The Official AVS Antenna and Related Hardware Topic! - Page 347

I have been entirely too busy to post lately, but after the initial transition date, I noticed something...

Fox 55 in Wausau, WI was never allowed to broadcast in digital because it was a station that was created after the original DTV Table of Allotments was created. When the February 17th date came around, they began broadcasting on physical channel 31. It took them a few weeks to iron out some problems and then they were up and running at full strength. I installed a dedicated antenna for this channel. I ran it through a pre-amp and down to my basement where I used a channel 31 Jointenna to combine it to the rest of my system.

The Jointenna works great. In fact, it works better for me than advertized. The Jointenna is supposed to do exactly what it does...insert a single channel antenna into a system without combiner loss. However, according to the manufacturer and retailers (as well as here on the forums) the Jointenna will attenuate adjacent channels due to its crossover slope. In fact, I have read in many places that it will attenuate channels up to 3 channels on either side of the inserted channel.

I have not seen this. I have a very weak and snowy low power religious station on channel 30 and a full power analog network channel that has not yet gone dark on channel 32. Neither of these adjacent signals have been decreased by the Jointenna as far as I can tell. The low power station looks the same as it did and the network station is not ghosting or showing any other artifacts of a weaker signal.

I just thought I would report that my adjacent channels seem unchanged after installing the jointenna. All other channels are still as strong as they were and the new channel is also perfect, even though it is 62 miles away and is received by an antenna mounted in my attic.

Bill

Could not agree more....you get what you pay for.

The only situation, I can think of, where the Antennas Direct SM100 HDTV Signal Finder might be useful....is where all the signals of interest come from the same transmitting tower....and even then, it's all about strength and not quality (i.e. multi-path).

Here is a DIY article using the LTC5508.

http://www.newsvhf.com/news0401.pdf

I thought about injecting an off-set signal (from a signal generator) into a mixer and then some filtering, one could make this into a frequency selective device.

However, the bottom line....(although this would help with directionality).....save your money and use whatever signal meter(s) are available in your tuner.

There is always a loss and never a profit, heh.



Thats good to know. I didnt think they could clip the frequencies so closely with a mass produced device.


Cool looking bent tower !


Yep. And factor in the signal meters in your decision when buying a new TV set.

"There is always a loss and never a profit, heh."

OK...yes, there may be a .5db loss, but not the 3.5db loss you get with a normal splitter turned backwards and definitely no interference between the 4 antennas I have hooked together.

From all I've read here, your situation is an anomoly (sp?). Perhaps there's more going on there than you realize.

In my own situation, I can't insert my channel 30 jointenna into my lead because it knocks my channel 33 signal down from a perfectly reliable level of 87 to a cutting in and out level that tops out at 62. On the other hand, my channel 14 jointenna admits enough of channel 17 into my lead that I may not need to buy a channel 17 jointenna ! And when I bought one of my others (41 I think) it worked so poorly that I had to send it back into the factory (not the vendor) to have its tuning reworked.

If you opened this issue up for more discussion, I bet we could hear many stories of success and failure regarding jointennas. It's a pity that there doesn't seem to be any product in between the jointenna and the Tinlee products.

True and totally sympathsize, but consider the total market $ sales a year for that type of specific product. Not that impressive.

I installed the AntennaCraft HBU22 this morning. I faced it North, with the hope of getting the Summerville and Ladson stations (18 & 26). I was expecting to get 20 as well (off the back side as it is due south). According to TV fool, 20 is only 5.8 miles away.
From the attic, the HBU22 really does not pick up anything I did not already get on the homemade antenna (also in the attic w/ 25 ft. of new RG6).

I may try the HBU22 on the roof, as I initially planned. If I do, I will write up the results.
Thanks for the help and suggestions.

My home is located on the highest elevation in the city. Unfortunately, the city is installing a 285’ water tower about 1500’ from me home. In other words, this monster will be next to my home.

Now, thinking like a total TV Geek, this may open the door for “catching” some DX signals. My stack of XG-91’s is 56’ in the air and would not be in direct sight of the water tower, so I am thinking the following:

1) Purchase a pair of the Antenna’s Direct DB8’s and stack them horizontally pointing them at an angle which aligns them to directly point at the edges of the water tower. They will only need to be off the ground by 10 foot or so as they are in direct sight of the tower and the purpose is to catch scatter.

2) I am choosing the DB8’s as they have a wider beamwidth. Actually, stacking them vertical would help more.

The goal is to catch reflected scatter off the sides of the water tower. Since, I am so close to the tower, I think this experiment will actually have some positive results.

Ideas or comments..

?????

Try pointing it West North West to get 18 & 26.

Thanks for the update! Attic installations can be a bit dicey and require checking many locations for the hot spot. The hbu 22 will likely work much better on the roof, but even then, requires checking multiple mounting locations and heights to determine optimal mount location. Good luck and keep us posted!

You darn right you may ! I was thinking of getting a bounce off the Goodyear blimps that occasionally go by, but my crazy DXing days are over, heh.


Quit spending money and build your own DBGHs or one of mclapps M8's, heh.

Is the DB2 available in any B&M stores? I can only find it online.

I tried West and that didn't work. WNW has a few trusses in the way. Based on my attic construction, I am pretty much stuck w/ N, S, E, or W.

Perhaps his is mistuned.

From the hdprimer site:

If it was mistuned, something would definitely be messed up. However, as I said, all of my digital channels are coming in perfectly and the adjacent analog signals are coming in the same as before as far as I can tell. I would have expected to lose them completely, and I can't see any difference.

The all channel UHF points to 92 degrees magnetic while the new channel 31 UHF points at 326 degrees magnetic. The station it receives while mounted in my attic is 62 miles away and is 2 edge reception.

You can say what you want, but I am not seeing considerable loss at the two adjacent channels and the channel it is tuned to is received at 100%.

Bill

Hmmm. Which of the three join-tennas do you have ?

Mine is factory tuned for channel 31, so I am sure it would be a 30-49 model. Actually, this is the only one with adjacent channels for me, and one of them goes away post transition. I also have a channel 11 Jointenna and have ordered a channel 16 Jointenna.

There was a discussion of the join-tenna here earlier : http://www.avsforum.com/avs-vb/showt...546066&page=44

Have you tried reversing it to see the effects ?

I have seen a triple vertical stack of antennas. How much more gain is had over a stack of 2.
I know having a double stack has 3db (minus coupler & cable loss) gain over a single array.

hmmm......there's something about this that reminds me about an old joke....something about a guy that lost a valueable coin in his basement, but he looks for it outside because the light is better there.

You might try to build your own antenna. There's a couple of designs online here that do not layout horizontally, they're mostly vertical (the DBGHs or one of mclapps). Think of a thick garment bag....if it can be hung in your attic, broadside to the WNW, then you have a good shot of one of the home made antennas working.

What Ive seen from modeling with a triple stack, it gives little to almost none additional gain, especially considering the extra effort. You want to stack in pairs to maintain the symetry.

The theory says 1.7 db.

The actual gain depends on the stacking distance and combiner losses.

Quiz time! Let's play What's wrong with this picture?

A


B


C


D


E


Frame A is a night scene, it is supposed to be dark.

D looks like what I get on my Channel Master or Zenith CECB when the signal is right on the edge of the "digital cliff."

E looks like an analog channel with some impulse noise.

The others look like tuner troubles. Have you tried other tuners ?

I love D. It looks like an impressionistic painting. Do it again.

C looks like horiz sync problem.

B looks like harmonic from another xmtr on that freq.

I agree with jtbell on E.

The OPB logo looks fine. It's a problem with the program itself.

As opposed to the blocky "Mondrian" school of many other receivers.

A typical, inexpensive two-way RF Combiner/Splitter contains a Hybrid Transformer
and an internal resistor that dissipates mis-match energy.
If the signals on the two ports are perfectly EQUAL and IN-PHASE, there
is no mis-match energy wasted and the output is 3 dB higher than either input,
less the internal losses, hence 2.5 dB is MAX combining gain.

If the two input signals are not perfectly matched in signal strength and PHASE,
the difference is wasted in the internal mis-match resistor. If one of the antennas
happens to be located in a multipath null, contributing very little signal to one
of the ports, the mis-match loss could negate all combining loss, resulting
in a net LOSS of perhaps 3.5 dB. [The same loss as pointing in different directions.]
http://www.macom.com/Application%20Notes/pdf/m568.pdf
http://www.macom.com/Application%20Notes/pdf/m560.pdf

In a THREE-WAY RF Combiner/Splitter there are a pair of two-way Combiners.
The first operates as described above for the first pair of antennas.
The second combines the OUTPUT of the first two-way Combiner with
the signal coming from the third antenna....unfortunately, when the inputs
to the first combiner are equal and in-phase, the output signal will be
2.5 dB HIGHER than the signal coming from the third antenna, resulting
in excessive mis-match loss. TWO antennas will nearly always be better than THREE.

Four antenna combiners performance is even more "complicated".....which
is why expensive Stripline Couplers make more sense....they only have a few
tenths of a dB internal loss and DO NOT require matching of signal levels...

That said, there is an additional factor to consider....DIVERSITY.
Multipath nulls can vary between antenna locations and heights, esp. in attics.
One of the antennas may pick up Chxx but not Chyy and the other antenna
picks up Chyy but not Chxx. Even though there is a loss in the combiner,
the signals may be strong enough so you receive both channels,
whereas with only one antenna you would not get both.

Or a Monet, when he was really, really drunk ??