I am especially interested in receiving Denver channels 7 & 9 which unfortunately are in the high VHF. I currently have an 8-bay bowtie antenna (Xtremesignal HDB8X) on a non-penetrating roof mount. The VHF gain of this beast is not available from Xtremesignal, although I've asked, so I assume it's NADA. I am using the signal level /signal quality of an LG FPTV to estimate quality. I also have a SiliconDust HDHomerun networked tuner attached, and the goal is to record OTA broadcasts using the available DVR software. So far I have learned that I need a pretty good signal to get a usable recording. A quality factor of 55+ is usually required.
What has me baffled is that before I mounted the antenna, I had it resting upright in the TVroom at the top of the house, indoors pointed at about 100 degrees (resting on the wall, pointed slightly down) and I was getting a pretty good signal. I thought no problem, up on the roof and pointed at the proper angle will make this a piece of cake! Well that was wishful thinking. Up on the roof, pretty unobstructed yields no usable signal, despite the calculated TVFool values for VHF Ch 9. I am wondering how I ever saw a decent signal indoors at all. It seems surreal.
Anyway I am forced to face the reality that the gain in the VHF for the HDB8X must be 0 (or less) and have purchased an RCA ANT751R antenna to see if I can rescue a usable signal. I have attached a spreadsheet with measured values at different angles, as well as a photo of the install. I have a Winegard LNA-200 at the antenna feeding 50 ft coax with a splitter at the TV feeding it and the SiliconDust network receiver. The amplifier makes only a tiny improvement in signal level, if any.
Thanks for the tvfool report, the interesting antenna photo, and the xls file. I had trouble with the xls file. It downloads as a php file, so I had to change the file extension to xls. I then tried to open it in OpenOffice Calc, which didn't work (too many errors), but I was able to open it in Microsoft Excel Viewer.
KMGH ABC, real channel 7 and KUSA NBC, real channel 9, are on VHF-High channels. Your antenna is primarily for UHF channels 14-51, and doesn't receive VHF channels very well because it isn't tuned for that band and the baluns are probably printed circuit baluns that don't pass VHF signals very well.
You need to add an antenna for VHF-High and combine it with your HDB8X using a UVSJ, or replace it with a combo antenna that will receive UHF and VHF-High.
In addition, the terrain between Denver and your location has peaks that will block TV signals. If you click on a callsign in your report you will see a terrain profile. The transmitter is on the left, and your location is on the right.
Anyway I am forced to face the reality that the gain in the VHF for the HDB8X must be 0 (or less) and have purchased an RCA ANT751R antenna to see if I can rescue a usable signal.
The ANT751 has more VHF-High gain than the HDB8X, so it might give you 7 and 9, but I think you need a little more VHF-High gain than that for your 2Edge Denver signals. The 751 has less UHF gain than the HDB8X.
Thanks for the reply. Yes I have looked at the terrain report, and located my place fairly precisely. It is in the transition from yellow to red, so I know it will be a challenge. I do not have enough experience (yet!!) to know if it is doable or not. As you may have noted from the spreadsheet (sorry about the difficulty opening; I have Office365 which uses the xlsx extension which does not seem to be allowed by TVFOOL, so I changed it) I get some channels from Kansas which is several hundred miles away! But those mountain peaks are a pain. I still cannot understand why I got a pretty good signal inside.
Inside I could easily get a viewable picture, just not good enough to record with the SiliconDust unit. I wonder if diffraction over the peaks is causing "hot" (and "cold") spots in the signal. To see the actual view, go to the webcam at www.apcat.org. I would move the antenna mount except it's weighted down with 140 lbs of concrete blocks and would need to be completely taken apart, moved and put back together...what a pain.
Anyhow I just put up the RCA ANT751R which I understood to be a high VHF antenna with a 7.5 dB gain. Still no joy. I get fewer channels, but surprisingly close to the 8-bay. Nothing whatever on VHF 9, just a bit on 7, but not enough for an image.
What has me baffled is that before I mounted the antenna, I had it resting upright in the TVroom at the top of the house, indoors pointed at about 100 degrees (resting on the wall, pointed slightly down) and I was getting a pretty good signal.
Pretty good signal of what?
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I still cannot understand why I got a pretty good signal inside.
That is odd, but there could be a reason, as of now unknown. There could be local noise interference that is stronger at the roof location; the noise level is higher on VHF which reduces the SNR (HDHR SQ).
Are there any trees in the signal path? Trees kill TV signals.
As the signals come over the peak, they are scattered, which presents an uneven wave front to the antenna. You end up with hot spots and cold spots. Some installers "walk the roof" with a temporary antenna before mounting it. Often the best location for the antenna isn't the most convenient location.
Yes I have looked at the terrain report, and located my place fairly precisely. It is in the transition from yellow to red, so I know it will be a challenge.
Based on my estimate of your location, I also see that. Red is a weak signal; no color is even weaker. The coverage is very spotty.
I do not have enough experience (yet!!) to know if it is doable or not.
You will, after doing the experiments for this project.
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Not sure what to do next; just give up?
Too soon to give up. You will not be happy until you have tried.
Sometimes it helps to tilt the front of the antenna up to catch the signals coming over the ridge. The 91XG has a tilt feature, but that is a UHF antenna. You would need to do a custom tilt with a VHF antenna.
First MANY thanks for the first rate suggestions and discussions. I haven't put up a TV antenna since the 60's (ugh!)
some replies:
"Pretty good signal of what?">>Channel 9,-it's all about 9 Hi-VHF 160 deg Mag
"Don't buy the MCM 33-2230 UVSJ UHF/VHF combiner.">>Too late. I bought it hoping to mount it on the mast, since it is in a weathertight enclosure. I agree it does not work well. I tried combining the VHF of the RCA751 with the UHF of the 8-bay and got zero VHF as a result. I intend to send it back.
Thanks for the antenna and combiner suggestions...ordering tomorrow.
Just to prove that I am not crazy and hallucinating I have attached two photos. I took down the RCA 751 and stood it on end against a wall, intending to rotate it by hand to find the best signal either inside or hanging out the window. The TV was set to Channel 19 (real #9). The signal was 54 and the quality 100%. Note that the tower is directly behind where the photo was taken! Moving the antenna just a little bit, less than a foot, reduced the signal strength. Moving it 4-5 feet and the signal disappeared. This is the same result I got with the 8-bay bowtie. Diffraction?! Is it possible the 25 ft cable is acting as an antenna?
Thanks for the interesting photos. CH 9 does need to be stronger.
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Moving the antenna just a little bit, less than a foot, reduced the signal strength. Moving it 4-5 feet and the signal disappeared. This is the same result I got with the 8-bay bowtie. Diffraction?!
The CH 9 signal at your location has a non-uniform field. You must locate your VHF antenna where the CH 9 signal is the strongest, which will require trial-and error. A preamp will not help you if a good signal isn't coming out of the antenna terminals; GIGO.
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Is it possible the 25 ft cable is acting as an antenna?
You can test that theory by grounding the coax.
If the antenna is outside, the coax shield should be grounded with a grounding block that is connected to the house electrical system ground with 10 gauge copper wire for electrical safety and to reject interference. For further compliance with the electrical code (NEC), the mast should also be grounded in a similar manner to drain any buildup of static charge, but the system will not survive a direct strike.
I still cannot understand why I got a pretty good signal inside.
Not sure what to do next; just give up?
I'd try the 751 antenna outside at a very low height - perhaps 4' or so, and clear toward the south. At this low height you should net about 6 db extra antenna gain.
Here's how I figured that;
I looked at the angle up to the nearest mountain at 168 degrees that is line of sight. It was 3 degrees up angle. The terrain in front of the antenna slopes downward at about -16 degrees. On channel 8, over flat ground, at 3.8' height, the uptilt calculates to 19 degrees. With the downtilt of your terrain, the main lobe of the antenna will be elevated at 3 degrees uptilt.
I'd try the 751 antenna outside at a very low height - perhaps 4' or so, and clear toward the south. At this low height you should net about 6 db extra antenna gain.
Here's how I figured that;
I looked at the angle up to the nearest mountain at 168 degrees that is line of sight. It was 3 degrees up angle. The terrain in front of the antenna slopes downward at about -16 degrees. On channel 8, over flat ground, at 3.8' height, the uptilt calculates to 19 degrees. With the downtilt of your terrain, the main lobe of the antenna will be elevated at 3 degrees uptilt.
Well that is certainly non-intuitive. One issue will be the trees. Some are ~30 feet high, to the top of the house. Perhaps I'll give it a try tomorrow.
Well I got the Stellar labs deep-fringe antenna (30-2476) and mounted it on the roof, and have tried it at two different orientations (about 160 and 140degrees or so). In order to do this I had to dismount the 8-bay bowtie. I thought I would put it back inside at the spot in the corner next to the TV where I got good reception for channel 9, which is close to the spot in the earlier photo I posted.
Well the Stellar Labs did virtually nothing. Got a signal that was better at 140 degrees instead of 160, the actual position of the station, but the signal level (~30) was too low for a reliable picture.
However, back inside with the 8-bay I have a pretty good signal (54 level, 98% quality). This is with the 8-bay just leaning against the wall, tilted slightly down. Any movement up, rotated, slid right etc., either reduces or zeroes out the signal. So I am right back where I started! I thought "doing it right" (up on the roof, proper orientation etc., could only make things better!)
To make matters worse, so far I cannot get channel 24 (PBS) with the Stellar Labs antenna on the roof which I could with the smaller RCA751, but perhaps rotating will help. It may also be that this more directional antenna is more selective and has little or no gain in the UHF, so it's just a wind vane at this point.
My conclusion so far is that diffraction over the hills has produced "hot" and "cold" spots and I just lucked out the first time. No joy following the traditional path. Much effort and expense for little gain (pardon the pun)
Anyway at a loss as to what to do except leave the antenna in a corner where it will no doubt raise serious objections. There is both an attic above and a large closet nearby, so I might experiment with those options.
I had to dismount the 8-bay bowtie. I thought I would put it back inside at the spot in the corner next to the TV where I got good reception for channel 9, which is close to the spot in the earlier photo I posted.
Were you using a preamp when you got good reception inside?
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Well the Stellar Labs did virtually nothing. Got a signal that was better at 140 degrees instead of 160, the actual position of the station, but the signal level (~30) was too low for a reliable picture.
Were you using a preamp for that test?
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However, back inside with the 8-bay I have a pretty good signal (54 level, 98% quality).
Were you using a preamp for that test?
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To make matters worse, so far I cannot get channel 24 (PBS) with the Stellar Labs antenna on the roof which I could with the smaller RCA751, but perhaps rotating will help. It may also be that this more directional antenna is more selective and has little or no gain in the UHF, so it's just a wind vane at this point.
That is to be expected; the 30-2476 has little UHF gain.
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My conclusion so far is that diffraction over the hills has produced "hot" and "cold" spots and I just lucked out the first time. No joy following the traditional path. Much effort and expense for little gain (pardon the pun)
Pun allowed; at least you haven't completely lost your sense of humor.
It doesn't make sense; something is missing.
Why would a UHF antenna inside pick up a VHF signal that a VHF antenna outside can't?
Indeed!
Were you using a preamp when you got good reception inside?
Were you using a preamp for that test?
Were you using a preamp for that test?
That is to be expected; the 30-2476 has little UHF gain.
Pun allowed; at least you haven't completely lost your sense of humor.
It doesn't make sense; something is missing.
Why would a UHF antenna inside pick up a VHF signal that a VHF antenna outside can't?
That doesn't compute.
All the inside measurements were done without the benefit of an amplifier. The Winegard LN200 that I use is outside on the mast, so all outdoor measurements are done with the preamp. That said I see little or no improvement with the preamp. I put some half inch wire mesh behind the bowtie to join the reflectors together and that might make a tiny improvement perhaps from 52 to 54 signal level.
I have found that the closet, which is behind the TV in the earlier photo, is a good place for the 8-bay as long as it is against the outside wall, essentially adjacent to where I placed it in the measurements in the last message. This will be acceptable as it is entirely out of sight. I am tempted to place the bowtie outside but against that same position which works indoors to "see what happens", but the last time I moved outside it did not go well.
One option to consider (only because I am a glutton for punishment) is to get another bowtie for outside to get the few missing stations (PBS, #24). However since I am getting reception across the VHF/UHF bands indoors, I fear that there may be a conflict trying to simply combine them. Is that correct?
Otherwise, perhaps building a UHF and a high VHF Hoverman type antenna (they're nice and flat) might be an approach.
I too am baffled by the VHF signal with the bowtie; unless theweather or some other variable emerges as the improvement I'm going to just take it.
The one thing I will try out on the Stellar antenna is to see if I can get PBS, #24 as I did get it with the RCA 751, even at a lower altitude. There I used a camera tripod to mount the antenna and simply rotated it until the signal was maximized.
All the inside measurements were done without the benefit of an amplifier. The Winegard LN200 that I use is outside on the mast, so all outdoor measurements are done with the preamp. That said I see little or no improvement with the preamp.
It sounds like there is a problem with the preamp. What happens if you go from the 30-2476 directly to the tuner?
Yes many things here don't make sense, which is always a red flag. I will do as you suggest today and remove the amplifier from the circuit. My recollection is that I see little benefit from the amp. I have a different, indoor only, amp that I can also try.
Yesterday using the VHF antenna 30-2476 I climbed on the roof and rotated the antenna as my wife monitored the signal. I pulled in UHF #24 (PBS) with a good signal (60/100 on the LG TV).
Alas, as good as the NBC channel 9 is with the 8-bay bowtie (another mystery) it is not good enough for the SiliconDust HDTuner. While it is visually perfect in real time, it is not good enough to view over the network regardless of a wired or wireless connection. The net result is a "Pyrrhic Victory". I still need more gain and I have solved only a small amount of the problem.
We'll I see that you have 2 good antennas I Wood go like ten feet higher OFF the roofs line, and a channel master 7778 amp, and they say height is everything when receiving tv channels,
I did that and oriented the Stellar VHF antenna to 160 deg to point at the VHF #9 KUSA station but no signal there at all. Essentially got "the usual" set of high power signals although as might be expected I lost the UHF#24 the PBS station.
I'm a bit at a loss as to what to do next except start moving antennas around on the roof to find a hotspot up there. I'm a bit reluctant to add height to the mast as we have extremely high winds here and the leverage created by height will surely bring this thing down as I have a weighted down, non-penetrating roof mount.
I might try bringing the VHF antenna down to the location I'm getting a good signal with the bowtie. It would look strange in the room but there is a small attic above.
Really bummed out. Lot's of work for very little gain.
