Bob Albert, thanks. What you say makes sense for the little I do know. It is a 9:1 matchbox. I have limited space and was trying to find an antenna to work all bands just by changing frequencies and hoping the tuner got me close to 50 ohms. I was going to try a G5RV if I can¡¯t make this work but will have to try and find a place to put it up. Otherwise I may be limited to a WRC, but coils seem temperamental and finicky adjusting between bands. Thanks
Darrell
By the way I am reading these recent to earlier posts.
Sent from my over-rated IPhone 7 Plus. Any Mis-spellings or grammar errors are due to my IPhone auto correct feature.
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On Sep 9, 2020, at 21:25, Bob Albert via groups.io <bob91343@...> wrote:
? First decide the frequency range of interest. Then program it either as start and stop, or center and span. Then set up for Smith chart and SWR display.
The Smith chart will plot the impedance of the antenna. The marker, which is controlled by the rocker switch, can be moved to any frequency point and the resultant impedance will be displayed. If the impedance is anywhere near 50 Ohms you will see the SWR at all frequencies in the range.
Antennas are complex devices and characterizing them is partly art and partly science. Most people think in terms of 50 Ohms as a standard, and the Smith chart is set up for that. If your antenna impedance is much different from 50 Ohms, say by a factor of three or more, it won't work well with a 50 Ohm system. The alternative is either to change the antenna to bring it closer to 50 Ohms or transform its impedance to something near that value.
Random wire antennas may do well enough for receiving but for transmitting it's a different story. A transmitter will not perform properly if its load is far from its design value. There are losses when mismatch is great, and these sometimes can cause problems such as arcing or favoring undesired frequencies.
There is, of course, no substitute for a good understanding of the principles. There are many books on the subject, and not all of them are good. Just because it's been printed and bound, don't assume it's correct.
I am a great fan of resonant antennas, and they have worked well for me. I routinely plot SWR across the appropriate band for each antenna and thus see if anything has changed much. I almost never use an 'antenna tuner'.
Bob K6DDX
On Wednesday, September 9, 2020, 07:00:10 PM PDT, Darrell Carothers <rescuemedic1@...> wrote:
Doubting the accuracy of my NanoVNA H4. Is there a way for a non electronics minded person to verify the accuracy of my H4? I am a beginner with the NanoVNA. I have calibrated the unit per recommendations. After calibration the open, short and load show where they should be.
I have used the helpful recommendations from members in this group. I am trying to analyze a random wire antenna that shows no resonant areas. I have a lot of noise and do not hear a lot of stations. I did make one contact last weekend, my only QSO, from Arlington Texas to Jinks OK on 7.280.00 LSB.
Thoughts, suggestions, solutions?
The antenna is a random wire 9:1, 135¡¯ element, 35¡¯ counterpoise, about 40¡¯ up in the tops of trees with leaves. Line was placed with a drone. I would like to learn to use the NanoVNA in and out for my benefit.
Thanks
Darrell
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Darrell Carothers