| Author |
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mike
| | Posted on Sunday, December 02, 2001 - 11:07 pm: | 
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I have a brand new whip with a gumdropmounton my pickup. I've added a seperate ground wire from the antenna mount to the frame useing 8 gauge wire but that didn't help at all. Now what can i do? |
B1kshad0w
| | Posted on Monday, December 03, 2001 - 10:26 am: |
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Where did you mount it at? |
mike
| | Posted on Monday, December 03, 2001 - 8:15 pm: |
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I mounted it on a 2' angle iron goin from side too side in the bed of my truck about 6"from my rear window in the center of the bed. |
Hydro
| | Posted on Tuesday, December 04, 2001 - 3:11 am: |
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A 102" wip is a resonant antenna for the 10 meter band you need to add a spring or coil that will give it approx. another 6 inches.
Hydro |
RoadRunner531
| | Posted on Tuesday, December 04, 2001 - 3:41 pm: |
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I have the same setup on my Berretta,i also had the same issue but what i did was change the ball mount and it brought my swrs to 1.3 |
Bigbob
| | Posted on Tuesday, January 01, 2002 - 9:09 pm: |
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Mike move antenna to center of bed bothways that'll fix it.It's to close to cab. |
Marconi
| | Posted on Wednesday, January 02, 2002 - 7:51 am: |
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I agree with Hydro, the 102" SS whip is too short. It was intended to operate with a spring that is 2"-6" long. Add a little lenght of wire to the tip and see if it does better.
Marconi |
Bigbob
| | Posted on Wednesday, January 02, 2002 - 10:18 pm: |
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Mike,the spring on my whip only changed the tuning .1 swr plus it allowed the antenna to lay nearly horizontal at 55.Your whip is capacitively coupled to the cab.Mount it to the rooftop,natural wind drag will get you under overpasses,but it's a bummer in the woods or at burger king hence the spring and clip. |
hydro
| | Posted on Saturday, January 05, 2002 - 1:24 am: |
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Now that i think of it, I took out 3 of 4 lights at a McDonalds drive through in OK.
Hydro |
Jerry Bryant
| | Posted on Friday, January 11, 2002 - 11:23 am: |
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Also you could try using an antenna tuner to lower the S.W.R. |
Bigbob
| | Posted on Friday, January 11, 2002 - 6:36 pm: |
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MIKE move the ant.at least 18 inches back it will greatly improve swr.All cb ant.s are current fed except "no ground" types which have a matching system.The bottom of ant.is the current node,the top is the voltage node.Current is distributed from bottom to top rather evenly,most at bottom,this refers of course to full length whips.Shortened ant.s radiate substantialy more at the load coil,a top load will have a lower angle of rad. than a base load.102" whips radiate along their entire length. |
Bigbob
| | Posted on Friday, January 11, 2002 - 6:45 pm: |
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One more thing 102" whips show a 1.4 to 1 swr.If it is much higher or lower try adding a 6' section of coax it will act as an inverting transformer and is much cheaper than a tuner and a lot safer from a driving standpoint. |
Marconi
| | Posted on Saturday, January 12, 2002 - 11:16 am: |
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Bigbob, true, a 1/4 wavelength radiator should show about a 1.4:1 SWR. But, a 102" whip is a shortened 1/4 wavelength and the input resistance should be much lower than about 35 ohms. So, the 102" probably would not remain at or near this SWR value for a true resonant 1/4 wave.
I am not sure how a 1/4 antenna actually matches out, but I will be checking this on a model rig in the near future. I will get back after I chart the SWR and impedance curves for a 102" and 108" inch whips at 27.205.
If you check your meter, you may find that it can only show you about a 2 or maybe a 3:1 SWR under almost any reflective condition other than maybe a direct short.
Let me give you a meter demonstration with some details on a 4 element Wilson yagi that will give some comparisons to what I note above.
I will be using a Dosy 4000 and 4002 comparing to a Palomar Vector Scanner 500, and the base line of this test will be the output from an Autek VA1. Understand that the VA1 readings are at the transmitter end of the line with meters, switch box, and amp in line, so this mix will skew the analyzer results a little from those reflected at my antenna. I use the antenna only as a tool to demonstrate because it is somewhat narrow banded.
Using the VA1 the beam resonates best at 27.270 with an SWR of 1.16 showing an R=43 and X=0. In this check I set the meter in the mode to adjust frequency for the lowest X value of reactance. That should be where true resonance is.
Autek VA1 readings
| 26.525 | 2.39 SWR | R=102 | X=+12 | | 27.270 | 1.16 SWR | R=43 | X=0 |
The SWR readings at both frequencies using the inline meters and my 148GTL with 3 watts input
At 27.275
| Dosy 4002 | 1.1 SWR | | Dosy 4000 | 1.0 SWR | | 500 | 1.15 SWR |
At 26.525
| Dosy 4002 | 1.5 SWR | | Dosy 4000 | 1.4 SWR | | 500 | 2.5 SWR |
Now, when we are close to resonance the Dosy's fair pretty well, but when we get away from resonance the Dosy's start to fudging a bit. Does this help a little?
Marconi |
Bigbob
| | Posted on Saturday, January 12, 2002 - 7:23 pm: |
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Marconi,my swr meter shows to 20:1 and a 102" whip gives me 1.4:1 at 27.685,true a 6" spring added would shift resonance lower. |
Bigbob
| | Posted on Saturday, January 12, 2002 - 7:30 pm: |
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MOVE THE DARNED THING AWAY FROM THE CAB,YOU'RE EFFECTIVELY GROUNDING THE BOTTOM HALF OF THE RADIATOR.IT'S CAPACITIVELY COUPLED TO THE CAB SPRING OR NO SPRING!!!!! |
Marconi
| | Posted on Sunday, January 13, 2002 - 2:03 am: |
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Bigbob, I think you misunderstood what my point was. Your meter probably does show 20:1 SWR on the scale for SWR. Idea was, have you ever seen a reading using your meter that was over 3:1 as a result of a significant mismatch that should show to be very high?
What kind of reading do you get on your meter if you were to remove the ground side, loosening the 259 fitting and pulling it out a little, and read the SWR? You know, where you just have the center pin in the SO-239. Of course, do this very quickly so you won't be hurting your rig?
Both my Dosy's will only show a 2:1 SWR doing this, but my 500 show more than 7:1 SWR. That was the only point I was making about meters. I really did not mean to impune your meter or you, that was not my intentions. I was merely trying to suggest something that you could do that might be convincing regarding what I was saying, but you missed my point completely.
If your meter can really reflect a high SWR value, then it is better than average. If it won't read high, only you will know, then maybe some of what I suggest might start to make some sense.
You don't have to believe me, just check things out for youself.
I will be sending along my report on the 102" and 108" whips real soon. I will see if a 102" whip will show an SWR of 1.4:1, OK! Look, I have been wrong before and I learn from those experience every time it happens.
Marconi |
Bigbob
| | Posted on Sunday, January 13, 2002 - 2:21 pm: |
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MARCONI;Yes I have.I've seen swr's at 6,14,and in fininity.No.2,I've seen this in practice where the shield is not soldered,twist the connector around with the mike keyed and you'll get an infinite number of readings and yes 6to1.But as I said location,location,if all connections are made properly,mikes antenna will work with or without a spring and won't damage his radio.But get that ant. away from the cab.One more thing,did you always wonder why cb was 4 watts?Consider this 27megs is very close to 30megs.,the human body is a resonant ant. at 30megs and wattages of 25 or more can cause damage to the eyes and so on.100watts = 1.7amps and 87volts. |
Vernonott
| | Posted on Sunday, January 13, 2002 - 6:41 pm: |
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Marconi: It will be good to see your report as I am considering putting a 108" whip on the back of my 86 Bronco full size truck. |
Marconi
| | Posted on Monday, January 14, 2002 - 11:34 am: |
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Vern, like Bigbob correctly stated, "...location, location..." That is what is important in a mobile installation. What I had in mind may not be very helpful for your plans, but a little additional information, if correct, can always be helpful.
Marconi |
Bigbob
| | Posted on Monday, January 14, 2002 - 5:49 pm: |
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HEY MARCONI,how sharp are you?Why is a fiberglass whip sans the spring 96"and the stainless whip 102"?I know, do you?And I'm not being a smart ***. |
Bigbob
| | Posted on Monday, January 14, 2002 - 6:06 pm: |
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VERNONOTT,my brother had a 96" fiberglass whip with 6"spring on his '71 blazer,as you probably know those trucks had a fiberglass top.He mounted it high on the rear fender,he had no trouble with it.Never checked swr,never ran extra power.But if you have a metal top you must have no more than 6"below the top for reasonable swr,further more your radiation pattern will be strongest in the direction of the most vehicle body from the ant. |
Vernonott
| | Posted on Monday, January 14, 2002 - 7:22 pm: |
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Marconi:I just had a brain storm.I can make an adaptor for my trailer hitch and extend it out about 18 inches or so to get it away from the body.It may look weird but I'm too old to worry about looks. |
Marconi
| | Posted on Tuesday, January 15, 2002 - 1:51 pm: |
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Hey Bigbob, I not sure I understand your question, because it looks like a mis-type in there, and I could be missing your point.
I figure you are asking me why does a fiberglass antenna at 96" and a SS at 102" or 108" all seem to work in 11 meters? If this is your question, then here goes. The two SS radiators are well within a workable range, in length, to be near resonance and match and thus are workable.
IMHO, the 102" was originally designed and intended to be used with a spring. The FG types vary in length, depending on the way the wire is layed out inside the FG. Since the wire is smaller it would have to be longer than the SS whip in order to be resonant at the same frequency. Being longer is not the way they wanted to go however. Those manufactures wanted to go shorter, so at some point in their radiators they probably wound the wire a bit, which made the overall length physically shorter.
It is a resonant electrical length issue we are talking about here. That is why I made my statement about your idea of a 102" whip showing an 1.4 SWR. Later you noted that that your results were made at 27.685 which is about 25 channels out of the 11 meter band. I have no problem with that but I, and maybe others, were assuming your were stating facts relative to the 11 meter area. Hydro told us that a 102" is a resonant length for somewhere near 10 meters and I agree. That is where we got crosswise, that is all. I did not realize that was an issue in your facts at first because you did not state your resonant frequency, which is always important and needs to be clearly stated. I felt that some may not understand why their 102" whips did not seem to work as you noted, if they wanted to work in 11 meters.
I think you are right Bigbob, and I know you have an understanding of the topic. I was just trying to be a little more clear about the issue. There is a lot of confusion out there in 11 meters and we owe it to all to be clear.
Good topic and discussion.
Marconi |
Bigbob
| | Posted on Tuesday, January 15, 2002 - 8:53 pm: |
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mike,get UNDERSTANDING AND REPAIRING CB RADIOS by Lou Franklin, look in the antenna section it's very informative.For deeper reading on the subject get your hands on an ARRL ANTENNA BOOK ,mine was copyright in 1984 although it was given to me by a friend in 1990. MARCONI I stand corrected,I thought the diff. in length was do to dissimilar materials,velocity factor,L/D Ratio.Try making a full length whip out of 5/8" aluminum tubing and guying it with fish line,not very durable but it was a blast. |
Sarge
| | Posted on Wednesday, January 16, 2002 - 10:07 am: |
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Fiberglass 1/4-wave whips are shorter than stainless steel 1/4-wave whips because the copper wire embedded in the fiberglass is a better conductor than stainless steel. There are no coils in the wire used for a fiberglass 1/4-wave whip. Big Bob was correct that the velocity factor plays a big role in the reason for the different lengths.
The length of the copper wire determines the resonant frequency, not the size. However, a larger diameter wire would have a broader bandwidth, which could be a benefit in some situations. Old ships used to have "cage dipole" antennas as a way to increase the antennas bandwidth across the shortwave frequencies being used for ships on the high seas.
The debate between fiberglass and stainless steel 1/4-wave whips can be endless. The stainless steel whips are almost indestructable, but they sure flop around a lot at 55-mph. As Big Bob mentioned, some guys keep them vertical by using low-test fishing line to tie them up. The whip stays vertical, but if you hit an obstacle the fishing line will snap and allow the whip to bend back. It's kind of a "fuse" effect. If you bang into something you will have to replace the fishing line, but it saves you from greater damage to your antenna or the overhead object.
I have both books by Lou Franklin, his "Tuning and Peaking CB Radios" and "Understanding and Repairing CB Radios". The second book is more technical and is intended for the repair technician. However, the first book is a great source of information for anyone interested in CB radios. I highly recommend it as well worth the cover price. It is written in simple language for the layman and explains a lot about the hobby. It also includes a section about wiring up microphones to various brands of radios. Great reading! |
Marconi
| | Posted on Wednesday, January 16, 2002 - 6:43 pm: |
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BigBob states, "...MARCONI I stand corrected,I thought the diff. in length was do to dissimilar materials,velocity factor,L/D Ratio."
BigBob, I don't disagree with some of your list of things that make up the differences in lengths in antennas. I do disagree with the part you note about dissimilar materials if you mean the same thing as Sagre states regarding copper and SS.
I would not totally exclude this factor, but the kind of material used in RF likely makes very little difference in that regard. The big differences are in the physical size (diameter) of the element and length. I also question your reference to the Velocity Factor here. Maybe you meant K-factor. The K-factor is what is associated with the L/D ratio in antenna design.
VF has a similar effect and is basically a like consideration, but in the context of RF, the VF exists as a characteristic in the production of coax. This factor is useful in making calculations for line transformation effects and resonant length considerations. Both factors are relative to time, distance, and space properties.
Sarge, you are right that length is the big thing having to do with resonance. But, the material diameter of any reasonable conductor has a direct and notable effect on resonance as well as adding a little to effective bandwidth. A thick element will be shorter than a very thin element, if both are to be resonant at the same frequency. I am sure that is what BigBob found out when he made his 5/8" diameter 1/4 wave. It was very likely shorter than a SS whip. This is where the L/D ratio and K-factor that BigBob mentions could have come into play. Look in Lou's material for a subject about taper and this will give you some incite into the effects of size of material in antenna design.
I would also go back and re-read Lou's stuff in general, I am sure he did not say anything that would lead you to your "absolute type" conclusion about material conductivity in this regard and that element size was of no importance to resonance. IMHO, both characteristics are a consideration to be made in some applications, but conductivity is just not quite that important to an RF antenna. Maybe Lou was discussing the nature of line resistance or another type of circuit when the conductivity issue came up. Let me know what you find. Discussion is the way we learn and that is good.
Marconi |
Bigbob
| | Posted on Thursday, January 17, 2002 - 9:07 pm: |
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MARCONI,2nd paragraph ,right side of page ,chapter 8-ANTENNAS & TRANSMISSION LINES ;UNDERSTANDING AND REPAIRING CB RADIOS,PAGE 337."THE LENGTH OF A FULL-SIZE WHIP depends upon its material. Steel whips are about 102" and fiberglass 96". Ever wonder why? fiberglass is shorter because its radiating element is a copper wire buried in the fiberglass;copper is a better conductor than steel,so rf propagates through it faster. Same idea as the coax Velocity factor. Shakespeare does sell a 102" fiberglass whip that's 3/8-wavelength in copper",etc.Quote,same idea,unquote.thats where I got confused.Francis makes a fib.whip with 3-16gauge copper wires in parallel. |
Bigbob
| | Posted on Thursday, January 17, 2002 - 9:19 pm: |
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Also I am of the opinion that anytime you surround a conductor with any di-electric material RF will be slowed to a certain degree depending on the di-electric :impedence change.A long wire ant. exibits impedence change where it touches end insulators. |
Znut
| | Posted on Saturday, January 19, 2002 - 4:23 pm: |
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I believe that 8' fiberglass whips such as the amazer and such are shorter than 102" stainless whips because the wire embedded in the fiberglass IS wound in a slight, even helix. Thus compromising the length issue without the characteristics of a specific loading coil. Also, I think the slight inductance of the slight helix increases the impedance. A normal 1/4 wave is what, 34 ohms or so @ resonance? The 8' fiberglass antennae were probably engineered with this more in mind than length and still radiate fairly evenly over the antenna, like the steel whips do. My old 1/4 wave base antenna's radiator was 104"-106" long and had a horizontal ground plane. The stardusters are an improvement in that the radials are raked to raise the impedance. Can't really do this with a vehicle can we? I know a guy who had some luck by exposing 4"-6" of the coax's center conductor, and soldering the shortened amt. of shield to the barrel of the connector after putting it together several times, less braid each time, then clamping it with the reducer and soldering it. Underneath the car it looked funny to me with that 6" half circle loop of center conductor exposed but it solved the problem of having to use a spring! |
Bigbob
| | Posted on Saturday, January 19, 2002 - 7:56 pm: |
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Mike check out post in SUBSCIBER(preview),articles;antenna installation. |
409
| | Posted on Saturday, January 19, 2002 - 10:06 pm: |
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Any time you wind a coil , such as on an antenna dipole, you make it electrically longer. This is why the fiberglass whips are shorter than the steel ones. That's why(one reason)they base load those short whip antennas with a large coil. |
Marconi
| | Posted on Sunday, January 20, 2002 - 7:27 am: |
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I have to agree with both Znut and 409 on the issue of coiling the wire in the FG antennas a bit, in order to reduce overall length and to raise the input impedance created by the thinner wire. I think I have an old Frances whip around here and I recall that it also has 3 wires in there that are not touching. I believe this is done to make the antenna act like a thicker (bigger diameter) radiator and thus it can be a bit shorter.
I also hold a belief that a thicker diameter radiator may have some advantages to overall effectivness in addition to its other qualities. I build my wires using RG8 coax. I use the center conductor as support and the shield as the radiator. I have also solder the two pieces of the coax together and this also works.
These antennas work great but they do have some structral shortcommings, they tend to stretch a bit and the shield does not holdup well in the weather. |
Znut
| | Posted on Sunday, January 20, 2002 - 10:30 am: |
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Mike, sorry about my long-winded post before, just trying to articulate in my way some ideas around your problem. You likely need to lengthen your whip electrically. Again, I know a guy who did this:
*Cut the old connector off (he had RG8X/mini-8)
*stripped 6" or 7" of jacket
*combed the braid out & twisted it
*attatched the center conductor temporarily to the center Lug.
*temporarily attatched the braid to the outer lug, checked swr, shortened braid, checked swr, shortened braid, checked swr (you get the idea) until swr was good and soldered and tightened everything.
The end result looked like I mentioned in my last post here. I'm not sure if the half-loop of bare coax core simply added electrical length to the antenna, or inductance, or what but it worked. |
Scrapiron63
| | Posted on Sunday, January 20, 2002 - 12:27 pm: |
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Good discussion on whips guys. Have any of you that runs the whip ever compared them to one of the fiberglass 4 or 5 ft antennas, like firesticks. I'm talking a real test, groundwave talking, which is completly different than skip.
Get out at night in a good location, when its quite, talk to some base stations out at a distant, let them get a good reading on signal and loudness, don't tell them what your doing, that way you don't deal with biased opinions. Then screw the whip out and the fiberglass stick in. You can take the spring out, just use the ball and it want change the SWR very much. You might be surprised in the results.
scrapiron |
Bigbob
| | Posted on Sunday, January 20, 2002 - 8:44 pm: |
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I DID that once,got a 60" wilson silver load with silver plated wire,top loaded fg ant.Talked to a station 40 mi. as crow flys,didn't tell him what I was doin'.He said the wilson gave better signal and modulation.The steel whip just wiggled his needle,the fg whip brought it up to a solid 1.Stock pc122 ssb 27.405. |
Scrapiron63
| | Posted on Sunday, January 20, 2002 - 10:54 pm: |
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You got the same results I did, only I've done it lots of times. I use to sell equipment, so I tested different antennas. I used my old 4 wheel drive truck since it has a cross bed toolbox, with the whip base mounted in the center of the box, makes it easy to change antennas. My regular bunch I talk to lives from 20 to 60-70 miles, they knew I was testing antennas, but not what kind. But the ones I was using were not near as good antennas as the wilson silver load, they were just 4 and 5 ft fiberglass firesticks. It made me wonder why I needed that ol whip flopping around. |
Ae548
| | Posted on Friday, January 25, 2002 - 10:14 pm: |
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I tried comparing a 5' firestick II to a 102" whip. It depends on the radio and it's bandwidth.
A 102" whip has better bandwidth with 10-11 meter radio. The firestick II was a better match for a 11 meter only radio. I havn't used any other top loaded whips (except Radio Shacks) and that was crap. What do you think is the best made, widest bandwidth top loaded whip? |
Bigbob
| | Posted on Tuesday, January 29, 2002 - 10:22 pm: |
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PROBABLY KNIGHT STICK 10K. |
Bigbob
| | Posted on Thursday, March 07, 2002 - 8:59 pm: |
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HEY MARCONI!!WHERE'S YOUR REPORT ON THE MOBILE WHIP ANTENNAS,HUH?? |
bullet/151 southern Indiana
| | Posted on Friday, March 08, 2002 - 4:29 am: |
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sarge,
i agree, i was going to put my 2 cents in here but youve said it for me in your post. and your right as to your reasoning. copper has less resistance than aluminum and stainless steal,plus having to take accout of placing this conductor in fiber glass hellow (vel. factor)............
"ok sarge take point to the obj get em in a diamond, marconi right flank,bigbob left flank,znut you got the 6, im my own rto, gear up & move out in 2 mikes whooaa!!!!" |
Marconi
| | Posted on Friday, March 08, 2002 - 7:17 pm: |
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Bob, I was just thinking about you and the fact that I have not kept my promise to you. At some point, I did post that you were right about your conclusions on the 102" whip. I have several whips and several home made coil type antennas with varions coil designs. A while back I started to do this using a 1000 lb+ cast iron smoker on wheels. I did do some work using the continious load whips and got some good results. However, when I got the whips, No-Way-No. The guys that I borrowed the coils from, each brought the coils without stingers. I have a homemade telescoping stinger made from an old radio antenna that will strech from about 13" out to about 49" and in most cases this will work just fine. I gave up on the coils because I could not find resonance in any of them which causes me to believe that the test rig is not providing an adequate ground or the presence of the 4' smoker chimney is causing serious reflections. I do know that coil antennas are very excitable in the presence of reflective metal nearby.
I haven't been around much lately and not to be making excuses, but my wife was operated on with a cancer tumor of the brain the week following Thanksgiving and I just spent 5 days in the Hospital myself with a rapid ticker that would not slow down and believe me, I wasn't even trying out for the Winter Olympics. I will get to it soon. The weather is starting to get nice also.
I just installed a Wolf Radio 50_11M antenna that is a metal substitue for an A99. It is a bit touchy to tune. Seems the ground has a very strong effect on this one. Eddie is very nice to deal with and has been very helpful as well. He builds a very substantial product and does all the right things, the things that others seem to leave out. Like buffing and de-buring, strong heavy wall materials that really fit well, and most important Stainless parts. Real nice. Give him a call, I think he has a winner there.
I will be giving a report soon I hope as I love to tinker with antennas. I got the antenna which is similar in design to both, a Maco V-5/8 without the ground plain, and a Crushcraft Ringo UHF/VHF vertical.
DX reports where good all day on 27.405 where I got true resonance. I have not run the analyzer on it yet, that will be in the report with a few tuning tips.
Marconi |
Bigbob
| | Posted on Friday, March 08, 2002 - 9:36 pm: |
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My prayers are with you. |
Taz
| | Posted on Monday, March 11, 2002 - 12:35 pm: |
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Marconi,
Is that your real last name?
are you related to the other marconi the scientist? |
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