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Bob Archer antenna & glide slope

BlackRV7

Well Known Member
I talked with Bob on the phone who stated the Garmin 430 has in internal "splitter" that will split the single coming off his NAV wingtip antenna and show both glide slope and localizer. In doing my final hookups yesterday, I saw the glideslope male plug on the back of the housing. Bob is truly an antenna wizard but I wonder about the above statement. I have the wingtip antenna plugged into the NAV antenna hookup at this time.
 
Dana, I'm pretty sure the last 430 I wired required an external splitter. Caveat; it's been a few years and I have CRS <g>
 
My 430 required an external splitter....and I doubt they've changed the design. I get good performance on an ILS with my wingtip antenna split to the VOR/LOC and GS inputs to the 430.

The crime is what you have to pay for an aviation splitter!

Paul
 
nav splitter

years ago, jim weir (rst-engr.com) had a kit for a nav splitter. iirc, it was about $20, including the enclosure. kit consisted of 4 bnc connectors, one resistor, one capacitor, some coax, and the enclosure and hardware. there was a good theory of operation included in the manual -- it was a "wilkinson splitter". i built one and it worked fine.

i have misplaced my construction manual, and wanted to build another, so i sent jim an email regarding the length of the coax and the value of the capacitor he used for glideslope pickoff. he replied to my email as follows:

16" of 70/75 ohm coax. 10 pf with half-inch leads on both sides.

Wilkinson splitter.

you can see the basics of the wilkinson splitter at:

http://www.microwaves101.com/encyclopedia/Wilkinson_splitters.cfm#twoport

i plan on building mine. after all, this is an "experimental" (and also because i had good results with the last one. i can't see the parts costing more than about $20.)

john
 
Ironflight said:
The crime is what you have to pay for an aviation splitter!

Paul

Even more of a crime is to pay for a splitter when you don't need one. I bought an AV-570 splitter before I realized my SL-30 has one built in.

Dana, if you need a splitter, I have one for $75. I'll pay shipping. Send a private email.

Jekyll
 
Jekyll said:
Even more of a crime is to pay for a splitter when you don't need one. I bought an AV-570 splitter before I realized my SL-30 has one built in.

Dana, if you need a splitter, I have one for $75. I'll pay shipping. Send a private email.

Jekyll


Jekyll, check your PM
 
Bob Archer NAV/GS antenna, diplexer/splitter needed??

Hi everybody, I am installing an Garmin GNC 255 with an Dynon Skyview HDX in my RV-8. I installed a Bob Archer antenna in the left wingtip. My question is: I need an splitter to give GS signal to the GNC 255?? When I put the antenna cable to NAV position in the 255, I have NAV signal but no GS. When I put the antenna cable to the GS position, I don't have NAV reception.
Thanks
 
Just a reminder for those who want to build one of these but aren't 'in to' electronics. The 70-75 ohm coax spec'd is *not* the same stuff you used to wire your a/c antennas. 75 ohm is used for TV antenna cables, so you probably have a ready supply in your household junk bin.
 
To help with a little bit of terminology, a splitter is used to send the full Nav signal to two different receivers. To hook up an antenna to a 430, you will need a diplexer, which splits the VOR/LOC from the GS signal. There is no internal splitter or diplexer in any 430. The GTN650 does have the internal diplexer, as does the SL-30.

Now, if you have an SL-30 and a 430, you can connect them to a single antenna. In this case you will need a splitter going from the antenna, then to the SL-30 on one side, then to a diplexer which will then go to the two ports on the 430.

If you have only a 430 you could install two Nav antennas and connect one to the VOR port and the other to the GS port.

A splitter may work for a 430, but a diplexer is what is normally used.
 
Hi everybody, I am installing an Garmin GNC 255 with an Dynon Skyview HDX in my RV-8. I installed a Bob Archer antenna in the left wingtip. My question is: I need an splitter to give GS signal to the GNC 255?? When I put the antenna cable to NAV position in the 255, I have NAV signal but no GS. When I put the antenna cable to the GS position, I don't have NAV reception.
Thanks

I don't see that anyone actually answered Juan's question...

Juan, the GNC255 only has a COM and NAV coax connection. How are you connecting an antenna cable to GS? Do you have a copy of the installation manual? According to the manual, a single cable should be connected between the NAV connector on the radio and the VOR/LOC/GS antenna.
 
Hi everybody, I am installing an Garmin GNC 255 with an Dynon Skyview HDX in my RV-8. I installed a Bob Archer antenna in the left wingtip. My question is: I need an splitter to give GS signal to the GNC 255?? When I put the antenna cable to NAV position in the 255, I have NAV signal but no GS. When I put the antenna cable to the GS position, I don't have NAV reception.
Thanks
I am not sure what you mean by: "When I put the antenna cable to NAV position in the 255, I have NAV signal but no GS. When I put the antenna cable to the GS position, I don't have NAV reception."

Are you talking about the antenna (BNC) connection on the rear of the unit?

rf-lg.jpg


If so, you only have one for the NAV (receive only) antenna while the other is for the COMM (transmit & receive) antenna. You have to have both connected (separate antennas) in order for the unit to work properly. :confused:

GNC 255 Installation Manual - Appendix D-6 (Single GTR/GNC Installation)
 
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Juan, you need to get rid of the diplexer and hook the cable coming from the antenna directly to the radio on the Nav side.
 
I do not have a GNC 255 but it is a radio that I would consider using in my RV-8. At the present time, my 15-year old SL-30 works fine in my RV-6 for VOR, ILS, and Glide Slope with a Bob Archer VOR wingtip antenna.

Doing a Google Search for the GNC 255 Installation Manual, I find that there is only one NAV coax connection. The other coax connection is for a COM antenna.

Checking the Garmin website for the GNC 255, I find that it has a (copy / paste from website) "Built-in VOR/Localizer converter".

This tells me that the GNC 255 is just like my SL-30 and does not need a splitter / diplexer for glide-slope operation. The Garmin GNC 255 Installation Manual says: (copy / paste from manual) "Note that if the NAV antenna is a combined VOR/LOC/GS antenna, it must meet TSO C40( ), C36( ), and C34( )."

My comment is that my Bob Archer VOR antenna mounted in my wingtip works for VOR, ILS, and Glide Slope in my RV-6 with my SL30.

Hope this helps. I am a retired Electrical Engineer so sometimes this stuff interests me enough to do some research.
 
Don't they make installation manuals anymore? Seems like the answers to the questions about the 430 and the 255 (and any other box) should be in there viz-a-viz antenna inputs/connectors...?
 
GNC255 No Splitter Needed

The GNC255 is the same as the SL30. The main difference is the transmit power output which I seem to recall is 10 watts for the A model and 16 watts for the B model. I've got a 255A, Dynon FltDEK 180 and a wingtip Bob Archer antenna that work great for VOR or ILS reception. Like has been mentioned, there are only two coaxial connectors on the back, one COMM and one NAV. There should be no switching involved other than selecting the proper frequency, and you should not need a splitter.
 
Reviving an old thread, when I built my 8, I installed the tray and wired things for a GNS 430, but before I made the first flight I sold the radio for financial reasons; having not completed the antenna connections.

So now, I've ordered a an IFD 440 as it'll slide right in, but I've got to complete the antenna install.

I have a Bob Archer wing tip unit and I see I'll need to either add another antenna or use a diplexer as the IFD manual states one would be needed and therefore not having an internal one. I vote diplexer.

Now that I'm poor again, and being relatively cheap, I need the correct unit.

I see on that big auction site that I can buy even a new one for just $40, but those say "ant" on one end, and "vor/loc or marker beacon" on the other.

Not being any electronics expert, I'm guessing there are different kinds of diplexers. Can someone give me some guidance?

Thanks
 
Reviving an old thread, when I built my 8, I installed the tray and wired things for a GNS 430, but before I made the first flight I sold the radio for financial reasons; having not completed the antenna connections.

So now, I've ordered a an IFD 440 as it'll slide right in, but I've got to complete the antenna install.

I have a Bob Archer wing tip unit and I see I'll need to either add another antenna or use a diplexer as the IFD manual states one would be needed and therefore not having an internal one. I vote diplexer.

Now that I'm poor again, and being relatively cheap, I need the correct unit.

I see on that big auction site that I can buy even a new one for just $40, but those say "ant" on one end, and "vor/loc or marker beacon" on the other.

Not being any electronics expert, I'm guessing there are different kinds of diplexers. Can someone give me some guidance?

Thanks
 
See Comant/Cobham CI-507 (https://www.aircraftspruce.com/catalog/avpages/coupler507.php)

Connect the Archer antenna to the ANT port, the IFD 440 to the VOR & G/S ports as appropriate

Alternatively, see https://www.minicircuits.com/WebStore/dashboard.html?model=ZFSC-2-4+, it's a nice unit and passes full bandwidth to all ports instead of "bandpass" like the CI-507.

In my prior RV-7, I used https://www.minicircuits.com/WebStore/dashboard.html?model=ZFSC-3-4+, 1 into 3 -- splitting the Archer antenna input into VOR & GS for the GNS 430W and 1 input into the Apollo SL-30 (which has an internal splitter)...
 
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So just because I like to understand things, if we're taking the signal from one antenna and splitting it to two different radio inputs, and diplexers are used to combine two sources into one cable, what goes on here that requires a diplexer? Seems backwards to my untrained point of view.
 
So just because I like to understand things, if we're taking the signal from one antenna and splitting it to two different radio inputs, and diplexers are used to combine two sources into one cable, what goes on here that requires a diplexer? Seems backwards to my untrained point of view.

If you think about the diplexer connected backwards in this case -- then it might make more sense...
 
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So the device isn't directional, and it becomes more an issue of allowing the full frequency width through?

Correct! - It's a notch filter / band pass device. This, and the higher insertion loss per port, and cost, is why I used the Mini Circuits ZFSC+ n-way splitter with my setup.
 
With your help and some sleuthing on the web, I think I got it.

It appears that glide slope signal frequencies are from 329.15 to 335.0, and localizer AND VOR signals range is 108.1 to 111.95.

So a diplexer in this case, standing between the antenna and the two receivers in the IFD, will filter out everything outside of the range for each receiver so as to keep the signal free of all the other clutter. This would explain why, in an earlier post, someone, I think Paul Dye, said a splitter may work, but a diplexer will work better.

I've also seen somewhere that the length of coax from the diplexer to the receiver should be short. Is this to limit area of cable that could pick up more clutter?

In my case, I have the Archer antenna in the wing tip with a single RG-400 coax running to the navigator. Can I just make a couple of 8" whips and split right before the navigator?
 
It’s not ‘clutter” but signal strength. An ideal splitter will send half the localizer to the (wrong) GS output, and half the GS (bad) to the localizer output. e.g., it litterally splits everything 50-50, so you lose half the signal, An ideal diplexer is frequency dependent - it sends all the GS signal to the GS input, and all the VOR/localizer signal to that input.
 
Close - as Bob T. states, it's more about the management of the received energy; ideal diplexer will send most of the energy at one band (frequency range) to one port, and most of the energy at another band to another, and so on vs a splitter which throws everything everywhere.

Ideally you want the cable runs as short as possible, to and from and in between everything (unless a specific amount of signal attenuation is required -- not the case here.)
 
I've also seen somewhere that the length of coax from the diplexer to the receiver should be short. Is this to limit area of cable that could pick up more clutter?

In my case, I have the Archer antenna in the wing tip with a single RG-400 coax running to the navigator. Can I just make a couple of 8" whips and split right before the navigator?

For these frequencies (BTW nav is 108-117 MHz) the length hardly matters, as long as you have good coax (RG-400 is "good"). Putting the splitter close to the nav radio will save you a few dollars, as the further away it is, the more coax you need, since you have two lines running from the splitter to the radio. Put it wherever it is convenient.
 
Can I tag along this conversation . . .

. . . and ask a somewhat relevant question regarding installation?

I own N888CR, an RV8 built by a Canadian aeronautical engineer, who sold it to a second Canadian owner, who sold it to me. The plane is now happily hangared in West Central Florida, and I'm drinking from the fire hose. Some issues I cannot resolve the second owner can help with. Some, not.

At issue is where might the diplexer or splitter be mounted on an RV8? I can see the GS antenna coax at the 430W but I lose the trace at the firewall. I imagine it goes out into the left wing. I know there is an Archer antenna installed from build logs. Performance of the 430W is fine!
 
Cabin side of the firewall, or somewhere under/behind the panel, are common locations for diplexers. If it’s in the wing there will be two coax cables (GS, Loc/VOR) heading out that way.
 
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