t_j
FRF Addict
If you are looking for info on SWR from one of the GJ Motorsports antenna mounts take a look here https://www.fordraptorforum.com/threads/gj-motorsports-3rd-brakelight.61019/page-15
My Ham Radio Install
- Thread starter RaptorGuyNC
- Start date
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t_j
FRF Addict
If you want a better ground plane, you can bond the light to the body of the vehicle and run any form of ground plane antenna. For most applications this is used for a ground plane less antenna works just fine, but as with anything the more specialized the installation/requirements the more prep work that has to be put in. You will have this same problem with most none drill NMO style antenna mounts, and most of the time people do not remove the paint from the underside of the panel to establish a proper ground bond. Feel free to reach out to us (GJ Motorsports) to discuss your application and requirements, we are always looking to provide solutions to new markets.
Kmandoske
Full Access Member
If anyone needs me I can be reached at 312-317-9444 or [email protected]
Spectragod
Full Access Member
Sti-Co makes an antenna, or just blow holes in the roof, fleet vehicles, not my own, lol.
WRCRaptor
FRF Addict
What ant. did you get? I am trying a shorter Larson 1/4 wave when I get mine installed on the truck I don’t have yet!
Laird, it has the elastomer.
Mspeed
Active Member
I need help with pick out an antenna for my set up. I just purchased an icom 2730A dual band radio. I plan to install it in my chase rack. I'm looking for the longest range size don matter. Any ideas?
OriginalToken
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Your Icom 2730 is a dual band, VHF/UHF, ham radio. It has a single antenna port. So unless you want to mess with diplexers and breaking the VHF/UHF signals out to separate antennas you will need a single antenna that does both bands.
The short answer is the tallest / longest dual band 2M / 70cm antenna you can find with the mechanical rigidity to hold up to your level of off-road shaking/twisting/torqueing and withstand the mechanical stresses that will be applied to the antenna.
Long answer below, antenna stuff follows, it can be lengthy, some people will be interested, others will be thinking “just suggest a make and model antenna already and shut up!!” If you fall in this later group jump to the last three paragraphs.
When you say “longest range” you have to understand what antenna factors go into that, and the advantages and disadvantages of those factors. Why? Because there is no one answer, what might fit the requirements of one person may not fit the requirements of another.
All other things being equal, and only talking about the antenna part of the range equation, size matters. Or rather antenna gain matters, and gain is closely related to size. As a general statement, for a given frequency larger antennas tend to have higher gain values. But it is not simply a matter of making the antenna longer to get more gain, unfortunately it is more complex than that as resonance and feedline matching are things that must be taken into account.
Way over simplified here, for a given frequency antennas of specific sizes (expressed in wavelengths and mathematically calculated based on the frequency of the signal divided by the speed of light) will be resonant and / or efficient. Some of those sizes will be easily matched to various available feedlines, others can still be matched, but require more complex, and costly, matching systems. Feedline, by the way, is the cable that connects the antenna to the radio, in mobile installations most often a form of coax, or coaxial, cable. Typically you go for the easily matched antennas for cost and complexity sake.
Using one simple size as an example, the ¼ wave monopole antenna, or the “quarter wave whip”. The advantage of this mechanically simple antenna is that it matches well to many available feedlines, and it is resonant. A monople antenna of ½ wavelength would have nearly twice as much antenna gain, signals would be received almost twice as strong. However the antenna would physically be twice as long / tall, and the impedance would be very high, and not a good match to commercially available feedlines, so you would require a matching system (extra cost / complexity) to make the antenna “match” the impedance of the feedline cable.
However, two quarter wave antennas fed in electronic phase and with the right mechanical spacing would have roughly the same gain increase, and each could still be matched to the feedline. But who wants two antennas on your vehicle that have to be exactly the right distance apart?
Enter the “collinear array”. Collinear means all in one line. An array is more than one antenna element. So more than one antenna element, all in one straight line. If you want to, you can make the “straight line” the axis of the antenna element, or in the case of a mobile vertical whip “up”, stacking element on top of each other. For example, one quarter wave mechanically stacked right on top of another quarter wave. Now, if you can “feed” the two elements in the proper electrical phase relationship the two elements will add together, and yield almost 3 dB of gain, or nearly twice as much signal and still match available feedlines. And, fortunately, you can feed the antenna at the base and use phase delay sections between each section to control the phase relationship. In other words, not a hard problem.
So high gain mobile antennas with physical lengths longer than about 5/8 wavelength are most typically collinear antennas. Or multiple antenna elements stacked on top of each other and working together, even if it looks like one whip antenna.
For those who understand the difference, I am not going to specify dBi or dBd in the gain numbers below, consider them all the same unit. The gain figures given are form the antenna makers, and have not been confirmed independently.
In the picture below you see three antennas.
The left (far) antenna there is a Daimond NR770 dual band antenna, 2 meters and 70 centermeters (VHF and UHF). It is a collinear antenna. You see a straight bottom section, what appears to be a coil of wire in the middle, and then a straight top section. Also, at the very bottom and not well seen in the picture, is a thicker section. The thicker bottom section is a matching system. This antenna, the total thing top to bottom, is a half wave antenna (two quarter waves in phase) on 2 meters (VHF), and the matching section on the bottom makes it “match” the feedline. So this antenna has roughly 3 dB of gain on 2 meters, or twice as much gain (signal) as a quarter wave. The coil in the middle treats VHF and UHF differently. So the two sections, top and bottom, are two elements at UHF, in this case two 5/8 wavelength sections. The gain of this antenna at 70 cm is roughly 5.5 dB, or almost 4 times as much signal as with a simple quarter wave whip.
The center antenna is a simple quarter wave whip on 6 meter (VHF Low, 50 MHz). It has roughly 0 dB gain. Despite it being the tallest antenna of the three it has the lowest gain, it is physically longer because the frequency of operation is lower and remember I said gain is related to wavelength, which is determined by frequency divided by the speed of light. So it is physically the longest, and electrically the shortest.
The right hand antenna is a Diamond CA-2x4SR and is the shortest and most complex of the bunch. Again, it is a collinear on multiple bands covering the VHF/UHF segments. However, instead of having simple coils as phase shifters / matching sections, it has closed devices. Really, these are coils also, but made of thinner wire and inside plastic housings. This antenna is two loaded half waves on 2 meters (VHF) and three 5/8 wave antennas on 70 cm (UHF), so it has more gain at about 3.8 dB on VHF and 6.2 dB on UHF. And because of some interesting specifics of design it does fairly well as a receive only antenna on other bands, outside the specified VHF/UHF transmit range.
So in this picture, the shortest antenna has the highest gain (and in theory longest range) and covers the frequencies you want for your Icom radio. However, it might not be the recommended antenna because of its mechanical limitations.
Plastic loading coils, as seen on the CA-2X4, have a tendency to be mechanically less robust than simple wire coils as seen in the NR770. They can crack or loosen up around the whips and cause issues in the long term, issues that do not happen in a solid one piece design. If you off road a lot, and the antennas whip back and forth a lot, this can speed the failure process up.
Of these three antennas the simple quarter wave whip in the middle will handle off-road abuse the best. With regards to longevity off road the one piece mechanical design of the N770 will do the next best, and the complex, highest gain, CA-2X4 will do the worst. The “best” (highest gain, nominally longest range) of these antennas will probably fail first.
And the difference in gain between these antennas, 0 to 6 dB of gain across the three, is not a huge factor. Yes, in the lab it is important, in the field it is much less of an issue. To be sure, it is something, but less of a factor than some would try to make it.
What it all comes down to is that the “longest range” option, the highest gain, might not be the right solution for you.
For an off-road application I would select the longest mechanically robust design I could find from a brand name and I would try to avoid plastic loading coils. On road, or fixed station, I would worry less about the mechanics and go more for higher gain numbers.
I have used dozens of different mobile dual band VHF/UHF antennas over the decades. If the installation is done right (installation is important) there is little real world performance difference between most of them when new. For off-road installation I have had good luck with the Diamond NR770HB (or HA if you want silver instead of black finish) as long as the mount is well installed.
Solid, robust, mounts, combined with mechanically simple antennas go a long way. If possible avoid mounts with multiple axis of adjustment, a through mount on a body panel or a simple not adjustable L bracket mount is the way to go if that is possible for you. The more complex the mount, the more things can go wrong with it.
With almost any antenna with a “fold over” feature I have seen the need to drill and pin the fold over fixture (drilling and pinning stops this feature from functioning) for off-road use. It is best if you can find an antenna without that feature, but that can be hard. The NR770 has a fold over, and about half the time I have had to pin it in off-road installations.
T!
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Mspeed
Active Member
Wow thanks.
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