Do I need two Nav antennas if I have two Nav receivers?

2nd505th

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2nd505th
I know I need two Comm antennas so they don't blow each other up. I think I only have 1 Nav antenna yet I have two have two Nav receivers and don't think there is some special diplexer involved - maybe I'm wrong. However wouldn't the DME portion xmit and blow up the other Nav?
 
DME uses its own antenna on the belly....different frequency than nav....no need to worry. Nav receivers can share the same antenna...there is probably a diplexer or triplexer hidden somewhere. Glideslope receiver can use the same Nav antenna as well...thus the triplexer.
 
I know I need two Comm antennas so they don't blow each other up.
FYI: By using a duplexer, 2 VHFs can share a common antenna. It's not the preferred method but in cases of limited antenna mount area it's one solution.
However wouldn't the DME portion xmit and blow up the other Nav?
DME different freq, i.e., different antenna. If you have 2 NAVs and one antenna, money is there will be a multiplexer somewhere in the system.
 
Very few radios have a DME built into the same unit as a VHF nav or com. The only ones that come to mind are the Narco Mk12D+ and the King KNS80 and I'm pretty sure these had separate antenna outs for the DME and VOR stuff. Duplexing the glideslope (also UHF) in with the VOR/LOC is common either within the radio or externally, but you do see an occasional separate glideslope antenna (sometimes stuck to the inside of the windshield). I've never seen the DME or Transponder duplexed with anything.

Note that DME and GS are on completely different frequency bands than the VOR/LOC, even though you set a VHF nav frequency in it, the radio translates it into a matching UHF frequency.
 
FYI: By using a duplexer, 2 VHFs can share a common antenna. It's not the preferred method but in cases of limited antenna mount area it's one solution.
I was thinking of installing a separate antenna for the handheld I carry in case of problems with the panel mounted coms. The duplexer sounds like a good solution for the application.

I have 2 coms and would most likely only use the handheld if I had a problem were the alternator was disconnected or failed.

is there a loss of efficiency with the VHF's when using a duplexer?

edit: I have an antenna that was use for an old LORAN and was gong to mount the antenna for the handheld in its place. Would it be better to have a separate antenna for the handheld or go with the duplexer?
 
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@AKBill - I'd keep em separated. [Queue the Offspring music]

You've already got a hole to put it through, and in a failure mode will you remember to shut off the radio it is sharing with? If the failure is intermittent or was just operator error (audio panel switched wrong) you could end up doing more harm to both the panel and handheld radios.

Cheap insurance.
 
The duplexer sounds like a good solution for the application.
Weird Jim would be the one to answer that. My only experience with them is on dual 28v panel mounted VHFs, plus the fact I once ordered a diplexer to replace a duplexer and was properly schooled on their difference.;)
 
@AKBill - I'd keep em separated. [Queue the Offspring music]

You've already got a hole to put it through, and in a failure mode will you remember to shut off the radio it is sharing with? If the failure is intermittent or was just operator error (audio panel switched wrong) you could end up doing more harm to both the panel and handheld radios.

Cheap insurance.
Understood, thanks for the input.
 
A duplexer is expensive...it is used to connect two com radios to a single antenna. Adding a second antenna is a better option in most cases.

A diplexer or triplexer is used to connect multiple receivers like 2 nav’s and glideslope to a single nav antenna. It costs less because it is receive only.
 
For a handheld, Icom makes a box that connects inline with one Com antenna. It has a valve that plugs into a handheld and when you plug it into the port it disconnects the panel-mounted radio and connects the handheld to the external antenna.

https://www.amazon.com/dp/B00IUF3BI0/ref=cm_sw_r_cp_api_i_TQglEbFAK9Y95

for 2 navs, a diplexer (or tri- or quad-) can be and usually is used.
 
A duplexor will decrease the signal to each radio but it won't usually be a problem. My radio guy looped the output of my com radios just below the bottom of the panel and put a connector there. To use my handheld, all I had to do is reach up and disconnect the cable at that connector and plug it into the radio. That was a great idea, and would have been even greater if he'd told me he had done it. I found it about six months later when I was under the panel doing something else and found it there.
 
For a nav receiver, you'd use a diplexer to isolate the receivers from each other. The downside is there is 3db insertion loss, so that reduces the receivers' sensitivity slightly, but it is insignificant. They're not cheap, but installing one would save you the expense and drag of another antenna. Aircraft Spruce has one for $113.75:

https://www.aircraftspruce.com/catalog/avpages/av547coup.php?clickkey=209783
 
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They're not cheap, but installing one would save you the expense and drag of another antenna. Aircraft Spruce has one for $113.75:
RST Engineering has one on the ways and launching in mid-Feb for $40-50 or so but there is a catch. You have to solder it together yourself. Here is the pc board layout. We are using microstrip instead of transformers or coax. It is a triplexer -- two VHF navs and a glideslope.

RST-513 pcb.jpg


Jim
 
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IThe duplexer sounds like a good solution for the application.

edit: I have an antenna that was use for an old LORAN and was gong to mount the antenna for the handheld in its place. Would it be better to have a separate antenna for the handheld or go with the duplexer?
You don't EVEN want to know the cost of a VHF duplexer. The old LORAN hole is a MUCH better solution.

Jim
 
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