[time-nuts] ACE-III GPS receivers

[Didier Juges]

Nice Symmetricom antenna there, Jason. I need to find a similar mount. I 
have made an S shaped support with PVC tube, but I have not found a 
clean way to secure it to the wall. The metal bracket looks much cleaner.

I will look for laptop hard drive hardware. Even though I have yet to 
find one where there actually was a cable (as someone else pointed out, 
they tend to be mounted rigidly), it may be easier to find than the bulk 
cable. I'll check the local computer store, they may have cables. The 
Jupiter receiver that is currently running is soldered directly to the 
header, and it sure looks ugly. By comparison, the soldered antenna 
connection looks much better. I looked for MCX connectors or pigtails 
and they cost as much as the GPS receiver :-(

Only problem with all these different antennas and receivers, they all 
have different connectors: MCX, SMA, F, N, SMB, and my "good" coax 
cables have BNC!

Speaking of antenna cable: when I got the Thunderbolt, I locally bought 
50 feet of relatively expensive (may have been $18 or so), high grade 
(at least advertised as such) and good looking 75 ohm coax cable with F 
connectors (I say good looking because the outside jacket is clear, and 
you could see the braid is thick and has good coverage, and the 
connectors look well mounted). Then I found the antenna/cable did not 
work too well with the Thunderbolt and I switched to the puck antenna. 
Then, independently, for my ham radio hobby, I also bought 10 rolls of 
50' 75 ohm coax cable with molded BNCs for $1 each (I bought 10 to 
amortize the $10 shipping)!! on eBay, and the $1 cables ($2 if you 
include shipping) are better than the expensive cable by about 1.5 dB at 
1.8 GHz for a 50' cut. This was a good measurement (signal generator and 
power meter). I also compared leakage by spreading the cables upstairs 
in my house (I have a big house...) with a proper termination at one end 
and the other end hooked to the spectrum analyzer and looking for local 
FM stations (not very scientific, I'll admit, feel free to propose a 
better method). The cheap cable was better (lower signal) by about 10dB. 
For what I paid for the expensive cable, I could have gotten a bunch 
more of the $1 cables... Made in China of course :-) Oh well...

Regarding the Thunderbolt, it simply works much better with the puck 
than with the Bullet, so it's not the receiver setting. It could be 
location, as even in the same approximate location (unless that location 
is perfectly in the clear, which is not the case), different antennas 
may have different performance by being differently affected by local 
reflections. My puck antenna went from marginal to great by raising it 3 
feet in the shack.

Didier KO4BB

Jason Rabel wrote:
> As Joseph said, notebook hard drive cables are 2mm. You can just peel off
> the number of wires that you need from the ribbon. If I remember I'll try to
> find all the proper pages in Mouser for the various bits.
>
> I had to mount an antenna outside to get reception because the building is
> all metal. My office is on the north-side and setting a receiver in the
> window I *might* be able to get 2 or 3 satellites for brief moments, but not
> long enough to do any good.
>
> http://www.rabel.org/archives/Images/Misc/GPS_Antenna.jpg
>
> The mount was already there from an existing antenna (which reminds me I
> need to take pictures of it, maybe one of you ham guys would have a use for
> it). Having a scissor lift made it extremely easy to mount that sucker up
> there. :) I *think* I paid like $30-$40 for mine, it was NIB. I had to run
> about 100ft of RG-58 from the antenna across the building and finally down
> to my office.
>
> The Jupiter receivers has a MCX connector, but it sounds like your
> direct-connect method works great (and much cheaper).
>
> You know I was reading some GPS manual (don't ask me which), and you could
> actually set the minimum signal strength for the receiver to use a
> satellite. Perhaps the Thunderbolt has a similar setting and it is turned
> higher than a normal receiver?
>
> I totally can sympathize about the lack of time. I need about a dozen clones
> of myself!
>
> Jason
>
>