[mythtv-users] Mini Coax connectors

[David Moore]

On 11/06/12 15:16, Jay Ashworth wrote:
> ----- Original Message -----
>> From: "Jean-Yves Avenard"<jyavenard at gmail.com>
>
>> On Sunday, 10 June 2012, Mike Perkins wrote:
>>>   60's. We were always told to assume a 3db loss for any connector
>>>   inserted into a test line.
>>>
>> This is also what I've been told to assume for any adapter added to
>> a 75 ohms antenna cable: assume 3db losses
>
> Note that an adapter is *2 connectors*, so one of those things has to be
> incorrect, and in fact 3db is a *lot* of loss, I wouldn't expect that from
> an adapter even if it was changing the characteristic impedance of the cable.
>
> 0.1db is *high*.
>
> And in fact, a couple of hams polled on the topic agree with me, with good
> arguments to back them up:
>
> http://forums.qrz.com/showthread.php?297709-RF-connector-adapter-loss
>
> Cheers,
> -- jra

That's correct. Connector loss (attenuation) should be a small fraction 
of a dB depending on quality of the connector. The 3 dB loss probably 
comes from the rule of thumb "loss" for a splitter which isn't actually 
a loss but simply the consequence of splitting the power in half to feed 
two outputs. None of this depends on cable type/impedance BTW. It's 
generally true for RF.