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  • 1 Post By Terryl3
  • 1 Post By Terryl3

Spacing for XG91 and RS VHF antenna?

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Old 02-01-2007, 06:57 PM   #1  
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Default Spacing for XG91 and RS VHF antenna?

Hi -

Thanks to this forum I've got my XG91 and 7777 receiving most stations reasonably well 85 miles away from Sacramento!

Now I'd like to install my older big Radio Shack VHF/UHF combo yagi antenna on the same pole as the XG91. I've removed the Radio Shack's UHF elements so it's now a VHF-only unit.

Question 1) Any rules-of-thumb for how much distance I should have between yagis?

Question 2) If I run the VHF antenna through the 7777, will I degrade UHF performance of the 7777? Or should I use my older Radio Shack preamp (which works ok on VHF) for the VHF yagi with a separate downlead and A/B switch?

Thanks for all previous help. I searched to see if these questions had been asked (I assume so) but couldn't find my answers....

Chico
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Old 02-01-2007, 07:23 PM   #2  
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About 3.5 feet spacing on the mast is sufficient.

http://home.indy.rr.com/challengerul/antenna.html

you did not need to take the front section off the RS antenna.

The cm 7777 has similar circuitry as the cm0549 vhf/uhf combiner...about 30 db isolation on each port. The cm7777 has separate circuitry for vhf and uhf when switched to separate.

you can amplify the 2 antennas separately but it is not necessary. I would not bother with the rs amp for vhf since it is rather noisy and the gain is excessive

you do not always need to amplify vhf. Sometimes amplifying both vhf and uhf causes co channel interference issues from powerful vhf and fm signals nearby. You usually do not have this issue in the boonies.

At my home, I amplify the uhf off the 91xg and do not amplify vhf. I run 2 separate coax into the home. combine the amplified uhf off the preamp powersupply and unamplified vhf off the hd8200p through a cm0549 vhf /uhf combiner.

I did not remove the front section of the hd8200p. I even added a vhf band pass filter prior to the cm0549 and did not see any improvement. So I would not be concerned at your home.

The 91 xg should be on top. I am going to switch the antennas around at my home in the spring. was experimenting and the 91 xg was at a convenient spot for puttering..
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Old 02-01-2007, 08:23 PM   #3  
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Quote:
Originally Posted by chicowoodhill
Hi -

Thanks to this forum I've got my XG91 and 7777 receiving most stations reasonably well 85 miles away from Sacramento!

Now I'd like to install my older big Radio Shack VHF/UHF combo yagi antenna on the same pole as the XG91. I've removed the Radio Shack's UHF elements so it's now a VHF-only unit.

Question 1) Any rules-of-thumb for how much distance I should have between yagis?

Question 2) If I run the VHF antenna through the 7777, will I degrade UHF performance of the 7777? Or should I use my older Radio Shack preamp (which works ok on VHF) for the VHF yagi with a separate downlead and A/B switch?

Thanks for all previous help. I searched to see if these questions had been asked (I assume so) but couldn't find my answers....

Chico
The only thing I might add is to drill a couple of new holes in the VHF boom to balance it better,since you've removed the UHF section.Move the switch inside the amp to Seperates and you're good to go.
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Old 02-02-2007, 10:23 AM   #4  
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Thanks for the info. I'll do some signal measurements before I put up the vhf to make sure it doesn't affect the uhf performance.

Later...

chico
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Old 07-31-2018, 05:13 PM   #5  
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For the 2/91xg,stacked is 3ft and the feed line too the splitter the same length
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Old 08-01-2018, 09:45 AM   #6  
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Removing the UHF elements has changed the forward gain and directivity on the antenna, all elements in the main design of a combo UHF/VHF antenna affect each other, the UHF section was used to give the VHF selections a bit more forward gain, this is why the UHF section was at the front of the antenna.
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Old 08-01-2018, 09:53 AM   #7  
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Why provide info to one that loves to reawaken 11 year old threads?
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Old 08-01-2018, 10:43 AM   #8  
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Yes that is why you should space the uhf&vhf 4ft apart??13
And in your eyes buy know,13.

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Old 08-02-2018, 09:37 PM   #9  
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Quote:
Originally Posted by InYourEyes2 View Post
Why provide info to one that loves to reawaken 11 year old threads?
Because we have nothing else to do.
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Old 08-03-2018, 05:19 AM   #10  
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Originally Posted by Terryl3 View Post
Because we have nothing else to do.
For someone who likes to start trouble with everyone I think
He needs a time out for a little while lol
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Old 08-03-2018, 07:29 AM   #11  
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Spelling is getting better! Congrats!
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