Triplexer, duplexer

n1chu

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I am running 3 radios in my mobile setup. A dual band 2 meter/440 MHz rig, a 220 MHz and a scanner radio in my new aluminum body F-150 pickup truck. I ran 3 separate antennas in my previous truck, 2 mounted on a BackRack cab protector that mounts in the forward stake holes on the rails of the bed and one on the hood. In order to park in my garage I needed to use the Diamond K9000 fold-over motors. These motors require “ground independent” antennas…. The K9000 is isolated from the truck body/chassis. The scanner doesn’t care if the scanner antenna is ground independent or not, but this is just background for my asking advice on using a triplexer or duplexer and reducing my “antenna farm” on the new truck. Ideally, a single tri-band antenna that is ground independent would work for all 3 radios but does anyone make a tri-band ground independent antenna? (I figure I could run the scanner off of the same antenna provided there is protection against feeding power through the triplexer.) in short, I’d like to provide as few antennas to my 3 radios as possible, using available triplexer/duplexer/ground independent antennas. Any ideas?
 

mmckenna

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At minimum, you are going to need 2 antennas. One of the ham radio, one of the scanner.

The tri-plexer will give you the common antenna input and give you 2 meter, 1.25 meter and 70 centimeter ports.
There won't be a port that will work with the scanner. Since duplexers and triplexers are tuned to their ports, it's only going to pass signal in the individual ports passband.

So, an antenna will be required for the scanner, separate from the ham antenna. You could try tapping the AM/FM radio antenna. Not ideal, and won't be an outstanding scanner antenna, but might work well enough.

I'll also point out that parking a full sized truck in the garage with antennas on top isn't an issue. My dad's Chevy Silverado 4x4 was parked in the garage ever day with a VHF antenna on the roof. He never removed it, and the 1/4 wave whips flex well enough that there's no damage to them. A 220MHz antenna would be shorter than a VHF whip, and the UHF whip would be about 6 inches tall.
 

n1chu

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Ok on all. Thanks for the input. I agree with your take on the setup it creates another stumbling block. The 220 MHz radio is a mono band. The other is a dual band 2meter 440 MHz with only one antenna connection. The three leads coming from a triplexer are 220, 2 meter and 440… the 220 lead is simple, but would I need to add a 2 meter/440 duplexer, in reverse direction, and attach the two leads from the triplexer? How much signal loss should I expect to see when stacking the two?
 

mmckenna

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The three leads coming from a triplexer are 220, 2 meter and 440… the 220 lead is simple, but would I need to add a 2 meter/440 duplexer, in reverse direction, and attach the two leads from the triplexer? How much signal loss should I expect to see when stacking the two?
Yes, you'd have to recombine the 2 meter and 70 centimeter ports back through a diplexer to get them into the radio.

Depends on the diplexer/triplexer, but losses are usually in the 0.3dB range. So, usually manageable, but if you are running two back to back, then double that. Not a great solution, but will work if it's really what you want.

A 220MHz quarter wave whip won't have a problem going through a low garage.
A 144MHz quarter wave whip won't have an issue either, and it'll work as a 3/4 wave on 440MHz.
You can also run a dual band antenna with a spring at the base that will ~probably~ withstand low parking garages for a while.
 

n1chu

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Yes, you'd have to recombine the 2 meter and 70 centimeter ports back through a diplexer to get them into the radio.

Depends on the diplexer/triplexer, but losses are usually in the 0.3dB range. So, usually manageable, but if you are running two back to back, then double that. Not a great solution, but will work if it's really what you want.

A 220MHz quarter wave whip won't have a problem going through a low garage.
A 144MHz quarter wave whip won't have an issue either, and it'll work as a 3/4 wave on 440MHz.
You can also run a dual band antenna with a spring at the base that will ~probably~ withstand low parking garages for a while.
Well, listen… thanks for the technical input. I welcome your expertise. But I’m not going to debate my garage door height. I could send you a picture but I really shouldn’t have to. Take it from me when I tell you my garage and my truck conspired against me and my antennas. I’ve replaced a couple of antennas when I forgot to fold them over before backing in. The only way they would have survived was if they were even shorter than what you describe. (I’ve even thought about the low profile antennas they stick on undercover vehicles the police use and probably would have used them had they not been so expensive and range restrictive.) besides, you know what they say about improving your received and transmit signals… doubling the height of your antenna is better than doubling your power! I can attest to “The higher the better”, it does make a noticeable difference.

I guess no others care to offer alternatives or agree with you… as I do also. Thanks again.
 

900mhz

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Low profile antennas are not as bad as the OP believes...at least for UHF and 700/800. I run them. They work just fine. My UHF and 700/800 ones work as well or better than 1/4 wave conventional antennas. I use the proper NMO mount installed correctly and swept for confirmation. 220 of course is a different animal. I would bet the OP must want max coverage off the 220 box off South Mountain in Bristol. Know the site well.
 

n1chu

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Low profile antennas are not as bad as the OP believes...at least for UHF and 700/800. I run them. They work just fine. My UHF and 700/800 ones work as well or better than 1/4 wave conventional antennas. I use the proper NMO mount installed correctly and swept for confirmation. 220 of course is a different animal. I would bet the OP must want max coverage off the 220 box off South Mountain in Bristol. Know the site well.
Low profile antennas are not as bad as the OP believes...at least for UHF and 700/800. I run them. They work just fine. My UHF and 700/800 ones work as well or better than 1/4 A

wave conventional antennas. I use the proper NMO mount installed correctly and swept for confirmation. 220 of course is a different animal. I would bet the OP must want max coverage off the 220 box off South Mountain in Bristol. Know the site well.
Granted, the low profile UHF and 800 MHz antennas may work fine for reception in areas where an agency needs coverage, but they are still expect to see a bigger price tag… that may be due to their market being mostly commercial and govt agencies, certainly much more than a traditional amateur antenna cut for the same bands. I expect that is merely the use of higher power on UHF systems and additional transmit/receive remote sites of the higher frequencies. (I would expect you see good coverage within an agency’s area.)

220 MHz is South Mtn as you surmised and Avon Mtn. But mostly 440MHz DMR has been where most all have migrated on those 220 sites.
 

n1chu

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Just let the air out of the tires next time you drive into the garage. Problem solved.
Best solution I’ve gotten so far! But my wife still thinks her solution is the one to go with… park the truck outside in the driveway and use my bay for storage! (We don’t have a basement and the junk just keeps piling up! If I had a dime for every time I threatened to park a roll-off trash hauler in the driveway I’d be rich!)
 

mmckenna

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Best solution I’ve gotten so far! But my wife still thinks her solution is the one to go with… park the truck outside in the driveway and use my bay for storage! (We don’t have a basement and the junk just keeps piling up! If I had a dime for every time I threatened to park a roll-off trash hauler in the driveway I’d be rich!)
Yeah, no way my own truck would fit in a garage, so not an issue for me. My wife's truck does, and I have no issues with a 1/4 wave antenna.
Finally got my garage all cleaned out and then had to use it to store furniture while I install new flooring.
 
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