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Log Periodics for Rovers

from Tim Ertl, KE3HT on February 8, 2010
View comments about this article!

"Editor's Note: Due to the popularity of some of eHam's older articles, many of which you may not have read, the eHam.net team has decided to rerun some of the best articles that we have received since eHam's inception. These articles will be reprinted to add to the quality of eHam's content and in a show of appreciation to the authors of these articles." This article was originally published on: April 27, 2003

Rover Antenna's

Log periodic's are as strange as us Rovers but they really work!

Like most great discoveries I discovered this one purely by accident. In the fall of 2001 I made a decision to further my Microwave distance in a big way.† Like most rovers the first question is how big a dish can I take this out with me? Where can I find one? Do I have to sacrifice my 50-432mhz (low) bands? What I found was my 50-432mhz Low Bands work better than ever! First let me tell you what lead up to my discovery. MY old microwave configuration was a 2x4foot dish that came out of the trunk of my van at each site. The beams were fixed on the roof, which meant I had a 4-wheel rotator that required gasoline to operate. †Lots of set up time and poor scores.


I borrowed a 4 foot round dish in the hopes that it might help my gain. I am sorry to say it did not help too much but I did make a 200+ mile contact on 5ghz, which got me excited. I also got a traffic ticket for blocking the rear center break light. So this configuration had to go. Still had poor scores but I told myself I was having fun on the microwaves. Something very new to me.


Now comes a bigger problem. A friend of a friend had a 6foot dish!† 4foot to 6foot had quite a nice advantage in gain so I started to look for answers. I found no one doing this. This only made me want to do it more. I figured I might make a real leap in distance with a 6footer. I finally had a friend tell me to strap the dish to the roof of my car and sacrifice my low bands. Low bands being anything I could not put into the dish, 50mhz thru 432mhz. I started to lift this 6foot dish onto the roof when I suddenly discovered this was heavy. My brother Robin (KK5SS) and I looked into how I could maybe use something like a Ginn pole that we used as kids to raise a large sail boat mast. I factored in information gathered from many people such as KJ1K, N1FGY, WA2AAU and others. One of the most interesting ideas had to do with air flow across the dish at 55mph. Face down it looks like a aircraft wing so it might take off! So I mounted it upside down with the feed pointing to the stars. This gave me a new problem. I needed new shocks on the van since now it pushes down! At least I didn't have to worry about it ripping the roof off my van. The end result of my 6 months of ideas and tinkering with this was something like this:


After road testing I was convinced that it was going to stay on the roof of my van and I started to look at the low bands. As you can see from the picture there is no real room for beams the way I had them before. I found a number of people like N2JMH that had solved this problem by leaning them down over the front of the vehicle pointing at the road or the sky. Itís a little hard to see but this is the best pic I could find. I took it at a gas station. If you look carefully you can see that the beams are only 1 foot or less apart from each other. On 144 and 222 this arrangement shows a loss of †pattern, which seriously curtails your usable range. It also showed some strange impedance bumps in the smith chart I could only explain by the proximity of the beams to each other. My old configuration was not much better than this so I started to look into doing the same thing.

After creating a mast and laying it on the top of the van I discovered that my beams would have to be shortened as well to keep them from hitting the road. Maybe a higher van would work better. N2JMH had a high standard style van and I had a Dodge Grand Caravan I purchased to do HF in the PA QSO party contests. I was about to give up on the low bands when I saw a cable TV truck with some bent up pipe on top near my home. I then had the idea to put a hinge on the mast that would allow me to have everything on the roof †and not hit the road!


Now I was cooking! Yea right. How many of you non-truck drivers ever notice how low some of those bridges are? Especially troublesome to us hams with beams on the roof are the low trees when your on a dirt road attempting to get to the top of a hill. I almost gave up again until I saw a HUGE †LF †log periodic antenna at the Long Island Macarthur airport. On a repeater I struck up a discussion about it and I had my first lesson on Log Periodic beams. Before you stop reading on, yes, I know log periodic's have a bad reputation for performance per dollar. Its true. When your trying to get three or 4 low band beams on the roof of a van you have to suffer one way or another. Since I was already borrowing many of the beams I used in the past the thought had occurred to me to purchase new ones. Yep, big $$$ for 4 beams. †I had already priced a few. I searched the beam companies for log periodicís and the only thing I found was that all these companies knew was that Log Periodicís are poor performance (gain) per dollar. I happened to hear about an IF rig (I needed a 28mhz IF RIG) from a friend. It was listed on eham.net. To my surprise I saw something that mentioned KMA antennas. I had not heard of them so I clicked. WOW ! They already had a log periodic called a "ROVER". Only problem was that it was too big to put on a van without assembly at each site. I struck up a discussion with Ed Griffin (W4KMA). He was listening to my needs and designed a better ROVER antenna. The thing that made the old one so big was 50mhz. So we made one that worked from 144 thru 432 which includes 222mhz. It was only 4 feet wide plus or minus which is plenty narrow for most roads. I looked around and found that W8SMD made a halo antenna for 6 meters. Ok none of these antennas are great but I †figured I could make some of the close in contacts and even if I could not work the same long distance stations I would be satisfied because now I had a 6foot dish on the roof of my van! This is what the result looked like.

In the travel position (down)


In the up position:

My next contest was June 2002 and boy it was interesting. Unfortunately I blew the power supply that runs many microwave things like 28v relays and such. I made almost no microwave contacts. I did have the low bands though. So I played with them†and worked a few stations over 200 miles! Even on 6 meters! I figured maybe the bands were good and I missed out on some real good contesting. The next contest was August 2002. My 144mhz IF rig died. I borrowed one the day before the contest from Sigurd (KJ1K). He is a real good friend. Again my contest had problems. Was I every going to get any luck? †Rain, hail, lightening and some wind created hazards I did not know how to cope with. Its interesting how loud hail can be in a 6-foot dish facing up. I made some huge contacts as long as 280 miles on 5ghz and yes I made 289 and longer contacts on 50-432mhz. It seemed that anyone I wanted to talk to I could. Same rigs and PAs for the most part but things were good. September 2002 it was my turn to fall apart. I slipped on a wet ladder and sprained my ankle real bad. Zzzzz if you know what I mean. After I woke up I made a couple of local contacts but decided to get down the hill before I hurt myself more. I slept a little and then went to a near by medical center that was open on Sunday! Some luck! Before my ankle I had made some incredible contacts on the low bands. This is now my third trip out and this contest the bands were reported by everyone as not being great. Add to that my down time and soreness on Sunday. So how come I was doing better than ever? My score was the best I ever had (20k points) I started to analyze what I was doing over these last three contests. Here are my conclusions:

  1. Height, I was now at more than 14 foot above the ground and at least 8 foot above the roof of the van.
  2. Less interference with other antennas. I now only have the dish, log, and halo.† With some fair spacing.
  3. The Halo was at 16 foot above the ground. Amazing 6meter contacts in all three contests.
  4. Rotation, Where I was fixed to the van before. Now had 360 rotations. Easier to find those other signals.
  5. Even my dish was higher up off the ground than any of my earlier attempts.
  6. Road clearance 11foot.
  7. Site set up time, less than 10 minutes including alignment to compass.


These factors made my low band performance much better than using larger individual beams. The result was that my 5ghz record is now 289 miles! (FN00 to FN32) thanks to a lot of patience from a big gun (W2SZ). I made low band contacts on all bands with every station that had the bands I did. Even though I did not make any really tropo type contacts it was clear after three contests that my new configuration was not only as good as but better than anything I had before. Mostly thanks to W4KMA for the KMA140-460 Log Periodic (See: http://www.kmaantennas.com) that everyone said would not cut the mustard. In the case of a rover less is more. Less set up time, less hardware, less interference and less coax. This has really worked out well for me. I thought it would be good to share this surprising discovery. Many of you would not have considered it. If I don't sprain my ankle this next trip out I plan to break my 20k point score big time this year... Look out you other rovers!
Tim Ertl KE3HT/r
http://www.lmrgroup.com/ke3ht/rover


Tim Ertl 3/27/2003

Member Comments:
This article has expired. No more comments may be added.
 
Log Periodics for Rovers  
by K9ZF on February 8, 2010 Mail this to a friend!
Nice setup!


73
Dan
--
Amateur Radio Emergency Service, Clark County Indiana. EM78el
K9ZF /R no budget Rover ***QRP-l #1269 Check out the Rover Resource Page at:
<http://www.qsl.net/n9rla> List Administrator for: InHam+grid-loc+ham-books
Ask me how to join the Indiana Ham Mailing list!
 
Log Periodics for Rovers  
by K0FF on February 8, 2010 Mail this to a friend!
Thanks for sharing. Nice workmanshp.

73 Geo>K0FF
K0VHF radio club
 
Log Periodics for Rovers  
by KL7AJ on February 8, 2010 Mail this to a friend!
A log periodic is an antenna that you can periodically log QSO's with. :)

Nice job. Obviously PDAs work, or they wouldn't have used them for TV reception for the past 60 years. :)



eric
 
RE: Log Periodics for Rovers  
by AC6IJ on February 8, 2010 Mail this to a friend!
I would really feel funny driving arround with all that contraption on my roof of the car. People would say it's just another Ham.
 
RE: Log Periodics for Rovers  
by WB2WIK on February 8, 2010 Mail this to a friend!
Very nice article!
 
RE: Log Periodics for Rovers  
by KC8VWM on February 9, 2010 Mail this to a friend!
Beautiful!

Thanks for sharing!
 
RE: Log Periodics for Rovers  
by WY3X on February 10, 2010 Mail this to a friend!
You should change your callsign to K3ALW.
(Awful Lotta Work!!!)

And I don't mean that in a derogatory way, I mean that it appears you've spent a gargantuan amount of time perfecting being a rover! Best of luck in the pileups!

73, -KR4WM
 
Log Periodics for Rovers  
by G6NJR on February 11, 2010 Mail this to a friend!
You Have of course checked with G0BG that these antennas actually do work i hope would not want another antenna to join the list of Myths would we now ..
 
Log Periodics for Rovers  
by KB0NMQ on February 15, 2010 Mail this to a friend!
very cool! Good luck in the contests & have fun!
 
RE: Log Periodics for Rovers  
by KINGFISH on February 15, 2010 Mail this to a friend!
Who is G0BG ? I don't understand your comment.
 
Log Periodics for Rovers  
by WA3UFN on March 5, 2010 Mail this to a friend!
Boy that sure looks familiar! Hope to see you again during our rover travels.
73 de WA3UFN
 
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