Category Archives: satellites

Satellite Antenna build – 70cm antenna

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So during a break from studies and the fact this 70cm antenna had been sat in the shack since mid July, I decided this morning to at least make some progress with it.

The warm weather continues here in England/IO90BS – neighbouring Hampshire is now on a hosepipe ban, I’m hoping with the plentiful rivers and springs that Bournemouth will not be subjugated to such things, but with another 30c week forecast next week, who knows. I’m having to do any outside work very early in the morning else its just too hot to work.

wx in IO90BS

I enjoyed my attempts at satellite communcation with the Kenwood THD7 and Arrow antenna, this is great for portable operation. In the shack I have the ICOM 9700, which is built for satellite operation, as yet I’ve only used the 9700 on simplex and repeaters per-band, so probably 50% less than what the radio can actually do ! The Satellite feature allows split channel and (2m&70cm), so I wanted a solution to use the 9700 at the QTH.

I didnt want to spend a fortune on antennas, so I hunted out a reasoniibly priced 2m and 70cm antenna. For today will talk about the 70c antenna, the DUAL PA432-8-1.2RA. I got mine from Nevada Radio, other places sell them, but I’ve never had any problems with Nevada radio in terms of getting products to me and after sales care.

The specifications for the antenna are very good for the price, and with satellite communications you don’t want an antenna that is very focused (i.e. with alot of elements on it) else it makes tracking the passes a very precise movement across the sky. As I’m using an old TV rotator at 30 degrees fixed tinflation, this should be a good antenna for me.

Assembly was easy enough, the instructions and labelling of the elements are very good to ensure they are put in the right way first time. I have yet to threadlock my screws until the antenna goes up, but will do when I know it is working correctly and raised. There is a choke on there, its important *not* to unclips/cut these, if you’ve not seen a 70cm antenna before you might be tempte dto cut them thinking its packaged this way, and its not, just leave as is 🙂

Once completed I erected the antenna on the bike stand. Initial results were disappointing with the SWR very out of the 70cm band. Rembembering how volitle and sensitive equipment is at this frequency I swopped out the coax, which resulted in much better results.

70cm band and the PA432

I was very happy for about an hours work to get an antenna with high gain and good SWR reports.

As I want to mount the antenna on a horizontal beam, I will need to work out how to attach it (probably another 90 degree holder), but for now I’m glad the antenna is out its box and ready to use.

measurement tools and longer coax
antenna on bike stand

Next week I’ll hopefully get the 2m Yagi built (Diamond A144S5R2) and then can see how to tie it all together.

2E0FWE – AO91

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Today (19/6/22) was my first attempt of using satellites put in place for amateur radio. Having read up and joined Amsat (a very modest fee for quality content!) I targeted AO-91 as my first satellite.

AO-91 – GoSatWatch

I could see there was at least a possible chance of making a contact at 09:14 BST, so I set out with the Arrow II 146/437-10WBP 2m/70cm antenna and my TH-D7 hand-held.

antenna packing
in parts
constructed

Having got the antenna built and radio ready (I pre-programmed the optimal tuning in the shack) I setup a comfortable postion to operate from.

I made sure i was ‘aligned’ to the sky with a real magnetic north compass to ensure that I would stand the best chance of being able to hear the satellite as it came over on its relatively low and short pass.

I was astounded that with pointing the antenna on frequency I was soon hearing QSOs from Italy and the Netherlands via the satellitle on 2m and 70cms. As I was about to try calling my THD7 stopped working ! In a rush I got the THD7 plugged into the Bongo power and could continue to receive, but was unable to complete a QSO this time.

Whilst the battery had got the better of me making a QSO, I was really happy that the antenna and receiver worked and even on a ‘low’ short pass I was able to hear QSO’s. I was amazed at how quickly people gave callsigns and grid locations – there was little time more for anything more – I can see why people recommend recording contacts on satellitle and make the log book after.

I headed back to the shack and tried the AA battery pack that came with the THD7, this also failed to power the radio, so I had to engineer a solution ! I found a ‘spare’ connector from an adaptor set and ‘butchered’ that to make a DC power supply from the batteries I usually use on the IC705, these would be more than enough power for the THD7, even with the squelch fully open, to operate receive and transmit for the times the satellites came over.

Conclusion

Whilst my first attempt at satellites didnt result in a QSO I gained valuable experience and could confirm my antenna and transceiver worked correctly. Whilst the in-built battery was bad, and replacements unreliable/dangerous, I was able to manufacture a replacement. I’ve since ordered a ‘cheap’ Digital voice recorder and headset for QSO’s – I think I have a splittler cable, but will find out when the digital recorder arrives how to drive both headphones and recorder.

In all I was very happy to go from 0 experience, to at least listening, which is pretty much what I done on all the bands in the past anyway, so was very happy to make my first steps in amateur radio satellite communication.