Reception in Boulder, CO Foothills
 

Iam struggling to receive OTA signals from Denver. My TVFOOL reception report is here:
http://www.tvfool.com/?option=com_wr...e2cbfa5f7ed489

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.

Any advice would be welcome.

Here is the spreadsheet and photo. Didn't come thru first time.

Welcome, acat:

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.

KMGH
http://www.tvfool.com/?option=com_wr...dALLTV%26n%3d7
KUSA
http://www.tvfool.com/?option=com_wr...dALLTV%26n%3d8
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.

A suitable VHF-High antenna would be an MCM 30-2475 or 30-2476. They are inexpensive, have poor assembly instructions, but perform well.
http://www.mcmelectronics.com/produc...-2475-/30-2475
http://www.mcmelectronics.com/produc...-2476-/30-2476

UVSJ
http://www.solidsignal.com/pview.asp?p=uvsj
http://mjsales.net/products/tru-spec...ant=1198505857
https://www.antennasdirect.com/store...FUmRfgod9YAKRw

Don't buy the MCM 33-2230 UVSJ UHF/VHF combiner.

Aim the VHF antenna at 159 degrees magnetic. No guarantee because of the hills, but I think it will work.

A suitable combo antenna would be the Winegard HD7698P.

Thanks for the reply
 

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.

Not sure what to do next; just give up?

Did you use the preamp with the 751?
Pretty good signal of what?
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.

http://forum.tvfool.com/attachment.p...5&d=1466633825

http://forum.tvfool.com/attachment.p...6&d=1446858514

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.

http://forum.tvfool.com/attachment.p...6&d=1466635850

KMGH and KUSA are both using circular polarization, so the best reception might be at an odd angle for the elements, rotated away from horizontal around the boom axis.
http://www.rabbitears.info/tvq.php?r...ms&facid=40875
http://www.rabbitears.info/tvq.php?r...ms&facid=23074
You will, after doing the experiments for this project.:)
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.

Thank You
 

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.

"A suitable VHF-High antenna would be an MCM 30-2475 or 30-2476. They are inexpensive, have poor assembly instructions, but perform well.
http://www.mcmelectronics.com/produc...-2475-/30-2475
http://www.mcmelectronics.com/produc...-2476-/30-2476

UVSJ
http://www.solidsignal.com/pview.asp?p=uvsj
http://mjsales.net/products/tru-spec...ant=1198505857
https://www.antennasdirect.com/store...FUmRfgod9YAKRw"

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?

This is pretty frustrating!

Thanks for the interesting photos. CH 9 does need to be stronger.
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.
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.

http://forum.tvfool.com/attachment.p...9&d=1441917363

Yes, I agree. It will require perseverance.

The terrain between KUSA and your location is difficult. but VHF signals can usually make it over the peaks by refraction better than UHF signals.

http://forum.tvfool.com/attachment.p...9&d=1466694834

This is what the profile looks like using different software:

http://forum.tvfool.com/attachment.p...0&d=1466705013

http://forum.tvfool.com/attachment.p...1&d=1466706541

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.

Lowering the Antenna
 

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.

Diffraction, Diffraction, Diffraction
 

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.

Pretty humbling experience.

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.

It sounds like there is a problem with the preamp. What happens if you go from the 30-2476 directly to the tuner?

NO, NO. The 30-2476 is a VHF antenna. K24HQ PBS is a UHF station. The 30-2476 is NOT suitable for UHF.

The 751 is for UHF and VHF.

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,

Disconnected the LN-200 Preamp...
 

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.

We'll I no what you mean about that wind ,I am not that far from you I am in Massachusetts do you have an outdoor amplifier ,it makes a big difference in receiveing in ARE neck of the woods, well let me tell you ,a little bit about my antenna set-up I have 2,OF the labs 30-2476 stacked side by side with,2,HDB 91xg stacked side BY side 90Ft high, with the vhf I receive,17channels,And the uhf 29 channels, I ALL most for got,the Johansson amplifier kit, it's K o o l it has one VHF in at 30:DB ,and two uhf at 40DB and one to the tv, WELL make sure you, guide wire the antennas,and if you need!! helping!!Hands shout,it's better with 4,hands then 2,we'll be,safe and good luck,ps when the hard work is done, you will be happy with the results,

acat:

Thanks for making the test outside without the preamp.

That eliminates that possibility.

I'm running out of ideas, and it bothers me that I can't find a solution for you.

The 751 seems to work better than the VHF antenna outside for CH9. That suggests there is a problem with the VHF antenna.

The 751 and the 8-bay seem to do better inside without a preamp for CH9. That suggests that the CH9 signal is better inside, but why?

I wonder how the VHF antenna inside would do?

We'll may be the splitter might not be the right one OR hooked up wrong,

Next Steps
 

I have removed the splitter on more than one occasion and made a direct connection to the TV. I only use the splitter to feed the Silicon Dust Tuner & TV simultaneously. I have at one time or another removed everything from the circuit and put it back in to see the effect.

I too have been thinking of moving the VHF down from the roof inside to where the signal seems "better". The SiliconDust HDHR Tuner has some nice software that measures "Symbol Quality" as well as "Strength" and "Quality". When I checked the 46 Channels being received from the 8-bay indoors the symbol rate on CH9 and most of the others was ZERO and both signal and quality were bouncing around. I do have an extensive 2.4 & 5 GHz wireless network, but the only nearby source of interference is a Boulder County emergency services tower above me and 1 or two miles away. There could be reflected signals from the mountains in front of me I suppose. Grasping at straws a bit.

The fact that the antennas don't seem to be behaving as they are supposed to (VHF on UHF8-bay & nada on VHF) suggests that either diffraction, the local environment
or local sources of interference dominate reception. The signal reports from TV Fool & FCC both indicate I SHOULD have a signal...but I don't. I think it's time to start moving things around (and down).

I would wholly agree with that assessment. Pinning it down gets more difficult and usually requires more tools and more patience.

That's usually a good place to start. If you could get your hands on either a spectrum analyzer or the poor guy's equivalent, an SDR setup, it would speed things along tremendously as you could nearly immediately see if there are localized interference sources.

One other thought comes to mind. When I was troubleshooting cable TV distribution systems that had old lengths of RG59 connected with F-81 adapters, sometimes the high (UHF) channels were OK, but the low (VHF)channels were snowy (analog).

What was usually wrong was a bad connection at the F81 adapter. The connection LOOKED OK, but either the center conductor or the shield wasn't making contact. This created a gap that had a small capacitance which would allow the UHF signals to pass with little loss, but the low channels were attenuated because of the high reactance at low frequencies.

So I replaced the F-81 adapters or just ran a new length of RG6, and everybody was happy.

Other Thoughts...
 

Fortunately no F81 connectors in this setup!

I do have a Cellular Amplifier in the house (and an antenna outside) to aid with data and voice communication. I'll try taking that offline to see if it's broadcasting a signal that may be interfering. I don't know why I didn't think of that before.

SDR (software defined radio) usb sticks are pretty cheap; do you thing they would provide a handy way of evaluating signal strength with a laptop? Somehow have "radio" and "TV" in separate locations in my mind...never thought to connect the two!

It doesn't only happen with F-81s, it can also happen with the F connector at the end of a coax line.

If I were there with you, I would be making measurements of signals with my signal level meter (SLM) as I try different antenna locations. You can do almost the same thing with the signal strength readings from your TV and HDHR.

What ADTech was talking about is a way to locate signals that are on frequencies not used by TV transmitters that could be strong enough to interfere with TV reception. The tool that is usually used is a spectrum analyzer. but they are expensive. A SDR dongle and the appropriate software can do almost the same thing.

Forum member chris1379 just put one together. You can see his scans here starting at post #45:
Help with one VHF Channel, Page 3
http://forum.tvfool.com/showthread.php?t=15968&page=3

http://www.rtl-sdr.com/buy-rtl-sdr-dvb-t-dongles/

http://www.highdefforum.com/local-hd...r-10-00-a.html

The next step up is the RF Explorer, a small hand-held spectrum analyzer
http://j3.rf-explorer.com/42-rfe/faq...ine-discussion

If you go to Pete's SDR thread
http://www.highdefforum.com/local-hd...r-10-00-a.html

you will not see his images unless you are signed in, but will find them in the attachments below.
attachment 1 is from his post #1
attachment 2 is from his post #7
attachment 3 is from his post #10

Latest Results...
 

Rabbit-many thanks for the links & photos; it would be great to take a more quantitative approach and nice to not have to lug antennas and cables around. I'll give it a look and see if it's something I can undertake.

Over the weekend I took both antennas down from the roof and deployed them around the outside of the house in various locations. I have been using the SiliconDust software to record signal level, quality and symbol quality. The latter is supposedly the most important. I mounted the antennas on a tripod so I could rotate them easily and also tilt them vertically with some reproducibility. I put the SiliconDust software on a Windows 10 Slate so I could read the signal quality factors while standing at the antenna. This made life easier than running around.

I found a good symbol quality (nearly 100%),and signal level by pointing the VHF antenna off the 160 degree direction for channel 9, but it was very sensitive to the exact position & orientation of the antenna. This direction was towards a low hill several miles distant. I was prepared to leave well enough alone, but suddenly and inexplicably lost the signal and could not get it back. Still a mystery.

I placed the 8-bay bowtie in approximately the same position and tuned its orientation to maximize the various signal level/quality factors and it did just as well without the extreme sensitivity to pointing direction. All in all the quality (symbol level also 100%) level was high enough so that I was actually able to record! We'll see how reproducible this is.

In a separate experiment which I did first, I thought I might be able to combine the VHF & UHF signals using a Hi-low filter combiner (Blonder Tongue) but that seemed to degrade the overall signal quality so I didn't pursue it any further. Perhaps a better method of combining UHF and VHF signals exists?

So for now I'm going to see how "robust" the signal is day-to-day with the 8-bay. If it remains stable I'll mount it permanently. I am getting about 37 channels ranging from channel 7 upward including the main one, channel 9. Oddly, I cannot receive the nearby channel 24 (PBS). This has been true all along; I can either get channel 9 or channel 24, but not both. The orientation also makes no sense as I am not pointed at the Denver antenna at 160 degrees. I am pointed at perhaps 100 degrees straight out to the eastern plains. I will not be surprised to receive a few Kansas stations when atmospheric conditions are right; that has happened in the past.

Sdr
 

Rabbit

Thanks for the SDR references. I checked out Pete Higgins posts and Chris's use for his challenging reception via your links and this looks useful for my problem, not to mention the myriad other uses. Ordered one today from Amazon.

I've gotten bitten by the Raspberry Pi bug and looks like a turn on SDR is to follow!