What is the UHF simplex frequency?

What is a simplex frequency?

Simplex – In the amateur radio context, simplex operation means the radio stations are communicating with each other directly, on the same frequency. Both stations take turns transmitting and receiving on the same frequency with no repeater or other device in between.

In most places, the channels immediately adjacent to 446.000 MHz are used as simplex frequencies, spaced by 25 kHz. This means that 445.925, 445.950, 445.975, 446.025, 446.050, 446.075 MHz are all valid simplex frequencies. But other areas have assigned these frequencies to repeater operation.

The 70-centimeter or 440 MHz band is a portion of the UHF radio spectrum internationally allocated to amateur radio and amateur satellite use.

What Frequency Do I Use on 70 Centimeters?

FCC Rules

The first thing we need to know is the FCC frequency authorization for our particular license class. Just like the 2 Meter band, Technicians and higher class licensees have privileges across the entire 70 cm band, 420 to 450 MHz. The 70 cm band is BIG…providing 30 MHz of spectrum compared to only 4 MHz on 2 Meters. The FCC rules do not specify any mode restrictions on this band. There is a restriction on operating below 430 MHz if you are close to the US border with Canada.

Band Plans

One of the interesting modes used on 70 cm is Amateur Television or ATV. These signals are typically 6 MHz wide, so it makes sense to only use a wide amateur band like 70 cm for ATV operating.
We need to use our authorized frequencies wisely by sharing the band with other users and avoiding unnecessary interference. Thus, it makes sense to have a band plan that divides the band up into segments for each type of operation.

70 cm Band Plan

As shown in the table, the ARRL 70 cm amateur band plan supports a wide variety of radio operation. Large portions of the band are dedicated to FM operation, consistent with the popularity of the FM mode. There are portions of the band designated for repeater inputs and outputs. The standard repeater offset used on this band is 5 MHz. Some areas of the country use + 5 MHz offset while others use – 5 MHz. Within any region, the offset will be usually be the same on all repeaters. This means that in some parts of the country, you’ll dial in the repeater output frequency in the range of 442 to 445 MHz and select a +5 MHz offset. In other areas, you’ll dial in a repeater output frequency in the range of 447 to 450 MHz and select a -5 MHz offset.
On the low end of the band, we see segments for some of the more exotic modes, starting with ATV, then Earth-Moon-Earth (EME) operation. EME operators communicate by bouncing their signals off the moon.

70 Centimeter Band Plan

Summary

The fine points of the band plan can be a bit confusing. However, a few simple guidelines can help, especially if you are operating only FM.
FM voice simplex and repeater operation should only occur in the designated band segments for your area. Stay out of the weak signal, ATV, beacon and satellite subbands.
When operating through a repeater, make sure you are tuned to the published repeater frequency with the proper transmit offset.
When operating simplex, use a simplex frequency designated by your local band plan