VHF "can" style low profile antennas

apco25 · Post by **apco25** » Tue Jan 18, 2005 8:36 am

Is a low profile can style antenna being produced for VHF that will handle more than a lousy 60w on tx?

Going to try the Larsen model for APRS use, but had thought of using one on the main VHF radio for appearances.

All my other antennas are MAXRAD MPLV series cans

nmfire10 · Post by **nmfire10** » Tue Jan 18, 2005 8:48 am

I've never heard a single good thing about VHF low profile antennas. All I've ever heard are complaints about them taking on water, not working worth a damn, low power ratings, etc. I don't know what makes the VHF ones different than the other bands, but seems to be a problem across all the manufacturers.

mark577fd · Post by **mark577fd** » Tue Jan 18, 2005 11:54 am

Well I have to of the VHF "cans" on my van. Needed to use them due to low garage door height. They work ok to good if that is a rating. THEY MUST BE TUNED for the freq you wish to use and they are very narrow banded. Mine are tuned for about 154.5 mhz. anything below 152 or above 159 and they are deaf. For my use in Metro Chicago they are fine.

tvsjr · Post by **tvsjr** » Tue Jan 18, 2005 12:42 pm

nmfire10 wrote:I've never heard a single good thing about VHF low profile antennas. All I've ever heard are complaints about them taking on water, not working worth a damn, low power ratings, etc. I don't know what makes the VHF ones different than the other bands, but seems to be a problem across all the manufacturers.

Simple... you gotta have more radiator for VHF than UHF/800. I suspect a lot of the taking on water issues is because the higher bands are smaller, therefore they seal to the roof better. I've seen several where the mount is on a ridge, and the can extends out over the channel on each side.

Bottom line... Maxrad BMFT120 .062" stainless steel field-tunable quarter-wave.

wa2zdy · Post by **wa2zdy** » Tue Jan 18, 2005 1:48 pm

A compromise in size is always a compromise in performance.

Taking a 6 inch antenna and winding it into a can is a lot different than taking a 19 inch antenna and winding it into a can.

Of course that's not quite how it's done, but the graphical representation should be enough to give you the idea.

apco25 · Post by **apco25** » Tue Jan 18, 2005 3:09 pm

I'm well aware of the technical limitations of the can type antennas. I was specifically trying to find ones that take higher output power - so far they're all rated at 60w.

Mainly considering it due to a height issue - the burb is quite tall being the 3/4 ton model and I'm getting really tired of taking off my 1/4w VHF whips everytime I come home and enter the garage. My old garage was a lot taller so there was no need to remove anything.

Any thoughts on the Larsen models? They're at least a 3' high by 4.75 diameter can compared to the tiny Antenex models. Maxrad doesn't make them at all for VHF.

I may try it for the APRS antenna since that's working through digipeaters most of the time.

JohnWayne · Post by **JohnWayne** » Tue Jan 18, 2005 3:52 pm

I am going to make a hypothesis that an antenna such as the Antenex VHF Phantom, which is rated for only 60W, will handle more power for shorter intervals. The typical APRS station transmits a 1-second or so data burst every few minutes. I would think that the antenna could handle this, but I may be wrong.

If you want, I will call the Antenex factory tomorrow and ask their engineering department what they think about it. How much power are you running and how often do you transmit while mobiling?

Jeff