430w gps antenna -cable length

tomhanaway · #1 11-28-2009, 01:54 PM

Installation of the 430w gps antenna calls for a total loss of 3-7 db's.

This may be accomplished by approximately 15-30 feet of antenna cable. Tnc/bnc connectors create approx. 0.2 db loss.

Is there any sort of adaptor that one can put in-line with the cable to reduce db's so that a total gps antenna length of 5 feet or so can be used?

In other words, 5 feet of rg400, two tnc/bnc connectors and some sort of resistor to create a total loss of 4-5 db?

Obviously, I'd want any mod to keep signal clean. Otherwise, I'll just loop a portion of 20 feet of cable within the overhead console and next to the gps antenna.

Thanks in advance,
Tom Hanaway
Boynton Beach, FL
rv-10

wfinnell · #2 11-29-2009, 12:01 AM

Tom,

You can use an RV attenuator. Digikey has them in stock. They are a little expensive $50-$70. Go to Digikey and search for attenuator. Scroll down to the RF section and select Attetenuators again. Then in the pacakage drop down box select BNC In-Line Modules then apply filters.

You can find them other places. I don't know if you can get them directly from Pomona.

http://search.digikey.com/scripts/Dk...me=290-1922-ND

Bill Finnell
RV-8 Wings
Tucson AZ

tomhanaway · #3 11-29-2009, 05:59 AM

Bill,
That looks great. I'd rather pay the $56 and not have the snarl of 13' of extra coax.

Unless I get major warnings from someone today, I'll order tomorrow.

Thank you,
Tom Hanaway

molson309 · #4 11-29-2009, 06:09 AM

Correct me if I am wrong, but I believe that the GPS antenna relies on power conducted through the cable from the receiver for its operation. Unless there is a DC bypass in the attenuator, there will be problems using a device like this.

81270 · #5 11-29-2009, 06:24 AM

...this antenna has a built-in LNA (Low Noise Amplifier) that is powered by the bias voltage on the signal line and provides 27dB gain in addition the antenna's 3dBi. Currently it is supplied with a 8 feet of RG174 (but can be tailor made if you leave instructions on the purchase filed text box.

Check it out .... it's link is on the left hand column of advertisers of these forums

Peter

tomhanaway · #6 11-29-2009, 08:01 AM

I love these forums as a source of information. I hadn't considered whether the antenna might be receiving power from the 430w receiver.

I've sent an email to the manufacturer of the antenna Aeroantenna Technology for a response.

Will post response.

Tom Hanaway

tomhanaway · #7 11-30-2009, 03:11 PM

Garmin gps antenna requires an attenuator with power pass through.

Sold by www.gpssource.com as ATHM-02-BF (other configurations available but this is 2db with female bnc connectors). Pretty expensive at $95.

I'll have to decide if it's worth getting rid of 10 extra feet of coax overhead.

Tom Hanaway

AlexPeterson · #8 11-30-2009, 06:24 PM

The problem the 430w gps can have is coupling with certain com transmission frequencies. How does increasing the attenuation fix this? Does it have to do with tuning the frequency at which oscillations are resonant? I'm not questioning that it does fix the 430W's gps receiver, I'm just curious the mechanism that the longer coax fixes. Been 30 years since I took that power transmission course...