Sidebar Sidebar
  • You can now help support WorldwideDX when you shop on Amazon at no additional cost to you! Simply follow this Shop on Amazon link first and a portion of any purchase is sent to WorldwideDX to help with site costs.
  • Click here to find out how to win free radios from Retevis!

Change in antenna causes change in power?

T

The Jerk

Active Member
May 6, 2008
647
66
38
Reading, PA
I changed from a Wilson 5000 to a 102...with no other changes than obviously the coax and antenna, the power went from 80/220 to 60 (didn't check swing)...

SWRs are identical with either antenna (1:1 off, 1.2:1 power)...amp is straight 4-pill, ab-1...

What's the reason? Would one be preferred over the other?
 

PM??? Define PM please...

Is there anything to worry about using either setup?

I assume the Wilson probably works more efficiently since its allowing more power??
 
Your experience is the same as mine with that meter. High fluctuations when using antennas as loads. Pure resistive loads work real well with that meter for measuring power.

Check to make sure the amp, meter, radio, and antenna are well grounded and that you have adequate ground plane.
 
So its the meter showing a different reading from the change in antennas? So the reading is more of a baseline than anything?

I believe everything is well grounded. I know the antenna is grounded well.

Should I believe the reading or should I just run the setup? If I remember correctly, isn't the "load" of the 102 supposed to be pretty much correct since its not adjustable?
 
I think it's a matter of the impedances of those antennas (impedance = reistance + reactances). It's a very safe bet that they are not the same, no matter what that SWR meter tells you. Also why I asked about the antenna analyser, an SWR meter can't tell you anything about reactances, or resonance. The more reactance present the less power that can be generated, reactance doesn't contribute to making power, only resistance does that.
So which power readings are really true? Good question, and one a simple SWR meter can NOT tell you, or provide very reliable information to calculate power with.
- 'Doc
 
  • Like
Reactions: Groundhog KSS-2012
I know a local shop that has a MFJ antenna analyzer, I will stop by hopefully Thursday afternoon and see what each antenna reads...see if we can shed some light.

Funny thing is, now the 102" is about the same power output as the Wilson was...no changes other than time.
 
There is an almost limitless combination of radiation resistance, ground losses, and reactance that all factor into what makes up a given SWR reading. You may have the same SWR on two differant antennas but the combination of resistances and reactance that makes up that SWR can be quite differant. The way in which that power meter interprets those factors can also be quite differant. Doc, W5LZ, was correct about checking things out with an analyzer. that's all I ever use now when installing/retuning antennas.
 
The Jerk,
No, it probably wouldn't be worth it. That's entirely up to you. You ready for some "radio heresy"? I'd rather spend that chunk on an antenna analyzer than a Bird watt meter. Gasp, choke! Oh well...
- 'Doc
 
  • Like
Reactions: Groundhog KSS-2012

dxChat
Help Users
  • No one is chatting at the moment.


      Top Bottom
      Back