> Today, I wound an autotransformer (se p. 7-18 in Low Band DXing) on the
> large toroid core that previously had the balun KF7MD and I had built. Using
> a 1K resistor for the load and my MFJ Analyzer, I taped the coil where I got
> about a 50 ohm reading. The SWR was about 3:1. I soldered the tap there and
> replaced the cheapy TV balun with the autotransformer. The MFY analyzer read
> 30 ohms on 160M (I forget the 75M and SWR readings), and my beacon 1600 KHZ
> Denver station came up over a S-unit compared to the cheapy TV balun.
> Tonight I'll see how it works. I think I've recoved 2-3 S-units by going
> from no balun to the autotransformer I installed today. And I can probaly
> tap the transformer for even more signal.
While that does test the balun for impedance, it does NOT test it for
loss. Many books recommend the WRONG core material for baluns, The
cores have too high an initial permeability, some as high as
10,000! Those cores are VLF cores so the loss tangent on 160
meters is much too high, usually making the transformer needlessly
lossy.
You may be able to get a few more dB of signal if you are using a
poorly speced core.
> pull them close enough to reconnect. A few of them I could not pull lose
> from the ice- ice pick any one! Anyway, most of them have been reconnected.
> For some reason, the resonnant frequency of my antenna has crept up from
> 1900 KHz to 1930 KHz?
In most cases, the better the ground the higher the resonant
frequency. The effect you observed is normal.
73, Tom W8JI
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