[time-nuts] Re: The Collapse of Puerto Rico’s Iconic Telescope [April 5th, 2021 New Yorker]

[Lux, Jim]

On 3/30/21 2:56 PM, Wes wrote:
> You would know better than I, but I was thinking of physical size; 
> 100m v. 70m.
>
> Obviously a BIG difference in TX power.
>
> Wes


It's all about EIRP, baby.

I know they're talking about half a megawatt for GB, but I don't see it 
happening. They've spent so much time making it "radio quiet", putting a 
big honkin transmitter there seems odd.   Just think, a return loss from 
the feed of -30dB (which is pretty good) is good fraction of a kilowatt.

I think a phased array of some sort is more likely (both for Tx and Rx) 
- the cost of RF parts has come down a lot, and, as we on this list 
know, phasing them all up to a fraction of a gnats eyelash is doable. 
Fiber optics are cheap. And you can form multiple beams simultaneously 
(the LEDA correlator at OVRO-LWA forms hundreds of beams).


What *is* a challenge (and hasn't really been solved) is how to do 
cryogenic feeds in mass production.  DSN looked at building an array of 
100 receivers, and nobody would sign up to delivering 100 cryocoolers 
that would have sufficient MTBF.   But transmitting - that's easy.


>
> On 3/30/2021 2:00 PM, Lux, Jim wrote:
>> On 3/30/21 6:40 AM, Wes wrote:
>>> Was a pity.  China's FAST is receive only.  I believe that leaves 
>>> Green Bank as the biggest transmitting telescope.
>>
>> More likely the Goldstone Solar System Radar function of DSN on the 
>> 70m (DSS-14) - 500kW in X band at 8560 MHz
>>
>> There *is* a new transmitter for GB - but it's a demo - 700 W and 
>> temporarily installed up at the feed for a test.  I don't know what 
>> frequency.  People are pitching a 500kW system, but we shall see.
> _______________________________________________
> time-nuts mailing list -- time-nuts at lists.febo.com -- To unsubscribe 
> send an email to time-nuts-leave at lists.febo.com
> To unsubscribe, go to and follow the instructions there.
>