Please help with reception in Tucson, AZ

[vt6364]

Hello all,
I have been using TVFool for many years; Thank you for all the great info. We recently moved to Tucson, AZ, and it's my first time posting for helps.

I read the recent post by DesertRat ( http://forum.tvfool.com/showthread.p...ghlight=Tucson ) with much interest because I am also in the NW area of Tucson.
My location is: http://www.tvfool.com/?option=com_wr...5b94f9637b9d00

As DesertRat described, Tucson has the main cluster of broadcast towers on Mt Bigelow in the East/NE, and some repeater towers in the South/SW. I receive most of the repeated channels from the south/SW, using an amplified rabit-ear-set placed inside my southern-most wall of my 2nd floor back bedroom. But I cannot get NBC, the one I want the most, from the South. I can get both the stronger (27.1 on 28 PBS) and weaker (9.1 on 16 ABC) ones, just !not! the NBC (4.1 on 4) from this same area. I bought a DB8e, the strongest antenna from my readings, tried aiming it to this 148-158 degree. Still no better results than my rabit-ear.
So this is my first question. Any idea why I cannot get channel 4 from the south? I have 2 theories: One is that maybe a nearby Police/Fire dispatch antenna is intefering with channel 4. I can see some very high, thin antenna sticks in the same direction to my channel 4 area. Or, Two is that channel 4 is a low-VHF which is much harder to pull in? But I think the rabit ear would be better for VHF already, and it's only 10-11 miles away anyway?

Then, my other attempt is trying to get the main broadcast from Mt Bigelow to the East instead. It'd be nice to also get other channels not repeated in the South like Fox and MyN. With the DB8e pointing to the 69-79 degree direction, hand-held outside my front window just to test (one 10-ft RG6 cable to a single TV), I can get ALL the channels listed in my TVFool profile. I even get some repeated channels from the South with this aiming (so I get 2 sets of PBS). This really surprised me since my location is in the mountain shadow, like DesertRat described. And admitedly, some channels are on the edge, sometime getting pixelated as the DB8e moves with my tired arms.
Excited with this, I proceed to set the DB8 in my attic (my house is in an HOA, and in a small lot, making an outdoor mount option not realistic). In the attic, I lost all from the East, only get some from the South and they are even weaker than my rabbit ear in the bedroom; and still no NBC! This test is still using a single TV, but with a longer, 25-Ft RG6 cable.
So here is my second group of questions:
- Would adding a preamp to attic-mount help pulling East channels? Which unit?
- I have barely enough space in the attic to house a long-boom style antenna of up to 8-Ft long, 1-2 Ft wide in the front and 4-5 Ft wide in the back, and luckily this thin box of space is pointing at the right direction for Mt Bigelow, but it's right next to the roof. Would an antenna of this style perform better than the reflecting-disc style DB8e? Which unit?

Thank you all in advance for your helps.

[GroundUrMast]

Reliable reception of real CH-4 will require an antenna designed to operate at that Low-VHF frequency. An Antennacraft Y526 would be an example of a specialty L-VHF only antenna. Large all channel antennas could be used as well. The problem with Low-VHF reception is that there is more interference in that frequency range (Real CH-2 through CH-6).

Sadly, your description leads me to conclude your attic is a challenging location for reliable reception. I have little hope that a preamp will overcome the impairments caused by the attic. But an RCA TVPRAMP1R is about $25... if that is not too much to risk you could try it.

I would exercise my right to install an outdoor antenna... The FCC is on your side... http://www.fcc.gov/guides/over-air-r...n-devices-rule. The HOA does not have the authority to stop you from installing and using an antenna for reception of OTA TV signals. I'm not advocating that you act as a bully, but I've got no sympathy for an HOA or neighbor who thinks they can act as a bully.

Given that you already own the DB8E, I'd suggest it be installed outside where it can do it's job. For reliable reception of real channel 9, KGUN, I'd use an Antennacraft Y10713. Of course, If you are able to reliably get the same programming via real CH-16, the large Y10713 can be ommitted.

[dmfdmf]

How committed are you to getting NBC (RCH4,VCH4)?

As GroundUrMast explained, RCH4 is on the low-VHF band at around 69MHz. The lower the frequency the longer the antenna elements need to be. The DB8e is a UHF antenna so its not going to work to pickup RCH4. The rabbit ear antenna may not even extend long enough to get sufficient gain for RCH4. If it has an UHF loop built in as well that tends to make its performance on VHF worse.

My recommendation is to run a test to see if you are wasting your time trying to get RCH4. If you have an extra piece of coax with F-connectors on each end that you can sacrifice, I would build a half-wave dipole antenna following the diagram at the bottom of this page; http://www.northcountryradio.com/Articles/fmdip.htm You don't need a balun for this test.

According to the math you need a T-length across the top of 6.8 feet. That is 3ft 5" per leg! Clip the connector off one end of the coax cable and get some lamp cord (solid wire might be better but will be harder to work with) from a dead appliance and cut a 3ft 5" length and then split into two wires. Attach it as shown in the diagram. Ideally the connection should be soldered but if can't do that just twist the connections and secure with e-tape. Mount the top of the T along the ceiling of a southern facing wall as high as you can go and still reach the TV input on the other end of the cable. Keep it about 8-10 inches from the top of the ceiling. Re-zero your TV tuner (very important) then plug in this test antenna and rescan. If it comes in okay with this custom tuned antenna then there is hope.

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hoa's and housing covennuts and etc. are well aware of the Federal Antenna Law.

http://www.fcc.gov/mb/facts/otard.html.

The Federal Antenna Law says that Yes you can install Broadcast Tv Antenna/s above the roof of any size so as to have Reliable Reception.

Some people that make up local hoa's housing covennuts and etc. are Bullies and are thinking you are not aware of the Federal antenna Law and even if you are , you will not understand the Federal Antenna Law that says Yes you can install antennas above the roof , and the hoa bullies can push you around.

Bullies come in all flavors , ones that will try and lay a line of 'logic' on you.

To talk you out of installing a Broadcast Tv Antenna.

And even sweet talking Bullies.

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The Current Tv Channels that are being Transmitted and Received in the , USA , Canada , Mexico , are.

VHF low band channels 2 thru 6.

VHF high band channels 7 thru 13.

UHF band channels 14 thru 51.

Your reception location has receivable Tv channels in all 3 Tv bands.

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Install antenna Above The Roof.

The Tucson area , close in to the mountains is not the best reception location due to multi-path reflections Tv signals bouncing all around off the mountains and reduced signal strengths of some Tv stations on Mount Bigelow.

The Tvfool report shows that the transmitters on Mount Bigelow are in the Yellow Reception zone.

I recommend a , ANT751/R antenna.

or

http://www.antennacraft.net.

HBU11K antenna.

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Here are some places to buy antennas and etc. .

http://www.amazon.com.

http://www.antennacraft.net.

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Aim the HBU11K or ANT751 antenna Up at the top of the mountain toward Mount Bigelow at about 69 degree magnetic compass direction.

Here is how to aim antennas , http://www.kyes.com/antenna/pointing/pointing.html.

Use a Real and Actual magnetic compass to aim antenna. Do not trust the compass in your phone.

Aiming the HBU11k or ANT751 antenna Up , puts the length of the antenna & antennas reception elements in line with the Tv signals that are coming over and bent downward from the ridge of the mountain.

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K04QP-D That is channel 4 , is Strong Signal Strength , at 48.7 NM(dB) , in the Green reception zone and is also LOS=Line Of Sight.

And will be received with the HBU11K antenna or ANT751 antenna even though the antennas are designed for VHF high band channels 7 thru 13 and UHF channels 14 thru 51.

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Can also Test reception by aiming the antenna at the surrounding mountains to get reflected signals.

This seems complicated , it is not complicated , reception of the Tv stations will most likely happen in short order.

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Most likely a antenna system amplifier will not be required.

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For 1 Tv connected use No splitter.

For 2 Tv's connected use a 2 way splitter.

For 3 Tv's connected use a 3 way splitter.

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Digital Tuners can develop -Digital Glitches- that are not cleared out with simple channel scans.

To clear tuner do Double Rescan.

http://www.wchstv.com/DoubleReScanAlert.pdf.

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More on Multi-Path.

Multi-path signal reflections bouncing all around are to be avoided , However some situations such as your reception situation , the mountains are mostly bare rock , multi-path can not be avoided , so is best make the best of the situation.

This is done by adjusting the aim and location of the antenna to get the Most Favorable Multi-Path and or Direct LOS Line Of Sight Reception.

[dmfdmf]

I'm beginning to think that teleview is right, the DB8e is just the wrong antenna for this location. In a true fringe area with this thing in clear air it probably works fine but if you put it in your attic you might as well rename it the MultiPath2000. Here are your choices as I see them;

Plan A: Get an ANT751 or HBU11 as teleview suggests and sell the DB8e on craigslist. Try it in the attic, try it in the attic with an amp, put it on the roof and wait for the HOA to call.

Plan B: You could get away with 1/2 of the DB8e so use one of the halves as a stand alone DB4. Put it in the attic and aim at 80 deg true and see what you get, try it with an amp. For this to work you'd probably have to modify the antenna a bit to get VHF-Hi channel ABC from the east. Let me know if you are interested and I can explain the mod.

Plan C1: The full on engineered solution. I'd still break up the DB8e into two DB4's and mount them independently as far away from each other as possible in the attic but one optimized for the stations at 180deg true and one optimized for stations coming from 80deg true. To minimize multipath I would notch out 495-545 MHz on the 180deg antenna and bandpass 495-545 MHz to get MyN, NBC & FOX from 80deg true. You would have to add the VHF mod to the 180deg true antenna to pickup NBC@69MHz and CBS@210MHz. Your line up would look like this [180d:NBC/CBS/ABC][80d:MyN/NBC/FOX][180d:PBS/TEL] if the notching works.

Plan C2: Alternatively, if you didn't care about southern stations Telemundo on RCH40@629MHz or the PBS RCH28@557MHz (PBS is also coming from the east, so you'd still get that network) you could filter and then join them. To minimize multipath, you could put the South facing antenna through a Low Pass filter with Fc at 495MHz and the East facing antenna through a High Pass Filter with Fc=495MHz and then combine them in a splitter and amplifier if needed (I think in the attic it would be necessary). Your line up would look like this [180d:NBC/CBS/ABC][80d:Myn/NBC/FOX/PBS/CBS/UNA]

Plan A would almost certainly work, Plans B, C1, C2 would be contingent on my VHF mod working so that would need to be tested first. Plan B would probably work but who knows. Plans C1/C2 would be highly experiment, hobby projects and cost at least $150 for filters in addition to a lot of testing of each antenna independently and then more testing when combined.

[vt6364]

I setup a dipole antenna following dmfdmf's instruction and confirmed RCH4 is available. Didn't work at first, but after some adjustments and aim it instead of just south-wall mounted, I was able to see 4.1 and 4.2. It's interesting how precise the aiming & dimension must be for this rudimentary indoor setup to get a clear picture (even from a LOS source). Simply changing the T-length by about an inch would cause it to pixelate, and about 3” would lose reception all together.

Will get the popularly recommended ANT751 & a TVPRAMP1R, and try them out next weekend. Then will keep one antenna that works and return the other -assuming I won’t accidently drop it from the 2nd floor window, or trip and land myself on it during this many trials Will also try pointing the DB8e at other mountains for reflected signals as teleview suggest; I still have some 20 days to return it.

Yes I read about FCC rulings. Attic installation is still preferred, simply because it’s a lot easier. My house is facing N-NW, and we are in small lots on a hill side, with the house to my east higher than mine. To get east channels, the antenna better be in the frontal-most part of the house to avoid having to reach higher than east-neighbor’s roof, and I don’t like having an antenna in front of the house myself, regardless of whether the HOA cares. The only pocket of attic space I have is luckily in this front part of the house, but it’s tiny.

I have some more questions, coupled with some details I didn’t mention before:

- Is it detrimental to put antenna on a flat roof (asphalt shingle)? I have such an area of one-story roof in the back (the front part is 2-story with gable-end tiled roof). If I cannot get anything from the attic at all, I am thinking I’d build sort of a wood stand, attach it to the roof to hold the south-aiming antenna in proper orientation; still easier than erecting a mast. My south view is mostly clear looking down hill, no need to go high (the 40/40 and 13/13 channel towers are visible from my back window).

- After trying the DB8e outside my front window, I also tried pointing half of it at 80degT, and lost many channels. Did not record exactly which ones were lost though, just quickly concluded that I need a full DB8e, even for outdoor.

- I did try pointing the 2 halves of DB8e separately to 180degT and 80degT in the attic. But they were still right next to each other, both connected to the DB8e’s combiner. Results were pretty much the same as when they both pointing at either direction. This is probably due to reflected multipath, since I don’t see as many South channels when outdoor pointing 80degT (only the RCH40 and RCH28 I think). So the DB8e (and any reflective-disc style) is more prone to multipath than the Yagi-style 751?

To dmfdmf,
Do you still think it’s worth rigging up 2 DB4s (if the 751 doesn’t do)? There is very little space (that is >= 40” hi for the DB4s) in the attic, so they will not be more than maybe 2-3 Ft apart in there. I am curious how you modify it to improve VHF (at the cost of some UHF performance I assume?), but not sure I’d spend $160 on the DB8e to experiment. Is the mod reversible and I can still return it?

Thank you all. You folks are really amazing, not just because of your knowledge, but also for how you’d spend the time to read and answer people’s questions like this.

+=>
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Many buildings in Arizona have stucko and stucko Wire.

Stucko Wire is a Effective , Disrupter , Reflector , Blocker , of Tv Reception.

Many buildings in Arizona have , Metal Foil Backed Insulation Panels.

The Metal Foil is , Disrupting , Reflecting , Blocker , of Tv Reception.

Tv antennas receive the best when nothing is , disrupting , reflecting , blocking , reception in the directions of reception.

[dmfdmf]

Originally Posted by vt6364

I setup a dipole antenna following dmfdmf's instruction and confirmed RCH4 is available. Didn't work at first, but after some adjustments and aim it instead of just south-wall mounted, I was able to see 4.1 and 4.2. It's interesting how precise the aiming & dimension must be for this rudimentary indoor setup to get a clear picture (even from a LOS source). Simply changing the T-length by about an inch would cause it to pixelate, and about 3” would lose reception all together.

That's good news. The difficulty is probably due to a number of factors such as VHF-Lo being difficult to pickup, homemade antenna and indoor mounting (with your body right there to change the field and impedance). At least you confirmed you are not chasing a ghost.

Will get the popularly recommended ANT751 & a TVPRAMP1R, and try them out next weekend. Then will keep one antenna that works and return the other -assuming I won’t accidently drop it from the 2nd floor window, or trip and land myself on it during this many trials

This is teleview idea and what I called Plan-A, I would focus on this as this probably has the best shot.

Will also try pointing the DB8e at other mountains for reflected signals as teleview suggest; I still have some 20 days to return it.

This is a good idea to do more testing till the other antenna arrives. The more you can test the signals the better chance you have of finding a good configuration. If you can still return that antenna I'd be reluctant to do any testing or modifying for fear of damage then you'd be stuck with it.

Yes I read about FCC rulings. Attic installation is still preferred, simply because it’s a lot easier. My house is facing N-NW, and we are in small lots on a hill side, with the house to my east higher than mine. To get east channels, the antenna better be in the frontal-most part of the house to avoid having to reach higher than east-neighbor’s roof, and I don’t like having an antenna in front of the house myself, regardless of whether the HOA cares. The only pocket of attic space I have is luckily in this front part of the house, but it’s tiny.

These details are the tricky part of an antenna system as online advice can only go so far and these specifics make a difference. It sounds like the attic is so small that you could not really separate the DB8 into two DB4's anyway so the ANT751 will probably fit better in that tight space.

- Is it detrimental to put antenna on a flat roof (asphalt shingle)? I have such an area of one-story roof in the back (the front part is 2-story with gable-end tiled roof). If I cannot get anything from the attic at all, I am thinking I’d build sort of a wood stand, attach it to the roof to hold the south-aiming antenna in proper orientation; still easier than erecting a mast. My south view is mostly clear looking down hill, no need to go high (the 40/40 and 13/13 channel towers are visible from my back window).

Again, hard to judge without seeing it but is this an actual outdoor location? That would be the best. Putting an antenna right on top of an asphalt roof might not work well but you could try it. Is the area in the attic the part of the roof covered in ceramic tiles? Hmmm... that seems like its going to really block the signals inside the attic.

- After trying the DB8e outside my front window, I also tried pointing half of it at 80degT, and lost many channels. Did not record exactly which ones were lost though, just quickly concluded that I need a full DB8e, even for outdoor.

If you have the antennas coupled (per the design) and then aim them in different directions you will get multipath and trashed signals. This antenna is designed to be installed high up in free air and in a fringe area where signals are weak and reflected singles are weaker. Can you physically separate the antennas and use one as a DB4 for testing? Plug the TV directly into the balun for that antenna. Also, rezero your TV tuner once in a while because with all this testing and rescanning its going to pickup spurious parameters.

- I did try pointing the 2 halves of DB8e separately to 180degT and 80degT in the attic. But they were still right next to each other, both connected to the DB8e’s combiner. Results were pretty much the same as when they both pointing at either direction. This is probably due to reflected multipath, since I don’t see as many South channels when outdoor pointing 80degT (only the RCH40 and RCH28 I think). So the DB8e (and any reflective-disc style) is more prone to multipath than the Yagi-style 751?

A coupled antenna of any type is going to be prone to multipath. The Yagi style has a more focused beam so maybe less multipath trouble.

To dmfdmf, Do you still think it’s worth rigging up 2 DB4s (if the 751 doesn’t do)? There is very little space (that is >= 40” hi for the DB4s) in the attic, so they will not be more than maybe 2-3 Ft apart in there. I am curious how you modify it to improve VHF (at the cost of some UHF performance I assume?), but not sure I’d spend $160 on the DB8e to experiment. Is the mod reversible and I can still return it?

My Plans B & C were based on the assumption that you could not return the DB8 and didn't want to buy another antenna. Also, I was assuming that there was enough room in the attic to get at least 10 to 20 feet of separation, if you pile them up in one corner multipath will be a problem even if you notch channels. I'd return the DB8e.

That said ;-) the VHF mod is pretty simple, reversible and I'd be curious how it does. You have to start by extracting one of the DB4s as a stand alone antenna. On the back of the balun input are two set screws shown here; http://imgur.com/K9aeFDv
These are the inputs from the feed elements into the balun. The trick is to get a piece of 8 or 10 AWG bare copper wire and fold a loop on the end and smash it with a hammer so it makes a thin spade-type connector. Attached a straight piece of wire on each balun input measured for VHF reception. It should look like this;

>|<
~~
>|<

Where the tildes (~) represent VHF elements coming off the balun set screws. Be very careful not to over tighten the set screws with the attached wire, just make it snug for contact and support the ends of the VHF element at the end of the reflectors with zip ties and/or small pieces of plastic pipe or tubing you have lying around.

For RCH4 each element would need to be 3ft 5" but you could probably get away with 3ft elements and that might be short enough to get VHF-Hi channels RCH13/CBS from the south or RCH9/ABC from the east.

Thank you all. You folks are really amazing, not just because of your knowledge, but also for how you’d spend the time to read and answer people’s questions like this.

No problem. I hope it works in the end.

[vt6364]

To dmfdmf,

is this an actual outdoor location? That would be the best. Putting an antenna right on top of an asphalt roof might not work well but you could try it. Is the area in the attic the part of the roof covered in ceramic tiles? Hmmm... that seems like its going to really block the signals inside the attic.

Yes, the flat roof is outdoor, but it's facing South where there are fewer channels (the north side of this area is hitting the south wall of the 2nd-story part). And Yes, the attic is under the concrete-tile roof; not only that, there are lots of foil-covered air ducts and AC/FAU equipments in there too!

Can you physically separate the antennas and use one as a DB4 for testing? Plug the TV directly into the balun for that antenna.

When I "tried pointing half of the DB8e at 80degT outside my front window, and lost many channels", I actually detached the 2 parts and connect the TV directly to the balun (didn't know that box houses a balun inside though). Once I conluded that a DB4 is not enough, I put them back and never decoupled them again. So I left the 2 halves coupled when trying it in the attic.

The trick is to get a piece of 8 or 10 AWG bare copper wire and fold a loop on the end and smash it with a hammer so it makes a thin spade-type connector. Attached a straight piece of wire on each balun input measured for VHF reception.

Ah, I see what you're doing. Sounds simple enough I will try it and let you know. What's the max thickness this VHF element can be? I have some of the more-common 12-14 AWG wire around in my garage, but not 8 or 10. I am thinking maybe I can find some aluminum sticks or something that are as thick as the bowtie elements themselve. Would that be even better?

Thank you, again.

[dmfdmf]

Originally Posted by vt6364

Yes, the flat roof is outdoor, but it's facing South where there are fewer channels (the north side of this area is hitting the south wall of the 2nd-story part). And Yes, the attic is under the concrete-tile roof; not only that, there are lots of foil-covered air ducts and AC/FAU equipments in there too!

Attic install is going to be a challenge.

When I "tried pointing half of the DB8e at 80degT outside my front window, and lost many channels", I actually detached the 2 parts and connect the TV directly to the balun (didn't know that box houses a balun inside though). Once I conluded that a DB4 is not enough, I put them back and never decoupled them again. So I left the 2 halves coupled when trying it in the attic.

Did you rezero the tuner after dropping one of the DB4s? This could make a difference in the channels found. Also, you have decent signal coming from the South, I'd think a DB4 would be sufficient for that direction but the 80deg direction it might not be sufficient.

Ah, I see what you're doing. Sounds simple enough I will try it and let you know. What's the max thickness this VHF element can be? I have some of the more-common 12-14 AWG wire around in my garage, but not 8 or 10. I am thinking maybe I can find some aluminum sticks or something that are as thick as the bowtie elements themselve. Would that be even better?

Wire gauge gets thinner as the number goes up. You could use 12 or 14 AWG as a test, it will be easier to attach to the set screws. Thicker is better for radio reception but I'd be very careful about over torqueing those set screws trying to get some big fat element under them. They probably would strip out pretty easily so be careful. If you are planning on returning the DB8 you could just run the test with the thinner wire, it should work but support them with some kind of plastic standoff at the ends so they don't sag too much. The nice thing about copper is that it is very malleable so you can just flatten the ends with a hammer to make a thin connector that will fit under the set screws.

The real point of the test is to aim a DB4 South and rezero and rescan your tuner and see what channels you get at what signal levels. Add the VHF mod and rezero and rescan and see if you pickup the VHF stations or if they come in at a higher signal level and it doesn't trash the UHF stations you got in the pre-test.

[vt6364]

Did all the tests (took 2 weekends), but haven't had time to get back to posting them until now. Here are the final updates.

First, Outdoor tests: I tried the DB8, then the DB4, then the modified DB4, then the 751, at different locations and directions outdoor. I made a simple 'stand' of corrugated cardboard to hold the DBs upright; the cardboard only clips to the bottom element and not blocking the front of the antenna. For the 751, I mounted it to an 8Ft wooden rod (an old closet pole that I have in my garage), and carried the pole around, pointing it at different directions. All outdoor tests were done with no amp, and with the same 25Ft RG6 connected to one TV that was also moved around following the antennas. And, Yes I re-zero the tuner every time.

Outdoor results ('north' and 'south' here refers to the 80degT and 180degT as plotted by TVF analysis):

- DB8: When high enough (about > 15Ft above ground) it can get almost all channels.
Pointing south, it gets all the south channels, INCLUDING the low VHF CH4.
Pointing north, it gets all channels both from north AND from south, but no CH4 (and some are weak, cutting in and out).
Pointing to other mountains trying to get reflected signals from the north. Got none!
So, I can get the stronger signals from the south reflected off the higher north mountain, but could not get the weaker signals from north reflected off the lower south and west mountains.

- DB4: Quite less powerful than DB8, only got a few channels pointing north.
Pointing south, it gets all south channels EXCEPT the low-VHF CH4.
Pointing to other mountains around trying to get reflected signals from the north, getting none.
So, DB4 is not enough to catch any reflected signals for my location.

- 751: Results very similar to the DB8 (yes, getting CH4 OK). So this antenna is enough for the ranges in my location. Like many of you pointed out, the DB8 can pull in longer range, but I don't need it, while the more-directional 751 helps rejecting multi-path signals reflecting from the surrounding mountains.

- Modified DB4:
Then I added the VHF elements to the DB4 like dmfdmf suggested, using 12-gauge bare copper wire. (Don't have any thicker wires on hand, and couldn't find any aluminum rods like I planned to). It is easier to attach to the front than to the back of the balun box because the screw is secured by a nut on the front (see pictures attached) inside the box. This box is easy to open, the front cap just slip on/off 2 small notches. So I attached the wires to the front instead, using appropriate nuts going on top of the existing nuts.
Result: Still got all the UHF channels the original DB4 got, but this does not help the DB4 to get CH4! I tried it at different T lengths, first at a total of 8Ft across, then cutting it down by 4-in at a time, going down to 6Ft in last test. None of them can pull in CH4 like the DB8 did. So it must be that the other elements and the reflector were altering the signal, because my simple dipole worked before (and I used the same type of wire, indoor).

Next, I attached the 751 to the J-mount it came with, pointing the J pipe down and forward, attached the J-foot to a piece of plywood, and I have a perfect stand. I placed this on top of the flat roof on the back, and it works just as good as when the 751 was on the pole. So being only 16-18-in above the asphalt shingles does not impair it. This is at about the same total height as it was on the pole when carried around on the ground anyway. Didn't try laying it directly on the shingle roof, but no need to (didn’t know it comes with the J mount).

Finally, I took the 751 into my attic. Lots of trials at different directions and placements, placing it (with the J-mount stand) on the attic floor as well as hanging it (w/o the J) close to the top ridge using plastic strings, ...
Results were all similar to the DB8. I never could get any channel from the north, only some from the south, and never get the low-VHF CH4. Then I tried adding the preamp, with a 3-Ft RG6 connecting the TVPRAMP1R to the 751, and the usual 25Ft RG6 going from the preamp down to the single TV. The preamp only helped improving the few analog channels I already got, but did not help getting any more channels.

I returned the DB8 right the following Monday; still have the 751 and the preamp. I believe I have exhausted all possibilities and I cannot get any north channels without mounting an antenna outdoor higher up in front of the house. The only other thing to try is getting a larger Yagi antenna for the attic. I think I have room for either the Winegard 7694 or the CM-5016, but the reviews I read suggest that they are not a lot stronger than the 751 anyway.
So perhaps I will instead settle with the 751 mounted on top of my back flat roof and get only the south channels. At least I will get NBC on the CH4. Will next take my time to run an RG6 through the wall out to the back roof and permanently attach the 751 there. But I need to take a break for a while; with that much tests in many consecutive weekends, it feels I have done nothing but antenna tests for months now :-)

Thanks again for all your inputs. Your services are really appreciated, and I learned quite a bit from the process.

[dmfdmf]

Originally Posted by vt6364

- Modified DB4: Then I added the VHF elements to the DB4 like dmfdmf suggested, using 12-gauge bare copper wire. (Don't have any thicker wires on hand, and couldn't find any aluminum rods like I planned to). It is easier to attach to the front than to the back of the balun box because the screw is secured by a nut on the front (see pictures attached) inside the box. This box is easy to open, the front cap just slip on/off 2 small notches. So I attached the wires to the front instead, using appropriate nuts going on top of the existing nuts.

Your mod looked great! I would have bet money you would get some kind of signal for RCH4, especially after your test. Sorry it didn't work.

Result: Still got all the UHF channels the original DB4 got, but this does not help the DB4 to get CH4!

Again, I am really surprised at this result. I am curious, did you rezero your tuner after the mod?

I've added such wings to other antennas (DB2 and a Yagi) with some success but not a DB4. I have read about others that have used this trick on DB4s (where I got the idea) with success which is why I mentioned it. Designers say that this method should work but it trashes certain UHF frequencies which is why they don't add it to bow tie antennas. If, as seems to be true in your case, the VHF wing trashes UHF channels you don't care about then it can be a good mod.

[GroundUrMast]

The strip-line type balun used on many of the AD UHF antennas will tend to be close to a short circuit in the L-VHF band. I wouldn't expect much VHF signal will pass the stock balun on the DB(n)E antennas or the 91XG.

You may have better success if you use a UHF/VHF signal combiner to insert the VHF dipole into the down-lead. That would also require a separate balun for the VHF dipole.

[dmfdmf]

Originally Posted by GroundUrMast

The strip-line type balun used on many of the AD UHF antennas will tend to be close to a short circuit in the L-VHF band. I wouldn't expect much VHF signal will pass the stock balun on the DB(n)E antennas or the 91XG.

I think you might be right, the PCB balun must be tuned (and thus more efficient) for the UHF band and not pass VHF signals. The antennas that I've used this trick on all had the toroid balun which is just a coupling transformer. The PCB balun looks like it might even have tuning stubs to block out-of-band signals but I'm not familiar with the design.

[vt6364]

You got me intrigued. If the balun in the DB4/8 does not pass L-VHF, then how would I got CH4 from the DB8e OK?

And BTW., Yes, I did rezero the tuner every time; and I really mean everytime, even after a small direction change. I had formed a routine to follow exactly each test: Disconnect the cable from the TV; start a scan; then go on to move/reset/swap the antenna; come back to check the TV and confirm that it finished scanning with 'No signal' and no channel logged; reconnect the cable; start a new scan.

Anyway, I did all the DB mod tests with my own curiosity too. Before getting the 751, I thought about combining in a dipole (and I was going to ask: a vertical dipole would be omni-directional, right? It would be much easier to setup). But as of now, there is no need for all that since the 751 handles it all for me nicely -if I am giving up the N/NE-channels dream.

[GroundUrMast]

You got me intrigued. If the balun in the DB4/8 does not pass L-VHF, then how would I got CH4 from the DB8e OK?

The strip-line balun used in the AD UHF antennas will not block the VHF band entirely, some small amount may make it through.

[ADTech]

Actually, the UHF PCB baluns allow the coaxial cable within the first several feet to become the "VHF element".

[GroundUrMast]

Originally Posted by ADTech

Actually, the UHF PCB baluns allow the coaxial cable within the first several feet to become the "VHF element".

So the random nature of length and orientation of the coax in each installation would lead to widely varied VHF results?

[dmfdmf]

Originally Posted by ADTech

Actually, the UHF PCB baluns allow the coaxial cable within the first several feet to become the "VHF element".

That's a great trick! I thought one purpose of the balun was to stop the coax from becoming an antenna, never would have thought of that.

[dmfdmf]

Originally Posted by GroundUrMast

So the random nature of length and orientation of the coax in each installation would lead to widely varied VHF results?

Perhaps the DB8e's better VHF performance is due to the horizontal runs of coax between the two banks? (as compared to a DB4 which typically has a vertical coax line drop)