Yes, they are Digiwave ANT2084--available on-line through WalMart as it
happens. But any similar 4-bay antenna will work.
We use 6 of them in a 2 x 3 array. I was using a commercial combiner,
but it was lossy and had poor phase balance (actually any hybrid-tree
style combiner will have issues if the split ratio isn't a power of 2).
I built my own transmission line combiner that combines all six in one
go, transforming the 12.5 parallel impedance of all those lines into
50ohm for the LNA. Next time I build one, I shall use a
slightly-different layout that will improve phase match a bit.
One can, of course, calculate the line lengths required to effect any
given pointing, but using matched-length lines from each module means
that the beam is pretty much aligned with the mechanical axis.
The LNA is prefixed with a pair of shorted-quarter-wave stubs, and it's
a TQP3M9036, using the eval board available through DigiKey. But there
are SPF5189Z LNAs on eBay at the moment for quite cheap that would do
just as well.
If you have an 8-10ft dish already, then use that. We went with the
"modular" approach, since it allows us to increase antenna gain without
taking down a dish and putting up a new one, and the HDTV antennae are
fairly cheap, and readily available anywhere. They typically usefully
cover about 300Mhz to 850MHz.
On 2016-12-01 15:19, Iain Young, G7III wrote:
> Hi Marcus,
> Brilliant. I am in the middle of assembling my own radio telescope,
> but had not thought Pulsar reception would be possible.
> I have a couple of questions on the RF Hardware. I see from some other
> updates, that the antenna is essentially sets of a 4 bay HDTV antenna.
> How are you phasing them all together ? Just additive combiners with
> same length coax ? What amplification are you using before feeding
> them to the SDR ? Or ?
> Best Regards
> On 01/12/16 18:45, Marcus D. Leech wrote:
>> One of the many goals we set for ourselves at the Canadian Centre for
>> Experimental Radio Astronomy was to successfully observe
>> pulsar B0329+54 before spring. This pulsar is the only one bright
>> enough for a small observatory in the northern hemisphere to
>> See our update:
>> The software is available via github:
>> https://github.com/ccera-astro/pulsar_pfb _display
>> No custom blocks required--just a modern Gnu Radio install, and ideally,
>> Doing this with Gnu Radio was so very easy...
>> Discuss-gnuradio mailing list
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