Information collected and measured from my antennas.
Advertised details:
This antenna was replacing my Diamond X-50 2/70 antenna in 2025 The base of the antenna is at about 8.5m above street level, and just about the highest point of my house in JO21sj.
It appears that the VSWR in the 144-145 MHz band is well above 1:2.0 as can be seen in the picture above. This is confirmed measurinmg the VSWR with the FT991 + SX-600 SWR meter. (SWR=2.0) Odd detail: the FT991 SWR reads low and ok at about 1.1 - 1.2
The NanoVNA measures:
This afternoon there was substantial rainfall, so I wonder if there’s some kind of moisture ingress that affects the antenna?
The next day, the situation remains unchanged, although they antenna has fully dried up over night. Therefor the MA2000 is removed and replaced by a brand new Diamond X.50 (2025-SEPT-16).
My plan is to mount this antenna in the backyard on a temporary mount some time in the future to further investigate what is wrong with it.
On 2025-09-21 a setup was made in the backyard. Unfortunately the antenna was behaving perfectly fine, with a VSWR of 1.2 on 145.5MHz (MFJ-259b), and a clear low dip between 430-432MHz on the nanoVNA
Suggestions from other hams: - mounting pipe too close to base pipe - moist ingress that has evaporated since the antenna has been indoors for about a week now.
Given the intermittent behavior of this antenna it will not be put back as my main VHF/UHF antenna for local traffic (until I understand what’s going wrong).
Advertised details:
This antenna was installed on 16 september 2025, replacing the Lafayette MA2000. The base of this antenna is at about 8.5m above street level, and just about at the hightest point of my house in JO21sj.
A quick SWR check on 2m with my trusty-old MFJ259b shows that the VSWR is acceptable in the 2m band. As this antenna analyzer does not cover 70cm I also take a look with the nanoVNA.
This is what the nanovna H4 shows for the 2m band. The entire band is clearly showing an VSWR < 1.5 (yellow curve), which is as advertised. Marker 1 (at 143.0MHz) and Marker 3 (146.3MHz) are set on the VSWR 1.5 line. The minimum is found at 144.5MHz (VSWR 1.3).
The same measurement is done for the 70cm band.
Using the FT991 with a K-PO SX-600 VSWR meter in the coax feedline, show a VSWR of 1.3 on 145.450MHz using 5W of RF power.
And with the same setup we get a VSWR of 1.4 on 431.7MHz, which is a typical frequency for repeater relay input.
The same VSWR measurements were done with a 60dbm.com reflection bridge from Ukraine, connected to my Rigol DSA-815 Spectrum analyzer.
Based on information from PA3GER on the internet, a 2 meter “Slappe Arnold” was created using the following dimensions:
This antenna is normally connected to my Kenwood TK-780 for local traffic monitoring.
This antenna is similar to the slappe arnold, but has a slightly deeper VSWR dip.
It’s normally connected to my trusty old Teletron T-813 for local traffic on 2m.
Due to tuning it for optimal SWR on 2m, it’s currently not having good VSWR on 70cm, which is not an issue as it’s not used on 70cm at all :-)
