hawk51
Member
Has anyone got a lot of experience with these?
Does window heater and factory tinting hinder the quality of reception?
Does window heater and factory tinting hinder the quality of reception?
Through glass antenna
- Thread starter hawk51
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I have one on my car, and it works good, to be honest I dont think the whip on it does a damn thing, I took the whip off once when I was going through the car wash, and didn't notice any difference in reception.
jim202
Member
There are a few do's and don'ts of on glass antennas.
1. They don't work on glass that has metal tint built into it. Some of the auto glass actually
uses metalic particles to cause the tinting. On this type of glass, no on glass antenna will work
at any frequency band. It acts as an RF shield also.
2. Do not mount any part of the antenna on or over the heater wires on or in the glass. These
metal strips will cause a problem with the coupling of the on glass antenna components. There
are small coils inside each of the two parts of the on glass antenna. These coils are what
does the transfer or coupling through the glass. The spacing between the two parts is
critical. If one of the pieces falls off, you just can't go to the local hardware store and get
some 2 sided sticky tape to put it back on with. Most of what you will find is too thick and
will effect the coupling through the glass.
3. VHF frequencies are hard to couple through the glass. The coils inside the 2 sections of the
antenna can not be made large enough to work properly. At UHF and 800 MHz, these type of
antennas work well. I have compared the glass mount to other antennas mounted through
the roof. If you use the same gain antennas, it is hard to see the difference.
4. The higher frequencies, like the 800 band should use the lower loss coax cable. So
if your going to use one of these, it pays to go after the better coax cable.
5. Don't plan on running any high power through the glass mount antennas. Your top
power point is about 50 watts. Above that you get into trouble with burning holes in
in the coax cable, issues at the through glass point and poor reliability in the
coupling coils. They just can't take the high power.
DO NOT UNDER ANY REASON WHAT EVER TURN DOWN A 100 WATT RADIO TO
50 WATTS OR LESS. The solid state PA's in radios today become very unstable at the
lower power levels. They tend to generate a bunch of noise, spurs and birdies. In general,
they don't make for good radio neighbors. You also stand the chance of letting the smoke
out of the PA stage of the radio.
Hope this gives you a little thought. One other comment, at least one on glass company
makes a VHF model. The down side to it is that the whip used is 36 inches long. Not
something what I would consider putting on my windows. When I talked with the engineer
that designed the antenna, I asked him why he couldn't use a 1/4 wave whip. His comment
went back to the coupling problem through the glass and the current points along the
coax cable.
Jim
1. They don't work on glass that has metal tint built into it. Some of the auto glass actually
uses metalic particles to cause the tinting. On this type of glass, no on glass antenna will work
at any frequency band. It acts as an RF shield also.
2. Do not mount any part of the antenna on or over the heater wires on or in the glass. These
metal strips will cause a problem with the coupling of the on glass antenna components. There
are small coils inside each of the two parts of the on glass antenna. These coils are what
does the transfer or coupling through the glass. The spacing between the two parts is
critical. If one of the pieces falls off, you just can't go to the local hardware store and get
some 2 sided sticky tape to put it back on with. Most of what you will find is too thick and
will effect the coupling through the glass.
3. VHF frequencies are hard to couple through the glass. The coils inside the 2 sections of the
antenna can not be made large enough to work properly. At UHF and 800 MHz, these type of
antennas work well. I have compared the glass mount to other antennas mounted through
the roof. If you use the same gain antennas, it is hard to see the difference.
4. The higher frequencies, like the 800 band should use the lower loss coax cable. So
if your going to use one of these, it pays to go after the better coax cable.
5. Don't plan on running any high power through the glass mount antennas. Your top
power point is about 50 watts. Above that you get into trouble with burning holes in
in the coax cable, issues at the through glass point and poor reliability in the
coupling coils. They just can't take the high power.
DO NOT UNDER ANY REASON WHAT EVER TURN DOWN A 100 WATT RADIO TO
50 WATTS OR LESS. The solid state PA's in radios today become very unstable at the
lower power levels. They tend to generate a bunch of noise, spurs and birdies. In general,
they don't make for good radio neighbors. You also stand the chance of letting the smoke
out of the PA stage of the radio.
Hope this gives you a little thought. One other comment, at least one on glass company
makes a VHF model. The down side to it is that the whip used is 36 inches long. Not
something what I would consider putting on my windows. When I talked with the engineer
that designed the antenna, I asked him why he couldn't use a 1/4 wave whip. His comment
went back to the coupling problem through the glass and the current points along the
coax cable.
Jim
Both of the ones that I have are specific in their instructions that if you have to mount on a window with defroster lines, to center the antenna between two lines, do not have a line passing through the center of the base, it states that the coil is fairly small and in the center of the base and will not be affected by the defroster wires if they are near the edge of the base. If you have no original instructions and have no choice of mounting it may get you by.
This is correct, I've had the same experience. That should tell you something. The radio is receiving a signal just by having a length of coaxial cable run from a connection box to a scanner. That means that this connection box and the coax is a sufficient antenna. But sufficient for what? When I took my whip just to see what would happened without it, it worked OK in a big city where nearby repeaters are located. But, receiving a lot of radio systems in an urban setting is relatively easy.
Next I tried the whip less "antenna" in a rural area. The results were dismal. All I could receive were repeaters within 5-maybe 8 miles from the vehicle. If you are in a rural area don't try to use a through-the-glass antenna. In urban areas you will not be able to receive distant repeaters, especially the non-trunked type on VHF-High, because trunked radio systems use a lot of repeater sites, and UHF, VHF-High, and VHF-Low radios systems do not have to use as many repeaters.
If I were you I would look into trunk lip mount antennas. They have a good ground and you don't have to drill a hole in your vehicle. Google "Comet" antennas and you will find their product line. It includes a variety of antenna mounts that will work for almost any vehicle and in many locations on each vehicle. I have a hatchback station wagon and use Comet mounts on each side of the hatch back window. One antenna is a short length Larson scanner receiver antenna and the other is a short length 2m/70cm, both 18" high so I can get my car into a small garage without taking off the antennas. I'm going to drill into the roof one of these days as nothing beats using the roof as a ground plane.
I presume you were asking about antennas for receiving only. If you are looking into using an antenna for ham radio use then Jim's advice is good. You can find trunk lip mounts for almost any 6m/2m/70cm application and power limits are not as much of a factor.
Both AES and HRO have a variety of trunk lip mounts. It might be best to start with their websites.
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