Using a Screwdriver Antenna as a Base Antenna (
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- เผยแพร่เมื่อ 30 ก.ย. 2024
- Carl, N4KCM, wants to know if he could use a screwdriver antenna as portable antenna but it might not be the best solution for him.
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Video title says "Using a Screwdriver Antenna as a _Base_ Antenna" however the discussion was all about it being portable?
Just don’t move around, then it becomes a base antenna. Biggest issue with screwdriver antenna is water getting into the mechanism and the like. On a car or POTA, you need can put them indoors and dry them out. On the apex of your house it won’t get the same TLC but on a balcony you can give it the right maintenance. As the man says, a lot of compromise in the design. It’s a balance between convenience and antenna efficiency.
1st, I gave a thumbs up. But I couldn't help noticing that Dave sort of changed the topic partway through the video, so -
"Using a Screwdriver Antenna as a Base Antenna", the title of the video.
I highlight this because for many years from the CB Radio to Ham Radio I've used ALL SORTS of mobile antennas as a "base station" antenna from various apartments. And they ALL worked quite well! I've incorporated a counterpoise that was 14 ga. wire about 18 feet long at which the end was wrapped around (in a coil) a peanut butter jar filled with water to weigh it down and keep the wire tight. Seemed to work quite well keeping the SWR low, AND THE BANDWIDTH quite wide on our meters and such. In the past, I thought about using "Screwdriver Antennas" for an apartment base station antenna until I discovered the Chameleon matcher rated @ 500 watts and the collapsible 17-foot telescoping whip antenna. Since then that's been my "base station vertical antenna at a mere 20 feet that for the last couple of years on the HF Ham bands has worked quite well.
KD83FQ/73
Been using a screwdriver antenna at the base for years. Works great. I did add a shunt coil to the antenna which helped. I cut the grass very short around the antenna pole. I added a metal mesh under the pole and connected it to the pole. 6 ft x 6 ft. Now the grass hides the metal mesh. 80 thru 6 is good to go. Don't over thing this. Its basic antenna theory.
I watched a video yesterday of a group at a park. One operator had a screwdrive on a ground spike that was through middle of a 5'x8' piece of aluminum screen. They said it worked great.
Same here, some 1” square concrete reinforcing mesh covers a 10’ x 10’ area thumped & pegged just into the ground, below grass level. The antenna is in the middle and ground bonded to the mesh. Works fine.
I have used a screwdriver antenna for several years on the roof of my patio. I live in a condo and understand no antennas. You have to be looking for the antenna to see it. It isn’t seen by casual observation. I use a Yaesu ft991 with a atas 120. I tried using random wire lengths for counterpoise. Never was very happy with the results. Then one day I was looking at a MFJ antenna (I think it was called a spider antenna) that uses ham sticks to make several dipoles. I went to Lowes lumber picked up an electric box (8 sided) that I could use 2 each on opposing sides for 40,20,15 and 10. Mounted two each onto the box. You need to spend the afternoon tuning the counterpoise to the center of each band. Made a mounting bracket used three magnets from old mag mounts and mounted it on a vent on the roof of my patio. I found this arrangement works well for me. Yes it still has a high Q but if I move off the freq. I originally set I just hit tune and it realigns to the freq. I want.
So, you added tuned counterpoise wires to your screwdrive antenna and are satisfied with the performance.
I have an ATAS-120A that will be putting on my car, but I plan on playing with it as a portable antenna. Perhaps sticking it on a cast iron BBQ grill by a park pavillion, or on a ground stake with radials. Maybe with elevated tuned counterpoise wires. I have two sets of couterpoise wires from SuperAntenna cut for 20m, 17m, 15m, 12m, and 10m.
Its all about playing and knowing what should work in an emergency.
I've run the Buddistick vertical portable forever and it works, however, now I'm using the Wolf River 90-10 meter coil and like it better - of course with ground radials. The Wolf River coil is more stable than the Buddistick coil. 73/K6SDW
I love my Wolf River Coil antenna.
What do you mean by stable? Like less likely to fall over?
@@aurtisanminer2827 I like the buddistick set up too, but the SWR would vary depending upon temp and especially rain/wet. So far, I haven't experienced this using the Wolf River coil which I feel is better made.....your mileage may vary.
@@eddy2561 ok, I see what you mean. I get the issue of varying swr on my mobile in the rain. The worst is road grime building up on my loading coil. It bridges over the coil and becomes untunable with my internal tuner. At that point I have to stop and wipe it off. Snowy and slushy roads are the biggest offenders. I cant say I’ve ever had variances based on temperature, but it doesnt get that hot up her in the north. I’ve heard of people in california catching their loading coils on fire while sitting at a stop light. Lol
What wolf river should I get
I run a Wolf River Coil and a 5 ft fiberglass “CB” firestik in my attic for HF. I typically leave it set for 40m but it’s right by the hatch so I can change it easily enough. Works quite well.
I would actually say that even at resonance a ham stick is a low Q device.
An elongated inductor cannot be high Q.
A pancake or conical inductor has much higher Q.
I think Dave made the point that you probably not be less than 3:1 across any band, but perhaps just the voice or digital portions.
Hello all, I have a model 100 screwdriver antenna from Tarheel Antennas and I have used mine while camping. How I setup mine is, I have the mounting bracket for the vehicle mounted on mine. I took 2 u-bolts and drilled holes in the mount and used about a 2ft 1/2" inch water pipe and drove it in the ground about 1ft just to support the antenna. I made up a ring of #12 bare copper wire about 10" diameter and soldered it together. I then connected 10-8Ft. radials to the ring and attached the ring to the mount. It worked well for me. I made several contacts with that setup. Now I didn't leave it setup while we were not there. That's how I did mine. Hope this helped. 73 Dave AG4QH
A Radial is a capacitive element that directs the E field vectors between the active vertical element and the radial(s).
The changes that occur along the E field lines between the active element and the radial(s)
cause rotating magnetic fields
and the direction of propagation for the TEM wave signal is 90 degrees to the E field lines and away from the source.
Pretty simple really.
I have no idea why this remains a mystery to the majority of Hams.
Try drawing it. I'm picturing E waves leaving the vertical antenna in all directions vertically and rotating 360 degrees over one wavelength. Drawing one finite wave is ok. Drawing all the wave in radiating in all directs towards the horizon gets ugly.
@@vironpayne3405 I think it is much easier to imagine the lines of potential difference between the elements (like across the plates of a capacitor)
and then when we consider Faraday's/Maxwells laws that tell us changing or moving charges create a rotating magnetic field around the axis of the e field lines,
we get to see an expanding ring of alternating magnetic rotations at frequency.
The magnetic lines are perpendicular to the direction of propagation
and this is why we call it a transverse em wave.
These rotating magnetic fields create alternating electric fields in any area subject to the changes.
There is a great video on maxwells laws on youtube that is animated.
It really helps get a visual idea of how moving/changing charges create magnetic fields etc.
@Dave - Rather than PORTABLE, can you talk a bit about using a screwdriver as a BASE antenna (as in the attic of a house or condo) and what you can do to optimize the setup?
I think Larry above addresses that above a set of tune counterpoise wires cut for each band.
About using a screwdriver antenna such as a Yaesu ATAS120A. In a car or truck, using the chassis as a counterpoise works. However, in an RV, the chassis can be connected to electrical ground through the shore power plug. How will this affect the antenna?
Adminral/Capt Picard may not like the screwdriver antenna. Has high Q!
Im glad you emphasized the term "Designed As " a mobile antenna . Most hams dont understand that a mobile antenna design assumes an average size ground plane and a maximum height to clear trees and overpasses (8 to 10ft seems to be the magic number) . My 5 ft balcony isn't quite suitable for most mobile antennas below 20M especially when you have people living above and below me .
If you don't mind the work of tuning or you are an digital guy that seldom changes frequency, you would probably like a magloop.
I have two magloops as I am a condo dweller and I always look for easy to deploy portable antennas. They are not my favorite antenna because I like to frequency and band hope working phone. For me the tuning is too much work.
However, they are great antennas when it comes to nulling out local noise by pointing the antenna at the noise source. For me it is all the airconditioners beside my condo. Unfortunately I have to place the loop at the front of my condo in order to null the airconditioner noise, so I cannot leave it up.
There is a tree canopy that I throw an EDHW antenna over that usually has almost tolerable QRM noise that use the most at home. As its a tree canopy I leave the wire in the tree and just put away my transformer and coax. Very few people know its there. I work 80m-10m.
Yes, You can use your screwdriver antenna as a home base if you give it a good ground reference system
though you might be better using a longer wire in the air and a ground wire or wires being fed by a good ATU.
Thanks again for another great antenna video Dave. 73, K7KS
Why buy "off the shelf"? Make your own antennas inexpensivly, then you will know how it works and how to fix it in case it breaks! You can copy ALL commercially made antennas. Who is out there to tell you NO!
If I weren't so lazy.
I was kinda hoping that this video would explain how to use a screwdriver antenna as a BASE ANTENNA as the video title stated.
I suppose a discone wouldn't be called a dipole, would it?
Its a fan dipole.
Good screwdriver + autotuner = $$$$
Scorpion makes a dual screwdriver dipole for remote ops. You’ll pay quite the premium, though. Each screwdriver antenna is around a thousand dollars.
What about two screwdriver antennas to build a dipole?
Smells like hoa antenna to me
Hello Dave. Great video. I have a Hi-Q screwdriver antenna. It worked quite well when attached to a trailer hitch on my car. It did not work as well when I used it as a portable antenna. It was okay, but not as good as a dipole. There is one thing that I had a hard time understanding with the screwdriver antennas and or stick antennas. It was the impedance matching coil at the bottom of the antenna. I think that the antenna has a very low impedance at the feed point. If you do another video on portable antennas, I would like it if you could explain the matching coils or devices for impedance matching for portable antennas. Thanks
Make ground radials out of insulated wire. Thanks for that pearl. I stand mine up on driveway marker sticks. I took your advice and doubled the number of radials and made them short. Worked great!
Dave, another excellent video. Could you comment on COMPACtenna 20m/2m/440 which might be another option?
I have a Tarheel screwdriver I have mounted on the side of my Pool cage here in a Florida HOA. The cage acts like a counterpoise and works Great.
Thanks for the tip.
Question, can you mount one on a pole to raise it up off the ground? Mine has been setting in the shop since I don't have it mounted on the truck anymore. I was thinking of using it at home for vertical use. 73, ke4ooo
Try it and see. It will work. The question is whether you use ground radials or counterpoise wires to make it work, and how many.
An old fashioned GM bumper jack, which the Jeep folks still commonly use under some name like a high lift jack, can pull out ground rods and even sign/fence posts. You may need a way to weld or coonect a ViceGrip to it in order to grab the pole.
Just wrap some chain around the ground rod and jack it out. It will pull rebar out of rocky soil.
ALWAYS use a ground round! Easy to remove 2 4' sections connected afterwards with 6 ga. Copper wire. To remove: stand over rod straddling both sides. Bend down and snap some vise grips on the rod parallel with the ground. Grip the handles in one hands fingers and slip your other fingers around the jaws . Twist 180° left, then right while firmly and slowly pulling out of ground. Been doing it for years and never lost a rod. This is a variation on an old fence man's trick...large pipe wrench on a temp fence post can be twisted out easily as well. Obviously, I wouldn't try to pry an 8' rod.
Dave, you do not only sacrifice bandwidth with the screwdriver or any other base loaded antenna, you also might mention the losses in the coil. A 40m screwdriver is about as efficient in regards to ERP as a 2m rubber duck.
There is a hospital system in the greater Houston area that uses screwdriver antenna's and long wire antenna's for it's ham radio stations at each hospital location for EMCOM's.
de W5KAL
That sounds like a great plan. Frequency agility in both vertical and horizontally polarized antennas to optimize signal strength that could occur from cross polarization between stations. Someone was thinking.
If it acts like a full sized vertical,
How does it compare to a 1/4 wave GP antenna on let's say 40 metres?
Is it down in dB or the same as a 40m GP ant?
You can use for POTA
KQ4CD PAUL ⚓️
In the Army Signal Corp back in the mid to late 1980s I handle 8ft grounding rods on my generator and comms shelter on a 2.5 ton truck by driving them in at a 45° angle. When it came time to leave I wrapped the 1in ground braid several times around the ground rod below the head of the rod. Then I tied the other end to my truck and almost never had a problem.
I do remember breaking my ground strap a couple of times. One time I remember taking one of the big shelter tiedown cables and putting its hood below the head of the ground stake. The head snapped off and made a pretty good projectile. Obviously the rod was pounded into a large rock.
That equipment is what in Britain we call Squaddie-proofed. Designed for the “practical” approach of the military😂
And here I thought a haiku was a Japanese poem😂!
Woow