I have an assortment of whip antennas for various RX & HT devices such as a 2M/70cm FT740, a Uniden race scanner 29-54Mhz/108-174Mhz/406-470Mhz/806-956Mhz, a similar Realistic Pro-32 scanner and couple of CB stubs. All the antennas look similar and are easy to mix up. Only the FT470 stub is marked as a dual-band YHA-28. I have a Rigol DSA815TG and a Mini-circuits ZMDC-10-1 500Mhz directional coupler for doing VSWR measurements. I have the DC attached to a 12x12” Al plate to act as a counterpoise. The DSA is attached to the DC with 10” RG174 and the antenna is attached directly to the DC IN port.
The YHA-28 has an obvious loading coil in the base. In free air it resonates sharply at 142Mhz 1.5-2.5SWR and broadly from 350-450Mhz 4-8SWR. But the 144Mhz resonance can easily be shifted 10-15Mhz lower with my hand in proximity. How can this work effectively as a 2M TX antenna.
Another spiral stub antenna sharply resonates at 154/196/358/465 all with SWR in 1.2-3 range. Clearly not for the 2M HT and likely for the Uniden race scanner. Though not matching all the available RX bands.
The OEM Uniden stub sharply resonates at 149 & 438Mhz 1.2-1.8SWR and broadly from ~350-400 2.2SWR, a better match to the mid-bands anyway.
I get it that most single or double conversion receivers are rather unaffected by SWR, but how can and amateur HT work with a 1/4 wave antenna that shifts out of band so easily? Maybe I am missing something here. The current ARRL handbook doesn’t really address HT whip antennas.