AeroElectric-List Digest Archive

Thu 03/30/17


Total Messages Posted: 6



Today's Message Index:
----------------------
 
     1. 04:03 AM - Minimum GPS Antenna Cable Length (user9253)
     2. 05:12 AM - Re: Minimum GPS Antenna Cable Length (steve harmon)
     3. 06:12 AM - Re: Minimum GPS Antenna Cable Length (Charlie England)
     4. 06:36 AM - Re: Minimum GPS Antenna Cable Length (Kelly McMullen)
     5. 07:50 AM - Garmin GPS antenna (Carlos Trigo)
     6. 07:50 AM - Backup Power (Ron Springer)
 
 
 


Message 1


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    Time: 04:03:14 AM PST US
    Subject: Minimum GPS Antenna Cable Length
    From: "user9253" <fransew@gmail.com>
    I am installing an Appareo Stratus ESG transponder with internal GPS. It did not come with antenna cables. I purchased a 19 inch RG400 GPS antenna cable before reading the installation directions which state, "All wiring should have a cable loss of minimum 2 dB . . . .Using RG400 the minimum cable length is 10 feet". Will the GPS work satisfactorily with the short cable? If not, what is a cheap and easy way to increase the dB loss? What is the theory behind the requirement for at least 2 dB cable loss? -------- Joe Gores Read this topic online here: http://forums.matronics.com/viewtopic.php?p=467824#467824


    Message 2


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    Time: 05:12:24 AM PST US
    From: steve harmon <sharmon32@juno.com>
    Subject: Re: Minimum GPS Antenna Cable Length
    I also installed an Appereo in my cozy I called the factory they said you need at least 10 foot of antenna cable so you have some resistance my antenna is 2 ft. From the stratus they told me to just roll up the extra so that is what I did . It. Works who am I to argue with success. Steve build on Sent from my iPad > On Mar 30, 2017, at 5:01 AM, user9253 <fransew@gmail.com> wrote: > > > I am installing an Appareo Stratus ESG transponder with internal GPS. It did not come with antenna cables. I purchased a 19 inch RG400 GPS antenna cable before reading the installation directions which state, "All wiring should have a cable loss of minimum 2 dB . . . .Using RG400 the minimum cable length is 10 feet". > Will the GPS work satisfactorily with the short cable? If not, what is a cheap and easy way to increase the dB loss? What is the theory behind the requirement for at least 2 dB cable loss? > > -------- > Joe Gores > > > > > Read this topic online here: > > http://forums.matronics.com/viewtopic.php?p=467824#467824 > > > > > > > > > > ____________________________________________________________ This Simple Step To Flawless Skin gundrymd.com http://thirdpartyoffers.juno.com/TGL3131/58dcf56de30bf756c6215st01duc


    Message 3


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    Time: 06:12:23 AM PST US
    From: Charlie England <ceengland7@gmail.com>
    Subject: Re: Minimum GPS Antenna Cable Length
    On Thu, Mar 30, 2017 at 6:01 AM, user9253 <fransew@gmail.com> wrote: > > I am installing an Appareo Stratus ESG transponder with internal GPS. It > did not come with antenna cables. I purchased a 19 inch RG400 GPS antenna > cable before reading the installation directions which state, "All wiring > should have a cable loss of minimum 2 dB . . . .Using RG400 the minimum > cable length is 10 feet". > Will the GPS work satisfactorily with the short cable? If not, what is > a cheap and easy way to increase the dB loss? What is the theory behind > the requirement for at least 2 dB cable loss? > > -------- > Joe Gores > > The 1st thing that comes to mind is this. Most radio receivers have multiple gain stages (in addition to frequency down-conversions) to get weak RF signals up to a level that's useful. Each gain stage will typically have automatic gain control (AGC) that prevents the amplifier from being driven into distortion by a too-strong input signal. But there's a limit to the range of AGC. They've probably calculated the max possible output from the GPS puck (which probably has both the 1st frequency downconversion and gain), and the cable loss prevents overdriving the 1st gain stage in the box. When the GPS RF signal is weaker, the box's AGC circuit can ramp up gain to compensate. If you ever fly formation, you might hear the same overdrive effect in your comm radio. The wingman's radio might sound fine until they get within a half mile or so, but as they get closer, their audio sounds fuzzy & garbled. When they break formation & move a mile or two away, it clears up again. The bad audio is your radio's AGC being overwhelmed by too much RF or intermediate frequency signal level while the wingman's transmitter is too 'hot' for your receiver to compensate. Charlie


    Message 4


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    Time: 06:36:30 AM PST US
    Subject: Re: Minimum GPS Antenna Cable Length
    From: Kelly McMullen <kellym@aviating.com>
    IIRC each connector in the line adds about 1/2 db of cable loss. So in theory, 2 extra adapters in the cable would get you there. Don't know if that is exactly correct. So maybe with an extra foot, a union connector and 2 BNC connectors, or BNC to TNC adapters and you might have enough loss. BTW, BNC to TNC adapter is lot cheaper than just buying a crimp on TNC connector. On 3/30/2017 4:01 AM, user9253 wrote: > > I am installing an Appareo Stratus ESG transponder with internal GPS. It did not come with antenna cables. I purchased a 19 inch RG400 GPS antenna cable before reading the installation directions which state, "All wiring should have a cable loss of minimum 2 dB . . . .Using RG400 the minimum cable length is 10 feet". > Will the GPS work satisfactorily with the short cable? If not, what is a cheap and easy way to increase the dB loss? What is the theory behind the requirement for at least 2 dB cable loss? > > -------- > Joe Gores > > > Read this topic online here: > > http://forums.matronics.com/viewtopic.php?p=467824#467824 > >


    Message 5


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    Time: 07:50:07 AM PST US
    From: Carlos Trigo <trigo@mail.telepac.pt>
    Subject: Garmin GPS antenna
    > > The G3X Installation Manual says, in a "Note" on page 20-1, that "GA35, GA36 and GA37 antennas cannot be used with GDU 37X/4XX units". > > Does anybody know why? > > (I'm asking because I bought the pretty expensive GA35, as an excellent GPS antenna, before reading this "Note") > > Thanks > Carlos


    Message 6


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    Time: 07:50:36 AM PST US
    From: Ron Springer <ron228rj@gmail.com>
    Subject: Backup Power
    I had a different thought on backup power for the EFIS I am installing in my day VFR plane. I figured the most likely scenario of having a problem with the EFIS is loss of power to it. I would like to at least have airspeed available while landing to troubleshoot the electrical problem, but why not just restore the whole EFIS? Also, I always have on board a couple freshly charged batteries for various purposes. One is running the Raspberry Pi Stratux system. Another is standby power (if needed for very long flights) for my Android tablet running Avare. So, why not put a round 2.1 mm jack for 12 volts on the panel routed the secondary power input on the EFIS and then keep one of these cables stored in the plane to go from 5 volts on the USB output of the battery to 12 volts for the EFIS: https://www.amazon.com/LANMU-Module-Converter-Barrel-Connector/dp/B01G3ERI6U Ron




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