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Discussion Starter · #1 ·
At my location, I have stations coming from two different directions and can't seem to find a good compromise on antenna placement.


I am in an apartment facing a bit west of south and cannot roof-mount an antenna. I am limited to bolting a mast to my balcony railing and attaching the antenna to that.


According to AntennaWeb, the signals I want are SW and E/NE of where I am.


I have a Channel Master 4 bay bowtie antenna and a Radio Shack small directional YAGI UHF antenna.


What I had in mind was to use both of these and connect them with a piece of 300 ohm twinlead before using the balun to send the signal down the coax.


The 4 bay antenna can only be aimed south and slightly east and west of that because it bumps into the building. I would say I have about 15 degrees in either direction.


The YAGI has a wider range of positions. I could go about 30 degrees in either direction.


What do you think of this idea? I am in Columbia, MD and facing towards DC. If I aim for DC, I can't get any Baltimore stations and if I aim towards Baltimore (or as far as I can in that direction) I can get most of the Balto stations to lock but have problems with most of the DC stations.
 

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Sorry to say, but it probably won't work at all.


There are many posts in this forum on this subject, try searching on something like "joining antennas" or some derivative of that.


Your best bet would be to buy an A/B switch from Radio Shack to select between the two antennas unless your set top box has separate antenna inputs.


Joining antennas in the manner you mention is rampant with problems. The 2 300 Ohm connections will destroy the impedance at that point, causing multiple reflections through the feedline. The 2nd antenna will probably pick up multipath and cause additional problems. The signal from the first antenna will be split between the downlead and the 2nd antenna (antennas work as receptive as well as transmissive devices), meaning less signal strength remaining for the set.


If it is easy to try, give it a shot. Chances are slim it will work. So, don't climb the roof, go to a lot of trouble, and take a chance on killing yourself planning on it working. If it is just a couple of antennas on the balcony,it doesn't hurt to play.


Bob Smith

 

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Or just pick the best antenna and get a rotator.


-Glenn
 

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Or check out a ChannelMaster JOINtenna if the channel seperation and distribution of channels makes sense. You can use more than one.


Tim
 

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Discussion Starter · #5 ·
Well, as I said, I don't have access to the roof. I have the mast mounted to my balcony railing (or, really more like a safety railing because there isn't a balcony to stand on; just a sliding door and a railing). So, there is only about 8 inches from the wall to the mast. No room for a rotor.


I invested 60 cents in a length of twin-lead today and will wait for the temp to go down some before I go out there and mess with it.


Hopefully, I can get something to work a little better than what I have got now. It is so close to working perfectly but I am in a dead spot I think.
 

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if the two signals are really almost 180 degrees opposite in direction, you might want to try a bidirectional antenna like the winegard GS2000.


here in NJ i get signals from Philly and NYC, and they're close to 180 degrees apart so I figured I would give it a shot. It turns out I have so many reflections that it's a crapshoot no matter how you slice it, but I have managed to receive signals from both places at the same time with one antenna. i just haven't managed to get more than 1 signal from either. Poor me.


dinesh



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DVI/HDCP sucks. DFAST sucks. Boycott JVC.
 

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I think your best bet would be to pull the reflector screen off the 4-bay and try to use it bidirectionally. Antenna placement would make all the difference there, but you might get lucky and find a place and orientation that would work, if you have enough maneuvering room. Using a horizontal arm to extend the antenna out a few inches to a foot from the railing could make a huge difference


If you do combine antennas, I suggest putting baluns on both as close to the antenna as possible, and using a 75-ohm splitter to combine them. The biggest problem will be finding the optimal antenna lead lengths. At frequencies of 600MHz, cutting just a few inches off one of the antenna coax leads can mean a big difference in phase match (or mismatch) of the two antennas. This effect will vary with channel/frequency, so I think the chances of find a good match for all the channels you're after is pretty slim.


If you want to combine on a channel-by-channel basis, forget JOINtenna. The cases are plastic; they have no shielding (even in the 75-ohm versions), and nowhere near the selectivity necessary to deal with the close frequency spacing of digital channels.


You could use Tru-Spec MX4s or BPF-UHFs (available from Davis Antenna in Waldorf, MD) for digital combining, but you might have to chain two or more together to achieve the necessary selectivity, and even then, for adjacents like WJZ-38 and WJLA-39, you'd probably still have to phase-match two antennas. Granted, matching antennas for just two channels would be easier than for the whole UHF band, but all the bandpass filters and channel combiners could quickly get very expensive. A few years ago, I built a board to combine all the Washington-Baltimore analog and digital signals onto one line in northern VA, but the amps and filters to do it would probably cost more than $1000 at today's prices. Part of my problem was very weak signals close to very strong signals, so your costs would probably be lower, but still not cheap.


Really, the best advice is to try the easy stuff and if that doesn't work, use a switch.



[This message has been edited by joblo (edited 07-25-2001).]
 

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I have digital stations coming from opposite directions too. My fix was to mount 2 of the Channel Master Stealth antenni on a single short mast. The DTC100 STB has dual antenna ins so it was an easy hookup. I believe that the Sony STB does as well and perhaps others.
 

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Discussion Starter · #10 ·
I took another look at antennaweb. The stations they show are coming in a fan of about 170 degrees with most of the important ones at the opposite ends of that.


My building intersects that angle such that I have the DC stations coming from about 30 degrees south and to the west of me and the rest of them 90-150 degrees to the southeast to almost northeast behind me.


The twin lead idea did not work and it was too hot today to mess with the baluns and splitter. Once it gets down a little lower this AM I will mess with it again and tell y'all what I came up with.


Removing the reflector might just be what I need but I don't think I can get it any further out from the building without getting complaints. I am kind of pushing my luck as it is.
 
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