Where does the signal radiate from?

[Marchboom]

Great, thanks for the info. The chart allows me to try other alternatives.

 

[Marchboom]

I decided to go with the Midland 6db antenna. Have to get a metal plate to act as the ground plane. Does it matter if the plate is aluminum or steel?

 

[mmckenna]

I decided to go with the Midland 6db antenna. Have to get a metal plate to act as the ground plane. Does it matter if the plate is aluminum or steel?

Doesn't matter as long as it is conductive.

Aluminum is more conductive (lower resistance) than steel, not that it will make a difference. I have my own aluminum body Ford pickup with a permanent mount antenna, plus several at work, not an issue. A lot of fire truck/ambulances use aluminum….

 

[RFI-EMI-GUY]

MicroMobile® MXTA26 6db Gain Whip Antenna

Looks good. Note this does not include the NMO mount and cable in most sales.

 

[prcguy]

It takes about 7ft of antenna to achieve 6dBd of gain at UHF with either four dipole elements at the right spacing in phase or with eight colinear elements, but eight colinear elements only gets you about 5.25dBd. How did Midland get 6dB gain in 2ft of antenna? Or maybe they didn't and they lied?

MicroMobile® MXTA26 6db Gain Whip Antenna

Looks good. Note this does not include the NMO mount and cable in most sales.

 

[alcahuete]

It takes about 7ft of antenna to achieve 6dBd of gain at UHF with either four dipole elements at the right spacing in phase or with eight colinear elements, but eight colinear elements only gets you about 5.25dBd. How did Midland get 6dB gain in 2ft of antenna? Or maybe they didn't and they lied?

It's magic. Same way they make 45 mile FRS radios.

 

[RFI-EMI-GUY]

It takes about 7ft of antenna to achieve 6dBd of gain at UHF with either four dipole elements at the right spacing in phase or with eight colinear elements, but eight colinear elements only gets you about 5.25dBd. How did Midland get 6dB gain in 2ft of antenna? Or maybe they didn't and they lied?

Note that Midland says 6db not 6 dBd. So I assume it to be isotropic gain, which for the purposes of LMR is a white lie.

 

[prcguy]

If they claim 6dBi gain that would be 3.86dBd gain, still hard to believe. Two half wave elements at the proper spacing (not stacked on top of each other with a pig tail coil) and fed with a power divider can achieve about 3dBd gain. The Midland does not have optimum spacing between elements and they are stacked colinear, so it should be about 1 to 1.5dBd gain in my estimation. But I guess big numbers sell antennas and they have no shame in making up numbers out of thin air.

Note that Midland says 6db not 6 dBd. So I assume it to be isotropic gain, which for the purposes of LMR is a white lie.

 

[RFI-EMI-GUY]

I have one NOS example of Motorola's TAE6062B which is rated at 5 dB over a 1/4 wave. I will have to look deep into my notes as to Motorola's dBd rating of a 1/4 wave. The TAE6062B is about 38 1/2 inches overall including the base and adjusting for 1/2 inch telescoped tuning rod depth.

 

[RFI-EMI-GUY]

For more confusing reference; Motorola has used two methods to state 1/4 wave dipole gain -1 dBd for coverage prediction (very old data), and -3.8 dBd for 14 feet black RG58U cable (est 1.6 dB loss at 460 MHz) and -2.8 dBd for 14 feet of white Teflon. Other sources have stated that a 1/4 wave dipole has a theoretical 3 dB gain over a 1/2 wave dipole as all of the energy radiates from the mono-pole.

 

[prcguy]

I have several TAE6062Bs and they are the highest gain UHF mobile antennas I've ever used. But they are not 5dBd gain and I doubt they are 5dBi, which would be 2.86dBd gain. However, a 1/4 wave is less than 0dBd gain and something around -1.5dBd so 5dB gain over -1.5dBd gain is 3.5dBd which still sounds like too much. I've heard of some mfrs like Shakespeare rating antennas over a 1/4 wave whip on their own antenna range where anything can happen, so maybe Motorola did get 5dB over a 1/4 wave behind closed doors.

I have one NOS example of Motorola's TAE6062B which is rated at 5 dB over a 1/4 wave. I will have to look deep into my notes as to Motorola's dBd rating of a 1/4 wave. The TAE6062B is about 38 1/2 inches overall including the base and adjusting for 1/2 inch telescoped tuning rod depth.

 

[prcguy]

A half wave dipole radiates from the entire antenna, which is 1/2 wavelength long. A 1/4 wave ground plane only has the 1/4 wave monopole to radiate as the ground plane or ground radials do not radiate, so the 1/4 wave monopole is only about half the surface area of a 1/2 wave dipole.

For more confusing reference; Motorola has used two methods to state 1/4 wave dipole gain -1 dBd for coverage prediction (very old data), and -3.8 dBd for 14 feet black RG58U cable (est 1.6 dB loss at 460 MHz) and -2.8 dBd for 14 feet of white Teflon. Other sources have stated that a 1/4 wave dipole has a theoretical 3 dB gain over a 1/2 wave dipole as all of the energy radiates from the mono-pole.

 

[RFI-EMI-GUY]

I have several TAE6062Bs and they are the highest gain UHF mobile antennas I've ever used. But they are not 5dBd gain and I doubt they are 5dBi, which would be 2.86dBd gain. However, a 1/4 wave is less than 0dBd gain and something around -1.5dBd so 5dB gain over -1.5dBd gain is 3.5dBd which still sounds like too much. I've heard of some mfrs like Shakespeare rating antennas over a 1/4 wave whip on their own antenna range where anything can happen, so maybe Motorola did get 5dB over a 1/4 wave behind closed doors.

Yeah I was FTR in Iowa and had a UHF 100 watt Syntor with a roof mounted TAE6062B and can report that setup talked forever in the plains.

 

[Marchboom]

After hearing all those explanations above, I'll go with what alcahuete said, "It's magic". That makes the most sense to me.

Looked at a lot of antennas, got thoroughly confused at times and this one looked like the best (within reason). If it doesn't work out I'll look for another.

Many thanks to those who offered advice to my post.