signal strengths

[VK2FAK]

Hi all..

A question on what sort of signal strength should be expected for these current Sats...

I was thinking and I may be wrong...that one coming over around 20 deg or higher would give a decent strength even on small whip....I may be assuming way to much here though....

Are beams required for most of these Sats.....I would think so if its only a few Degrees and in this case what sort of power is needed...5w preferred can go to 25w....

Just looking at whats going to be needed.....and have been having a listen but not hearing much.....

John

[VK2GOM]

Hi John,

Hard to say - depends on your actual antenna and the surroundings. You mention a 'small whip'... you will find that base-type verticals have their pattern compressed to effect gain out towards the horizon, and thus suffer miserably as a satellite antenna when you want to receive satellites at any sort of elevation above the horizon.

A simple 1/4 wave groundplane can work reasonably well at higher altitude passes, but still suffers at passes over the zenith.

Or the Eggbeater antenna (I have two half-built ones here) - very omnidirectional right across the hemisphere.

But for maximum versatility and hearing/working the most satellites, certainly a Yagi in the correct polarisation and some means of following the satellite across the sky is the best method. My 8 x 4 ele crossed home brew Yagi works great with just 5W or less, but it means standing in the back yard holding the antenna for any passes in the Eastern sky. For the Western sky I can't operate as my front door faces West and that faces our neighbours just a few m away. Oh for a mast on the roof and a rotator!

73 - Rob VK2GOM / G0MOH

[VK2FAK]

Hi all...

Yeah I really was not expecting to much from the whip...and its inside....was just using it to have a listen..

I did look at whip, the designer says works great on LEO's....its a 3/8 vertical section and 1/8 ground planes, from memory, and it has a pattern from about 4 deg and goes up and has a small dip then another peak around 60 deg.....but not much in the gain area obviously...

I was also reading that having a small beam say 5-6 el that has a wide pattern and then just fix the antennas to about 15 deg and they say the pattern should take care of the rest...more gain for the distance and still some gain for the higher passes......not much for overhead but the % of time that actually happens is small..

Messing with a small 70cm 7ele beam...I will get that going and go from there.

John

[VK2GOM]

That is do-able too John. I have seen numerous people work satellites like that. Another trick is to tilt the antenna over 45deg so you get the best of both worlds for polarisation changes between horizontal and vertical. Some satellites tumble a bit and the polarisation changes during the pass, slowly.

Have a listen out for SO50, VO52, and AO27.

73 - Rob VK2GOM / G0MOH

[VK2FAK]

Hi all....

Ok...I will stick with this thread instead of opening another for a question on 2...


As the radio's I have can't be computer controlled and I can see this Doppler thing is going to be a pain, anyone know of a recent design for handling the Freq of 2 radios only using the Mic connector which allows for push button control of freq..

I have a design from years ago to do this....having a read, just wondering if there is anything new around...

John

[VK6ADF]

What is usually done is to program the main stated frequency and 5 up and 5 down, or if your transceiver allows it more steps and then it is easier to switch between them to pick the best.

There is an old paper about how to use a handeld to work the satellites that may have some tips in it suitable for using a mobile type radio which is what I assume you are using. The paper can be read here. http://hvsatcom.org/sats.pdf

Remember it is a few years old so newer satellites are not mentioned.

[VK2TDN]

Hi all....

As the radio's I have can't be computer controlled and I can see this Doppler thing is going to be a pain, anyone know of a recent design for handling the Freq of 2 radios only using the Mic connector which allows for push button control of freq..

John

John you dont want to be changing the freq of both radios (TX and RX) else you will just be chasing yourself across the passband. leave the TX fixed and tune your RX to keep up with the doppler

Dave

[VK2FAK]

Hi All...

Yeah Dave when I thought about it , that was my conclusion.... and the PDF mentioned on here was a good guide..

While its been non stop raining here....no antenna testing, I have been having a read of the types of antennas being used......it seems to always come back to a beam of some sort......

John

[VK2GOM]

Hi John, have a look at my 8x4 ele 2m/70cm satellite Yagi design on the AMSAT website. In fact it has been published in a few places and magazines, a Google search should find the build document with all the dimensions etc. I was looking at some pictures this morning of someone else who has just built one.

It works really well and there are a good few people around the world using it.

Incidentally, using FM, there are no issues with Doppler on a 2m uplink; the deviation is wide enough to handle any Doppler change, and as Dave says, tune just the 70cm downlink.

73 - Rob VK2GOM / G0MOH

[VK2FAK]

Hi all.....


Rob ...I had seen that antenna but did not know it was yours....it looks good, in a strong construction...

I have an 8 ele 2m beam and made a 70 cm still waiting testing when this rain goes away....

I may eventually go your way after I have a play...

John

[VK2FAK]

Hi all....

Just had a listen on the So-50 as she flew over .....nothing dead as a door nail....no activity here...

And here I was thinking I could enjoy the Sat's on the hot summer nights outside....geez

John

[VK2GOM]

Hi John, you may have just been unlucky. Depends what the regular ops are doing during the pass. On a good pass you can hardly get a word in, it's full of ops.

Don't give up.

What antenna were you using that time?

If you want to borrow my satellite Yagi you are welcome. I can even lend you the two handhelds that go with it too if you need them?

73 - Rob VK2GOM / G0MOH

[VK2FAK]

Hi All...

Thanks for the offer Rob but I should be fine...I have 2 radios, all mode VHf and all mode UHF both 5-25w.

I was using my Un-tuned 70cm beam on the Downlink.....I have heard a call or 2 on this a few days ago so it will pick up signals...The pass was about 10pm so maybe that was more the problem..

I am checking right now that I have the details of the Sat. right....ie 70cm downlink...and not 2m...

John

[VK2FAK]

Hi All...

I wonder if anyone uses the Satellite Status page where sighting contributions are posted...

http://oscar.dcarr.org/


And has anyone tried to work SO-67......it does seem to have a different tone to activate it...

John

[VK6ADF]

Hi All...

I wonder if anyone uses the Satellite Status page where sighting contributions are posted...

http://oscar.dcarr.org/


And has anyone tried to work SO-67......it does seem to have a different tone to activate it...

John

According to AMSAT SA page "No service all activities suspended " on SO-67 and no tone required when it is there.

[VK2FAK]

Hi all.....

Thanks for that....was not sure by the amsat site if it was totally down or whatever...

John

[VK2FAK]

Hi All.

I decided to take a visual look last evening at ISS, at least I know the software is working. Coming from the south west just after sunset with a good dark sky......this thing was so bright thought it was a plane coming over..hihi Till it got to be overhead when it vanished....and right on time with the software also..

Managed a few years back to see it moving along with the Shuttle moving along behind it.......looked geat.

John

[VK2GOM]

I saw that pass too John. I also saw quite a bright (Mag -6) Iridium flare about an hour before that. They are good fun to watch.

73 - Rob VK2GOM / G0MOH

[VK2FAK]

Hi all...

Just thought I would lend a hand and send in some telemetry off ARRISAT-1.....I had tried twice before but just now got a good decode....

This bird is coming down soon so they say...

John

[VK2FAK]

Hi all....

Still messing with the 70cm antenna...its been extended now to 11 elements....still using what I have laying around..

Made the Bazooka balun seems to work great...

A question I thought I'd asked already here..but maybe not......as I am doing most of the testing during the week indoors what sort of signal reduction is expected if any, from receiving 70cm inside....as far as the satellites are concerned..

John