Topband: Return Loss Question?

[Wes]

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