Satellite Working - Cheap Style!

Some months ago, I started taking an interest in working satellites on FM.  I built a lovely 2m, 5-element quad, which shows very strong gain and even stronger directionality.  It quickly came into very useful service for remote repeaters (up to 158 miles so far on 1.8W!) and for more local work.

But that's where satellite progress stopped.  Always too busy with one thing or another.

So, with clear autumn skies telling me to get a move on and make my 70cm downlink antenna, I went to see what junk I had to cobble together.

I like quads, so my 70cm antenna is a 7-element quad, built with one supporting arm per element because at 70cm, when using hard drawn copper, the elements are mostly self-supporting.   I used standard online calculators, which don't always give good results, to guide my wire and spacing lengths, and, for once, this did yield a good antenna.

The completed 70cm, 7 element quad.  Works a treat, even if it looks a bit rough!

The boom is just 25mm x 25mm pine, with lightweight timber square section spreaders, all heavily varnished for the weather.  If you are building one, use moderately smaller section boom timber, as this one proved a bit too heavy for comfort, especially if operating two antennas at the same time!

Connection is just a short length - about 60cm in this case - of junk RG58/U, which has very minimal losses over such a distance, connected directly via spade connectors at the driven element.  There's no need for a balun or matching section, especially as this is just a receiving antenna for this purpose.

Does it work?  Yep!  I wondered why, with 10+dBi gain, I wasn't hitting one of the toneburst-activated 70cm repeaters even when directly underneath is.  Thiss seems to be a problem with the stability and tolerance of the 1750Hz tone, now rarely used due to CTCSS taking over, on my very cheap, but otherwise very good, Chinese handheld.  Using a pure tone did access it, even from inside the house.

And on satellites?  Excellent!  Easily picks up SO-50 as soon as it hints at coming over the horizon, with very clear, stable signals at about S 6 across the vast majority of the pass (SO-50 transmits with only 250mW at launch).

Very pleased indeed!  Total cost: about £6 in all new materials.  Essentially nothing if you have bits lying around. Just remember to make it as lightweight as possible.

Update: I made my first sat QSO with EA7HZZ using the antenna for downlink.  I used just 4W into the 5 element 2m uplink quad.  Not bad!  I'm now making plenty of contacts on each pass.

Next step: Operating two separate antennas is too cumbersome, so I'm going to build one of these tape measure antennas, again at next-to-nothing cost.  I'll mount the quads on a motorised mount some day.

An example of a 2m tape measure sat beam.  This gets the signal up fairly well, but the 70cm receive antenna is too weak for SO-50 unless it has an unfeasible number of elements.

Update on the next step!  I built a lovely 2-band tape measure antenna for higher elevation passes, and managed to get a very good match on both.  But, and as is my experience with quads vs. yagis, the yagi is very much poorer in performance than the quads. The yagis are also much, much harder to get to the right resonance and match than quads.  All that said, I have managed good QSOs into SO-50, showing the 2m yagi is adequate at 3 elements, but it is rare that I can hear my voice clearly coming back, though others seem to hear me fine.  That, then, must be down to the 70cm antenna's gain - I have no such difficulty at all with the 7-ele quad for 70cm.  I really can't say it was worth making this antenna because of the fiddly matching and performance issues, and that a non-elevated quad system works very well for most passes.