[time-nuts] Lucent KS-24361/Thunderbolt antenna advice

John Marsden oghma at live.co.uk
Wed May 6 03:53:19 EDT 2015


On Tue, 5 May 2015 17:58:06 -0400

Bob Camp said (inter alia):


> Ok, all of these receivers are designed to work with an amplified antenna. The typical antennas have between 20 and 30 db of gain.
> They allow a cable loss of ~ 10 db between the antenna and the receiver. A 3 db splitter would come out of the “cable loss” budget.
>
> The receivers put out 5V on the coax. You can find antennas that only work with> 7V. You can also find 3.3V antennas that will be
> damaged by 5V. Most of the low cost antennas you come across will work at 5V.

OK, Bob,  that's made things a bit clearer - at least I have some pointers now on what to look for :)

> They (mag-mount antennas) also are a bit tough to mount solidly. You will spend weeks letting the GPSDO’s stabilize and many days doing
> surveys. Throwing that all away each time the antenna moves is no fun.

That's an important point - one which I hadn't really considered until now...


> The auction sites will sell you a “timing” antenna for < $40 delivered. With some shopping, you can get a very good antenna for < $150
> delivered. You already have $300 to $500 invested. Skimping on the antenna does not make a lot of sense.

OK, so one last question before I head off to scour FleaBay for something suitable:  What's the difference between the $40 and $150 ones?  That is to say, what is it about the $40 ones that makes them a bad choice, that isn't an issue in the $150 ones?


>There are a number of different
> antenna designs out there. You can make a good one any number of different ways. There is nothing magic about a quad helix style.
>

Ok, I only ask becuse there seemed to be a big thing about LHCP quad helix antennas - even to the point of seein an article showing how to 'unwrap. a RHCP Q-H, and rewrap it 'inside-out' to change the polarisation to LHCP.
I'm seriously considering making an active Q H if I can't find anything that looks promising - pending the answer to the question above, of course - I don't want to spend $100 making a '$40' one ;)

I take your point about not skimping, given the investment I already have, and obviously am keen not to limit the equipment's capabilities in order to save a few quid.

Many thanks for your continued advice/help

John


 		 	   		  


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