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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