91XG or DB8e
Hello all,
Here is my tvfool report: http://www.tvfool.com/?option=com_wr...b97d707e909613 Here is my original thread for reference: http://forum.tvfool.com/showthread.p...ighlight=8200U Here is a flow chart of my setup: http://forum.tvfool.com/attachment.p...7&d=1452206931 This setup worked great until RF19 started their repack process and has lowered power. Since this has happened, reception is very poor, but it is still watchable, sometimes. RF19 is eventually moving to RF25. After that RF44 is moving to RF19 and back to full power, RF23 is moving to RF16, and RF49 is moving to RF22. I will have 2 RF22s in opposite directions when this happens. All this is supposed to happen by the end of 2018. Fun times. Anyway, after the repack, my highest frequency will be RF28. Do you think I should change out one or both of the 91XGs to increase gain at these lower UHF frequencies in an attempt to make RF19/RF25 watchable, or will I lose directional capabilities and get too much multipath interference? Is there another option you would suggest? Thank you for your advice! |
Hello again, welkin
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http://forum.tvfool.com/attachment.p...1&d=1489973660 The DB8E must have both panels aimed in the same direction, which should be obvious. Also, both panels must be equally illuminated by the incoming signal, which might not be true. The 8-bay has a larger capture area than the yagi. Quote:
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https://www.google.com/search?q=G0KS...k1.bNCN0I0-jCw http://www.g0ksc.co.uk/2013-yagis/11...-lfa-yagi.html The last resort would be a method of combining that avoids using a splitter in reverse as a combiner. |
I think I'll wait and see what happens when they move RF19 to RF25. The gain of the 91XG improves about 1 DB and signal seems to get better the cooler the weather. If it's not better after the repack is finished, I'll move on to other options. I have to be able to get my AntennaTV and watch Johnny Carson. :) Thanks for your time.
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Several points for consideration:
Please also use call signs, RF channels alone are no longer sufficient in Springfield to identify what's going on. The TVFool plot provided is woefully out of date (2015 database). Probably an old link.... However, as the consequences of the recently complete spectrum auction unfold, the changes will be coming in hot and heavy as stations who were bought out go off the air and as channel sharing agreements are implemented. Given that this site's owner hasn't implemented changes submitted for quite some time, it remains to be seen whether or not such updates will be made in the future. Just don't know... Gray pretty much threw the channel and programming assignments in Springfield into a Cuisinart and I'm still trying to sort out the details since I hadn't looked at the market in quite some time. Since Antenna TV is only available on low-powered digital stations (15 kW or less) ERP and you're 70 miles away, the odds of ever picking them up reliably is probably somewhere between slim and none except under rare atmospheric conditions. That you're picking up the channel 19 signal at all is, in itself, quite an accomplishment. Regarding your concerns for having a co-channel issue on channel 22 when KRBK moves, I wouldn't worry about it. I'd suspect that KQFX-LD will be displaced and will have to file for a new operating channel when that filing window opens. You can likely improve your system noise figure for your UHF antennas by around 4 dB by amplifying them separately before combining the signals in your reversed splitter. An improvement in the system NF by that magnitude would provide the same improvement as would an antenna with an increase of gain of 4 dB on your channel of interest. |
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ADTech, Thanks for your input. I appreciate it. The Longley-Rice coverage map for the future home of KYCW-LD doesn't give me much hope, but it will be broadcasting from a 2000' tower, so I've got to try. :) I'm getting 32 channels/subs reliably now. I acquired a 50' Rohn 25G, so I'm going to gain 15' in height soon, which should help.
http://www.rabbitears.info/contour.p...2.941138888889 Quote:
Also, I think I know the answer, but is there a method of combining the 4 antennas that doesn't introduce the loss of a splitter/combiner? Multiple tuners are not an option. Thanks! |
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So, having two preamps and having two coax lines would allow you to combine after the two power inserters and avoid a custom power supply needed to power two preamps through one coax. No matter where the combiner is located, after the UVSJs or after the power inserters, you are still combining two UHF antennas aimed in different directions and two VHF antennas aimed in two different directions. This means that if two antennas pick up the same signals, when they arrive at the combining point they will interfere with each other if they are not in phase. The only way to avoid that is with single channel amplifiers, single channel antennas if necessary, and combine into one coax like a CATV headend. http://forum.tvfool.com/attachment.p...0&d=1439422441 |
KYCW-LD is using the antenna previously used by now-gone KSPR at just a bit over 1800' AGL.
I have to tell you I generally despise the 7777 because it's used so inappropriately so often. Too many people think that more gain is better and it usually isn't. If that thing was kept behind the pharmacy counter and sold only by expert prescription, I'd have a very different perception about it. Powering multiple preamps with a single line can be done, it does require some knowledge about the amps in use, some creativity and it's not without its possible drawbacks. |
There is still a sensitivity problem if a splitter used as a combiner after both preamps. It occurs because any front end noise contributed by the preamp connected to the mis-aimed antenna adds to the noise of the preamp of the marginal signal. To get any advantage, you could either notch out channel 19 from the mis-aimed preamp output, or attenuated the output of that preamp by enough to allow the desired signal to override the undesired noise. If you opt for an attenuator, a good place to start would be 6 db.
If you opted to filter the noise from the mis-aimed antenna, Warren electronics says that they still have some channel 19 Jointennas. http://www.warrenelectronics.com/ant...Jointennas.htm A Jointenna may only allow channel 19 through, or not; you'd only know if you tried it. |
Warren Electronics has closed (owners retired).
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If this is real, they have some NOS channel 19 Jointennas.
https://picclick.com/Channel-Master-...718785944.html |
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If a 2-way splitter, used as a combiner, has to pass power to two preamps and it has diodes, will the diodes be reversed biased and not pass power?
https://www.amazon.com/Valley-2-Way-.../dp/B001X3MGFU http://www.homedepot.com/p/Ideal-2-4...-332/202276264 This will work: http://forum.tvfool.com/attachment.p...2&d=1502409722 This will not: http://forum.tvfool.com/attachment.p...1&d=1502412698 |
Those are both examples of incomplete markings that don't include the diode symbols. Sat splitters have to pass power from any of the "output"" ports back to the "input" port so the receiver can power the dish-mounted electronics.
The Ideal splitter you indicated is one of my favorites as is the Holland HFS-2D whose label does properly indicates the internal function. http://pimages.solidsignal.com/HFS2D_zoom.jpg If polarity matters for DC-passthrough (and it would in the case of the splitter that is performing antenna combiner duty), there is at least one splitter out there that does not used DC-blocking capacitors on the output so it doesn't need diodes. That would be the Channel Plus 2512A. |
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Yes, the Channel Plus 2512A might work. I wonder what is inside and how much current it will pass?
http://forum.tvfool.com/attachment.p...1&d=1502411380 1 GHz bandwidth • 3.5 dB insertion loss (as a splitter) • Passes DC IR signals on the coax • Use as a signal splitter or combiner • DC and I/R passing • Provides a 1 GHz bandwidth • Ideal for antenna and coax operations If the 2512A is used as a splitter between the preamp and the power inserter, would it be necessary to put a DC block on the output for the second TV? |
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I appreciate your help. I believe you are proposing something like this?
http://forum.tvfool.com/attachment.p...1&d=1502464374 |
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Add to the list of potential splitters that include direct pass-through of DC the basic Ideal cable/TV splitter that anyone can pick up from Home Depot for $4 (85-132). The basic splitters that do not pass DC power simply have a low-value blocking capacitor in series with the output port. For "satellite" splitters, they simply put a diode in parallel with the blocking cap to allow power to pass from either output back to the input. The sat-rated splitters also appear to use higher quality transformers and much better layout and construction techniques so as to extend their bandwidth. As far as maximum current carrying capability, it's hard to say. It appears the transformers through which power must pass are all wound with a wire somewhere around 28-32 gauge. Several of the samples I have include DC pass on one port only. All of these simply have a coil connected directly from the input to one of the outputs and include the blocking cap on both output legs. Quote:
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Thanks, |
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There seems to be a difference of opinion between ADTech and Tower Guy about the potential success of combining 4 antennas in this manner. With so many factors involved, I would just have to try it. Quote:
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At first I was puzzled by ADTech not suggesting the Juice preamp which is made by the company he works for. The Juice has a low noise figure (good) and is resistant to overload. My guess is that the power supply would need to be custom to power two preamps through one coax. Their power inserter would handle the current for two, but the power supply might not. The PCT SMPS512UTRH for the second generation 7777 might work: http://forum.tvfool.com/attachment.p...1&d=1502498374 I favor the two coax and combine after the two power inserters approach, because it avoids the power supply problem and allows you to test each antenna system separately. Also, there is the FM interference problem. The Juice does not have an FM filter and you have a strong local FM transmitter that might cause a problem with VHF reception. I did an FM signal report based on your TVFOOL report, but it isn't accurate enough because you are so close to KMYK: http://www.fmfool.com/modeling/tmp/5...3/Radar-FM.png Can you please do an exact address FM signal report so that I can see how close my estimate was: http://www.fmfool.com/index.php?opti...pper&Itemid=29 Any maybe while you are at it, a more recent TVFOOL report (which will still probably have some errors because the tvfool database isn't up to date): http://www.tvfool.com/index.php?opti...pper&Itemid=29 |
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I am inclined to believe Tower Guy because he has extensive RF experience and knowledge, but I would have to demonstrate it to myself to see what would happen and I don't think I have the necessary equipment. If one antenna and preamp was receiving channel A with an SNR of 18 dB, and the second antenna (aimed in a different direction) and preamp was receiving channel B also with an SNR of 18 dB, would the SNRs of both signals then be 15 dB after combining because of the NFs adding together, or would the result be difficult to predict because of the contribution of other "noise" from the antenna not properly aimed at the desired channel? |
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Thank you for the clarification.
I think I understand how the notch filter (or attenuator) on the output of the antenna not aimed at the desired channel will help, but is there any other way of combining that would retain the SNRs of the antennas not combined for the OP other than single channel amps as in a headend? Is combining after the power inserters using two coax lines, equivalent to combining after the preamps using just one coax line as far as results are concerned? |
Combining the Ouput of Two Preamps can Reduce Weak Signal Sensitivity
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I assembled what equipment I had on hand to investigate what happens when the output of two preamps are combined with a splitter in reverse.
Equipment used: Blonder Tongue HAVM-1UA Agile Modulator - 470-806 MHz, output ~ +30dBmV Sadelco DisplayMax 800 Signal Level Meter (SLM) Sadelco 719E Signal Level Meter (SLM) 2 Channel Master 7777HD Preamps RCA TVPRAMP1R Preamp to increase sensitivity of SLMs 2-way splitter used as a combiner 3 20dB fixed attenuators 1 10dB fixed attenuator 1 6 dB fixed attenuator For a test signal, I used the video carrier of analog channel 20 from the modulator. The 6 dB attenuator was used to adjust the sensitivity of the SLM to keep the readings centered on one range of the SLM to avoid switching to another range. The noise floor of the measurement system was well below the noise from the 7777HD, so the NF of the RCA preamp could be ignored. http://forum.tvfool.com/attachment.p...1&d=1440873529 I made the first measurements with the DisplayMax 800 SLM, on the right in the photo. The modulator signal is quite stable within 0.1 dB, and the SLM has 0.1 dB resolution. However, I had a problem measuring the random noise from the CM7777HD because the SLM digital display would follow the rapid changes, making it difficult to read. I switched to the 719E SLM (on the left) and its slower response was able to average the noise reading for me. The noise was measured on a nearby channel not used by the modulator. http://forum.tvfool.com/attachment.p...1&d=1502665287 http://forum.tvfool.com/attachment.p...7&d=1498343132 Code:
SNR of CM7777HD #1 Code:
SNR of CM7777HD #1 combined with CM7777HD #2 My equipment isn't lab grade, but I have enough confidence in my measurements to conclude that combining the output of two preamps with a splitter in reverse causes a loss of sensitivity that can have a critical negative affect on marginal signals near the digital cliff. |
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Hello,
I wanted to show off a bit. I completed erecting my tower. I am receiving all channels I expected. What surprised me is I didn't need a preamp to get all those channels. 35 miles is the closest tower and 70 miles is the farthest. I appreciate everyone's help along the way. I'm thinking about what else I can play with. Maybe something with FM or FTA. https://forum.tvfool.com/attachment....7&d=1553180949 https://forum.tvfool.com/attachment....1&d=1553180974 |
What a great looking setup! How high is your tower? Is that a project box or a rotor I see up there?
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Thanks! It's a 50' Rohn 25G with a 10' mast. The box is a demarcation box for coax connections. It made weather proofing the connections easier. It's big enough to house a preamp if I need to when the trees leave. I had to play with different length coax cable connections to deal with multipath interference.
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Wow that's too much on that tower and is the tower grounded
and when you use a Gray box's that size I can believe the insert loss And you should have the uhf on top and the seller's below. Multipath.is becuse of the box??stand back and tack a good look at where it sits and when you put your VHF in the same box. Is not good that is why you keep the vh F out of reach.frum the uhf. And that is why you are getting multipath and if you are looking for true vh F you should use a separate feed line for vhf.AND use an A/B switcher frum VHF/UHF!!! and the uhf antenna Direct 91x are too far apart that should be 3ft apart and the feed line frum the ANTENNA to the T connections should be 3ft long,and the ANTENNA Direct 91x Should be faced the same way and the same for the seller's LAB antennas too that can all so creat MULTIPATH as well It looks like you have a good mess too fix well I had the same set up but the other way around and with the title sistom for the 91xg!!!and no MULTPATH Prblem'S and the hi vh F 1500miles of RECEIVE range with a channel master 7777amp And for CABLE I used RG8u frum the ANTENNA to the amp's board and close to the ANTENNA as possible for best results!!!and a good rotor too tern all 4.ANTENNAS And the uhf RECEIVE range with a 45+45dbg,Johansson anp kit 200miles of RECEIVE range SIGNAL strength of 100%on A 150ft tower and no dropouts with my inverted V antenna for the HAM band use and my spectrometer for all my needs. |
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Do not need a combinder? Or a T connections to add a vhf/uhf ANTENNAS |
WELKIN,
That is a fine looking and performing setup you have! Congratulations on a job well done! Joe AZ |
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And yes look'S that'S a lot of money involved And the best ANTENNA and a NICE TOWER!! And what A shame on the RECEIVE range But with a few changes and a good tweak!! And defentle no dropouts and all channels Day or night and then you will have One He'll of an ANTENNA set-up!!!! Let's tweak it and have no dropouts single!!!! Just like ten Hours of work. |
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HI Gain antenna when stacking them Have to be TRUE in line with one another not off set,same with the ANTENNA Direct 91st an OTHER HIGH gaIN antenna when stacking them they have to stay true Not off set it makes MultiPATH, maybe you can adjust your antenna 'S And to tune the ANTENNA 's but you have to get rid of the DISTRIBUTION AMP. Hi GaIN antenna do not like them they all so creating MULTIPATH. And they say not to use them on hi gain ANTENNA like the 91xg&seller's lab! HI Gain!!! And why you should use a good amp I know you do not want too spend more money!! But when stacking ANTENNAs the amp is used to tune the ANTENNA's iT's Just not about the dbg,it all so tunes. The antenna. |
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I went in to this to achieve the goal of getting all channels available in my area to combine in to one input on my DVR (TiVo). I understand why I have multipath and the inherent problems with this setup. While not ideal, this set up is performing flawlessly with no dropouts and all available channels. There are NO amount of tweaks or changes that would make ANY noticeable difference to the end user to enhance the experience. 100% signal vs. 85% signal does not matter in this case. I do not know how else to put it. As ADTech said, every antenna installation is an experiment. I had a blast over the last 3 years getting to this point and have learned some things on the way. I did all the work myself with the help of my 8 year old son. Nothing you suggest will make anything about this experience better. I am done responding to you now. Have a nice day. |
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Let the man have his joy; he earned it. rabbit |
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