[time-nuts] What outdoor antenna for Tbolt?

[J. L. Trantham]

Dave,

I have used a Symmetricom 58532A timing antenna ($69 on eBay as I recall, N
connector), a Synergy Systems timing Antenna ($49 on eBay as I recall, TNC
connector) (I think these are the same antenna with different connectors),
an after market 'Garmin GA 29' marine antenna
(http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=9718208656&ssPageName=AD
ME:B:EF:US:1123), and an AeroAntenna Technology Inc. aircraft GPS antenna,
P/N AT 575-9, originally used with a NorthStar (now Canadian Marconi
Company) M2 or M3 aircraft GPS system.  

Jeppesen, a major supplier of database updates for aircraft navigation
systems, will stop supporting the NorthStar units in April of 2009 and I
suspect these might be coming on the market cheap.  I wonder if they could
be converted for timing applications?

I was looking for antennas designed for 'outdoor use', relatively
inexpensive (and therefore disposable if struck by lightning, destroyed by
falling limbs, etc.), and useful with long runs of coax.

I also use them with the TBolt and a HP Z3816A.  Both units put out 5 volts
to power the antennas and both have 'alarms' for open or shorted antennas.

All antennas worked well with the TBolt with no alarms.

All antennas work well with the Z3816A but the two timing antennas show
'alarm' having to do with too little current draw.  This can be corrected by
adding some 'DC' resistance in parallel to the antenna line.  I have not had
an opportunity to experiment with this yet to make sure the RF impedance is
high enough that it does not interfere with signal strength though I did
connect a 680 ohm (as I recall) resistor with the wires wound into a 1/8
inch form to create 'coils or chokes' in series with the resistor, to a BNC
male to banana jack adapter plugged into a BNC 'Tee' in the antenna line
that eliminated the 'alarm' and still allowed the unit to receive.

I particularly like the 'Garmin' antenna because of the high gain and
relatively inexpensive price.  Unfortunately, it has an RG58 pigtail to a
BNC connector requiring an adapter to connect to 'RG8 like' or other coax
and it has a 1 inch 'marine thread' mount which requires some effort to find
or a trip to the boating store, but they seem like a small price to pay.

Joe



-----Original Message-----
From: time-nuts-bounces at febo.com [mailto:time-nuts-bounces at febo.com] On
Behalf Of David Medin
Sent: Saturday, September 13, 2008 3:28 PM
To: time-nuts at febo.com
Subject: [time-nuts] What outdoor antenna for Tbolt?

   What outdoor bullet antenna are people using for their Tbolts
   (manufacturer and model number), where did you find it, and how much
   did you pay for it? I'm looking at several eBay antennas and the like
   crossing my fingers that the bias voltage and current will work, but
   I'd rather get some advice from those of you that have actually done
   the deed. I'm only really interested in antennas designed for permanent
   outdoor or marine installation.

   Thanks!

   Dave Medin
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