DECEMBER 27, 2018

Matching Vertical Feedline Impedances

L-Match in the Feedline

As we tune the experimental vertical its feedpoint impedance changes, progressing lower as its resonant frequency rises. With 25 radials deployed, the vertical's impedance and resonance is not within comfortable ranges for the amplifier. To temporarily correct for this in the shack, a L-match has been inserted into its feedline allowing a 50 Ohm impedance with zero reactance to be presented to the amplifier. 

L-Match for Experimental Vertical Installed in Shack

Shows 50 hm impedance and zero reactance to amplifier when experimental vertical is being fed
No need to re-tune vertical while radials are being deployed. 

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Another L-Match in the Other Feedline

A second L-match has been constructed to take care of the impedance transformation for the reference vertical. Matching the impedances of the two verticals to 50 Oms and zero reactance eliminates the possibility that a mismatch to the amplifier affects results of A/B comparison of the verticals. 

L-Match for Reference Vertical Constructed & Installed

Provides 50 Ohm impedance and zero reactance to amplifier when experimental vertical is being fed. 

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More comparisons performed tonight. A71AM reported 3 S-units in Qatar. Ireland reported no difference and then 2 S-units differnce over span of 20 minutes. 

System Used to Switch Between the Verticals

Both vertical feedline impedances can be independently set to 50 Ohms before being switched to the amplifier

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DX data below.

DXSummit Spots • December 27, 2018

NOTE: Propagation fluctuated from low to high angle in a matter of minutes. 

Check out the wide variety of compass headiings reporting in, characteristic of an omnidirectional radiator.

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