Topband: Return Loss Question?

[Chortek, Robert L.]

How much return loss is acceptable certainly does “depend”. 

I’ll throw in another consideration to further complicate matters:

The higher the VSWR, or lower the return loss, the more power is lost in the cable due to the mismatched condition. 

How much power is lost depends on the type of cable, the cable length, the quality of the cable and of course the frequency.

The higher the frequency the more power will be lost in the cable due to the mismatch.

So while your transmitter and or antenna tuner may well be able to operate into an increasingly high VSWR (or low return loss) the price you will pay for that is more power loss in your cable. 

Thus, return loss becomes more important as you operate higher in frequency or use longer cable runs.

Not too important at 160 meters but probably very important at VHF.

73 es DX,

Bob/AA6VB 
Robert L. Chortek

> On Jan 17, 2021, at 9:07 AM, Wes <wes_n7ws at triconet.org> wrote:
> 
> [External Email]
> 
> 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
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