Re: QRPp Antennas #u3s #antenna


 

Tnx Andy, my QCX/20 comes out with 2,8 watts
HK6J 
Juan Herrera
Enviado desde mi iPhone

El 7/09/2018, a la(s) 9:33 a. m., Rick, DJ0IP <Rick@...> escribió:

Mark's reply was very good.  I'd like to add a bit if I may.

Asking if a matchbox (not tuner) has a lot of loss can only be answered with "it depends".
All matchboxes have sweetspots (frequency and impedance ranges) where the loss is so low that it is negligible.
I have a drawing showing this, here:  http://www.dj0ip.de/antenna-matchboxes/perfect-matchbox/ 

The ARRL defines this to be less than 10% loss.
So the answer to whether or not the matchbox has noticeable loss is, it depends on whether it is operating within its sweetspot or not.

In addition, the ARRL has tested a couple dozen matchboxes over the past 20 years.
I have summarized their findings into a single, MONSTER Excel spreadsheet.
It clearly shows the sweetspots of each matchbox model tested.

Unfortunately, you need to know the impedance of your antenna system where it connects to the matchbox, not just the SWR.
A 3:1 SWR can be either 150 Ohms or 33 Ohms.
150 Ohms is within the sweetspot of most matchboxes.
33 Ohms is often not within the sweetspot.  
So just knowing the SWR (alone) does not always give us the right answer.

If this interests you and you have a bit of time, you may download my MATCHBOX SHOOTOUT  at the bottom of this page:
http://www.dj0ip.de/antenna-matchboxes/matchbox-shoot-out/ 

Remember guys, a dB is a dB, whether we're running 500 Watts or 50 mW.
If my signal happens to be 55(9) with 100mW, one dB of loss is meaningless - unless the guy's noise level is also 55 (hi).

73 - Rick, DJ0IP
May the Sunspots be with us!

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