Can you tell me the frequency traveling
in the coaxial cable ?

According to the 2004 ARRL handbook your losses
in an RG8 cable with foam insulation at
100MHz will be about 1.7db per 100 feet of cable
500MHz will be about 4db per 100 feet
if you are using some other kind of dielectric
the losses might be almost twice that.

the velocity factor varies according to
the manufacturer but varies somewhere
between 82% and 86% speed of light
for cables with outside diameters in the range of
0.2 - 0.24 inches. You can use this number to trim
the cable to the proper multiple ot partial multiple
of a wavelength.

I have found RG8 to be the best cable to use
when connecting the front end of a receiver
directly to an antenna.

Most antennas have a very low impedance
50 ohms or less in the case of Yagi-Uda.

You can match impedance's using various techniques
and you can place ferrite beads near both ends of the cable
to isolate signals on the outside/inside of the shield.

The study of antennas and transmission lines
is everybit as interesting as seismology itself.
What is a geophone but a kind of electro mechanical antenna.


----- Original Message ----- 
From: "Stephen & Kathy" 
To: 
Sent: Monday, May 22, 2006 6:49 PM
Subject: Re: Extending coax on Motorola Oncore GPS antenna


> Hi,,  I simply clipped the antenna cable close to the antenna and 
> soldered RG58U (what ever the 50 ohm number is), cable to it!   I used a 
> short piece of the RG58 interior insulation and sloped it to match the 
> 174 to cover the solder connection, then folded the outside conductor, 
> from each cable, over it, taped it, and waterproofed it!!  About 10 feet 
> went up the pole where the antenna sits,, about 10 feet went through the 
> attic with about a foot down from the ceiling where it is connected to 
> the GPS, (GPS is still indoors), then about 30 feet of RS232 to the 
> computer!  I use telephone cable and connectors for the GPS power and 
> one second data!  I get strong satellite signals, even with the cable 
> diameter mismatch!
> 
> Just my two cents worth of experience!!
> 
>  Stephen
>  PSN Station #55
>  near Pilot Hill Ca. USA
>  38.828N  120.979W
> 
> apsn wrote:
>> OR, has anyone moved their Motorola Oncore GPS engine and antenna to a 
>> remote spot (waterproofed, of course) and used a long run of RS-232 
>> cable plus power back to the digitizer board?  This is similar to what 
>> Motorola or Synergy Systems sells in their Timing2000 product.
>>
>>
>>> Date: Mon, 22 May 2006 11:16:49 -0800
>>> To: psn-l@..............
>>> From: apsn 
>>> Subject: Extending coax on Motorola Oncore GPS antenna
>>>
>>> I need to move my GPS antenna (Oncore GPS for WinSDR timing) to a 
>>> location such that I need to add 50' of coax.  What do you suggest 
>>> for coax and where can I find adapters for that tiny right-angle MMCX 
>>> connector?
>>>
>>> Thanks,
>>>
>>> Bob Hammond
>>> Public Seismic Network - Alaska
>>> http://apsn.awcable.com
>>
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>>
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