SM7LCB - 1.9m Dish
Last updated 20 August 2009.For 2 year ago (2007) I order a 1.9 meter dish from RF HAMDESIGN with ring feeder for 23/13/9cm. Now during summer 2009 I build it and also installed in on the barn there I until today have my antennas for my remote microwave station SM7LCB. This page will show the steps for my assembling, tuning and installation of the antenna.
Assembling the antenna is very simple but it take some time. I just follow the description which was included in the shipment.
Antenna is mounted on the new antenna platform.
Building the antenna
I start build the antenna,
It looks quit good,
How to install the reflector?
The dish is looking great but still missing the feeder...
The antenna with feeder and setup for antenna gain measurement.
The white plastic bag is the transmit antenna during testing.
Here a photo of the network analyzer Anritsu MS2036A (up to 6 GHz).
Making measurement of beam width at 3 and 10 dB.
Mounting of feeder to dish with the possibility to adjust it in the future.
Measurements
To test the antenna and also to see were to set the feeder I build a small antenna measurement setup as shown on photos above.
To build this measurement setup I borrow following equipment from Niklas/SM7UFW,
- Network analyzer Anritsu MS2036A (up to 6 GHz)
- Transmit antenna, AEL H-1479 (1-10 GHz).
- Coaxial cable, Bedea # 2261 HFX 50 1336 - PVC.
First I start to measure gain at each band and for each change the feeder focus point.
The picture below show how gain changed when I moved the feeder.
I finally selected to use feeder focus point at 882 mm.
Beam width
At selected feeder focus point I when measured the beam width on all three band, see photo above.
This measurement gave following figures.
| Band | Measured value | RFhamdesign value | ||
| 3 dB | 10 dB | 3 dB | 10 dB | |
| 1296 MHz | 8.4 | 11.8 | 9.1 | - |
| 2320 MHz | 4.7 | 8.3 | 5.1 | - |
| 3400 MHz | 3.3 | 7.6 | 3.4 | - |
Absolute gain
I have also done absolute gain measurement but I still don't have correct data on the transmit antenna.
The absolute gain measurement gave following values,
| Band | Measured value [dBd] | RFhamdesign value [dBd] |
| 1296 MHz | 25.4 | 24.2 |
| 2320 MHz | 30.5 | 29.2 |
| 3400 MHz | 33.8 | 32.4 |
Return loss
Measurement of return loss,
1296 MHz
2320 MHz
3400 MHz
Feeder loss
As coaxial cable from focus to the back of the antenna I have used Bedea # 2261 HFX 50 1336 - PVC.
Measurement of this cable gave following data,
| Band | Attenuation for 1.9 meter [dB] |
| 1296 MHz | 0.8 |
| 2320 MHz | 1.1 |
| 3400 MHz | 1.4 |
Measurement of 14 meter of Bedea # 2261 HFX 50 1336 - PVC,
The first signal to be heard
As you see in the log from the first evening with the antenna it's very good. But I think I have good luck with conds this evening.
Still it was very nice as first signal hear OH2SHF on 23 cm with 599+++ signal! By using this beacon I did the first calibration of the rotor direction readout. Later I by using the sun adjusted this first calibration 2 degrees.
I'm very pleased to get OH6NVQ on both 23 and 13 cm this evening. We have tried several time during this week with my previous antenna system (55 el Tonna). I'm not sure that the new antenna made it but sure I lucky that it seem working very nice. Well OH6NVQ was not the first QSO with the new antenna. That was LY2VA. The day after I work many nice QSO on 23cm during the ESFD contest.
For more information about QSO see my logbook.
20090807 1840 OH2SHF 599 BCN 2.3G CW
20090807 1840 OH2SHF 599 BCN 1.3G CW
20090807 1841 ES0SHF 599 BCN 1.3G CW
20090807 1842 SK1UHG 599 BCN 1.3G CW
20090807 1843 SK0UHG 559 BCN 1.3G CW
20090807 1844 SK4BX/B 519 BCN 1.3G CW
20090807 1952 SK7MHL 579 BCN 1.3G CW
20090807 1953 DB0VC 599 BCN 1.3G CW
20090807 2003 LY2VA 559 599 1.3G CW 400 km
20090807 2005 LY2VA 559 599 2.3G CW 400 km
20090807 2015 OH6SHF 519 BCN 1.3G CW
20090807 2016 OH6NVQ TRY 1.3G CW
20090807 2024 OH6NVQ 419 HRD 1.3G CW
20090807 2025 OH6NVQ 559 539 1.3G CW 888 km
20090807 2029 OH6SHF 559 BCN 1.3G CW
20090807 2030 OH6NVQ TRY 2.3G CW
20090807 2043 OH6NVQ TRY 2.3G CW
20090807 2059 OH6NVQ 529 HRD 2.3G CW
20090807 2104 OH6NVQ 539 539 2.3G CW 888 km
20090807 2121 SK2SHF 559 BCN 1.3G CW
20090807 2124 SK2SHF 579 BCN 1.3G CW
20090807 2136 SK3UHG 579 BCN 1.3G CW
20090807 2142 SK3UHH 539 BCN 2.3G CW
20090807 2146 ES5PC TRY 1.3G CW
20090807 2150 ES0SHF 579 BCN 1.3G CW
Now I hope it will survive the winter and that I get many nice QSO in the logbook!
| SM7LCB |
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