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Author Topic: SWR/Tuning  (Read 975 times)
K3ZL
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Posts: 7




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« on: November 21, 2017, 06:28:50 PM »

Today I put up a 40 meter Delta Loop in vertical position.
My antenna analyzer shows me that I have swr on 7.0 to 7.1 is about 1.7 SWR. Not perfect, but I figure my tuner could easily handle it...but, no.
I bought a clean TS-590s with built in tuner.  When I attempt to tune I am hearing their built in "SWR" warning in CW. And apparently it is limiting my power out to about 25 Watts.  All thoughts on this are appreciated.
Thanks, K3ZL.
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VE3WGO
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Posts: 163




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« Reply #1 on: November 21, 2017, 07:20:12 PM »

Hi, my first inclination, since you said the radio was clean, would be to confirm the frequency accuracy and SWR measurement accuracy of the antenna analyzer.

(1) If you have a frequency counter, check the accuracy of the analyzer's actual test frequency.  Alternatively, can you hear the analyzer (with a dummy load on it!) in the TS-590s receiver to confirm the analyzer's frequency?

(2) With a purely resistive load on a 50 ohm system, it turns out that SWR = R/50 if R > 50 ohms, or SWR = 50/R if R<50 ohms.    So if you have a resistor of precisely R = 85 or 29.4 ohms connected to the analyzer, you can check it's SWR accuracy because it should display SWR = 1.7, but more common values of resistors are easier: for example R = 82 ohms gives SWR = 1.64 and R = 27 ohms gives SWR = 1.85 which are both worth checking to make sure your analyzer is working properly. Also you should confirm their actual resistance values, then calculate the expected SWR reading with the formula above.

If you happen to have high wattage versions of those resistor values or something similar, (not wirewound ie, inductive) but purely resistive ones perhaps made up of a bank of old carbon resistors, then you could even check the TS-590s' tuner to see if it can actually tune a match at SWR = around 1.7, to cover all the possibilities.

73, Ed VE3WGO
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W1VT
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Posts: 2529




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« Reply #2 on: November 22, 2017, 08:40:25 AM »

What frequency are you trying to use the tuner?  What is the SWR at that frequency?

What mode are you running?  What are you using to measure that 25 watts?  The mode can make a difference if you don't have a true peak reading wattmeter. 
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K3ZL
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Posts: 7




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« Reply #3 on: November 22, 2017, 10:28:32 AM »

Tnx, Ed.  Got it going. 73
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