[time-nuts] Antenna recommendation for Timing Amateur

Randy Warner randy at geodetics.com
Thu Jun 14 13:10:01 EDT 2007


The M12M will actually put out +5V to the antenna. The antenna voltage that
you supply from your electronics are just "passed through" to the MMCX
connector on the board. If you have 5V available on your board you can
simply use this to run the antenna. The only thing the M12M electronics do
is that they will protect the antenna supply against short circuits. If you
draw over about 80-90mA (or short the coax) the M12M will interrupt the
antenna power.

In general, timing antenna electronics are just about the same as "good"
mobile antennas. By good I mean that they have at least one ceramic/SAW
filter. These usually add about -20dB of rejection at +/-50MHz from Fo (1575
MHz). This really helps reject nearby RF, especially if you are surrounded
by cell phone towers and the like.

The major physical difference is that timing antennas carry around their own
ground planes (that's why they are usually bigger than typical mobile
antennas). Timing antennas are also more easily mounted to a mast or other
structure. They also are usually just terminated with a TNC or N type
connector so that the user can size the antenna cable to fit the
application. They'll last a lot longer outside too....

My suggestions:

Budget installation: AR-10N, AR-10S, or ART-10S. I have a lot of experience
with all of these. They all have dual-pole filters (-40dB @ +/-50MHz).

Low-Budget Timing: Timing3000. Again, dual-pole filter.

High-End Timing:   VIC-100. Triple filter. If you are in a bad RF
environment, this is the one to get. -60dB @ +/-50MHz.

Cable: 10m of cable will not be a problem. You could get away with RG-58
(-6.5dB for 30'). If you go with the Timing3000 you might want to bump up to
RG-8X as the Timing3000 LNA gain is a little on the low side. If you can
find some dual shielded cable (LMR-195 (RG-58 equivalent) or LMR-240 (RG-8X
equivalent) these would be preferable due to the better shielding and RF
characteristics. They will also stand up to the weather much better because
the jacket is much tougher than PVC.

Hope this helps,

Randy Warner

-----Original Message-----
From: time-nuts-bounces at febo.com [mailto:time-nuts-bounces at febo.com] On
Behalf Of Jim Miller
Sent: Thursday, June 14, 2007 9:12 AM
To: time-nuts
Subject: [time-nuts] Antenna recommendation for Timing Amateur

I'm planning on getting a M12M and would like a recommendation for an 
antenna for timing purposes.

I'm just an amateur looking to discipline an oscillator. No scientific uses 

My antenna coax is likely to be 30ft or more so I suspect I'll need an 
amplified antenna.

The M12M outputs 3v so the "timing" antennas offered by Synergy don't 
directly apply.

What is the real difference between a "timing" antenna and one meant for 
mobile use?

Synergy offers several amplified mobile antennas that would work with 3v.


jim ab3cv 

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