ARRL

VHF/UHF/Microwave/Weak Signal

Introduction

Weak signal operating refers to long distance communications that requires an unusual combination of luck, skill, and equipment on the VHF and up amateur frequencies. When everything clicks, it is possible to span distances in excess of 400 miles on all bands up to 10GHz, taking advantage of a phenomena known as tropospheric ducting, also known as "tropo."  More reliable are contacts made with tropospheric scattering--a good station may have a typical range on the order of 200 miles, much farther than range of most FM repeaters.  This is achieved with a combination of more power, a high gain beam antenna, and a modulation method better suited for signals near the noise floor. It is called weak signal because signals are close to the noise level after traveling great distances--expert operators are used to digging signals out of the noise.  Nearly all weak signal operators participate in contests, exchanging grid squares. 

Equipment Required

On 6 and 2M, it is common to use a minimum of 100 watts to large rotatable beam on tower, perhaps 50 ft high, from a location that has a clear view of the horizon.  Your range is significantly reduced by an obstructed horizon.  On these bands, upper sideband or USB is the mode most commonly used, though it isn't unusual for contest stations to switch to CW to make contacts that would otherwise not happen.  Stations have a lot of incentive to make those little improvements--as once you get to a station range of 100 miles, relatively small increases are needed to get it  out to 200 miles.

On the higher bands, power gets harder to come by, but high gain antennas get easier.  Thus, a few watts on 10GHz might have as much range as 100 watts on 2M, provided those razor sharp beams are pointed accurately. Most operators stick to 2' or smaller dishes on 10GHz, though there are expert operators who use 4' dishes with the aid of beacons for azimuth calibration. By convention, beams for terrestrial use are horizontally polarized, as opposed to the vertical polarization standard for FM.

Where to Operate

On 6M, most of the activity occurs between 50.1 and 50.2MHz.  On 2M, the activity centers around 144.200, the National calling frequency. Remember not to use voice in the CW only parts of 6 and 2M. The very low end of 2M is reserved for EME, stations bouncing their signal off the moon!  On the higher bands, almost all of the activity is close to the calling frequencies, typically 100 kHz up from a 1MHz multiple.  Examples are 432.100MHz, 10368.100MHz, 1296.100MHz, and 2304.100MHz.  You should contact the nearest weak signal club if you intend to operate the microwave bands to find out exactly when and where you are likely to find signals. 

Contests and Awards

The Contest Department maintains pages on Contest Rules.

The ARRL offers the VHF/UHF Century Club award for working 100 Grids Squares on either 6 or 2M, though getting the award is rather difficull on 2M if you live on either coast of the USA.  But, those living on the coasts find it much easier to obtain microwave Grid Square awards.  Details can be found on our VUCC web page.

Microwave

How to Work 10-GHz DX, Part 1 Members Only
(149,177 bytes, PDF file) 
QEX Jan/Feb 2002, pp. 58-60
Location, Location, Location

How to Work 10-GHz DX, Part 2 Members Only
(399,911 bytes, PDF file) 
QEX Mar/Apr 2002, pp. 55-69

W1GHZ (N1BWT) 10 GHz Page
This is the Paul Wade or W1GHZ guide to 10 GHz operation and operators.

San Bernardino Microwave Society
Technical Information / Papers & Software, Microwave Beacons and more

North Texas Microwave Society

The NTMS has hundreds of members and sponsers the annual Microwave conference that moves around to accomodate microwave experts in all parts of the country.