when the band is open to the West. NOAA stations in Mississippi use a female "text to speech" computer voice, while Alabama is an all male voice state. If I hear a female voice, then I know the band is open! Just remember these are in FM mode, not USB.
Another great source of information is the Internet. I can't recommend installing a high speed Internet connection in the shack enough. Cable modems, DSL, or satellite can provide high speed connections to the web. For VHF Men, there is nothing like it. Here are some of the sites that I often keep opening while operating:
- DX Sherlock VHF-UHF Real Time QSO Maps: This pulls data from the DX Spotting networks and displays them as points on a map of North America. There is a lag in the information of several minutes, but it can give you a great idea of where the band is open to. Very useful for 6 Meters and 2 Meters...less so on the higher bands.
- 144 Mhz Propagation Logger: Kind of a combination DX Spotting tool and "chat room" for weak signal 2 Meter operators.
- VHF (APRS) Propagation Map: The technology here is very cool. This map uses the 2 Meter APRS network to detect signals that are being propagated past the normal range of digipeaters (LOS) and plots them in shades of yellow, orange, and red. Areas of red usually indicate tropo or Sporadic E openings. There are "false positives" from time to time, but in general it's a great tool. I only wish that the page would update itself every few minutes, instead you have to remember to "refresh" it if you want real time information.
- Bill Hepburn's Tropospheric Ducting Forecast: Basically a "weather forecast" for tropo propagation. Like your weatherman, Bill's map are not always accurate forecast, but they are reliable enough to make them daily viewing for most VHF DX'ers.
- Sidewinders On Two (SWOT) Radar Map: Sidewinders on Two is the oldest organization for 2 Meter DX'ers and membership is highly recommended. Their web site also contains instructions and a real time map of NWS radar. Unlike your local TV station, the NWS maps don't filter out "ground clutter" or "false returns". This ground clutter often amounts to tropo or strong backscatter openings on VHF
Remember though, nothing beats "chair time" and your ears!
73 DE N1LF
Wednesday, June 25, 2008
Sorry I forgot to post the photo of the KU4AB.com 6 Meter loop which is also mounted in my attic. See the photo on the left.
It's mounted on the other side of the house, well away from the "stack". It's fed with Andrews 1/2" hardline which runs about 25 feet down into my shack in the garage.
To make installation of all my antennas easier, I cut a hole in the ceiling drywall, about 2 feet long by 1 foot wide. I then attached some very pretty maple shelving boards in the form of a "box" to route cables from the attic down to below desk level at my station. This makes running even hardline a snap! And it looks great, matches the maple workstations in the garage, and passes the "XYL Test".
The KU4AB loop is connected to my Icom 746 Pro, while the 3 element beam works into the Icom 756 Pro III. The advantage of the loop is that I often hear stations off the back of the beam that I would otherwise miss. I've also worked over 35 grids and many, many states on the loop alone.
I also have a KU4AB 2 Meter loop mounted on my pickup truck. I run a Yaesu FT-857D in the truck, and use it to work weak signal 2M stuff. Again, not a world beater, but very solid, stainless steel construction. Plus the price is nice, and delivery was super fast.
If you're like me, I usually read the product reviews of any amateur equipment at www.eham.net. Take things there with a grain of salt, cause some guys post negative reviews to try to screw up ratings, and some don't really know how to operate the equipment that they buy...but with enough reviews you get a sense of how good the product really is. KU4AB antennas receive good ratings, and I can see why.
I've seen some indoor installations where they stacked or "phased" KU4AB loops to give a bit of gain. Haven't tried it yet, but I may do so on the mobile.
Originally, I didn't think I'd have room for the 3 element Yagi on six meters, and planned to use the loop as my primary antenna. While it won't beat the beam, I have no doubt I could have worked 90% of the DX to date with it. Maybe the really weak double-hop stuff from the West Coast wouldn't have made the trip, but most everything else would have. VUCC would certainly be in range using just this antenna and 100 watts.
See you on the Magic Band!
73 DE N1LF
Above you'll see several photos of my attic mounted antenna installation. Some look at this and see very short "rover" style Yagis, with large beamwidth and modest gain. Instead, I see "Big Iron" where every available inch of space available as been converted into gain for my signal.
It's not even comparable to the average rover station, but it's an optimized design given the circumstances. As a former engineer, I can appreciate the elegance of that. All designs are compromises. The secret is in making the ones that hurt you the least.
You'll see photos of the VHF Shack (Icom IC-910H). Not pictured is the Yaesu FT-736R that I use for 222. (Though I've ordered a Down East Microwave Transverter to replace it). You'll also see the Andrews 1/2" hardline mounted to the attic floor, pictures of the KU4AB 6 Meter loop (I use this as a "spotter" omni-directional antenna on my Icom 746 Pro. It's also fed with 1/2" hardline)
Also pictured is my original 2M/440 short beam, returned to vertical polarization, and some other innovative antennas from my "attic farm".
Hope this gives folks a better idea of my installation and maybe inspires some work in the lofts of your homes!
73 DE N1LF
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.
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
Big Iron. For serious VHF men, this brings to mine multiple antennas, phased arrays, and power dividers. Monster sized Yagi's perched high on towers, mounted on mountaintop locations.
Or in my case, a tongue in cheek reference to both the Marty Robbin's song and my very limited VHF/UHF "stack". I won't bore you with the details, but my wife's back surgery and recovery dictated a move into a single level house, and here in the South if you want that in a decent neighborhood, you're also talking about deed restrictions and Nazi-like homeowners associations.
Here in EM63, near Birmingham, Alabama that means "No outdoor antennas, period". No flagpoles, no TV "Log" antennas, nothing bigger than a small satellite dish. Yes, I could go to court. Yes, I could move, yes, I could do a lot of things. Thanks...but I've heard it all before. The fact is that for most of us ham radio isn't the most important thing in our life, and other considerations often come first.
My wife loves the house. She wants to live here, and I want her and my neighbors to be happy. If that means that I never make the DXCC Honor Roll, so be it. For the first year after we moved here, I made due with a couple of J-Poles in the attic, and a horizontal loop around the inside of my privacy fence for HF. It's an NVIS (cloud burner) antenna for sure, but it works great for ARES stuff---and I managed to work 90 countries without a lot of effort. Then, I was to fall victim to "The Bug".
It started harmlessly enough. I had mounted a small 2M/440 vertical beam in the attic to get into some distant repeaters. It was attached to a small TV rotor and some RG-213 coax. One Saturday afternoon while working in the attic, I switched it to horizontal polarization and went down into the "garage-shack". I tuned the radio to 144.200 and USB. Nothing but static on that December afternoon.
I remember thinking, "There's nobody on weak signal stuff around here". Ten minutes passed while I soldered a jumper cable for my soundcard interface. Then I heard a very loud, CQ. It was Jim, K4AAF in Birmingham. I responded to his calls, we exchanged "grid squares" and I told him he was my first ever weak signal contact after being a ham for nearly 40 years. We talked for over half an hour about VHF/UHF....and at some point, I started to feel light headed.
I was seriously ill, but didn't know it yet. The following weeks were spent looking at pre-amps, and Yagis...re-reading every issue of CQ VHF and The World Above 50mhz. Hmmm...the January ARRL contest was just around the corner. I wonder if I could work a few guys on that little beam. What the heck? The Icom 746 Pro had a 100 watts on 2 Meters, and it wasn't totally deaf, right?
Years ago, I had been a very serious TV DX'er. I had low noise pre-amps, hardline, an Icom R7000 with NTSC adapater, and even a phase box for e-skip. This VHF stuff wasn't totally new to me....I'd just never tried the ham radio side of things. How hard could it be, right? Besides, I'm not serious about this. I mean, I live in a deed restricted neighborhood. I'll just play with it a little. It'll be fun. Harmless.
That's how the sickness works. Within a few months, I had gone completely crazy. I wanted to earn VUCC on all the "low bands". 6 Meters. 2 Meters, 222, 432, and maybe even 1.2ghz. Purchases had been made. An Icom IC-910H, several pre-amps, a Yaesu FT-736R with 222 module, some brick amplifiers, and oh, yes...lots and lots of 1/2" Andrews hardline. Houston, I think we have a problem.
Thus begins the quest for VUCC using only indoor antennas. Like most travels, it's about the journey as much as the destination. Along the way, I'll try to share my experiences and inspire others to take up the challenge. I'm very much indebted to folks like Jack Bruce-WA5UUD, Jim Long-W4ZRZ, and Bill Olson-K1DY for their help and encouragement.
If you haven't tried weak signal work on the VHF/UHF bands, all I can say, is "Come on Up, the Weather's Great!"
73 DE N1LF