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Old 01-03-2015, 9:19 AM
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Default Got my two antenna's installed.

Installed Icom 7100 with two antennas - Tarheel Screwdriver and 5/8 wave. As clean as I could get them.


Ram update – Antenna, SideBars, and Fenders | NickToday Blog
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Old 01-03-2015, 1:50 PM
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General rule of thumb is to keep antennas away from each other at least a quarter wave distant at the lowest frequency. How do they seem to be working out for you?
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Old 01-03-2015, 4:02 PM
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Jealous because Santa brought a 7100 to me... but I have to wait for warm weather to get my antenna up. Putting the rig in a camper, but will use a 40M-2M Windom while parked at home. Haven't figured out what I'm going to do yet for a camping antenna. The Windom is about 138 feet long... so that's probably out. Anyway, the 7100 should be sweet in the camper... XYL said OK when she saw how small the control head was and that I could hide everything in the cupboard and bring out the control head when I wanted to do the annoying ham radio stuff.
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Old 01-03-2015, 4:23 PM
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Quote:
Originally Posted by KG4INW View Post
General rule of thumb is to keep antennas away from each other at least a quarter wave distant at the lowest frequency. How do they seem to be working out for you?
I didn't have many options with the broadcast antenna on the other side so I took a chance. Seems to be working great so far and no swr issues
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Old 01-03-2015, 4:52 PM
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WAY TOO CLOSE... hope you do not blow out your receiver.
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Old 01-03-2015, 5:02 PM
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Even if you're not noticing any desense right now, RX problems can develop fairly quickly. I see the 7100 has two separate SO-239s on the back but I don't know how much isolation they have built in. Can't put the screwdriver on say the rear bumper?
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Old 01-03-2015, 7:11 PM
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Even if you're not noticing any desense right now, RX problems can develop fairly quickly. I see the 7100 has two separate SO-239s on the back but I don't know how much isolation they have built in. Can't put the screwdriver on say the rear bumper?
I can't put on my bummer due to towing. I don't expect issues, but if there becomes a hint I will take off the 2m. Options were just limited.
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Old 01-03-2015, 7:18 PM
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You're gonna toast those radios.
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Old 01-03-2015, 7:31 PM
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Didn't want the high band antenna on the roof then? I've seen too many radios burned up by adjacent TX antennas and not enough separation.
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Old 01-03-2015, 7:48 PM
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Didn't want the high band antenna on the roof then? I've seen too many radios burned up by adjacent TX antennas and not enough separation.
Again challenge is towing when you have a 5th wheel that covers the roof
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Old 01-03-2015, 7:59 PM
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I see. That's a tough one. I'm not sure how you'd best remedy that then. Move it to the other side, you run the risk of burning up the factory receiver (as you already noted) and moving one further forward down the hood/fender might not be so good either.
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Old 01-03-2015, 8:03 PM
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I see. That's a tough one. I'm not sure how you'd best remedy that then. Move it to the other side, you run the risk of burning up the factory receiver (as you already noted) and moving one further forward down the hood/fender might not be so good either.
Do you believe that sine its really just one band at a time there will still be such a risk? Also which would you suggest moving
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Old 01-03-2015, 8:13 PM
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Again challenge is towing when you have a 5th wheel that covers the roof
I know of no fifth wheelers that hang over the cab roof of a pick up truck. I have both VHF and UHF spikes on the roof of my truck and would not hesitate to place a taller one up there if needed.

This is my truck and trailer. There is no way that the trailer could interfere with an antenna on the roof of the truck.

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Old 01-03-2015, 8:15 PM
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I looked at the 7100 manual and it didn't specifically state proper antenna separation, only to use good coax and proper antennas (which I'm certain, yours are fine). That being said, yes, receivers can be damaged even when they're not in use at the time they're being exposed to strong nearby RF. I'd have to ponder where to suggest moving something.
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Old 01-03-2015, 8:34 PM
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Quote:
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I can't put on my bummer due to towing. I don't expect issues, but if there becomes a hint I will take off the 2m. Options were just limited.
It won't be a hint, it'll be a "poof". One day it'll work fine, the next time it won't. It isn't a cheap fix to send your radio back to Icom for repair.

By having the antennas that close together, they are going to couple to each other and likely affect tuning. That will also allow the RF to couple and get into either side of the radio. It won't matter what band you are on, the soft dangly bits of the radio that get toasted are well before the band switch.

Think SWR, if too much RF gets backwashed into the radio, it will cause damage. Same thing happens when an antenna is transmitting to close to another receive antenna, the RF couples and goes back down into the receiver.

I've seen this happen between a 50 watt VHF radio and a 35 watt UHF radio. Antennas to close and the 50 watt ham radio lost it's receiver. A 100 watt HF radio and a 50 watt VHF/UHF radio will likely have the same issue.

I'd tend to agree with the others, put the VHF/UHF antenna on top of the cab. Bite the bullet and drill the hole for an NMO. It'll work better in the long run. Other option would be to put the screwdriver antenna on the front bumper, or very front edge of the hood on the passenger side.
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Old 01-03-2015, 8:49 PM
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Look at the way the Aussies do HF antennas. Usually you'll see them mounted on the front brush guard. Keeps it well away from everything else and won't interfere with towing. Also, you can think of it as a "vertical curb feeler". Handy for finding exposed fluorescent tubes in parking garages and low tree branches.
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Old 01-03-2015, 10:05 PM
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I don't think transmitting on the HF antenna will have any bad effects on the VHF/UHF antenna or radio connected to it. The highest transmit freq on HF is around 29.7Mhz and the lowest VHF range of the radio is probably VHF air band, so there are a couple of octaves between them and some filtering in the VHF/UHF radio front end. Otherwise I think the the antennas are mounted way too close where patterns and performance will be affected.

I have a larger Tarheel (model 100HP) and mounted it about a foot behind the cab of my Toyota Tundra. Works like a champ and you could probably use a stake pocket mount on the Little Tarheel.
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Old 01-03-2015, 11:12 PM
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Quote:
Originally Posted by SteveC0625 View Post
I know of no fifth wheelers that hang over the cab roof of a pick up truck. I have both VHF and UHF spikes on the roof of my truck and would not hesitate to place a taller one up there if needed.

This is my truck and trailer. There is no way that the trailer could interfere with an antenna on the roof of the truck.

Mine comes up a little higher so it comes a little closer. I must have e missed something in my orinal design. I ram every test I could think of
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Old 01-03-2015, 11:25 PM
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I think you better check out this style mount before you blow up the receiver in the other radio.
https://breedlovemounts.com/site/74c...nt_2.html#2583
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Old 01-03-2015, 11:25 PM
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Quote:
Originally Posted by SteveC0625 View Post
I know of no fifth wheelers that hang over the cab roof of a pick up truck. I have both VHF and UHF spikes on the roof of my truck and would not hesitate to place a taller one up there if needed.

This is my truck and trailer. There is no way that the trailer could interfere with an antenna on the roof of the truck.

Could you fit a toolbox between you 5er and cab??? I thought that night br an option
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