Anybody run a 102 whip with an autotuner?

[Captain Kilowatt]

I picked up a Yaesu FC-40 autocoupler a week or two ago. While passing through Salem New Hampshire I just HAD to stop into HRO and see what they had. I have it just sitting in a small storage area in the rear of my '05 Escape but I need to mount it properly and relocate the antenna to allow for feeding with a single wire feed instead of coax feed from the tuner to the antenna due to losses on the lower bands.I also need to move the HF antenna from the passenger's side to the driver's side due to height clearances of the tree branches. Things tend to be a bit better down the middle of the street instead of next to the curb.Right now I am feeding a 20m Hamstick but I may switch to a regular 8 foot fibreglass antenna when I install everything properly. Anybody else out there run any type of autocoupler (autotuner) and an 8 foot whip for all band HF? It seems to tune fairly well and will load up on most of 80m straight up to 6m with the exception of 17m which I hope to solve with a change in feed methods and better grounding.

 

[C W Morse]

It will probably work OK on 20 Meters UP! 75/80.....not so hot! "Tuners" with a mobile just ain't gonna cut the mustard down on the low bands. Remember: a mobile antenna of the HIGHEST "Q" known to man is only about 5% efficient referenced to a 1/2 wave dipole. I have an LDG autotuner with a Cobra Ultralite Senior dipole at home. I like it OK. Only because I don't have room for dedicated dipoles for all the bands I must work (Ham, USAF Auxiliary, Fema, SHARES) I have to compromise. Mobile just doesn't lend itself to autotuners--tho people DO use them! I suppose that's why I go for the screwdriver so much! The screwdriver is so flexible and instantly resonate-able that it has about taken over much of the mobile HF market.

But good luck with the tuner. I hope it works well for you!

 

[Captain Kilowatt]

Actually it has been working quite well for me.10 and 15m have been pretty dead even on the beam here so not much of a chance to try it while mobile. 20m is a snap and I see no differance between the fiberglass whip,which I measured as 99 inches, and the 20 Hamstick.(I forgot I had cut a few inches off it a number of years ago for a better match on 10m.) Despite what some folks claim about the Hamsticks being nothing more than a dummy load on a stick I have made many nice DX contacts with it including 3B9C via longpath,15,000 miles. At this point I see no differance in performance between it and the whip on 20m. I have not tried 40m yet but I worked a couple guys in Britain and Ireland the other night on 80m so it can't be too bad. I don't know why you would say that mobile ops do not lend themselves well to autotuners Jerry.The military runs them on just about every kind of vehicle.SGC has been making them with good sucess for years. I opted for the Yaesu FC-40 due to price and the fact it is 100% water proof if I ever decide to mount it externally. One other nice thing is that once I get the memories set there is not a screwdriver antenna made,not even yours , that will tune as fast. LOL 200 memories and 1/2 second recall time.I just need some more time to try it out more.Too bad there were not more HF mobiles around here to compare too.

 

[C W Morse]

C'mon now! You asked about 80 Meters! And you came BACK with 10,15 and 20! The facts ARE: (and I said so in my original reply) 75 Meters on a mobile auto-tuner and a whip will STINK *IF* it is compared with a large diameter center-loaded
whip (bugcatcher) OR a screwdriver. All one has to do is read the California antenna shootouts on various ham websites! Take a DK3 by Don Johnson and both of you talk at the same time with the same type radio and 100 watts, the screwdriver will WALK over the top of the tuner/whip combo! It has nothing to do with
*my* screwdriver or anyone else's. It is simple, proven antenna
theory in practice. Forty meters is almost as bad! :shock: Now, I SAID that the frequencies would work pretty good above 20 Meters with the autotuner, now didn't I!

Same thing with the hamsticks. ABOVE about 10 MHZ, they start to work pretty well. On 40 and 75 Meters, they ARE dummy-loads-on-a-stick!!! An autotuner tunes................nothing. It matches the impedance of the antenna to 50 ohms, and absorbs the heat generated by the mismatch. You STILL have 9 feet of antenna where it is "asking" for 125! Sure, it will work, but at what level does it begin to disappear into the fog? The hamsticks are very FINE wire wound on a small core like a transformer. It's highest resistance is up in that eensy loading coil; the radio is looking for a total impedance of 50 ohms, and the major portion of that resistance is in that coil. The radio doesn't care where it GETS that total from. This is also why you can often run a hamstick without ANY matching device at the feedpoint--depending mostly on that coil--down on 75 Meters. All that resistance is also why you can't run much power with a hamstick; much of your signal radiating from the coil and above is lost as HEAT because the resistance is so high! But if you use a higher efficiency center or top-loaded coil and obtain the rest of the impedance at the bottom (taking into account the radiation resistance which, btw, we can't do much about), the antenna performs much better. And a mobile station, due to a number of factors, NEEDS all the help it can get! As you go higher in frequency, the resistance decreases because the coil requires fewer turns (inductance)

The military runs autotuners--I work with them, too, BTW, for a number of reasons. One is the same reason *I* run one on the base shack. I have to run so many frequencies I can't possibly erect enough dedicated dipoles to cover them all! So compromise is in order. However, the apex of the 140 foot dipole is at 60 feet, I have another NVIS antenna at about 8
feet running at right angle to the regular dipole, a Cushcraft vertical, an A99, a 6 Meter dipole off the tower and a 2 Meter beam. But the base station has a HUGE advantage over the mobile for a lot of reasons. So I choose the most efficient antenna I can for mobile AND, for convenience, the screwdriver wins. OF COURSE, it won't tune fast, but fast enough to do the job! I choose Performance over convenience of band-hopping!

However, if you get satisfactory results with a pie plate and a tuner, that would be wonderful !

I didn't mean to disparage the tuner, QRN, I was just trying to answer your question honestly from known theory and my own experience!

73

CWM

 

[CDX1220]

hmmm :roll:

 

[Captain Kilowatt]

C'mon now! You asked about 80 Meters! And you came BACK with 10,15 and 20!

Uhhhh...............where did I ask about 80m? I DID ask about ALL BAND operation. Yes I am well aware that the large diameter antennas will perform better than a straight whip especially in the bandwidth department but I did not ask what the best antenna was, I can read reviews as well as anyone else, I asked if anyone else had experiance running a whip and an autotuner.Due to mounting considerations,windload,and the need to remove the antenna often as well as just plain ugliness of the big screwdriver antenna (the uglier they are the better they are I find ) I have a need for a simpler antenna. My question was directed at those who use an autotuner while mobile and if they see any better performance using a straight 10 or 11m 1/4 wave whip or as some do, use a 20 or 40m Hamstick with the tuner for all band operation. I am leary of using a Hamstick on another band due to the extreme voltages that can develop and burn out the coil.A straight whip does not have this problem. I am also working on building a centre loaded mobile antenna with a wide spaced helix base on a fibreglass core with the wire,actually c o p p e r braid, spaced similar to that on a 20m Hamstick.The bottom is about three and a half to four feet long. The top is a steel whip 58 inches long.In the middle is an insulator 8 inches long on which I plan to mount the loading coil which is silver plated edge wound bar stock 3/8 inches wide.The coil will be about 3 or 4 inches in diameter.I just need to machine the ends of the fiberglass and the brass to make and install the 3/8-24 ferrules for mounting. This is just an experiment but I do plan to take relative field strength readings on the straight whip and the homebrew antenna for comparision.I'm not looking for worldclass DX operations from the mobile,just a decent station with flexibility and convieniance.

 

[paws264]

Little bit OT but, why would you ever mount an antenna on the passenger side for in the first place on a mobile; every kid in the neighborhood will swing on it, the drunks will try to tear it off to beat each other with and, as you mentioned, it smacks curb-side trees.

QRN, you must live out in the "country".

 

[Captain Kilowatt]

LOL at paws. Well it was mounted on the passenger side because it was a lot easier to run the coax cable straight back and there was already a dual band 2m/70cm antenna on the drivers side. The first HF antenna mounted was not so tall and hit extremely few trees,usually only when on one or two streets here in town. Since I went with the 8 plus footer mounted near the top of the hatch door it became almost 13 feet above the ground and started hitting a LOT more trees. I just switched it over to the driver's side and have yet to hit a tree branch. I do live in a mostly rural area and the town I live just outside of has a population of 1300. This area of the world is almost all rural or small towns of 3-5 thousand with a few larger towns and a few cities thrown in. The largest is Halifax about 45 minutes away and it is only 120,000. No I am not a hick but I am a rural dweller by choice.

 

[C W Morse]

Rural beats city anytime, IMHO! I wish you GREAT success with your antenna project! Sorry I misunderstood your first post.

73

CWM

 

[Captain Kilowatt]

Something else to consider Jerry, is that almost every installation I have seen of a large screwdriver antenna has it mounted either on the rear bumper or a trailer hitch mount. On a van,RV,or SUV that places a great deal of the antenna BELOW the roof of the vehicle which as you know is not good.It also tends to increase the ground losses which is one of the biggest losses in a mobile installation.With a lighter antenna with less wind load I can mount it about a foot from the top of the roof, and if it were not for the placement of the tuner,only a few inches from the top.This gives me a clear unobstructed mounting location second only to the middle of the roof.

 

[C W Morse]

That's true. I have a van with an SD mounted on a ball above the gas cap and braced to the gutter. Most everything with a mobile is a compromise as you know. While there ARE losses if you mount an SD on the very bumper itself, there are some mounts that take care of *some* of that loss. Like the slider seen on many SD installs. This is like an upside down "F" with the center cross bar facing outside. This serves as a "perch" onto which to mount the SD and also brace it part-way up.
I have one of these "F" mounts (spare) that puts the feedpoint of the antenna almost level with the truck bed. One other thing to consider is-----and this is just one ham to another as I realize that what works for one might not suit another----the losses aren't as BAD as you might think. While, yes, there is loss when the feedpoint is low to the ground, if you use a Hi Q coil, and get it above the roof of the vehicle, it will still probably
beat any tuner/whip, Hustler and certainly any hamstick. Now that's not an "argument", just an observation and a bit of experience (my own) as the saying goes, YMMV! It is why one says "Tomato" and someone else calls it "Ta-mah-tuh"

73

CWM

 

[Captain Kilowatt]

if you use a Hi Q coil, and get it above the roof of the vehicle,

True but I see sooooo many antennas where the coil,regardless of the Q, is not clear the roof at all or only partially.I am not arguing the fact about how good an SD antenna is but rather how good a simple whip CAN perform when mounted as I have suggested and fed with an autotuner at the base using a single wire feed and no coax between the tuner and the antenna.Of course grounding helps as it will with ALL antennas. Speaking of that the next step is to install straps across the hinges on the doors and hood as well as a few along the exhaust pipe.Then that just leaves the V6 COP engine to deal with for ignition noise suppression. :x The front 3 cylinders are easy but I can't even see the 3 in the back! :evil:

 

[C W Morse]

I had a guy who mounted his screwdriver on the left side of his
Ford "Exploder"--I mean, "Explorer" with the coil beside the car body and a long whip. The thing worked fair to less fair--if there's such a designation--and he complained that it didn't seem to do so well.

"Well, elevate the coil above the roof"

"Naw, I can't do that cause it would hit the garage roof"

(I assume he had it that short so as to get it low enough).

"Um, then why don't you raise the coil above the roof and
SHORTEN the whip?! It would be the same difference because you are losing more from the absorption than from a shortened whip!


For a moment, he looked like that Jack-in-the-Box fast food guy with the mouth straight across instead of upwards (smiling) "

"Now why didn't I THINK of that"! :roll:

CWM