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Dual-band Comparisons

The UHF/VHF dual-band antenna, no matter which manufacturer, seems as ubiquitous as any antenna for many hams engaging in local area or travel comms.

While the 3:1 2m:440 ratio thing doesn't work out cleanly, some clever design of loading and decoupling elements integrates the two bands/one antenna idea a little better than bare wire. Or does it?

I've measured (but not recorded some of these implementations with best match at odd places - 435 and 148, 449 and 143... and no better than >1.5:1 SWR - some match huh? No telling how that got onto the shelves as a viable 144-148/440-450 antenna.)

Are different makes/models any better? Better? Perhaps a consistent low SWR and maybe 45-55 ohm matches across the most used band segments? Nope.

I put a Tram 1180, a Workman clone of a Larsen NMO-2/70, and a Larsen 2/70 on the stand. The results were almost similar (Murphy must have liked me today) so I'm only posting the Tram results. One of the Workman units was really bad, until I found the center coil 'open' due to the intermittent mechanical connection inside, easily fixed.

Again, no impedance measurement at UHF yet. Native Low SWR at VHF was found to be 1.6:1 @ 146.8 at 40 ohms. 50 ohm points were down at 142 @2:1 SWR and I believe 149-150 also 2:1 - so match consistency is not. Low SWR at UHF was 1.5 at 445. 2:1 @ 440 and 1.8:1 @ 450. Again I remember one or the other Larsen being much less consistent or acceptable in the usual segments.

I'd like to take a look at the typical Diamond and Comet versions in low gain and high gain models because I know their high-gain base models are horrible someplace - I'll have to disconnect the garage repeater and retest my Tram dual-band base.

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