antenna-theory.com

[charleshstratford]

Hello there--I am new to amateur HF bands and can't seem to figure out why my antenna is not working properly. I was using an MFJ 223 vector antenna analyzer, and read on a QST review that it was rather inaccurate, so I purchased an AA-30 from Rigexpert. I am using a buddipole antenna system in two different configurations: 20m dipole and 40m vertical with a counterpoise. I was getting fairly accurate SWR readings on my rig expert while configuring my 40m operation, meaning the SWR readings were the same outside my shack as inside. However, when switching to my 20m dipole, I set the whips to the same length that resonated at about 1.2/1 when using my older analyzer. This time, they read at about 1.4/1 outside the shack. When bringing my feed line into the house, the SWR on the rig expert was really high: about 5/1. When I plugged the feed line into my HF rig, and keyed up on AM on 20m, the SWR was around 1.5-1.8/1, depending on the wattage output. On five watts, it was 1.5/1 and around 95 watts almost 2/1. I am not sure which reading to believe! My HF radio is not grounded. The only ground I have is the third prong on my linear power supply. Why is my rigexpert giving me such a high reading (a very reputable analyzer) while in the shack? Outside the shack, the SWR reading on both analyzers is consistent with my months of operating the buddipole. I checked my feed line for damage, and found none. I am using the balun supplied with the antenna, which I assume is intact. All connectors seem to be intact. Not sure where to check next. Any help would be appreciated. Thanks and 73s - Charles KG6EID

[helix]

What do you mean when you say you make measurements both inside and outside the shack.

One thing, you report different VSWR readings at different power levels. That shoukdn't ordinarily happen, and suggests nonlinearity, either compression in the instrument, balun saturating, or perhaps arcing/breakdown somewhere.