Fiberglass vs. Metal Whip? (Static Comparison)

[radiation8]

Long post here folks SORRY! Hello all, so I have been into Shortwave, HF listening, and CB for quite sometime, maybe not for some of you older folk but lets say 12 years...

I have played with all sorts antennas, but one kind I have never had experience with are Fiberglass whips... A little back story, I recently (about 2weeks ago) installed a hard mounted "L" bracket bolted onto the back of my Chevy HHR about 7 inches down from the Roof ON the hatch part it is all grounded to the rest of the body of the car, I checked continuity. When I put this all together the antenna I bought was a Francis 4ft Whip, which has the coil/load inside the antenna, although they do not tell you the "wavelength" it's supposed to be 1/4, which is either seriously false or I ended up with a dud.

I have 2 CB radios I tested this with, a Colt 355 (4watts), and a Galaxy 93T (8watts) , both were throwing High SWR alerts. So I was like crap, something is wrong with my wire or mount. I triple checked everything, nothing seemed out of place or wrong. So I grabbed my old no name Mag mount, I do not know the actual wave of this guy but it measures 1.5ft long and has a coil at the bottom. I think it might be less than 1/4th, but I installed it on the top rear of my HHR, and to my amazement not only did it have a SWR 1.3:1 it received WAYYY better than the 4ft Francis that extended 2ft above the mag!.......WTH? So scratching my head.....I took the Fiberglass off the base, and installed the "Whip and Coil" part from the Mag mount onto my Hard mount, and bam! Same SWR as the mag and same receive, so I now know nothing is wrong with my mount..

So I went and bought 2 more fiberglass antennas just for giggles and one of them came with another mount I needed anyways. One is a 3ft "1/4th" wave I can tell for sure because the coil is on the outside and the other is a 4ft "5/8th" wave super flex fiberglass antenna. I installed and tried each one and both do have a slightly higher SWR than the mag mount, and receive is just a smidge poorer but not nearly as bad as the Francis.

I have been looking at forums and the packaging to some of these antennas, and they say
"reduces static up to 50%!!!" or "lower noise floor" At first I kinda just threw this out but to what I am finding out this might actually be true, and some forums around the web some people say they get more static and "signal" with Metal whips than fiber glass...

So my question is this, If the antenna is the same physical length from mount point to tip, yet the fiberglass is ""supposed"" to have MORE wire, how is this possible????!!!! Seems to me like these fiberglass antenna companies are shorting us on our wire....and how is it that my mag mount "coil and whip" measuring a measly 1.5ft is outperforming 4ft "5/8th wave" fiberglass antennas, no matter what mount I use?

 

[NDRADIONUT]

All mobile cb whips are shortened 1/4 waves...

 

[radiation8]

All mobile cb whips are shortened 1/4 waves...

So that means 90% of these companies are spiting "false advertisement"?

 

[N4GIX]

They are spinning "Golden Dreams" to the gullible, just like most advertising these days.

 

[NDRADIONUT]

Anything under 102" has negative gain also.... A 4 foot antenna would have -3 db gain and a 2 footer -6 db gain but from what i have seen its even worse than that....

 

[radiation8]

Anything under 102" has negative gain also.... A 4 foot antenna would have -3 db gain and a 2 footer -6 db gain but from what i have seen its even worse than that....

A 102" whip might look a little funny on my HHR I understand performance over aesthetics....but aside from that the 102" might bend the crap out of my hatch!

 

[radiation8]

Another question is, does the fiberglass and or covering "the plastic" on the outside reduce receive and transmit that much?

 

[NDRADIONUT]

This antenna was only about 1db less than a 102" whip when I tested it.... http://www.amazon.com/Wilson-305-49..._UL160_SR160,160_&refRID=1ZQHQR194M67YRMX68QZ

 

[wa1nic]

The "electrical length" just makes the impedance be some where near 50 ohms if the base is properly installed to make the radio happy.

As far as performance goes, it doesn't matter how much wire is coiled up in there The physical length is what matters.

Antenna efficiency is roughly related to the length squared. a 4' antenna has about 20% of the efficiency of a 9 foot whip. That is about 7 db... or a bit over 1 S unit.

The fiberglass or insulating tubing really doesn't have a measurable affect on performance.

I measured a whole bunch of antennas two years ago on the same mount... for a given length, you cant tell one brand from the other.

You didn't mention if you checked the SWR. An antenna that doesn't need some adjustment is pretty rare. I know Francis claims that, but the one I tested needed some tweaking. I adjusted all the antennas that I tested with an MFJ impedance analyzer to bring them to resonance. FWIW, that isn't always the same as the lowest SWR, but the two cases are usually pretty close to each other. Unless the SWR is on the higher side (well above 2:1), adjusting for resonance will typically give a higher field strength reading and, well... field strength is what it is all about.

 

[radiation8]

NDRADIONUT: Thanks for sharing your find!

wa1nic: I did test SWR on all the antennas, I need to do some more testing when I get home from work.

1. The Francis (4ft) was 3:1 or more on the L mount, the worst of the bunch.

2. The Mag mounts "Coil and Whip" part had basically the same SWR (1.3:1) on both my hard "L" mount and mag mount

3. The "so called" RoadPro 3ft Whip 1/4th Wave has (1.3:1) but seems to receive slightly less than the Mag.

4. The no name FlexWhip 4ft 5/8ths Wave has (1.4:1) and actually receives worse than the 3ft'er.....Which makes me think the 3ft has "more wire" than this guy. Although by what people are saying the physical length of the 4ft should be better....

 

[NDRADIONUT]

I tested 3 older realistic 4' fiberglass whips and they were only 2-3 db weaker than the 102"... A friend was doing the rx levels from about 2 miles away on a base with the s meter on a kenwood hf radio....

 

[wa1nic]

If the SWR of the Francis was 3:1, it needs tuning. Was it lower on channel 1 than it was on channel 40?

Can you post a picture of your setup? Are you using a spring?

 

[SpugEddy]

CB is all about recipe and ingredients.
I'll explain. I had an RCI 2950 in my Xterra with a
Little Wil on top. I had some really good feedback about my radio.
I got into a little bind and decided to sell the radio. About
a year later I bought a used van to do my work. Since I was doing
a lot of Super WalMarts and traveling I wanted a new radio.

I bought :
Cobra 18RV from eBay for $25.00
A friend gave me a 102" fiberglass whip
Bumper mount for antenna for $12.00
Another friend sold me a Palomar 225 for $50.00
Workman DM-452 echo mic $17.00
(I didn't want to buy a new cord for the mic so I used an old coiled
telephone cord. Soldered it to the mic and the connector. It looked
ridiculous, but it worked)

The only time I ever used the Palomar was locally
because I live right outside of Phila and a few smart
a$$eS like to lock down the channels just to be annoying.
Aside from that, the Palomar actually dropped my SWR
so i left it hooked up.

Total co$t: $54.00 for radio antenna and mic
$50.00 for the amp. $104.. total

I got more compliments on that setup than I did with the RCI
I even pulled into a few rest areas and truck stops to prove myself to
the non-believers.

I swapped out the 102" for 3 different antennas and NONE of them worked
nor performed as well as the 102" fiberglass. If you have the antenna and it
doesn't look stupid (to you) use it.

 

[radiation8]

If the SWR of the Francis was 3:1, it needs tuning. Was it lower on channel 1 than it was on channel 40?

Can you post a picture of your setup? Are you using a spring?

I did try to tune it by cutting a little bit off at a time....each time it got worse, I had to have either ended up with a DUD Francis or for whatever reason my setup doesn't like it, I even hooked up my scanner to it, and it wont even pick up the local NOAA weather channel which is located 1 mile from me.....

So here is a little update

I played with it a lot more when I got home this evening, and to my amazement the 3ft (1/4th wave) "Roadpro" seems to be performing the best now. Compared with a Firestik 4ft and the 4ft MoblieTronix SuperFlex (from a company called Lynco)

Don't ask me how, why, or say that I am wrong but somehow, for some strange reason the 3ft'er is kicking the others butts! The only difference between this antenna and the others aside from length is that the actual wire seems to be a larger gauge at 16g where the FireStik and MobileTronix seem to be 20 and 24.....Doesn't make sense I know seeing as how that goes against everything I have learned and researched, it's either that or the physical wire is something other than copper on the other antennas.

The Francis is going in the Trash, I took the FireStik back, and I made the SuperFlex into a scanner
(I lost the receipt) antenna on the other side of the car by cutting it down to 20.5 in Long (Tuned for 150 and 2 meter pickup), and I am keeping the RoadPro for my CB antenna.

I will post more pics when my BCT15X gets here!, but here is the pics I took when I installed the Francis, Yes the mount it properly grounded, I ground off paint down to metal, and even added extra "Ground Loops" from the hatch to the body of the car, as I felt the Hinges weren't enough.

 

[wa1nic]

It would be interesting to put an antenna analyzer on it.

Not sure, but I am noticing that there isn't a lot of metal connected to the base... all glass to one side and a big seam on the other side.

All the antennas that you are having issues with should work to some degree, and be adjustable for a low SWR. The base and "ground plane" is a critical component of the antenna installation however.

An antenna analyzer would give you some insight into the whole picture.

Typical mobile ground losses are in the 10 ohm range. While that is a loss, it actually makes a typical decent mobile antenna installation have a low SWR. If the ground losses are a lot higher than that, the SWR starts going back up again.

If you can find someone local with an analyzer, it would help figure your installation out.

 

[JayMojave]

Hello Radiation8: Impressive looking "L" bracket there.

NIC brought up a good point that the antenna may not have enough ground surface area. If the aft hatch is not properly grounded this would add to the problem. Flexible ground wires from the hatch to vehicle body might help.

The antenna is mounted just a few inches from the aft body of the vehicle, and this may also be throwing a monkey wrench into the gears of antenna performance.

At a BBQ with many distinguished radio enthusiasts one of the locals had a antenna mounted on a tool box just aft of the pick-up cab. He believed the SWR was off somewhat and it didn't perform as it should. Moving the antenna to the top of the cab improved his performance and lowered his SWR significantly. The antenna being close to near by metal, the cab was throwing off his SWR and antenna pattern no dough.

If the antenna could be temporally mounted to a higher location and tested, would be a good call.

Good Luck. Let us know how you make out.

Jay in the Great Mojave Desert.... No international airport yet, no freeway off/on ramp yet, but we got a big CB BBQ Pot Luck Break coming up in a few weeks.....

 

[radiation8]

Ahh yes, that is why I added 2, "lets call them ground loops" using 14g wire (I may increase this), from the hatch to the rest of the body of the car.

I am fully aware of the fact this isn't the best setup, but I can't get the antenna any higher aside from getting a mag mount, and a NMO roof mount isn't possible because removing the underside soft cover inside the car is royal PITA. That being said, don't let that "small strip" of metal fool you, the inside of hatch is a ton of metal.

BUT, I wasn't having SWR problems except with the Francis, and just a little with the Firestik, this RoadPro sits at 1.3:1, and this morning I talked with someone approx. 7miles away on my 4watt Colt 355, and it receives WAYY better than the others did...

I'm thinking now it had to have been quality control issues, either that or there is magic fairy dust in this RoadPro

Then I took the other MobileTronix SuperFlex cut to 20.5in and hooked it up to my scanner on the same mount and I pulled in 3 WX Channels on my BCT8!

But I will post more pics of the whole setup when I get my CB permanently installed as well as my Scanner

 

[wa1nic]

Jay makes a good point... the hatchback door might be insulated from the rest of the body.

1" braid to the rescue?

 

[radiation8]

1" braid to the rescue?

I did just this but I didn't use braid just 14ga wire, that I may increase to 12 or 10.

 

[gewecke]

All mobile cb whips are shortened 1/4 waves...

Not true. There are some helically wound half wave fiberglas antennas out there and base loaded half wave antennas for 11 meters. Look at the coils a little closer. Although STEEL is real, just my opinion. Fiberglas is crap once it strikes a tree limb or overhang. ... :wink: 73, n9zas