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Old 14-Oct-2011, 6:01 AM   #1
be236
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BLU920F 17dB UHF(CH14-69)

Anyone heard of this antenna.. Seems to get +1 - 2 dB gain over 91XG:

http://www.fracarro.com/internationa...logo/25-26.pdf
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Old 14-Oct-2011, 6:28 AM   #2
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These antenna specs use dBi instead of dBd. If you want to compare apples to apples, you need to subtract 2.15 dB from the dBi numbers.
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Old 14-Oct-2011, 2:59 PM   #3
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Yes, you're right. They are in dBi. But so is 91XG. Its "max" 16.7 gain is also dBi at that is at the high UHF range, say > RF 50, which is no longer used (the spec listed on AD's site incorrectly states "dB," I believe).

So, still if you follow the gain curve for both antennas, this one appears to be 1-2 dBi higher gain (not sure if that is 'net' or 'raw' gain... probably raw gain I would assume for their marketing purposes)....

Also, when looking at my NM value, I use dBi numbers to add to it, right? (not dBd?).
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Old 14-Oct-2011, 6:21 PM   #4
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Quote:
Originally Posted by be236 View Post
Anyone heard of this antenna.. Seems to get +1 - 2 dB gain over 91XG:

http://www.fracarro.com/internationa...logo/25-26.pdf
Carefully read the PDF that you linked to. This antenna was designed for Europe. The spectrum of channels that it is designed to receive is intended for those markets, not the North American market. Of the stations in your area, these antennas can't receive channels on the low-end of the UHF spectrum that are available to you, but is designed to receive channels on the high-end that are unused. For example, KTBW-DT broadcasts in real Channel 14. The lowest that any of the Fracarro models can receive is Channel 21. Your maximum channel is Channel 51 which KIRO-DT broadcasts on. For the sake of argument, I ignore K62FS on Channel 62.

Perhaps of greater concern is the mass of each Fracarro antenna. The BLU920F comes in at 9.88 kg (21.8 lbs) making it the lightest model from the company. The next lightest is the BLU220F, which tips the scales at 15.34 kg (33.8 lbs). Compare that to a Channel Master CM3020 Deep Fringe Advantage TV Antenna which comes in a 10 pounds. The Channel Master is a feather compared to the Fracarro. Less sensitive Channel Masters and Winnegards are even lighter. The mass of the Fracarros means that they require masts that Americans normally don't use or need. They also require guy wires stronger than normal. That mass actually makes it less likely that they will sway in the breeze, but if they do, then.... I wouldn't want my garage or dog house to be under one when it falls.
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Old 14-Oct-2011, 6:42 PM   #5
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Uh. that 290 model shows freq range starting at 470 (channel 14) to 862 (past RF 60)... so that seems to cover the low end UHF and past channel 51 .. so what's the problem? Other than its highest gain is past what's usable today (but same problem with 91XG).

Also, its weight says "unit" about 3kg (7lbs?) and "total" weight is almost 10kg (22 lbs?).. so not sure what's the different between these two weights.

91XG itself is about 6lbs... so if you compare to their "unit" weight. it's about the same..

if you're talking 22lbs, then yes, that is too heavy antenna to be for a regular user to use.

As for that CM model you listed.. that *looks* like my current antenna which I always thought is a Radio Shack VU-190 model.. though I have no idea who to tell, not sure if there is any label on it to say it's a RS, Antennacraft or CM model (those LPDA antennas all look the same). heh.
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Old 14-Oct-2011, 7:55 PM   #6
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Quote:
when looking at my NM value, I use dBi numbers to add to it, right? (not dBd?).
Actually, you need to use dBd. dBi is often used for marketing purposes because the average consumer doesn't realize that the numbers have a built-in 2.15 dB offset.

Broadcasters and the FCC use dBd as their reference. For example, if an broadcaster is licensed for a 1000 kW transmitter, that means 1000 kW relative to a 0 dBd antenna. Our reports follow the same principle, showing you the theoretical signal power (or EM field strength) "at a point in space" available to a 0 dBd antenna.

You'll find that in most real-world broadcast situations, people use 0 dBd as their reference. That's because it's something you can actually build and calibrate against. You can't build an isotropic antenna. Isotropic antenna gain is nice from a theoretical math (and computer modeling) standpoint, but it's not that useful in the day-to-day activities of a broadcast engineer.

It used to be that antenna companies like Winegard and Channel Master published their gain specs in dBd all the time. More recently, you see a mix of dBd and dBi specs which just makes things more confusing for the average user.
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Old 14-Oct-2011, 8:03 PM   #7
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I think the weights being listed are for individual units as well as for the total package weight (which comes in packs of 10 or 3). It looks like this brochure is aimed at bulk purchasers (installers? resellers?) as opposed to individual consumers.
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Old 14-Oct-2011, 8:29 PM   #8
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Ok, so for example:

I have a channel at NM -10 dB. I thought this meant the signal "in the air." So wouldnt using dBi be correct (I am guessing isotropic means in-the-air, or a no gain antenna).

So, if I have an antenna rated at 10 dBi gain, then you're saying I cannot do -10 + 10 = 0 dB signal NM.

Instead I need to do -10 + 7.49 = -2.51 dB NM?

This means I need to get an antenna about 12.5 dBi gain to get over this 0 dB NM threshold?
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Old 14-Oct-2011, 10:02 PM   #9
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The difference between dBd and dBi is 2.15 dB, not 2.51. But essentially, you got the right idea. In general, it's unlikely for people to get steady reception on channels that are below about -15 dB NM. You can certainly reach below that on good tropo days / evenings, but continuous reliable reception at these levels is pretty rare.

Also keep in mind that the NM values are at the center of a bell curve (think statistically). For a fixed transmitter and receiver, the time and space variability will cause the true signal strength to vary a bit. On average, you are expected to get the predicted NM values, but there will inevitably be changes that vary with time of day, seasons, weather, tropospheric effects, ionospheric effects, and other random factors.

Propagation modeling is just a tool. There are lots of things it does not account for, and there's always the possibility of errors in the data. The tools can never be perfect, but they can provide a good first-order approximation of the environment.
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Old 14-Oct-2011, 10:18 PM   #10
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My bad.. I got 2.51 confused with 2.15. :-)

Ok, well my target channels are from -8 to -15 dB NM. I assume then that NM value listed in Tvfool is dBd and not dBi, eh? Hence I have to do my measurements with dBd.

Well, yeah, I understand Tvfool gives us an approximation of signal at a given location... but I heard of a few people getting stable signal even at -18 dB NM... so I believe there's hope for me yet once I get the right equipment. :-)
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Old 14-Oct-2011, 10:27 PM   #11
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Another basic question.

If I measure across the terminals of an antenna (Yagi or LPDA, etc)... using DVM, should I get about 0 ohms (closed loop) or infinite ohms (open loop)?
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Old 15-Oct-2011, 7:11 AM   #12
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Quote:
Originally Posted by be236 View Post
Another basic question.

If I measure across the terminals of an antenna (Yagi or LPDA, etc)... using DVM, should I get about 0 ohms (closed loop) or infinite ohms (open loop)?
It depends...

The Antennacraft Y5-7-13 Yagi design will measure as a short circuit (close to 0.0 ohms) at the terminals. It uses a folded dipole. Other Yagi designs could be 'open' at DC (0 Hz).

The Channel Master CM3016 elements are open ended so you should expect near infinite DC resistance at the terminals.

The only antenna that would measure a moderate amount of resistance at the terminals (that I can think of at the moment) would be a terminated Rhombic which would be a rare custom build in the OTA TV enthusiast world.

Most 300/75 ohm matching transformers will present a DC short... but not all. So if the matching transformer is connected, the DC resistance could be near zero, then measure 'open' with the transformer disconnected.

You can usually look at an antenna and see the DC paths... The interactions between elements at radio frequencies are not as easy to observe. A typical DVM is not going to measure the RF characteristics of any of your antenna system components. The DVM is going to be limited to tasks like proving DC continuity of coax and preamp power supply voltage.
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Last edited by GroundUrMast; 15-Oct-2011 at 7:27 AM.
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Old 15-Oct-2011, 8:03 PM   #13
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How about measuring RG6 cable? With about a 60ft cable run with combiners, I measured across both ends.

The inner rod measures about 3ohms, which is good.

However the outer conductor (though I measured from the inside) of both ends show up as either 1K ohm or essentially not connected.

I know this needs to be connected (short) when using powered amp, but w/o a pre-amp, because the outer conductor is open, does this mean I'll lose much more signal?
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Old 15-Oct-2011, 11:15 PM   #14
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With the cable disconnected at both ends, you should see a very low resistance end to end when measuring the center conductor and also when measuring the shield. There should be near infinite resistance between the center conductor and shield.

It sounds like you have a poor connection at one or both ends between the connector body and shield. Poor shield connections allow signal to leak into and out of the coax. Signal energy will also reflect backward from the bad connection which will possibly radiate back into the air through the antenna, leaving you with much less signal at the TV.

Shield connections need to be solid, mechanically and electrically. If the high resistance connection is the result of corrosion, throw the cable away. Water in the cable destroys it by changing the characteristic impedance, anything other than 75 ohms is going to cause signal reflections.
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Old 16-Oct-2011, 1:53 AM   #15
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Kitztech KT-200

Just got this today.

Hooked it up next to my RS antenna, put in a brand new 100-ft RG6 cable run to Artec DTV converter box.

Now channel RF 19 (22.1) from Orcas Island has a picture (before it was just a signal blip on the signal meter).

Also, now I see a signal blip on RF 17 (CIVI) and RF 22 (CHAN) , RF 24 (Orcas Island), but still no picture yet.

So, I'm getting "closer."

Sounds like my next step is 91XG antenna, eh?

Roughly speaking on Sony TV, before I for a given channel, its SNR was at 18,19... then when I put in the KT-200, its SNR was 22-23... so improved about 2-3dB SNR.. Is that about right?
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Old 31-Dec-2011, 2:26 AM   #16
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Quote:
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Just got this today.

Hooked it up next to my RS antenna, put in a brand new 100-ft RG6 cable run to Artec DTV converter box.

Now channel RF 19 (22.1) from Orcas Island has a picture (before it was just a signal blip on the signal meter).

Also, now I see a signal blip on RF 17 (CIVI) and RF 22 (CHAN) , RF 24 (Orcas Island), but still no picture yet.

So, I'm getting "closer."

Sounds like my next step is 91XG antenna, eh?

Roughly speaking on Sony TV, before I for a given channel, its SNR was at 18,19... then when I put in the KT-200, its SNR was 22-23... so improved about 2-3dB SNR.. Is that about right?
The SNR improvement of 2 to 3 dB makes sense given the amount of coax between the amp and tuner.
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Old 1-Jan-2012, 10:18 AM   #17
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For comparison, please see:
Attached Files
File Type: pdf Fracarro BLU_920F.pdf (331.5 KB, 420 views)
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Old 1-Jan-2012, 4:21 PM   #18
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Originally Posted by MisterMe View Post
Carefully read the PDF that you linked to. This antenna was designed for Europe. The spectrum of channels that it is designed to receive is intended for those markets, not the North American market. Of the stations in your area, these antennas can't receive channels on the low-end of the UHF spectrum that are available to you, but is designed to receive channels on the high-end that are unused. For example, KTBW-DT broadcasts in real Channel 14. The lowest that any of the Fracarro models can receive is Channel 21. Your maximum channel is Channel 51 which KIRO-DT broadcasts on. For the sake of argument, I ignore K62FS on Channel 62.

Perhaps of greater concern is the mass of each Fracarro antenna. The BLU920F comes in at 9.88 kg (21.8 lbs) making it the lightest model from the company.
....
be236,

Don't rule out the Fracarro BLU_920F based on the above inaccurate comments.

The Fracarro pdf states:

1.) Bandwidth 470 – 862 MHz
Per Wikipedia,
North American Broadcast Television Frequencies:
  • UHF Channel 14 begins at 470 MHz
  • UHF Channel 51 ends at 698 MHz
  • UHF Channel 69 ends at 806 MHz
  • UHF Channel 79 ends at 866 MHz
2.) Weight
BLU920F
unit weight 3.16 Kg (= 6.96660 lb or 6 lb and 15.46 oz)
box 3 Pieces
total weight 9.50 Kg
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Old 1-Jan-2012, 4:48 PM   #19
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otadtvman,

So do you have this Fraca antenna? If so, how's its performance?

I just built my own M4 and SBGH and it seems pretty good. Then I got an HD-8800 and it has about the same performance... I'm trying to get stations from 107miles away, 2EDGE and NMs from about -8 to -15 dB.

On the right tropo weather conditions, I can pick up RF 20, 22, 26, and 43 with them.

Not sure if I want to order that model Fraca just yet... I might get a CM 3023 instead, though.
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Old 1-Jan-2012, 6:35 PM   #20
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be236,

No, I don't own a Fracarro. However, I'm considering the
  • 3-ft Sigma 6HD versus the the 7.75-ft A..D. 91XG for UHF
  • 4.9-ft Fracarro BLV6F versus the 8.3-ft Winegard YA-1713 or 10-ft Antannacraft Y-10-7-13 for VHF

If you're "trying to get stations from 107miles away" that is a tall order given the curvature of the Earth. You may be interested in the following article where they report such success:
Lots of Channel choices for Free Over-The-Air HDTV in Michigan’s Upper Peninsula
Attached Images
File Type: jpg yooper1.jpg (41.5 KB, 472 views)
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Last edited by otadtvman; 1-Jan-2012 at 7:33 PM. Reason: Added jpg
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