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Old 25-May-2017, 4:12 PM   #61
ADTech
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Is there a way to figure out the overall gain of the antennas you tested for their VHF High/UHF
With the data as previously presented, no. The comparable data from a reference antenna of known characteristics would need to have been included so that the mathematical comparisons could be done. See image and discussion following.

Quote:
...and FB numbers
F/B ratio could be measured by performing the same set of measurements with AUT aimed 180 opposite boresite. I didn't make that particular measurement using the linear frequency sweep procedure plotted above although I did do 360 rotational patterns which would discern this behavior though for specific frequency cuts.

Here's a sample that compares the RCA7511 to our clip-on VHF module which is tuned to 195 MHz, the center of the high-VHF band. See notes following.



Notes:
1) A hardware failure in my circuit that synchronizes the SA sweep to the rotor's start of rotation forced me to manually trigger the SA sweep using a manually activated micro-switch in conjunction with activating the rotor. Consequently, the data may be easily skewed by as much as a second or two (7.5-15 degrees). Kindly overlook this shortcoming, it's particularly noticeable in the 7511's pattern.
2) The data was normalized so that the maximum point in the paired data set was set to "0" and the rest of the data was adjusted by the same amount for the purposes of this comparison. Using Excel, there are, of course, a good number of possible data display methods possible, this happens to be the one I chose as I attempt to enhance my feeble Excel and VBA skills.
3) The VHF module, if balun and insertion loss adjustments were included (they aren't at this point) would be about as close to a reference dipole as a no-budget measurement effort could produce. I may explore this later and then compare it to the BicoLOG just to see how close they are to each other. In the meantime, I'd assume a 1 dB insertion loss @195 MHz and that will get you better than in the ballpark (probably into the infield) for an estimate.
4) Using the above described F/B definition, the F/B of the dipole is measured a almost zero, the 7511 is measured at about 15 dB.
5) Using the above described gain definition and including the estimated insertion losses, I'd estimate that the forward gain of this antenna, as tested, is ~ 5 dBd (7.15 dBi) at 195 MHz.
Attached Images
File Type: jpg VHF1_vs_RCA7511_195MHz.jpg (115.3 KB, 598 views)
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Last edited by ADTech; 25-May-2017 at 4:15 PM.
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Old 25-May-2017, 6:02 PM   #62
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I spoke to an engineer for Arizona PBS, KAET, several years ago
while at the summit of Mingus Mtn. I mentioned that his
translator, K42AC, was harder to receive than the others on
Mingus. He told me that the signal was directed away from
Prescott and Prescott Valley and that they were using
circular polarization. He then told me to tilt the 4 Bay antennas
from an "X" to a "+" which he said would help. It did help
but not much..... It continues to be hard to receive through
much of the area.
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Old 25-May-2017, 7:45 PM   #63
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K42AC shares a Jampro JA/LS-8 with K38AI and K40DD up on Mingus Mtn and the antenna is H-POL only, none of them are licensed for any vertical component in their signal. Their antenna is, however, highly directional to the east-northeast with a good amount of electrical down tilt (3). K42AC, however, maxes out at only 5 KW ERP along its maximum strength signal path compared to 12-15 KW for the other two stations on the antenna. The worst case, if one were situated in one of the weakest nulls, would be that only 920 watts might be sent in that direction. By contrast, K38AI peaks out at 15 kW with a minimum of 2.65 KW in its deepest null.

I suspect the much lower ERP and the directional antenna are the root cause for the difficulty in receiving K42AC as compared with its neighbors, depending o the relative direction and distance of the receiving location relative to Mingus Mtn. The weaker UHF signal of K42AC will be much less capable of diffracting to lower elevations where terrain is an issue or even for simple longer distance locations, even with LOS.

My interpretation, based on the antenna patterns and the City of License for each facility, is that KAET intends K42AC to cover the Cottonwood side of Mingus Mtn and for K43LW, located on Mt Francis, to cover the Prescott side.
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Last edited by ADTech; 25-May-2017 at 7:48 PM.
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Old 25-May-2017, 8:04 PM   #64
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Quote:
Originally Posted by JoeAZ View Post
That translator is most always a challenge to
receive over all the others.
K42AC is located on the Northeast side of the mountain with a short tower that doesn't see over the peak. Prescott is Southwest of the transmitter. There are shadows and weak signals in Prescott.
http://www.tvfool.com/?option=com_wr...q=call%3dK42ac

The use of circular polarization may not play a role with your spotty reception of K42AC.
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Old 25-May-2017, 11:53 PM   #65
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Quote:
Originally Posted by ADTech View Post
My interpretation, based on the antenna patterns and the City of License for each facility, is that KAET intends K42AC to cover the Cottonwood side of Mingus Mtn and for K43LW, located on Mt Francis, to cover the Prescott side.
Unfortunately, K43LW on Mt Francis, is only 1kw and is severely
hampered by the hills and terrain of Prescott. Additionally, there
is another RF43 on Bill Willaims Mtn about 40 miles away. Many areas
have LOS to Mingus and Williams but not Mt. Francis. That is why it
is imperative to capture K42AC. There is another PBS translator in
Flagstaff on RF14 but it cannot be received because there is also a
translator for KUTP, RF 14 on Mt Francis, here in Prescott.
It is what you could call " A MESS."
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Old 25-May-2017, 11:55 PM   #66
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Quote:
Originally Posted by Tower Guy View Post
K42AC is located on the Northeast side of the mountain with a short tower that doesn't see over the peak. Prescott is Southwest of the transmitter. There are shadows and weak signals in Prescott.
http://www.tvfool.com/?option=com_wr...q=call%3dK42ac

The use of circular polarization may not play a role with your spotty reception of K42AC.
I cannot help but wonder if the polarization was changed, if the F.C.C.
database is correct or if the engineer was mistaken.
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Old 26-May-2017, 1:34 AM   #67
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Originally Posted by JoeAZ View Post
I cannot help but wonder if the polarization was changed, if the F.C.C. database is correct or if the engineer was mistaken.
I'd guess that the engineer was wrong. Perhaps he was thinking about a different facility. The Jampro antenna listed is Hpol only. The FCC application does not mention a CP antenna.

The ability to pick up a signal while your antenna was mounted vertically indicates significant depolarization due to refraction off the mountains.

In mountainous locations antenna height can make a huge difference. You can try moving your antenna up or down to see if reception improves. Scientifically, you can calculate the angle to to the mountain, determine the slope in front of the antenna, and use ray tracing techniques to get a good starting point. I don't know where you live in Prescott, but you may find that an antenna several feet off the ground with nothing in front of the antenna might be better than the roof.
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Old 26-May-2017, 12:21 PM   #68
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I'm going to go with the engineer either mis-poke or there was a miscommunication. There's nothing in the FCC file that indicates the digital facility was ever anything but what it still is.

Quote:
It is what you could call " A MESS."
I'd expect it's going to get a lot messier as the repack progresses. All of the facilities operating on channel 38 and above must vacate those channels. And, since none of the translators (and other LP-class stations) are even guaranteed a post-repack channel, it's fairly likely that some will disappear completely and that the remaining ones get packed even tighter into the remaining channels, increasing the rate of co-channel and adjacent channel interference. Since this class of operator does not enjoy any interference protection under the rules, the mess will not get better.
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Old 26-May-2017, 5:56 PM   #69
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[QUOTE=
In mountainous locations antenna height can make a huge difference. You can try moving your antenna up or down to see if reception improves. Scientifically, you can calculate the angle to to the mountain, determine the slope in front of the antenna, and use ray tracing techniques to get a good starting point. I don't know where you live in Prescott, but you may find that an antenna several feet off the ground with nothing in front of the antenna might be better than the roof.[/QUOTE]

Agreed. In some locations I've lost RF13 but received RF22 which
transmit from the same basic location. Moving the antenna a few feet,
I was able to capture RF13, though weakly.
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Old 26-May-2017, 6:02 PM   #70
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Originally Posted by ADTech View Post
I'd expect it's going to get a lot messier as the repack progresses. All of the facilities operating on channel 38 and above must vacate those channels. And, since none of the translators (and other LP-class stations) are even guaranteed a post-repack channel, it's fairly likely that some will disappear completely and that the remaining ones get packed even tighter into the remaining channels, increasing the rate of co-channel and adjacent channel interference. Since this class of operator does not enjoy any interference protection under the rules, the mess will not get better.
Agreed. I've done some studies and found that in almost every case,
low band VHF will be used. There will be even more co-channel interference.
Invariably, some channels will simply disappear. Trying to find as compact
as possible antenna capable of RF 2-36 or Rf 2-51 is impossible.....
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Old 27-May-2017, 12:09 AM   #71
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Trying to find as compact
as possible antenna capable of RF 2-36 or Rf 2-51 is impossible.....
That's because of the physics of the lower frequencies. You can currently get a small Winegard (HD7000R) or a small Channel Master like the CM3016 or CM5016 but they're going to range from rudimentary like the HD7000R or fairly modest for the CM models which are still fairly large (relatively).

Personally, I'd expect the rural translator operators to do like all the majors and avoid low-VHF for the most part unless there's nothing less to pick from. IIRC, the filing window for the LP and translators being displaced is later this year so we'll have to see how it shakes out.
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Old 28-May-2017, 2:27 AM   #72
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ADTech
I bought two EU385CF for evaluation. I opened the black enclosure, and something didn't look right. I opened the second enclosure and it did look right.

I was able to figure it out, but if someone only purchased sample #1 with the upside down label, it might confuse them.

Sample #1 was sealed at the rear with epoxy; sample #2 with solder and epoxy, so I didn't mess with it.

Since you do QC, I thought you should know. I also called customer service to let them know, but didn't ask for an RMA because I wanted to look inside anyway to add to the AVS UVSJ thread.
http://www.avsforum.com/forum/25-hdt...ombiner-8.html

my post for the Antennas Direct EU385CF-1S UHF/VHF Diplexer (UVSJ):
http://www.avsforum.com/forum/25-hdt...l#post53267506
Attached Images
File Type: jpg 2_AD_EU385.jpg (137.6 KB, 47 views)
File Type: jpg 2_AD_EU385CFinside.jpg (162.5 KB, 42 views)
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Last edited by rabbit73; 29-May-2017 at 5:48 PM.
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Old 31-May-2017, 3:47 PM   #73
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Thanks for bringing that to my attention. Must have been a Monday morning at the factory!

I couldn't find any relevant tickets in our system. Any chance you received a ticket number?
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Old 31-May-2017, 8:13 PM   #74
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Sending ticket number in a PM on other forum.
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Old 6-Jun-2017, 2:41 AM   #75
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Originally Posted by OTAFAN View Post
That's a very tempting price.....sold I think!

I would be interested in your VHF findings when you're able to post, professor rabbit73.

Thanks!
I did some more testing with my GE 34792 Attic Antenna indoors on VHF-High because CH 13 is more difficult to receive than my UHF channels.

I found a convenient location in the bedroom for the antenna and made some measurements. In this location, CH 13 is picked up by the tuner, but there is picture freeze and many uncorrected errors, not too good:



The signal level meter shows adequate signal strength, but a bad channel scan:

Attached Images
File Type: jpg Loc1DiagNoRefl.jpg (120.1 KB, 536 views)
File Type: jpg CH13Loc1noRefl.jpg (53.3 KB, 667 views)
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Old 6-Jun-2017, 2:59 AM   #76
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I suspected that multipath reflections were causing a problem and decided to add a reflector element to the VHF folded dipole. A cardboard box is used as a temporary support.



The reflector is 13" behind the VHF dipole and consists of a 24" length of 1" aluminum tubing with a 12" length of 7/8" tubing in each end and clamps. The length has been adjusted to 27.7". I also tried a strip of aluminum foil on a yardstick with the same results:



The reflector improves the reception:



and the scan looks a lot better:

Attached Images
File Type: jpg Loc1tubingRefl.jpg (126.0 KB, 515 views)
File Type: jpg Loc1foilRefl.jpg (153.1 KB, 408 views)
File Type: jpg Loc1DiagwithRefl.jpg (109.1 KB, 518 views)
File Type: jpg CH13Loc1withRrefl.jpg (53.5 KB, 512 views)
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Last edited by rabbit73; 6-Jun-2017 at 3:07 AM.
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Old 6-Jun-2017, 3:18 AM   #77
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Since the convenient location for the antenna had some problems, I tried other locations in the room. The best location for the signal was in the middle of the room in a high traffic area (of course it was).



No reflector was needed in this location and the reception was excellent:



and the channel scan looks good, with increased signal strength:

Attached Images
File Type: jpg Loc2noRefl.jpg (100.9 KB, 509 views)
File Type: jpg Loc2DiagNoRefl.jpg (142.1 KB, 499 views)
File Type: jpg CH13Loc2noRefl.jpg (52.8 KB, 839 views)
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Last edited by rabbit73; 6-Jun-2017 at 4:00 AM.
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Old 6-Jun-2017, 3:29 AM   #78
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The Sadelco DislayMax 800 signal level meter makes 43 measurements across the channel and diplays the average of all readings. If one of the 43 measurements is below -20 dBmV, the meter says "Ur" for under range and doesn't give a reading. The scan covers about 5.3 MHz of the 6 MHz channel.



If the meter is switched to the single frequency mode, it will measure down to -35 dBmV at the center of the channel, but the correction for a digital signal is not added; +6.8 dB IIRC.



The screen on the meter actually shows a dark gray image on a dark green background and doesn't have much contrast. The image looks pretty good on a computer screen, but makes a muddy image on a print.

analog channel:



digital channel:



To make an image that has more contrast and room for notes, I set my digital camera for a B&W image, and then edit in Photo Gallery to increase the contrast.



Photo Gallery will only allow me to increase the contrast one time, AFAIK, so I use Lunapic to increase the contrast 4x more:

Attached Images
File Type: jpg DisplayMax800_43meas.jpg (90.3 KB, 393 views)
File Type: jpg DisplayMaxImg5.jpg (34.6 KB, 361 views)
File Type: jpg DisplayMaxImg1.jpg (92.7 KB, 369 views)
File Type: jpg DisplayMaxImg2_1.jpg (149.0 KB, 366 views)
File Type: jpg IMG_1010 (4).jpg (68.2 KB, 361 views)
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Last edited by rabbit73; 6-Jun-2017 at 7:54 PM.
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Old 6-Jun-2017, 5:00 AM   #79
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Smile Rca ant751

You may not have your outdoor antenna testing equipment available anymore, rabbit73, but your indoor results here are AMAZING!

As I'm beginning to understand much better now, indoor antenna set ups are even more complex and perhaps mysterious than their outdoor counterparts. LOS is a bit more straight forward out of doors, or so it seems. But like you previously mentioned, not everybody can put up an outdoor antenna.

If you keep up grading that GE Indoor antenna of yours, you might want to seek a patent, make a ton of money and really retire in a manner you're unaccustomed too--LOL! But necessity is the mother of invention. I'm copying your attachments for possible future inventive use. Ha! Ha!

Thanks for remembering my request here, rabbit73! I appreciate your dedication to this forum. It has been extremely enlightening. BTW, I've been watching your other posts. I'm learning something new every day!
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Old 6-Jun-2017, 2:23 PM   #80
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Thank you for your encouraging comments. I also learned a lot about indoor reception from this experiment.

Trip in VA, who runs the rabbitears.info web site and now works for the FCC, had an even more difficult time with reception of local signals. When he was living in Chattanooga he had to put his antenna inside a trash can to reject multipath reflections.



Background information on this technique:

http://www.avsforum.com/forum/25-hdt...l#post21358820

http://forum.tvfool.com/showpost.php...27&postcount=7
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Last edited by rabbit73; 6-Jun-2017 at 3:36 PM.
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