I bought my Diamond X200n antenna on a local ham fleamarket in october 2006. It was brand new and never used before. The antenna was mounted on the first of august.
There is about 21m of H500 coax between the transceiver and the antenna. The antenna performs well on 70cm with a very low SWR curve. On 2m however the SWR is not what I expected.
On 146.000 MHz the SWR is 2,3:1 dropping to 1,8:1 on 144.000 MHz. That could be better. My neighbour and amateur ON5NV has the same antenna, so we replaced mine to see if the problem still occurs. It may be the connector or something with the coax.

But with his antenna, the SWR was 1,1:1 on 144.000 MHz and 1,4:1 on 146.000 MHz. Perfect.

Diamond X200 capacitor detailsWe dismantled my antenna. As you can see in the picture there are two capacitors soldered in the foot of the antenna. The codes on the capacitors are 1C 500V and 9D 500V. This means 1 pF 500 volt and 9 pF 500 volt. And they’re ceramic types.
Measured the values with a meter and the 9 pF seems bad : 1,8 pF measured value. Gonna replace this one. Bought two capacitors just before Christmas 2007 on a hamfest in Bladel (The Netherlands). A few weeks ago replaced the bad C with the new one. Time to measure the antenna again.
Not what I had in mind. See this PDF document. It contains both swr curves from 2m and 70cm, one from my repeaired antenna and the other from Alex’s (ON5NV) antenna.

To be continued….