Kategorier
Antenner

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!

Kategorier
Antenner

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.

Kategorier
Antenner

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!

Kategorier
Antenner

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
Kategorier
Antenner

Moxon Dual Band VHF/UHF satellite antenna

I have built some simple yagis the last years and seen that many have tried a Moxon Dual Band yagi. I decided to try the model by George Smart – @M1GEO. For all details of the antenna please see George homepage.

I have used the following materials:

  • PVC pipe 32 mm diameter
  • PVC pipe clamps for 32 mm pipe. These are to attach the elements with glue and the just clamp it on to the pipe. See pictures.
  • 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 VHF element

Some pictures from building

VHF element construction
VHF element test outside
UHF elements completed

SWR measurment

VHF – very good SWR
UHF – better then VHF!

Real tests on UHF and VHF

UHF:
Below a very simple test with RS-44 on UHF SSB and with SDR Console. I will need to do better tests with FM sats like SO-50.

Very simple test on UHF with the RS-44 satellite

This is the second test with RS-44. Recorded with SDR Console v3 and Airspy Mini. As you can see the signal levels are not so high with this antenna so it’s sometimes hard to hear the QSOs. And the fading from the satellite is very clear. The antenna was in horizontal position, vertical was even lower signal levels. It would be fun to compare the antenna with an Arrow yagi…

Second test with RS-44 satellite on UHF

VHF:
Very good RX!
This is a test with DIY Moxon Dual Band VHF/UHF portable satellite antenna. Satellite received is AO-91 on 145.960 MHz FM. In the video you can see the signal fading when twitching the antenna vertically/horizontal. You can also see when pointing the antenna away from the satellite position that the signal drops.
In the last 20 sec of video you can see, in the background, my large yagis (2×6 el) tracking the satellite.

RX test on VHF AO-91 satellite

Kategorier
Antenner

VHF/UHF Diplexer till dual band yagi KW4FB

Beställningen pågår under september 2018 och de som varit intresserade blir kontaktade sedan.
Tack för visat intresse!

För ett tag sedan (december 2017) gick jag ut med en förfrågan att beställa byggsatser för en liten diplexer enligt följande:
http://kw4fb.com/micro-diplexer/

Då blev det inte av, men jag gör ett nytt försök nu!  Om du är intresserad så skicka ett mail till info@amsat.se. Ingen förbetalning krävs utan jag kommer att beställa hem allt och sedan sälja per färdig byggsats (PCB och komponenter) för självkostnadspris.

Jag behöver en volym på ca. 10 st för att det ska gå att lägga beställning.

Vad ska man ha denna till då? Jo om du har en dualband yagi eller annan antenn och behöver splitta på anslutning till VHF och UHF.  Eller om du har två antenner uppe i masten men bara vill ha en antennkabel upp från chacket.  Observera att den är specad till max 10 watt och är främst tänkt för portabelt bruk.  Priset kommer dock bli mycket billigare än att köpa en fabriksbyggd diplexer.

73
Lars SM0TGU