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

Bob Camp kb8tq at n1k.org
Tue May 5 21:58:06 UTC 2015


Hi

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. 

You want an outside / permanent antenna location. Magnetic mount “car style” antennas often do not survive well when kept outdoors
for a long time. They 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.

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. 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. 

Bob



> On May 5, 2015, at 11:35 AM, Oghma <oghma at live.co.uk> wrote:
> 
> Thanks to Vlad, Bob, and Chris for the responses so far - and for the helpful suggestions/advice.
> 
> Since the focus of the answers to my (I suppose, dual-headed) question has been on the splitting/sharing aspect, rather than on actual antenna type/model, I'm guessing that the actual antenna used doesn't matter - would that be a fair assumption to make?
> So, does that mean that I could use a simple patch type antenna intended for use with in-car gps 'satnav' style units - such as the ones Garmin sell?  I only ask because I have seen some discussion of quad-helix (and LHCP vs RHCP) antennas, and most of the pictures I have seen of the innards of antennas have been Q-H style. 
> 
> Also, given that dc feeds are provided by the receivers, it would suggest that some dirt of active/amplified antenna is expected to be connected. 
> 
> Foitnote: I'm in the UK, so I'm not sure that the 'cable TV splitters' referred to would be available here. We do have cable TV, but if I understand correctly, the signals (if not carried into the house on optical fibres) are all sent down the cable in the sub 500MHz range - perhaps someone on the list who is in the UK could comment further on that?
> 
> Regards
> John 
> 
> Sent tomorrow from my time machine. 
> 
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