Re: End Fed antennas w/ uBITX #ubitx


Jerry Gaffke
 

I have the unit that was reviewed.
Have checked it over with a vector impedance analyzer.
It is resonant on 80,40,20,15,10 as claimed showing low SWR as described in the article.
Including 40 and 20, you claimed that would not be the case.
And very high SWR in most regions out of those bands, indicating I am not just feeding a resistor.

Your central point seems to be you don't trust the transformers.
Yes, many such transformers are quite lossy.
In the review, they put two matchboxes back to back, so 50 ohms to 49*50=2450 ohms to 50 ohms.
Then monitored power going in from a transmitter, and going out to a dummy load.
Found there was very little loss.
How is this methodology deeply flawed?
 
You say you communicated with the folks who did the review.
Would be interesting to see if they agree with you.

Have you looked at the particular antenna system in the review?

Jerry


On Wed, Jul 25, 2018 at 12:44 AM, Warren Allgyer wrote:
Jerry

i am aware of that product review and I have have discussed the methodology with the author. Their methodology was deeply flawed and cannot be duplicated in a properly equipped test laboratory. 

The antenna is not the issue. The transformer is. When feeding a resistive resonant load the losses in the transformer are under 2 dB for bands 40 - 17, rising above 3 dB or 50% on the rest of the HF bands. 

When feedingING a non-resonant reactive load the transformer loss rises to 10 dB and more on all bands. I am happy to supply test data and methodology, which has been independently corroborated, to any who wish to see it. I am good in QRZ. 

WA8TOD

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