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Club VHF Contest - beams

The club VHF contest now allows use of home antennas including beams. If you  are using a beam you have to reduce transmit power to compensate if its gain is higher than these values:
 

6Mtrs     0 dBd (= 2.1 dBi)  

2Mtrs     3 dBd (= 5.1 dBi)  

70cms    6 dBd (= 8.1dBi)
 
NB Some antenna manufacturers specify gain relative to a dipole and give you a dBd gain figure. Others compare their antennas to a theoretical antenna type that doesn't really exist - the isotropic antenna - and give you a dBi figure. The latter is a bigger number by 2.1 dB, so looks good in sales literature. Other manufacturers muddy the waters and just give you a dB figure, which you can safely assume is the dBi gain.

Simply deduct the gain shown above from your own antenna gain to find out how much additional gain yours has, then look up your maximum transmit power in the table below.

 

Excess Antenna Gain (dB)

Power limit  (W)

0.10

10

0.20

10

0.30

9

0.40

9

0.50

9

0.60

9

0.70

9

0.80

8

0.90

8

1.00

8

1.50

7

2.00

6

2.50

6

3.00

5

3.50

4

4.00

4

4.50

4

5.00

3

5.50

3

6.00

3

6.50

2

7.00

2

7.50

2

8.00

2

8.50

1

9.00

1

9.50

1

10.00

1

 
 
 
 
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