Coax puzzle

[AudioShockwav]

And, usually why anything around 1.5:1 is considered the same as 1:1.

I agree doc, in most cases, the difference from 1.3:1 to 1.6:1 will not effect anything. The idea that you must have a 1:1 match is very over rated.
I am sure that some one will say this is horse pucky, but most guy`s are not running 8 or 16 2879`s at 20 + volts, were reflect is so critical.
For the average radio op, 1.6:1 is fine.


73
Jeff

 

[ken white]

Ah, but if the length of the coax always has an effect on the SWR of the system when operated away from it's design/measured frequency 'standard', why worry about it at all when away from that frequency? (Especially when the difference in SWR is so slight, and well within the measurement accuracy of almost any SWR meter.) The difference isn't in the velocity factor, but in the difference in impedances of system components, right? Same old story, re-tune the antenna.
- 'Doc


[And since the components of any antenna system will never be exactly what they are supposed to be, you typically find that a 1:1 SWR is more a miracle than fact. And, usually why anything around 1.5:1 is considered the same as 1:1.]

Doc, that is a different answer than coax has no effect, and I agree.

Coax will "always" exhibit a different impedance at differing electrical wavelengths when impedances are not exact so tuning of the antenna will nearly always be affected by coax length.

As a side note, VSWR says nothing about the ERP of the system even though most hobbiest think this - a field intensity meter would be used for this. VSWR is just a metric used to give an indication of the transmission paths transfer of signal power and losses through a point-to-point connection.

Many times a VSWR that is different from the ideal 1:1 is much better for radiation. When an antenna appears as a purely resistive load to the transmitter, and many times this value is not 50 ohms, maximum energy will be radiated. So, a vector impedance meter, or MFJ antenna analyzer, is used for tuning the antenna and coax.

The bottom line is its up to the operators to decide if they want to be anal, or not, and like you said, tweeking the system may not really make much of a difference.

 

[sportygreg]

OK-tuning the antenna was the trick! I got it down to 1.2-1.3 across the channels-probably as good as it's going to get and I didn't want to climb up on the roof anymore.The Dosy and PDC5 agreed on the reading and the radio meter hardly moves.Just wanted my antenna to be as efficient as I could get it-still not sure why better coax made such a difference but I'm satisfied with it now.Thank you all for a lively debate on the problem!