Stacking, Ganging, Combining TV Antennas - Page 85 - Canadian TV, Computing and Home Theatre Forums

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post #1261 of 1285 (permalink) Old 2017-02-12, 05:53 PM
 
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My experience with the coax 1/2 wave balun is that it is not as broadband as the ferrite core balun. I recently did some tests on the 4221HD and the performance with the 1/2 wave was disappointing. As a matter of fact the ferrite balun also out performed the original CM printed circuit balun.

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post #1262 of 1285 (permalink) Old 2017-02-13, 06:37 PM
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Although it MIGHT be better than the PROBLEMATIC RF Combiner [Hybrid Ferrite Transformer, with not only Internal Loss, but also Losses due to Input Port Amplitude and Phase Mismatches, as we've recently discussed], I'm NOT convinced that the Simple Interconnect described above comes anywhere near the performance of an OPTIMIZED HHH (Holl_ands Horizontal Harness) or HVH (Holl_ands Vertical Harness), which calculate the Harness LENGTH and IMPEDANCE [Separations] which will MINIMIZE the OVERALL SWR Mismatch, while Maximizing GAIN across the entire Frequency Band of Interest...and of course Internal Loss is Minimal, esp. using Open Wires vice Coax:
http://imageevent.com/holl_ands/stacked [The resultant Gain and SWR vs Frequency Results speak for themselves.]

In the 1/4-Wavelength Impedance Transformer, there is no such thing as a SINGLE Value for 1/4-Wavelength in UHF Band (Bandwidth Factor of 1:1.485) or even Hi-VHF Band (1:1.24] or FM Band [1:1.227], which degrades performance on the Band Edges:
http://whites.sdsmt.edu/classes/ee48...81Lecture9.pdf

The above 1/4-Wave Impedance Matching Network ASS-U-ME's that the Input and Output Impedances are a CONSTANT (whether 75-ohms or 300-ohms purely Resistive....a fairly good assumption for 144 and 440-MHz Bands, but NOT for TV), when in REALITY, the IMPEDANCE and esp. PHASE of pretty much ANY TV Antenna varies all over the place [see any of my 600+ Antenna Simulation Results, via my Signature Link], which is going to severely degrade what you THINK should be happening. [And if NOT using a Preamp, the Input Impedance of a typical Super-Het Tuner also varies quite a bit, due to using a Variable, Low-Q Band-Pass Filter on the Tuner's Input....although most (not all) Double Conversion Tuners would usually be much better SWR Match, since they usually do NOT have a Tuned Input.]

Antenna Simulations, Overload Calculations, etc: http://imageevent.com/holl_ands

Last edited by holl_ands; 2017-02-13 at 07:12 PM.
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post #1263 of 1285 (permalink) Old 2017-02-20, 03:00 AM
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1) "BEST" Interconnect between two Identical Antennas would be either the Optimized HVH (Holl_ands Vertical Harness) or HHH (Holl_ands Horizontal Harness) which OPTIMIZES the fol. SIX Independent SYmbol Variables: a) Separation between the Harness Wires (determines Feedline Impedance), b) Distance of Harness from Active Elements (e.g. Bowties) and c) Total Harness Length [actually SUM of 2 Horizontal pieces and 2 Diagonals connecting Harness to Active Elements, which are INDIVIDUALLY Optimized in all except some early versions). NO RF Combiner Loss and Optimizes both Impedance and Phase Matching. Indeed ALL Interconnect Losses are accounted for, incl. SWR Mis-match and (negligible) Ohmic Losses in the Harness Transmission Line:
http://imageevent.com/holl_ands/stac...q4hzwa41.dog_s

2) Second "BEST" is HHH or HVH, except with some sort of CONSTRAINT on the Design, such as forcing Horizontal pieces on either side of Common Feedpoint to be EQUAL, resulting in only FOUR independent SYmbol Variables (as I did in some of my early Designs).

3) Third "BEST" is HHH or HVH, except with even MORE CONSTRAINTS on the Design, such as Alternative (b) in the fol. Vertically Stacked CM4221 [old] webpage, where the Vertical Length in the Horizontal Harness was CONSTRAINED to be the SAME as the Vertical Stacking Distance and the Total Harness Length was determined by Optimizing ONLY the Distance of the Harness from the Active Elements. And of course, the Harness Separation determined the Transmission Line Impedance, while the Tapered connections to the Active Elements provided at least SOME Impedance Transformation. [This was one of my earliest KISS Designs with only TWO Independent SYmbol Variables.]
UHF Vert-Stack CM4221 4-Bays - OPT
Additional comparisons for mclapp's M4, incl. Performance vs Vertical Stacking Distance:
http://imageevent.com/holl_ands/stac...anglereflector

4) Fourth "BEST" is Equal-Length Transmission Lines connected to a Common Feedpoint, such as Alternative (a) in the Vertically Stacked CM4221 [old] webpage. Results are for 300-ohm Twin-Lead, although as noted, 440/450-ohm Ladder Line [as well as 600-ohm OPEN-LINE] would provides lower SWR [turns out that Impedance value is NOT critical]. Since there is only ONE SYmbol Variable [Length] for a given choice of Impedance, performance was significantly LESS than the above alternatives. Since Twin-Lead without an overall Shield has high loss when damp/wet/iced-over it it NOT recommended for Outdoor use.....and since Ladder-Line employs Plastic Insulator with perhaps 40-50% Air Cut-Outs, it only provides moderate improvement for the same problem. BTW: Instructions for DIY 300-ohm (or whatever) OPEN-LINE Interconnects can be found here:
Home-Brew Parallel Transmission Lines
[I'm still looking for the link to a particular Cable Stable P/N that was well suited for this purpose.....]

5) WORST is anything with an RF Combiner [typ. 0.5 to 1.5+ Loss, more on Higher Freqs].....which has not only Ohmic Internal Losses [see mrf Spec Sheets], but ALSO significant Amplitude and Phase Mis-Match Losses [which are dissipated by the Internal Resistor on the fourth Port of the RF Combiner's Hybrid Transformer], which can be seen in measurements at www.antennashacks.com ALSO, bear in mind that these measurements are for PERFECT 75-ohm Input/Output Terminations....whereas in the REAL WORLD, there will be additional, unknown Losses due to Impedance Mismatch to the Antennas and whatever Amplitude/Phase Mis-Match there may be between the two Antennas, esp. if Elements are damaged or Balun and Connections degraded.

Antenna Simulations, Overload Calculations, etc: http://imageevent.com/holl_ands

Last edited by holl_ands; 2017-02-20 at 03:39 AM. Reason: ,
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post #1264 of 1285 (permalink) Old 2017-02-20, 03:53 AM
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FWIW: Fol. 3-Bay Bowtie Investigation shows that there is a RIGHT way to Interconnect three Antennas [whether they be Individual Bowties or more Complex Arrays]....and some that are NOT:
UHF FF3 3-Bay Bowtie - NO Reflector

Antenna Simulations, Overload Calculations, etc: http://imageevent.com/holl_ands
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post #1265 of 1285 (permalink) Old 2017-04-18, 08:48 PM
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Hello, I'm looking for some assistance. I've ganged 2 CM4221HDs and I'm living near Fenwick, ON. I have one pointing NW to pull channels out of Toronto and Hamilton, and I have the other slightly SE (more east) trying to pick up channels from Buffalo, NY. The antennas are about 3' apart (vertically) from each other. Connections are made with fresh RG-6 and I'm using a good quality splitter to combine the connections with the cable length as close as possible.

I connected a TV today to test and I'm only getting 7 channels. At my old house just down the street I was getting 30 with an old VHF/UHF antenna poorly pointed. Reading the FAQ, perhaps I have a phase issue here but I'm confused by what I need to do to test this. Any thoughts? I suppose I need to repoint and test at the same time, but I figured I should be at a minimum be receiving all the green channels.

My TVFool is here.
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post #1266 of 1285 (permalink) Old 2017-04-18, 10:39 PM
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Hello, braunerf18

Thanks for the tvfool report.

Combining two antennas aimed in different directions with a splitter in reverse doesn't always work; you just have to try it.

The problem is that when the same signals from each antenna reach the combining point they will interfere with each other if they are not in phase (arrive at the same instant). It usually has the best chance of working if the two azimuths are 90 degrees apart, which is not true in your case.

If you don't get all the channels when the antennas are combined that you had when each antenna was separate, then combining that way doesn't work for you.

Do you get the channels you want when they are separate?

If the two antennas are aimed in different directions, making the two coax lines the same length isn't necessary; only when it is two identical antennas aimed in the same direction.

The rules are the same for two separate 4-bay antennas or for an 8-bay antenna that can be bent.

If you can not measure it, you can not improve it.
Lord Kelvin, 1883

Last edited by rabbit73; 2017-04-18 at 10:56 PM.
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post #1267 of 1285 (permalink) Old 2017-04-18, 11:02 PM
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Yeah definitely try it separately first. One antenna at a time and see what ya get from each. Also if using a preamp, remove it.

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post #1268 of 1285 (permalink) Old 2017-04-18, 11:19 PM
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Thanks for explaining. No preamp. I'll have to try them separately. I went with two since this whole area is plastered with either two 4221's or two 4228's configured in this way. Given that, is this type of setup different at each location? Is there a way to get them into phase?
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post #1269 of 1285 (permalink) Old 2017-04-19, 11:12 AM
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Quote:
I went with two since this whole area is plastered with either two 4221's or two 4228's configured in this way.
Each location is unique and they might be accepting what they are getting, not having your experience of knowing what might be possible. Testing each separate antenna at your location before combining will tell you what is possible at your location. If you still only get 7 channels when they are separate, then you have to find out what is wrong with your antenna system.
Quote:
Is there a way to get them into phase?
It is possible to adjust the coax lengths to make one channel in phase, but then it throws the other channels off. It works about as well as a dog chasing its own tail.

If you find that you lose some channels after combining that you had when the antennas were separate, you can settle for what you are getting or you can:
1. Connect each antenna to an A/B switch to select which antenna you want to use. If your TV isn't able to add a channel after scan, it might be necessary to rescan after changing antennas.
OR
2. Connect the main antenna to the antenna input of the TV and connect the second antenna to a separate tuner like the CM 7003 with it output connected to the aux input of the TV.

Some users have found that when the two directions are about 180 degrees apart, if they remove the reflector from their antenna, they can receive both directions with one antenna. Removing the reflector makes the antenna bi-directional. I don't know if it would work for you; it would be an experiment.

If you can not measure it, you can not improve it.
Lord Kelvin, 1883

Last edited by rabbit73; 2017-04-19 at 11:31 AM.
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post #1270 of 1285 (permalink) Old 2017-04-19, 02:53 PM
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You can TRY reversing the twin-lead connection on ONE of the Baluns, which will reverse the PHASE of that Antenna by 180-degrees prior to RF Combiner.

HOWEVER, you PROBABLY have something ELSE that isn't working right.....so try EACH Antenna individually and hopefully you'll find your REAL Problem....

And of course, it COULD be that the TVFool Report for you NEW Location is quite different than right down the street due to local Terrain, so you should enter your ACCURATE Location and post the Results [Weblink URL at top of Browser after running TVFool]. It also helps if you describe local Terrain & nearby Buildings/Trees....

Antenna Simulations, Overload Calculations, etc: http://imageevent.com/holl_ands
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post #1271 of 1285 (permalink) Old 2017-04-24, 07:00 PM
 
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braunerf18
You mention a 'good quality' splitter and it got me remembering that I tried t re-use some equipment from a satellite TV installation when I went to OTA. It didn't work.
In your location you should get more than 7 stations with a 'paper-clip' antenna so if you get no better results after trying what Holl_ands and Rabbit73 suggest, then look at that splitter.
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post #1272 of 1285 (permalink) Old 2017-05-22, 04:44 PM
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Ok I had some time today to play around with the setup. I removed the splitter and connected each antenna individually. Once I did this I was receiving about 13 channels from my Buffalo antenna (some in and out) and 10 from my Toronto antenna. All channels were relatively low signal, 20-30% tops (both antennas).

I replaced the splitter and ganged the antennas together once again. I'm getting about 10 channels and only one off of my Buffalo antenna. I have a feeling it isn't necessarily the ganged setup, but now with a splitter I'm degrading the signal to the point where I don't get anything off of my Buffalo antenna.

I should also make mention that the Buffalo antenna does have a few rows of trees before I see clear skies. At this point I believe I've ruled out the equipment, coax, and connectors, and now I'm wondering what I should do next. Perhaps I need a preamp here? If so, I'd like to keep the cost low if possible. What would you guys recommend?

Thanks for all your help so far.
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post #1273 of 1285 (permalink) Old 2017-05-22, 09:55 PM
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Thanks for making the test. Obviously, combining isn't working for you.

I agree with Red Knave, you should be getting higher signal readings with the strong signals on your report.

Something else must be going on, but we don't have enough information; could be the trees or equipment failure.

Can you tell us more about the splitter being used as a combiner?

What are you using to get those signal strength readings?

Can you show us a photo of the trees in the Buffalo direction?

L0S 1C0 is a pretty large postal code, so your report might not be very accurate.

What we would really like to have is an accurate report for your present location and your previous location.

You can use the TVFOOL Interactive Map browser to find the coordinates of your antenna by moving the cursor by drag-and-drop. The coordinates below the map change as you move the cursor.
TV Fool

The report that you gave us is centered at about Canboro Rd near the Saint Ann Roman Catholic Church and Elementary School.



Quote:
Perhaps I need a preamp here? If so, I'd like to keep the cost low if possible. What would you guys recommend?
I have been using the RCA TVPRAMP1R preamp with my indoor antenna. It works well for me and isn't very expensive.

If you can not measure it, you can not improve it.
Lord Kelvin, 1883
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post #1274 of 1285 (permalink) Old 2017-05-24, 12:29 PM
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I ordered a combiner/splitter with the antennas that was $10. As per Red's suggestion, I did swap it to another brand new RCA splitter I had.

There is a pine tree line with some visibility through it so it's not a complete wall of foliage, but it is less than ideal. To be honest I'm not sure what to do at this point, I just want to get it working and I appreciate everyone's help thus far

How do I take off the reflector on the 4221HD? I'm thinking maybe I should try to go that route instead. Either that or order one of these: https://angelelectronics.ca/shop/ota...r-hdtv-antenna

Or will removing the reflector achieve the same goal?

Thanks.
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post #1275 of 1285 (permalink) Old 2017-05-24, 05:34 PM
 
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I would remove the 4221 reflector rods. Worst case scenario, cut the rods off. I have seen 4221s with the reflector removed so for sure its been done before.

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