[time-nuts] Monitoring the Rapco 1804M - how antenna changesaffect the unit

Alan Melia alan.melia at btinternet.com
Wed Nov 2 17:26:42 EDT 2011


Hi Rob I picked up a couple of "mushroom shaped" (white flat top rounded
edges prob 70mm diam.) antennas with a small right-angle bracket and a TNC
connector (5v supply) no nameplate but they seem to work fine on 20 feet of
RG-58.

The manual for the 1804M says its an 8-channel receiver and I recollect it
being a  Trimble.

Alan G3NYK

----- Original Message ----- 
From: "Robin Kimberley" <robkimberley at btinternet.com>
To: <JLeikhim at Leikhim.com>; "'Discussion of precise time and frequency
measurement'" <time-nuts at febo.com>
Sent: Wednesday, November 02, 2011 9:01 PM
Subject: Re: [time-nuts] Monitoring the Rapco 1804M - how antenna
changesaffect the unit


> The ET6000 used Trimble Bullet antennae when I was selling them in the UK.
I
> seem to remember about 35db of gain in that antenna.
>
> Rob Kimberley
>
> -----Original Message-----
> From: time-nuts-bounces at febo.com [mailto:time-nuts-bounces at febo.com] On
> Behalf Of Joe Leikhim
> Sent: 02 November 2011 18:52
> To: time-nuts at febo.com
> Subject: [time-nuts] Monitoring the Rapco 1804M - how antenna changes
affect
> the unit
>
> I tried a similar Garmin antenna with my Datum ET6000 and the lock times
> were really long, even with the antenna on a 14 foot pole above the roof.
I
> attribute a lot of this to the long 8 ft RG174 style coax pigtail. I have
to
> wonder if the gain of the preamp as published actually includes the
inherent
> cable loss, and even if so the preamp must be screaming in gain to make up
> for the loss. I intend to get a proper antenna.
>
> Here is a comparison of specs of these type antennas:
>
> http://gpsinformation.net/main/gpsantrev1.htm
>
> --
> Joe Leikhim
>
> Leikhim and Associates
> Communications Consultants
> Oviedo, Florida
>
> www.Leikhim.com
>
> JLeikhim at Leikhim.com
>
> 407-982-0446
> WWW.LEIKHIM.COM
>
>
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