14 1/2 ft Texas Bug Catcher

[W7LPN]

I seem to have hit on a good combination. I mounted it on the towing stinger by welding a heavy duty washer over the ball hole to fit the nylon washer insulator.
1. CWS UNUN 28-12.5, water proofed, zip tied to the stinger,(18" Ground cable to frame) 28 Ohm on 20M & above, 12.5 on 40 & 80
2. Stainless 4 ft mast 3/8 X 24 both ends
3. Henry's 480 Coil from Texas Bug Catcher w/ new banana taps(Great Henry&#33.
4. 1 Ft mast above coil, from Henry
5. 2 FT X 6 stainless radial, aluminum hub, Capacity hat from High Sierra, adds 6 ft vertical hight.
6. 8 1/2 ft stainless whip w/ top 3 ft bent @ 45 degrees to keep from smacking street lights, Har! doesn't effect performance.
7. Auto tuner for 6-17 meters.
8. It has to be anchored to the top of the tail-gate w/ non conductive materials. I'm using a nylon cutting board, knotched w/ velcro to secure it.
Now I know it's tall, but it works so well I'm willing to have the inconvenience. I have been able to get thru the noise and Pile ups even with competing base stations.
I act as a relay on the west coast noon-time net.
If I completely bi-pass the coil, I'm resonant on the entire 20 meter band at >1.5:1. This is why I said that the large capacity hat seems to widen the band coverage. It's pretty narrow on 80 meters using 2 taps, one for the farm net 3.937MHz and another for country cousins 3.970MHz. A good impedence match is the key.

# Not to bash the Screwdriver crowd, but this seriously out performs them, unless getting out of your rig to change taps is difficult due to age or ailments forget the screwdrivers unless they have huge coils.
I just wanted to post my experiences in case someone else wants to do this. I won't use anything else mobile. #

[W5DXP]

Quote[/b] (w7lpn @ June 13 2007,00:51)]Now I know it's tall, but it works so well I'm willing to have the inconvenience. Not to bash the Screwdriver crowd, but this seriously out performs them, ...

At the last CA shootout I attended, three antennas tied for top honors. One was a bugcatcher with top hat, one was a screwdriver with top hat, and one was my top-loaded junk box antenna. All entries were limited to 12.5' above ground which I assumed to be the legal height limit in CA. You might check with the authorities in your state to verify that your 14.5' antenna is legal.

Shorting out parts of the bugcatcher coil with those taps is known to lower the Q and increase the losses. Screwdrivers don't have that problem.

[W0LPQ]

Cecil has 2 good points. Shorting out the coil and height.

Our shootouts in Indiana are limited by 13' 6" which is the height of overpasses and bridges (unless otherwise marked).

If an antenna is over that number, they are disqualified until they are lowered to meet the magic number.

The rules here say ... if you drove in with it ... and meets the height .. then you are good for the shootout.

If you have to assemble it ... then you are out of luck.

Top hats to improve things.

Bill, W0LPQ/9

[W5DXP]

Quote[/b] (W0LPQ @ June 13 2007,08:43)]Cecil has 2 good points.

How about one more point? The lower part of the antenna being parallel to the conductive tailgate will reduce the field strength of the antenna. As can be seen in the photo of my mobile screwdriver antenna at:

http://www.w5dxp.com/shootout.htm

I have removed the tailgate which increases the field strength.

[W0LPQ]

Cecil I had thought about that one ... but thought that one got chewed up quite a bit some time ago, but you are very correct ... any part of the mast in that close proximity to the tail gate (unless it is solid plastic) does in fact cause problems with the antenna radiation.

I am not sure that anything over 13' 6" is legal anywhere. One of our shootout guys (K6TEX) is a truck driver who has spent a lifetime on the road and getting nosie out of his radios ... has only 13 foot 6 inches total for his antenna. The tip of the antenna was (last time I visited with him) just over the top of the trailer.

Bill, W0LPQ/9

[K9STH]

Back in the 1960s there was a fellow in California who had a full sized quarter-wave (33 feet tall) mounted on the bumper of his Volkswagen "beetle"! He had the antenna "motorized" so that when he approached an underpass that he could immediately lower the antenna. He had an outstanding signal on 40 meters from his mobile.

There were several photos of the automobile in QST during the 1960s.

Glen, K9STH

[W7LPN]

1. Before I put the 45 deg bend in the top, I smacked an iron R/R overpass marked 14'6". Lately I havent hit anything but some low branches and knocked some leaves off. #
2. Most of the Antenna guru's I read from agree that a skinny screwdriver is nothing but a giant resistor. A friend of mine, who shall remain nameless, has narrow screwdriver from a major company that's worth less than a straightened coat hanger attached to a tuner. Another I know of, mounted above his P/U bed, next to a fibeglass camper shell, has about half my signal strength.
3. #14.5'- 3ft@45degrees= 13 ft. Idaho is a major thuroughfare for heavy/wide loads going northwest, so I doubt it's conservative on heights.
4. I'll tollerate the tail-gate, I need it to stabilize the mid mast section.
Thanks for the interest. It's probably got flaws, but I'll keep it anyway. Afterall an "Amateur" built it. #
# # # #:blush:

[W0LPQ]

I am not going to get into a P&M contest about Screwdrivers and Bugcatchers. Have seen both do very well ... If you want to slam them .. hey go for it. My Predator does quite well ... has even beat a couple bugcatchers in the shootouts here. But a giant resistor, I don't think so.

I know what Idaho roads are like. Born in Twin Falls, my cousin used to live next door to your trailer lot.

Center loaded antennas do quite well ... which includes Bugcatchers and screwdrivers.

Bill, W0LPQ/9

[N4CD]

In most states, if you are over 13'6", and you damage something, you are liable.....

However, even when underpasses are marked 13' 6", that was orignally!. IF they have repaved it, it is likely 2 or 4 or 6 inches less, as they add pavement on top.

There are places with only 12' 6" clearances, and some old underpasses with less than 11 feet. I've seen road tunnels with NINE feet of clearance..where folks have had to remove their antenna to get through (KY) ...or go 50 miles around.

Anything above the coil is doing 5% of the radiating, so you can substitute a plate, or whatever you want to get capacity to ground. It is just the capacitive tuning part of the resonator.

Look at how much unblocked mast is UNDER the coil, and you can quickly compare how antenans will do.

[K4KWH]

Quote[/b] (W0LPQ @ June 13 2007,17:22)]I am not going to get into a P&M contest about Screwdrivers and Bugcatchers. #Have seen both do very well ... If you want to slam them .. hey go for it. #My Predator does quite well ... has even beat a couple bugcatchers in the shootouts here. #But a giant resistor, I don't think so.

I know what Idaho roads are like. #Born in Twin Falls, my cousin used to live next door to your trailer lot.

Center loaded antennas do quite well ... which includes Bugcatchers and screwdrivers.

Bill, W0LPQ/9

AH, there's another thing about the Bugcatchers. #No question they are better..............................until. #

Until you are there with a super Hi Q coil and in QSO with that country you've been just dying to work mobile.

Until that tractor trailer pulls alongside and your contact just fades away. #Now you are in a mess until that truck gets by, you slow down or the truck or you turns off! #With a reasonably efficient screwdriver, you just tap the switch and you are right back in QSO! #Your contact may not know you had a slight problem. #Your Turbo Tuner or other auto-positioner may have taken care of it in a second.

Yes, some screwdrivers are inefficient. #Some of them try to offer all-in-one coverage in an attractive package. #Like 160 thru 10 coverage in a 9 foot package.
Look closely at the loading coil. #One model I know of uses #20 wire so close-wound, there aren't even any grooves (transformer winding) needed to separate the turns! #Sure, they work(?) after a fashion. # They are a slop bucket really with a Q of a 50 ohm resistor. Then there are the ones that are 2, 2 1/2, 3" diameter with #14, #12 wire wound at 6 to 8 TPI. #The 2"+ ones work VERY well, thank you! # The 3" ones (Predator, Carolina Cyclone II, Texas Twister by Henry Allen) will stand proudly and put out a really fine signal.

The question is, really, WHAT is a "good signal"? #What are you trying to accomplish? #Are you trying to establish bragging rights? Be the loudest thing on the air? #Squash the other mobiles? Or are you looking for a VERY reliable mobile signal that works VERY well, and does so even under dismal conditions? #The screwdriver is nothing to sneeze at. Neither is a Bugcatcher. But what *I* like about the screwdriver is the ability to operate in the presence of anomolies that sometimes work against the super Hi Q antennas. #When you start getting beyond that 4" diameter, the Q will, IMHO, sometimes work AGAINST you. The higher the Q becomes, the narrower the bandwidth and the MORE the surroundings degrade the performance---eventually to the point of making reliable communications impossible! #We once ran some tests with a 6" dia coil. #If you moved 10 feet away from the original spot, it was out of tune and unusable!

It's tit for tat! #Depends on what you want! For overall and all round performance I don't want to go back to the Bugcatcher (and I have MADE plenty of them)!

Hey, you mess with me, I'll build a 4" Carolina Cyclone!


73

Jerry