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Old 5-May-2017, 7:47 PM   #41
OTAFAN
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Smile Rca ant751

Fascinating classroom lecture today, Professor rabbit73!

I've written down your "experiential fix" of the stripped screw for future use when necessary. Thanks for the tip!

Now I'm beginning to see how the mysteries of antenna theory work in real time from your analysis. Still I'm a bit awe struck, to say the least.

It will be interesting to see Adtech's field testing of GEs latest antennas in comparison to the similar RCA (AKA ANT705Z) that JOEAZ mentioned in his post. IMHO, the plastic used on both these antennas and similar others probably are UV resistant and will give at least a few years of use even in harsh desert environments. But mileage may vary in each individual situation.

I'm guessing that other antennas on the market today which are using built in baluns like this GE 34792 are of similar circuit design. This should be informative for those who end up using them at their locations, or who might have to open the board up in case possible circuitry issues. Your provided information has been very helpful here.

Thanks, as always, Professor rabbit73 for your yeomans efforts! Much appreciated!!
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Old 20-May-2017, 6:30 PM   #42
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The tests that I have made so far tell how well the antennas work indoors with my signals, but I have been searching for a test method that would give a more accurate indication of relative antenna gain.

I have settled on an Antennas Direct DB2E antenna and a Blonder Tongue HAVM-1UA Frequency Agile Modulator for a stable transmitted test signal.

I read about the antenna test measurements done by Kent Britain (WA5VJB). He has made measurements with the test antennas at ground level and above ground level. When the antennas are elevated, the receiving antenna picks up the direct signal and a signal reflected from the ground. I tried it both ways. The ground level signals level are much weaker, but the gain difference between antennas is about the same, so I used elevated antenna measurements. Kent was making measurements at microwave frequencies with horn antennas, see p. 5:
http://www.wa5vjb.com/references/Ant...0Notes-keb.pdf





First I did a comparison between the antennas elevated on tables and on the floor. The HAVM is only for UHF:

Code:
Comparison between antennas on tables and antennas 
on the floor for gain comparison measurements.

                 TABLES                  FLOOR

Channel    GE PRO    GE Attic     GE PRO    GE Attic
            29884     34792        29884     34792
            dBmV      dBmV         dBmV      dBmV

15         -11.1     -13.4        -20.3      -22.3
28         -10.0      -9.8        -24.9      -23.4
39         -12.1     -12.7        -23.5      -24.2
Attached Images
File Type: jpg DB2EandHAVM.jpg (171.0 KB, 411 views)
File Type: jpg RCAANT7511rcvHAVM.jpg (147.0 KB, 412 views)
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Last edited by rabbit73; 20-May-2017 at 7:14 PM.
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Old 20-May-2017, 10:06 PM   #43
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Rabbit73, we really do owe you overtime wages for your continued testing results in this thread! Retired or not, I sure respect your life long experience in this technical field of TV antennas, et al. I'm back in your class sitting in the front row, no less.

And I wish there was some way we could repay you for all your very kind help on TV Fool. Like the best of my past teachers, you not only teach us students through narrative, but "show" us exactly what you're talking about with pictures, or rather, photos.

I just wish there was some way I could have say, Antennas Direct for example, send you an antenna or supplies of your choosing if I called them and placed the order. As long as they had a secure address I'd be willing to step up to the bar and pay the tab. LOL!

Anyway, it looks like the GE Outdoor has the edge with your testing so far. Interesting. And the AD DB2E looks like a very good antenna which could rival the GEs. With the VHF add on kit from AD, I'm toying with the possiblity buying one to see how well it would pick up signals in my area. Hmmm.....

Well, your loyal student is ready for his next lesson professor! Thanks so much again! BTW, very interesting article you linked from Kent Britain (WA5VJB). I have not heard about him before, but you can always count on the hams to come through!
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Old 21-May-2017, 12:28 AM   #44
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Kent writes an antenna column for CQ Magazine (amateur radio). He is the creator of the "Cheap Yagi" antenna. If you Google it:
https://www.google.com/#q=cheap+yagi&spf=1495326554715

This is his website:
http://www.wa5vjb.com/index.html

He did a version for TV reception:
http://www.wa5vjb.com/references/CheapYagi4HDTV.pdf

If you look at Figure 6 of that article, you will see an analog TV signal. That is what my HAVM modulator puts out. I am using the video carrier as a test signal.
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Last edited by rabbit73; 21-May-2017 at 12:30 AM.
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Old 21-May-2017, 12:58 AM   #45
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OMG, rabbit73!

I'm just a kid in a candy store!

Now, to the homework.....circuit board antennas.....easy build it yourself yagis.....I'm down with it for the rest of the weekend..... P.S. I'm fascinated by your test equipment!
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Old 21-May-2017, 1:24 AM   #46
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The next test that I did was to compare the GE PRO, ANT 751R, and the ANT 7511.

Code:
Relative Gain Comparison of three Antennas

Channel  GE PRO     RCA       RCA
          29884   ANT751R   ANT7511
          dBmV     dBmV      dBmV

15       -10.2    -12.5     -15.6
28       -10.4    -11.6     -13.4
39       -12.0    -12.3     -16.3

Equipment Used:
Antennas Direct DB2E source antenna
3 antennas to be compared
Blonder Tongue HAVM-1UA Agile Modulator
20 dB attenuator to reduce HAVM output
Sadelco DisplayMax 800 Signal Level Meter

Test Conditions:
Indoor Test Range; ground floor, carpet over concrete slab
Antennas 10 wavelengths apart
Antennas elevated on Table-Mate tables
Signal Level Meter measuring analog video carrier
Conclusions:

The GE PRO 29884 antenna is the best of the 3 antennas for my indoor location. The RCA ANT 751R is a close second. The RCA ANT 7511 is third. The RCA design change has sacrificed considerable UHF gain.

I have a little more confidence in these measurements, but there are reflections that will introduce errors. I miss my outdoor range with stable LOS signals.

Quote:
I'm fascinated by your test equipment!
So am I. Making antenna measurements is one of my favorite things.

You don't need a lot of expensive equipment. With just a variable attenuator and a TV, you can measure margin to dropout of the signal. The simplified form is shown in my signature link.

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Last edited by rabbit73; 21-May-2017 at 2:03 AM.
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Old 21-May-2017, 2:14 AM   #47
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I too, wish you still had your outdoor set up rabbit73. But your most recent test results probably would be similar out of doors, is my amateur guess.

Still, what you have shown here on this thread with the indoor equipment used, more than justifies my nomination of you as, THE DEAN OF TV FOOL.

And you just cannot take away certain vital elements in a TV antenna as RCA has done with their stripped down version 7511, without compromising overall gain. I'm fairly certain someone with a good understanding of physics, math and electronics would agree with me??? I'm still in undergraduate school as far as those subjects go.

But as far as everyday reception goes, RCA dropped the ball on a very good antenna with their newest version 7511. Fortunately, us OTA fans out here in the hinterlands have other choices going forward. And your help with this issue has been exceptional, rabbit73! THANK YOU!!
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Old 23-May-2017, 9:07 PM   #48
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I finally should be able to upload a summary plot of the relative boresite reception of a number of small Yagi/LPDA antennas from my testing earlier this month.

A few notes to ponder while you're waiting:

1. I'm not terribly happy with the quality of the data gathered. I identified, after the fact, a number of things that need improvement in my process including an huge signal "suck-out" (it will be painfully obvious) in the middle of the UHF band, probably due to an unwanted signal reflection or a fault with a cable or the transmitting antenna. I didn't find it until the range was broken down and I started pulling data into Excel for plotting. Since the anomaly is present for all of the antennas tested, it's still an equal playing field.

2. I did not have the opportunity to normalize the spectrum analyzer to the tracking generator (impractical), either before each measurement was made or via a correction file in the post-processing (didn't think of it) in order to smooth tracking generator non-linearities (up to +/- 2dB over sweep span) and other fast-changing (frequency-wise) impairments. If you know how to easily implement weighted average smoothing in Excel 2007, I'd be interested.... It would really clean up the presentation of the data.

The plot to be posted, once I finish tweaking it in the morning, is fairly congested with the data for seven antennas overlaid using Excel's default coloring scheme (ugh!). I haven't gotten around to changing the line style and color for better legibility and probably won't since this plot is a one-off from my normal analysis which normally compares ten different readings for each antenna done in a two-up comparison (Antenna A vs Antenna B).

I will say there are some interesting results to be seen.
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Last edited by ADTech; 24-May-2017 at 1:48 AM.
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Old 23-May-2017, 9:50 PM   #49
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Rca ant751

Thanks for sticking with this thread, ADTech!

Even though your testing is not under optimal conditions and rabbit73s too, both of you are probably doing ground breaking research here. I have found very little results for these type of antennas anywhere on the Net. Perhaps there are posts somewhere, but I have not seen any. If someone reading this thread can illuminate us here, I would certainly appreciate it.

Anyway, anxious for your test results ADTech!
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Old 24-May-2017, 1:17 AM   #50
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I did one final test in this indoor series, which is to compare the GE Attic Antenna with the AD DB2E, using the GE Pro as a source antenna.

Code:
Comparison of GE Attic Antenna with Antennas Direct DB2E

Channel   GE Attic   AD 
           34792    DB2E
            dBmV    dBmV

15         -15.4   -11.4
28         -12.2   -11.0
39         -15.4   -12.3

Equipment Used:
GE PRO 29884 source antenna
2 antennas to be compared
Blonder Tongue HAVM-1UA Agile Modulator
20 dB attenuator to reduce HAVM output
Sadelco DisplayMax 800 Signal Level Meter

Test Conditions:
Indoor Test Range; ground floor, carpet over concrete slab
Antennas 10 wavelengths apart
Antennas elevated on Table-Mate tables
Signal Level Meter measuring analog video carrier
The Antennas Direct DB2E wins.
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Last edited by rabbit73; 24-May-2017 at 2:07 AM.
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Old 24-May-2017, 1:47 AM   #51
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Thank you, Dean rabbit73!

Looks like AD DB2E more sensitive or gain than GE Attic on UHF channels you tested. Of course, you would have to add a VHF kit to use as all around antenna, whereas GE already equipped with VHF dipole. Also, cost comparison, GE is less. Something to certainly consider.

I can only speak for me, but all your testing here as educated me immensely in what to look for in good antenna reception. I cannot thank you enough for the information. As I previously mentioned, not much out there to judge these antennas nowadays.
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Old 24-May-2017, 2:08 AM   #52
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Quote:
Also, cost comparison, GE is less.
Not much difference; the DB2E was on sale.
http://www.solidsignal.com/pview.asp...u=853748001408

Quote:
Of course, you would have to add a VHF kit to use as all around antenna, whereas GE already equipped with VHF dipole.
Yes, you are correct.

That is my next project; channel 13 ABC is weaker because the folded dipole doesn't have much gain, and a reflector is needed for VHF because of multipath reflections.

It will be difficult because VHF-High antennas are about 3x the size of UHF antennas.
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Last edited by rabbit73; 24-May-2017 at 2:20 AM.
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Old 24-May-2017, 3:32 AM   #53
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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!
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Old 24-May-2017, 4:01 PM   #54
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As promised yesterday, I've attached the mentioned plot.

A couple of additional notes:

1) I added black vertical lines to denote the boundaries of the current high HF and UHF bands.

2) Low VHF reception was not a factor in this data collection effort.

3) The RCA751R was purchased at a local Menard's in late 2015.

4) The RCA 7511 and 705Z were purchased from a local Walmart less than a month ago.

5) The Winegard HD7000R was purchased from an online seller this spring. It is the newest (known) version that includes the low-VHF conversion kit which was not installed for this testing.

6. The GE 30741 was purchased about a year ago at a local Walmart.

7. The CM3010 was purchased directly from CM's web store last summer. COMMENT: This antenna fared so poorly against the rest of the pack that I suspect that it may have a faulty balun. The alternative interpretation is obvious.

8. The identical physical layout, cabling, test equipment configuration, and data collection procedures were used for each antenna to the best of my knowledge and ability.

9. Boresite reception as a basis for a relative antenna performance comparison is only one of the possible tests that can be performed to characterize any given antenna. Polar patterns are probably a more instructive characterization as they identify the additional parameters of F/B ratio, F/R ratio, beam width, as well as major and minor lobes, if any. They are not included in this posting for various reasons including several deficiencies that I identified post-testing and I'd prefer not to have to address.



Observations:

By virtue of it's UHF reflectors, the RCA705Z offered the best UHF performance of this cohort. It's VHF performance, however, was hindered by its single folded dipole element when compared to its stablemates. Now, if they tacked that UHF front end onto the VHF section of the 75XX, it would be an interesting combo for close-in work. It also probably would not end up on the shelf at Walmart due to the resulting larger package size, IMHO.

The other two RCAs and the WG (all three are manufactured by WG) are based on the same original design and are all very similar in performance with some observable minor differences. FWIW, it would be my opinion that the casual antenna user would probably never note any difference unless they happened to be right on the edge of reception for a station using a channel where a difference in reception can be discerned from the attached plot. YMMV.

If I think of more comments later, I will append them below this line.

Cheers!
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Last edited by ADTech; 24-May-2017 at 4:08 PM.
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Old 24-May-2017, 5:01 PM   #55
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Wondering what kind of polarization did you use? How much of a factor
would the polarization play in your tests??
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Old 24-May-2017, 6:12 PM   #56
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Quote:
Wondering what kind of polarization did you use?
Everything (TX & RX antennas) was horizontally polarized since that is the de-facto standard for North American TV broadcasting as well as the design of all of the tested antennas. I could just as readily, with a bit of hardware modification, have rotated everything 90 but it would have had little to no impact on the recorded results except possibly for ground reflection influence.

Quote:
How much of a factor would the polarization play in your tests??
Not sure what detail you're inquiring about, but I can say that from prior experience, that if I cross-polarize one of the antennas, there's usually a penalty of 20 dB or more.
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Old 24-May-2017, 7:28 PM   #57
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I asked because one of the translators we view uses circular polarization,
I have been told. Supposedly, circular polarization is somewhat better
with mountains and hills. That translator is most always a challenge to
receive over all the others.
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Old 25-May-2017, 6:34 AM   #58
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Wow, VERY INTERESTING results ADTech!

I'm still pondering your graph. But I do have a question first before proceeding with perhaps a few other comments.

Is there a way to figure out the overall gain of the antennas you tested for their VHF High/UHF and FB numbers? Sometimes on various antenna web sites you will see numbers like 5/7 for VHF/UHF gain and 12 FB. Perhaps a mathematical formula or even something less technical? Pardon me if I'm not asking the question in the correct way. I'm still very much learning about the technical side of TV antenna reception. But TV Fool has really helped me in this regard.

Thanks so much again for your results. This will be quite useful for me in evaluating possible future antenna purchases.
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Old 25-May-2017, 1:52 PM   #59
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In my opinion circular polarization is worse with mountains than H pol only. This is because the V pol reflects more than the Hpol. This multipath is the bane of 8VSB.

ATSC 3.0 will do better with multipath and circular polarization than 8 VSB.
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Old 25-May-2017, 2:17 PM   #60
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Quote:
Originally Posted by JoeAZ View Post
I asked because one of the translators we view uses circular polarization, I have been told. Supposedly, circular polarization is somewhat better with mountains and hills. That translator is most always a challenge to receive over all the others.
I've never heard of CP or EP being useful for that purpose. I've always heard that it helped with indoor antennas or mobile-type reception devices (which didn't pan out under ATSC 1.0).

What are the call letters of that translator?

Edit: I see TG chimed in while I was typing. His perspective on that subject should carry more weight since he works on the transmit side of the broadcast system.
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Last edited by ADTech; 25-May-2017 at 2:21 PM.
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