Category: Antennas

Artiklar om antenner, rotorer, LNAs och relaterat.
Posts about antennas, LNAs and rotors.

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Antennas

3 el UHF lightweight Yagi

This 3 el UHF lightweight Yagi by RA3TOX can be built with low cost materials like 20 mm PVC tube and tube holders as element holders. The element can be made of 3.2 mm aluminium welding rods. Making a second yagi on the same boom and it becomes a X-yagi, with correct made phasing cables.

I have built one X-yagi version and tests on the ground (see picture above) was very good, when I tested it as a SatNOGS antenna. Unfortunately, something broke when I mounted it on the mast so it is not in use.

The driven element (loop type) was kind of hard to get correct, I made several versions before I got the correct SWR for 436 MHz.

This is the drawing I used:

  • Original drawings, calculator and design by RA3TOX
  • Used by PE0SAT for his SatNOGS station. Link here.
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Antennas

Polarization switches and cables

This is a summary over some of the polarization switches and cables that can be used for satellite antennas. If you find more products please contact us and I will add the info.

First of all a very good page about polarization is this one by SV1BSX. Also DK7ZB has an excellent page about cross yagis and polarisations. And PA3GUO… Google and you will find a lot more pages…

I have also made a post about making the WRAPS switching, the post is in swedish but there is also a PDF in english by the creator Mark Spencer WA8SME.

UHF and VHF Antenna Polarization Switch from Minikits

Minikits have kits for both VHF and UHF. Note that this is a kit and not a ready solution. Link to the UHF version

Polarity switch from M2 Antenna Systems

M2 Antenna Systems have both VHF and UHF switches for the X-Yagi antennas. This switch is placed direct at the antenna, the original driven element is replaced. Link to the UHF version

Polarization remote switch from Wimo

Wimo has a polarization remote switch designed for the X-Quad antenna. It should also be possible to use with other X-Yagi antennas.
Link here
Link to product manual

They also have several types of phase line cables. Link to the UHF version

Antenna Amplifiers CROSS Antenna 1500W Polarization Switch H-V-RHCP

This is a brand new product in 2022 for VHF from Antenna Amplifiers. Link to product page

They also have a 144 – 146 MHz and 430-440 MHz Universal RHCP Kit. Link to product page

Categories
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]

Categories
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!

Categories
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.