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Antennas Ham Satellite news

AMSAT SA Dual Band 70cm/2M Yagi Mark II

AMSAT SA has launched Mark II of its dual band 70 cm/2 m handheld beam antenna with a new, easier to hold handle and improved coaxial terminations. The Yagi has been retuned for maximum performance in the amateur radio 2 m and 70 cm satellite bands. The coax cable is terminated crimped brass lugs instead of being soldered making it environmentally more robust. The driven element has been adjusted to accommodate the change in the connection. More about the Yagi. The antenna has a 50-ohm designed driver. The Yagi has a unique element called an ‘Open Sleeve’ which is a director very close to the driven element. The driven element is sized for 2 m. When operating on 70 cm the ‘Open Sleeve’ acts as part of the driven element on 70 cm (the third harmonic of 2 m).

The original concept was developed in 1946 by Dr J T Bolljahn of the Stanford Research institute but was not introduced into amateur radio until the 1950s. The AMSAT SA version is based on a design by DK7ZB with modifications by WB5CXC. The first South African version was a collaboration between Guy Eales, ZS6GUY and Gary Immelman, ZS6YI. It was developed for YOTA 2018 where young people successfully used the antenna operating satellites using hand-held transceivers.

The mechanical structure was redesigned by Gary Immelmann ZS6YI. A choke around the boom was added to isolate the antenna from the coax and reduce the effect human contact has on the antenna. A handle was added on the boom end which makes it more comfortable to hold and further isolates the antenna from the handler. The AMSAT SA Yagi is manufactured in one of Gary Immelmann’s factories in Vereeniging. It has two elements on 145 MHz and 3 elements on 435 MHz.

For its size, the antenna has excellent gain: 145 MHZ: 4.12 dBd or 6.3 dBi and 435 MHz: 6.23 dBd or 8.4 dBi. The Yagi is broadband with measured SWR being almost flat over the entire bands. The antenna is plug and play, no tools are needed except for soldering on a connector to suit the application. It comes complete in a carry bag with full instructions. This antenna can be assembled and dissembled in minutes. The price of the MKII Yagi is R400 for AMSAT SA and SARL members. Non-members pay R500 (approximately $36.75 US). The courier charge is R120 (approximately $9 US, Postnet to Postnet). Ask for a quote for other courier options. Find more details and order forms on http://www.amsatsa.org.za/

[ANS thanks AMSAT SA for the above information]

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Antennas

Avoid heading failure for Rot2Prog

The Rot2Prog rotor controller, sold with the popular RAS rotor series, have a nasty bug if using the rotor with a computer. I not sure when it happens, I have not been able to reproduce it on demand, but in some condition the “Heading adjust” (PP in the setup mode of the controller) seams to be set from the computer to a totally wrong heading….

To avoid this problem I think (but not 100% sure) this is the way to handle the controller:

  • Always turn off the Rot2Prog before shutting down the computer!
  • Turn off the Rot2Prog if you are not using it and the computer is on
  • If you are using the Rot2Prog manually, or using the setup menu, and the computer is on be sure that you do not have any controlling software (like PstRotator) running at the same time

But… If you get this error it is easy to adjust the heading with the PP “Heading Adjust”, turn the rotor to north and then reset the Rot2Prog with “On + F”.

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Antennas

Make the FOX-727 yagi more portable

The FOX-727 Dual band yagi is a budget yagi for VHF and UHF. Unlike the popular Arrow yagi it is not made for portable use and holding with one hand. The square bom make it hard to hold longer than one minute… (believe me, I have tried).

To make it more portable I cut some foam (just like the one you can use to sit on if you go camping…) and added some tape. I did it at two areas (see the picture) so you can choose where you would like to hold the antenna. The feedpoint and gamma match is located in the center of the antenna so it is not very good balanced to be able to hold it at the back. I prefer to hold it a little bit closer to the center.

The cost is almost zero and now it is possible to hold the antenna and pointing to a satellite!

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Antennas

Fixed UHF yagis for SatNOGS ground station

For my SatNOGS ground station I have tried several omnidirectional antennas for UHF without success – Dipole, V-Dipole, Eggbeater and Turnstile. I know that several SatNOGS station are using omni antennas for UHF with very good result – but at my QTH it seems not possible. I have high hills surrounding and a high level of local interference on 435 MHz.

So, my solution is fixed yagis. I’m using a lower budget yagi from Vinnant antennas – Y8E446 8 element yagi but tuned for 435 MHz.

Y8E446

This antenna is excellent for it´s price – very good SWR and good quality. At first I used only one antenna and now I could decode satellites when it was passing in front of the antenna loob.

To be able to decode more passes I added one more yagi and stacked the antennas with a short 75 ohm power divider coax cable. I used the instructions from this webpage.

After testing directions at several positions I’m now using an elevation of about 30 degree and azimut of aprox 120 and 240 degree. Of course the signal level is lower than just using one yagi but I can now decode satellites in bort west and east pass.

This is a decoded west pass:

And this is a decoded east pass:

Summary:
For my station this is a solution that makes it possible to receive at least the strongest UHF satellites. To receive better I should probably need a antenna rotor.

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Antennas

Vinnant antennas for satellite

Turnstile Dipole VHF

Stanislav Palo, maker of VHF and UHF antennas, has opened a web shop at www.vinnant.sk Stanislav have several antennas for satellite use, both for VHF and UHF:

  • Turnstile types
  • Eggbeaters
  • Yagis

I have used several of his antennas – one Turnstile VHF is in use now at my SatNOGS station and is performing very well.

I hope to be able to test some of the UHF antennas during 2020. Stay tuned!

Categories
Antennas

V-dipole for UHF – build a simple satellite antenna

A V-dipole for NOAA weather satellites on 137 MHz has been published by 9A4QV and it seems to get very good results. I decided to build one for UHF 436 MHz satellite band and also add reflectors to get the antenna pattern higher up.

I followed the instructions by 9A4QV but adjusted to 436 MHz. All SWR measurements are done with a NanoVNA. Please see the pictures below for some ideas how to build one of you own. You can also see test results below.

I have used the following materials:

  • PVC pipe 32 mm diameter
  • TIG Aluminium elements (Tigrod ESAB OK 4043 (3.2 mm/1000 mm)
    In Sweden you can buy these at https://www.svetsmaskinservice.se/
  • Coax cable direct connection to the element
  • All elements are aprox 16 cm long. Make the two elements for the dipole a little longer and cut for best SWR
  • Distance to radioators are aprox 10 cm
  • As you can see I use a lot of glue to make it water proof… 🙂

Some pictures from building

Mounted at the same place as my VHF crossed dipole. I use these antennas for my SatNOGS station.

Test results

When listening to local repeaters a got good readings, but when trying to receive satellites I did not get the result I think this type of antenna should deliver. I think it is a better antenna for the high power NOAA satellites on 137 MHz. But, it´s very simple to build!

Some results:

Bugsat-1 RX by my SatNOGS station. Two packets decoded.
Video: Receiving RS-44 satellit while holding the antenna by hand