which dual band should I use?

[rrfd43]

I will be putting a dual band 2m/70cm on the roof of my full size pick up. I have seen the shorter cell phone look alikes, and the center loaded 38 inchers with gain. I am a little concerned about height off the top of the truck. Any ideas which would be the best to use? Does anyone know if the cell phone styles work ok? Or should I just put the 38 incher up there for the best proformance. This antenna will be for ham only, the vhf syntor X9000 will stay with a 1/4 wave. Thanks!!!!!! Any antennas better than others?

[Tom in D.C.]

I run both types, NMO of course, depending on how long my Outback is going to be out of the garage. In my garage only the short (Antenna World) dualbander will clear the door. The longer antenna is too high to clear the door. The longer antenna is superior in performance, both receive and transmit, on both bands.
The short antenna, however, while electronically inferior is still a good match on both bands on the Bird meter, believe it or not. The long antenna gets installed when I'm going to be down in VA for while at my other place, and this is where I really need its gain. The short antenna around town works fine almost all the time.
All this with an Icom IC208H dualbander, which it turns has a really sensitive front end on both bands plus an honest 50-watts out.

It almost comes down to a choice of what antenna costs less, but not quite.

[TomSlick]

I compromised by getting a Diamond antenna with their fold-over feature. That way I get the performance benefits of the longer antenna, and when I run into a spot with low clearance, I hop out and fold the rod over to horizontal.

Check them out at:
http://www.rfparts.com/diamond/

Mine is an NR770HNMO.

[70351]

Like Tom in D.C. I also run both antenna types on my car. Both work well, and as noted the performance is a little better on the gain-type antenna. I also run NMO-only using a Larsen model NMO270 and the Larsen dual band cell-phone look-alike thingy (I forget the model #). Both are wide-banded and offer very good performance, with the higher praise going to the gain antenna. I use the gain antenna mounted in the center of the trunklid and the smaller antenna on the rooftop. Believe it or not the roof-mounted antenna, although having no gain on VHF, does about the same as the gain antenna on the trunk on VHF. But I've heard a quarter-wave on the roof offers the same performace as a 3DBd gain on the trunk. Hard to see any difference in my application. I noticed better performance from the gain antenna when I did some testing by swapping both antenna types back & forth, using the same mount, using a constant signal on VHF such as NOAA Weather on 162 MHz. I saw anywhere from 1 to 2 S-Unit difference in the receive between both antenna's.

I guess it's a matter of where you intend to mount the antenna, and any height restrictions you may have. That would definitely narrow down what you'll need.


Randy

[007]

As Randy said, a 1/4 on the roof will perform almost as good, if not the same, as a gain antenna on the decklid.

On my Impala, I ran around with an A/S mosaic 5/8w VHF antenna on my trunk for a while, powered by a 125w X9000, then switched to a 50w Spectra with a cheapo black Maxrad 1/4w on my roof, and noticed very little difference. Having the entire roof as a groundplane really helps the 1/4 perform, as opposed to the smaller decklid.

The only difference I noticed was a bit of loss in direct car to car comms, but I attribute that to the loss of 75 watts, not the antenna.

Both mounts are Maxrad NMO, both installed properly and well grounded.

Unless you are going to be bombing around out in the boonies where you need a flatter signal to travel further (5/8w), I'd go with a quality, no frills 1/4w on the roof.

[rrfd43]

Thanks for the help everyone, I bought em both and will spend a little time experimenting!

[wa2zdy]

Just for jollies and to keep in the back of your mind, the standard 19 inch 2m quarter wave will be an effective 3/4 wave on 440 and will work rather well, exhibiting some gain even. As an odd multiple, the feedpoint impedance will be right where it should be on the third harmonic, and being large (3/4 is even bigger than 5/8 remember) it shows gain.

Good luck.