Antenna manufacturer question

tn1999 · Post by **tn1999** » Thu Dec 13, 2001 10:54 am

Based on advice from the board I've decided on a 1/4 wave antenna for my GM300 UHF radio
its 8 channel with an output of 25-40watts I'm not sure which (I suspect 25w) Is there a difference between antenna manufacturers/models for this type antenna? What does NMO mean?
Any additional help is appreciated.
TIA
Tony

Monty · Post by **Monty** » Thu Dec 13, 2001 11:05 am

Hi:

The term ( NMO ) stands for a " very " common
antenna mount. This mount which rquires a 3/4" Hole for Mounting is used in many Commerical applications.

A very well made Antenna Mount.

Also, if you desire a low profile gain
antenna for UHF, I have found the Antenna
Specialist ASP-7795 ( 3db gain ) Mosaic
Mobile Antenna will handle a 150 watts, and
will work over the 445-470 Mhz range.

Is superior to a standerd 1/4wave antenna.

Also, the ASP-7795 is not much larger than the 1/4 wave antenna

Monty

Post by **wavetar** » Thu Dec 13, 2001 12:35 pm

If you do decide to go with a 1/4 wave antenna due to size, cost, etc., then take a look at the "SFT-118" from Sinclabs or the "MFT-120" from Maxrad. They are identical antennae which are cut to your specific frequency, they both come with a cutting chart for this purpose. You'll also need an antenna cable, the "MPL" from Sinclabs is a good choice, although there are other more expensive "low-loss" cables available as well. There are literally dozens of companies who can provide a 1/4 wave antenna, as they are essentially just a piece of wire cut to a specific length.

Todd

Tom in D.C. · Post by **Tom in D.C.** » Thu Dec 13, 2001 1:22 pm

Tony: The most common "gain" antennas you will encounter for UHF have a gain in the neighborhood of 5db, which means that you can boost the radiated power of the antenna by more than twice the amount of RF which is coming out of the radio. The tradeoff is in the radiation angle of the transmitted signal. For close-in "city" work you'll find PD and FD systems using only quarter-wave antennas to keep the signal angle down, but if you really need the additional power (which also works to your benefit when receiving) of the gain antenna then you should go for it. Again, where you are and what you need are the key questions. A good 5db gain UHF antenna is around 20 to 24 inches long, that's all, but your quarter wave is only about 6 inches.

Tom, W2NJS
...in D.C.

raymond345 · Post by **raymond345** » Thu Dec 13, 2001 3:02 pm

The nmo mount is very common and the 3/4
mini- hole saw for holes on a vehicle
is the only tool to own for this job.