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33 cm - 902 MHz Band Information

The 33 cm amateur radio band offers great opportunities for repeater, weak signal, digital, ATV and experimental purposes. Over the last few years, many new repeaters have been put on the air all over the country. This increased use of 900 MHz is partly driven by the availability of excellent commercial radio equipment at very reasonable prices. The greatest limitation to people jumping on the band has been the lack of “off the shelf” amateur radio equipment and a fear of interference from non-amateur users of the same radio spectrum including cordless phones, telemetry systems, data networks and other low power un-licensed applications. The purpose of this web site is to help you realize that you too can overcome your fears, get on the 900 MHz band and join the fun.

Frequencies

The entire band goes from 902 to 928 MHz. While there is some variation in different parts of the country, the vast majority of modern repeaters operate with outputs in the 927 to 928 range. Repeater inputs are paired with outputs using a 25 MHz offset.

902.0125 - 902.9875                 Repeater Inputs, 12.5 Khz Channels
903.0000 - 905.0000                 Digital
910.2500                                     ATV Repeater Input
915.0000 - 917.0000                 Digital
923.2500                                     ATV Repeater Output
927.0125 - 927.9875                 Repeater Outputs, 12.5 Khz channels, -25 Mhz Offset

NARCC Repeater Directory for Northern California

OUTPUT	INPUT	CALL	LOCATION	SPONSOR	STATUS	NOTES
927.0250	-	WA6JQV	Vacaville	WA6JQV	Coordinated	celx
927.0500	-	WB4YJT	Grass Valley	WB4YJT	Coordinated	c
927.1500	-	N6NMZ	Auburn	N6NMZ	Coordinated	c
927.2875	-	W6REB	Santa Cruz	KG6XY	Coordinated	oelx
927.3250	-	K6SJH	Moraga	K6SJH	Not Coordinated	#o100.0lr
927.3500	-	KM6PA	Novato	KM6PA	Not Coordinated	#o131.8
927.3750	-	N6QL	Pleasanton	N6QL	Not Coordinated	#o88.5elx
927.4000	-	K6ZRX	Napa	K6ZRX	Coordinated	o192.8el
927.4000	-	WA6AFT	Montara	WA6AFT	Coordinated	ce
927.4250	-	WA6JQV	Oakland	WA6JQV	Coordinated	celx
927.4500	-	WA6JQV	San Pablo	WA6JQV	Coordinated	celx
927.4625	-	WA6JQV	Los Gatos	WA6JQV	Coordinated	celx
927.4750	-	WA6JQV	Los Gatos	WA6JQV	Coordinated	celx
927.4750	-	WA6JQV	Oakland	WA6JQV	Coordinated	celx
927.4750	-	WA6JQV	San Pablo	WA6JQV	Coordinated	celx
927.4750	-	WA6JQV	Vacaville	WA6JQV	Coordinated	celx
927.5000	-	K6ZRX	Napa	K6ZRX	Coordinated	o203.5el
927.5250	-	K6ZRX	Santa Rosa	K6ZRX	Coordinated	o173.8elx
927.5500	-	N6OLD	Concord	ERG	Not Coordinated	#o141.3x
927.6000	-	WB6ASU	Lodi	WB6ASU	Coordinated	o114.8elrx
927.6250	-	KK6AT	Patterson	KK6AT	Not Coordinated	#o100.0
927.6250	-	WA6FUL	Palo Alto	WA6FUL	Coordinated	o151.4lrsx
927.7000	-	N6IMS	Half Moon Bay	N6IMS	Coordinated	ce
927.7500	-	K7WWA	Willits	K7WWA	Coordinated	o103.5elrsx
927.8000	-	WA6JQV	Vacaville	WA6JQV	Coordinated	o192.8e
927.8625	-	KJ6VU	Palo Alto	NCCRA	Coordinated	oelx
927.9000	-	N6TBQ	Seaside	N6TBQ	Coordinated	oel
927.9000	-	W6KAP	Volcano	W6KAP	Coordinated	o127.3x
927.9125	-	K6DND	Los Gatos	K6DND	Coordinated	o146.2aelx E:168199
927.9250	-	W6MOW	Felton	W6MOW	Coordinated	o123.0e
927.9750	-	WE6R	Monterey	WE6R	Coordinated	celrs

Repeater listing web sites
Ohio APRS web site – lists 900 MHz repeaters throughout the US

User Radio Equipment

While none of the typical manufacturers like Icom, Kenwood or Yaesu make 900 MHz amateur equipment, there is a lot of new and used commercial equipment on the market. The most popular mobile radios are Motorola Mactrac and GTX radios and Motorola MTX and GTX hand held radios. In addition to Motorola, many other manufacturers make 900 MHz radios that can be used in amateur service including GE, Kenwood and others.

All these radios are typical commercial “channelized” radios that don’t offer the notion of a “VFO” for frequency selection. This also means that in addition to the radio you will need the appropriate programming software for your PC and the proper interface cable. While this can seem like a big challenge to someone new to 900 you can usually find someone who has the appropriate gear to program your radio including your local radio service shop.

When selecting commercial radios, make sure you pick one that has the ability to program “conventional” channels. This means the usual simplex or repeater operation as opposed to the trunking networks that control the rados frequency and signaling codes.

Tone Signaling (CTCSS / DPL)

Since there is a chance of transient interference on the 900 band, just about all repeaters require either a sub-audible CTCSS (PL) frequency tone or digital PL (DPL) code. Most of the repeaters also encode tone on the repater transmitter. Unlike most other bands, experienced 900 users often set their mobile and hand helds to decode PL or DPL as well to eliminate interference.

"Normal" vs Narrow Band

All the radios in the 900 band are narrow band running 2.5 KHz deviation. While you can modify radios to make then operate on 5 KHz, the effort is not generally worth it.

Motorola Hear Clear

This is an optional mode that most of the Motorola radios support that provides voice companding and helps reduce noise and flutter. Hear clear is very popular and many repeaters run in this mode. While there is a lot to talk about, the bottom line is that if you operate in a marginal / noisy area, Hear clear can really improve your reception. If you are operating in an area where the reception is very good and you don’t experience mobile noise and flutter, you can run without Hearclear. While Hear clear makes a noisy signal sound better, it comes at a price of altering the quality of the audio. Hear clear audio sounds a bit mushy and lacks fidelity. If you are using 900 for point to point links, there is no reason to use Hear clear because you want to optimize for audio quality and a point to point link should not suffer path noise and fading.

Building a 900 MHz Repeater

A 900 repeater is just like any other repeater. You will need a receiver, transmitter, duplexer, power supply, control system, antenna and feedline. Good used commercial gear can be found in found in great supply these days as many paging and SMR operators replace or shut down their equipment. Commercial repeaters or a combination of mobile radios used as the receiver and transmitter can be found at attractive prices on Ebay.

Motorola Maxtrac

One of the most popular radios is the Motorola Maxtrac. The maxtrac comes in various power levels, channel configurations and bands. Motorola radios have long model numbers. The first few characters will tell you what band they are on and the transmit power level. Look for the following radios…

D27…   12 watt 900 MHz radio – works well for 927 Mhz transmitter and can be modified to receive in the 902 band. These are narrow band (2.5 KHz deviation) radios.

D37…   30 watt 900 MHz radio – works well for 927 Mhz transmitter and can be modified to receive in the 902 band. These are narrow band (2.5 KHz deviation) radios.

D35…   800 MHz radio – works well for 902 Mhz receiver. These radios are very cheap and require only the removal of a switching transistor to get them to work on 900. These radios will NOT transmit in the 900 band. They are only useful for repeater receivers. These are standard 5 KHz deviation radios so you will have to adjust your audio level in the controller to normalize the deviation going to a 2.5 KHz transmitter.

In all cases, make sure you look for a Maxtrac with the 16 pin accessory connector, not the 5 pin. The 16 pin connector can provide ALL necessary signals going to the control system. Flat Rx, Tx audio, COR, PTT, PL/DPL decode output.

On the repeater transmitter side, you will want to throttle the output power down to about ½ rated output. This means running the 30 watt radios at about 15 watts and running the 12 watt radios at about 7 watts. You must run a fan blowing air on the PA heatsink regardless of the power output. Even at ½ power output, the heatsink will get hot.