Ted,
In a nutshell, return loss is just another way to describe the mismatch in a
device, usually a transmission line/load combination. We usually measure VSWR,
which is defined as the ratio of the maximum to minimum voltage on a loss-less line.
(V)SWR, reflection coefficient and return loss are all scalar quantities that
are related by formulas:
Reflection coefficient p (Greek letter rho) is defined as:
p = (VSWR -1) / (VSWR + 1)
So p varies from 0 for a perfect match to 1 for a total mismatch.
Return loss (RL) is defined as:
RL (dB) = - 20 * log10 * p where (p>0)
Some common numbers:
VSWR = 1.02 RL = 40 dB
VSWR = 1.22 RL = 20 dB
VSWR = 1.92 RL = 10 dB
VSWR = 3.01 RL = 6.0 dB
To answer your question about what is acceptable the answer is, it depends.
Most modern transmitters want to see SWR below 2:1 so 10 dB RL is probably OK.
Some transmitters with internal tuners claim a matching capability for loads <
3:1., so 6 dB RL is OK.
Hope this helps.
Wes N7WS
.On 1/15/2021 1:01 PM, Salvatore ["Ted"] K2QMF wrote:
Hello All,
At the risk of asking a dumb question,
What is return loss and what is considered acceptable Return Loss on an
antenna??
Inquiring Minds want to Know!!!
Many Thanks and 73,
Ted K2QMF
_________________
Searchable Archives: http://www.contesting.com/_topband - Topband Reflector
_________________
Searchable Archives: http://www.contesting.com/_topband - Topband Reflector
|