2024-10-21

New Vertical Omnidirectional Antenna for 23cm.

Finally, today I got my new mono-band vertical omni-antenna up for 23cm. I was using the 3-band antenna X-7000 from Diamond on 23cm, only and it had one serious drawback. The signal into the preamplifier from an adjacent antenna a few meters away was killing the GaAsFET in the preamp.

The second srawback of the X-7000, also connected to the 3-band configuration, is that the gain of the antenna on all bands, and 23cm in particular is not fully optimized, and it probably does not radiate so much from the top end.

The X-7000 is nabout 5m long, and the new F1-230A II is only 3.5m long.
The new antenna has been mounted about 1.5m higher, with the feed point about 7.5m, and the old X-7000 was at 6m. The tip of both antennas is approximately 11m, so I suspect that the radiation from the new antenna is located higher in altitude.

The new antenna was intended to be raised yesterday, but it got caught in branches of nearby trees. Those trees ahve now been trimmed, so today we could finish the work, and make a test of the new antenna system.

A fresh preamp has been mounted, so the receiver sensitivity is back to the optimum, and a transmit test revealed improved signals from stations in several directions. OZ1GIN who could only hear an extremely noisy signal before, can now read my signal with an Okay-ish signal.

I can still improve the transmitter capability with a power amplifier module, probably increasing the power at the antenna from about 5W to about 25W.

Given that many stations do not work with preamplifiers near the antenna, this should be a solid improvement of my station range.

This is the best I can do with an omnidirectional vertical, so the next 23cm antenna project will be getting a modest 23cm horizontal antenna up on a rotator as high as I can. As far as I can see, I can get a small yagi up about 11.5 - 12m, and with a good preamp and decent linear amplifier that will be what I can achieve. 

It should be a decent setup at my QTH, the best I can do. 

As the small yagi is "front mast" mounted, I might add another one, vertical, in the opposite direction, when I can repair one of the3 destroyed preamplifiers. Yes, I have ordered new GaAsFETs.

For now I have the vertical omni-system to work with, and I think I will have some fun with that.

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