The Official AVS Antenna and Related Hardware Topic! - Page 164 - AVS Forum
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post #4891 of 16297 Old 06-13-2006, 11:02 AM
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Quote:
Originally Posted by tobybul View Post

Sorry, am sure this has been asked already. Recommendation on tv/hdtv antenna in Grand Rapids, Michigan area. Prefer multi-directional. Want to install in attic. Thanks

Gotta know where you are to determine if you even have a ghost of a chance with
a "multi-directional" attic antenna.
Go to www.antennaweb.org and punch in your address/zipcode.
Then do a simple copy/paste of just the results table into a new post on this thread.
If you don't care about analog stations, then you can select just the digital stations.
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post #4892 of 16297 Old 06-15-2006, 03:32 AM
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Quote:
Originally Posted by holl_ands View Post

Kerry Cozad of Dielectric... performed ACTUAL ON-THE-AIR measurements of REAL antennas and found SMOOTH frequency response for CM-4228 in hi-VHF band:
http://www.avsforum.com/avs-vb/showt...ad#post6423155

Ya gotta take the NEC computer simulation results with a grain of salt--and for very complex antenna structures better grab a mouthful...
Ya also should know that the CM4228 NEC results have been recently updated and were considerably different a year ago....

I can't infer that from the graph that Kerry Cozad furnished. It plots single values of 4 dBd for channel 7, 4dBd at ch 9, 5dBd at ch 11 and 5dBd at 13 and then connects them with straight lines, but that does not contradict the data that can be extracted from the HDTV Primer plot for the same antenna.

The HDTVPrimer graph does have a much lower gain value for channel 7, but its center value for channel 9 is about 3dBd, channel 11 is 5 dBd and 13 is also 5dBd, so if you connected 9, 11 and 13 with straight lines on the Primer graph, it would be fairly flat like Cozad's, but look what a roller coaster ride the plots take between those center channel values! On the HDTVPrimer graph, the lower edge value of channel 9 is 0dBd, whereas its upper edge value is +5dBd:, the lower edge of 11 is +6dBd whereas its upper edge is -1dBd, and the plots of channels 7 and 12 gain are bad jokes, with the channel 7 plot shooting up by over 8dB over the first 1Mhz before plummeting 10dB across the remainder of the channel band, and the channel 12 plot looks like someone tuned a notch filter into it, measuring -1dBd at 204Mhz, troughing at -7dBd at about 205.5Mhz, and then recovering to +5dBd at 210Mhz, yet these plots are perfectly consistent with Cozad's primitive graph, which depicts the same spans as flat.


As I recall, Blonder Tongue specs for both their Yagis and log periodics claim flatness across each channel of 1dB or better. With analog signals, the color purity of channels 7 and 12 derived from the irregular response of the 4228 would be putrid (NTSC = Never The Same Color), and I am concerned that digital processing of similarly distorted signal plateaus would be unreliable.
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post #4893 of 16297 Old 06-15-2006, 08:33 AM
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Quote:
Originally Posted by AntAltMike View Post

With analog signals, the color purity of channels 7 and 12 derived from the irregular response of the 4228 would be putrid (NTSC = Never The Same Color), and I am concerned that digital processing of similarly distorted signal plateaus would be unreliable.

I can't answer for the 4228, but I have used my AntennasDirect 91XG as a VHF-HI antenna on channel 10 and find the color to be similar to that of the digital signal. This holds for a large variety of antenna positions, although there is one or two angles where the colors are very distorted. My guess is that the distortion of the 4228 at "optimum" angles is minimal as well. Maybe someone with a 4228 can post some real-world pictures of analog VHF-HI reception and put all our fears to rest...
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post #4894 of 16297 Old 06-15-2006, 11:23 AM
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I currently live in a highrise built in the 60's that uses a daisy chain method for antenna distribution on a continuous loop. Each unit in the tier taps into the trunk to receive signal from the line. Recently comcast entered my unit after there was a sever in the loop and found that my antenna wallplate was the cause. Rather than replace the plate, he disconnected the two ends from the plate and capped them with male coax connectors and then used a female-to-female coax joiner and simply bypassed my unit. Since I was using cable, I had no issues with it. For some odd reason certain local HD broadcasts do not come through on cable and wish to use the building antenna for HD OTA. Do any of you know where I can purchase a new wallplate that supports daisychain antenna connection on the back to coax connector on the front?

Since the two ends of the loop were capped, I would like to know if there is a wallplate available that has two female connectors on the back that maintains the loop rather than me uncapping the two ends and screwing the raw ends to the plate if at all possible.
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post #4895 of 16297 Old 06-15-2006, 12:29 PM
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> if you connected 9, 11 and 13 with straight lines on the Primer graph,
> it would be fairly flat like Cozad's, but look what a roller coaster
> ride the plots take between those center channel values!

Good catch!

> As I recall, Blonder Tongue specs for both their Yagis and log periodics claim
> flatness across each channel of 1dB or better.

Blonder Tongue BTY-LP-HB claims 0.5 dB

Looking at the Kerry Cozad graphs, I have to wonder. The Silver Sensor is a
small indoor unamplified UHF antenna, right? Then how does it get over 6 dBd
at channel 4 when it only gets about 4 dBd at best in UHF?

http://www.avsforum.com/avs-vb/attac...chmentid=45041
http://www.avsforum.com/avs-vb/attac...chmentid=45040

} Maybe someone with a 4228 can post some real-world pictures of analog VHF-HI
} reception and put all our fears to rest...

Awhile back, Bob Chase posted a pdf with actual spectrum analyser graphs from a
field test done 2005-09-18 in Pearland Texas. If I'm reading it right, on channels
5 & 9, the CM4228 is significantly more ragged than the Scala, HD7210, and CM5646.
Nearly 10 dB difference within channel 5, about 4 dB within channel 9.

Also interesting:

Compare the slope of the various antennas on channel 9.

Compare the slope of channel 35 with channel 36.
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post #4896 of 16297 Old 06-15-2006, 12:32 PM
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Quote:
Originally Posted by Neonapple View Post

I currently live in a highrise built in the 60's that uses a daisy chain method for antenna distribution on a continuous loop. Each unit in the tier taps into the trunk to receive signal from the line. Recently comcast entered my unit after there was a sever in the loop and found that my antenna wallplate was the cause. Rather than replace the plate, he disconnected the two ends from the plate and capped them with male coax connectors and then used a female-to-female coax joiner and simply bypassed my unit. Since I was using cable, I had no issues with it. For some odd reason certain local HD broadcasts do not come through on cable and wish to use the building antenna for HD OTA. Do any of you know where I can purchase a new wallplate that supports daisychain antenna connection on the back to coax connector on the front?

Since the two ends of the loop were capped, I would like to know if there is a wallplate available that has two female connectors on the back that maintains the loop rather than me uncapping the two ends and screwing the raw ends to the plate if at all possible.

The fitting removed is called a directional coupler or tap. It is an electronic valve that bleeds off a small amount of signal to your unit while passing most of it along for the units below. Radio Shack does NOT sell them, surely because selection and application of this product requires knowledge that most do-it-yourselfers don't have, and therefore would result in a lot of customer dissatisfaction and returns.

Taps have different values, denoted in negative dB. At the top of a tall building, the value might have been -24dB. In the middle, it might be -16dB, the last few floors will typically have values of -9 or -6dB.

How many stories tall is your building? Is there another wallplate in another room that you can remove to read the tap value off it, so that you can replace the missing one with the same value?

Were you receiving reliable HDTV signal from the antenna system previously? Very few master antenna systems in Arlington distribute UHF signal, though some of the older, smaller garden style apartments that are just overblown residential systems consisting of one antenna and one VHF/UHF distribution amplifier will get you several broadcast HDTV stations, provided there are no taller buildings blocking the direct signal path.

What apartment or Condo are you in? I've serviced the antenna systems in quite a few of them in your market.
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post #4897 of 16297 Old 06-15-2006, 12:52 PM
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Quote:
Originally Posted by AntAltMike View Post

The fitting removed is called a directional coupler or tap. It is an electronic valve that bleeds off a small amount of signal to your unit while passing most of it along for the units below. Radio Shack does NOT sell them, surely because selection and application of this product requires knowledge that most do-it-yourselfers don't have, and therefore would result in a lot of customer dissatisfaction and returns.

Taps have different values, denoted in negative dB. At the top of a tall building, the value might have been -24dB. In the middle, it might be -16dB, the last few floors will typically have values of -9 or -6dB.

How many stories tall is your building? Is there another wallplate in another room that you can remove to read the tap value off it, so that you can replace the missing one with the same value?

Were you receiving reliable HDTV signal from the antenna system previously? Very few master antenna systems in Arlington distribute UHF signal, though some of the older, smaller garden style apartments that are just overblown residential systems consisting of one antenna and one VHF/UHF distribution amplifier will get you several broadcast HDTV stations, provided there are no taller buildings blocking the direct signal path.

What apartment or Condo are you in? I've serviced the antenna systems in quite a few of them in your market.

Mike, Thanks for the response. I live in the condo complex called "The Carlton" which is the tallest building in the South Arlington area; so obstruction shouldn't be an issue. It's a 12 story building with me living on the 7th floor. I will go to my neighbors and check her wallplate for the tap value. I unfortunately tossed mine away after it was found to be defective. I do remember seeing a resistor on the back though.

Since you've serviced this area, would you know the dB from your highrise tap value black book before I bother her?

I didn't have an HDTV prior to the bypass, so I don't actually know if I will be able to receive HD or not. Either way, I would like to have this feature back in my unit for when I rent it out in the future.

Also I found this site that sells the couplers, but not plates.
http://www.pacificcable.com/Picture_...Name=201%2D306

I can probably get something like this once I know the tap and get the male-to-male to screw to the back of the plate from the coupler.
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post #4898 of 16297 Old 06-15-2006, 01:17 PM
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I drive by it, but I don't think I've ever serviced it. Do you know who the management company is? I might know someone I can call to find out what the situation is there.

The ones with a visible resistor on the back are unshielded junk. Their tap value is usually printed in black ink on the plate itself. -12dB, -17dB and -23 or 24dB are common values for that kind of plate, whereas the more modern, shielded directional couplers are available in finer increments.
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post #4899 of 16297 Old 06-15-2006, 01:21 PM
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Mike,
The management company is "Armstrong Management." I also updated my post.

-Alex
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post #4900 of 16297 Old 06-15-2006, 01:23 PM
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I service a few other buildings for them. I'll give someone a call next week sometime.
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post #4901 of 16297 Old 06-15-2006, 01:31 PM
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I appreciate your help. I am in no rush and thanks.
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post #4902 of 16297 Old 06-15-2006, 05:37 PM
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Quote:
Originally Posted by Konrad2 View Post

>
Awhile back, Bob Chase posted a pdf with actual spectrum analyser graphs from a
field test done 2005-09-18 in Pearland Texas. If I'm reading it right, on channels
5 & 9, the CM4228 is significantly more ragged than the Scala, HD7210, and CM5646.
Nearly 10 dB difference within channel 5, about 4 dB within channel 9.

Also interesting:

Compare the slope of the various antennas on channel 9.

Compare the slope of channel 35 with channel 36.

FYI: Here are links to Bob Chase's UHF-only outdoor vs attic antenna comparison and an attic location test:
http://www.avsforum.com/avs-vb/showt...ic#post5399471
http://www.avsforum.com/avs-vb/showt...la#post5410432
and here's Bob's VHF/UHF outdoor antenna test you cited above:
http://www.avsforum.com/avs-vb/showt...60#post6246260

==============================================
When you see two strong adjacent channels, the transmitter and antenna have frequently been designed
as a single integrated structure. For example, NTSC CH8 and ATSC CH9 are different versions of KUHT.

However, antennaweb.org shows that ATSC CH31 and CH32 are on different towers in slightly different locations,
as are also ATSC CH35 and CH36.

Since ALL of the antennas experienced the SAME frequency response irregularities for CH35/36,
I would suspect either the transmitters or perhaps multipath conditions that affected all antennas equally.

===============================================
The CM4228 (cyan) has a variation of about +/- 4 dB on Low-VHF CH5,
but ya still have to be amazed that it has ANY gain for low-VHF channels and has more gain that any
of the other UHF antennas, including the SS-1000 Square-Shooter that still claims to be a "VHF/UHF" antenna.

Also bear in mind that most locations don't need much of an antenna for low-band VHF.
I've seen people strip off 12-18 inches of coax, leaving just the center conductor.
And Kerry Cozad's "coat hanger" antenna (see slides 11/12) also might be a viable candidate,
although I would take the time to unwind and separate the ends:
https://secure.connect.pbs.org/confe...ns/TC05_43.htm

It would be interesting to see how the gain changes as the CM4228 is rotated,
since the max VHF gain isn't always aligned with the UHF beam direction....

And it is also possible that the spectrum analyzer was responding to multipath variations in
that particular antenna location vice gain irregularities as it slowly scanned across the channel.

Long experience has taught me that it is difficult to conduct on-air tests in "controlled" test conditions.....
Requiring numerous additional steps (usually not reported) to exclude other confusion factors....

===============================================
on High-VHF CH9 the CM4228 variation across the channel is only about +/- 2 dB.
Compare this to the best VHF/UHF Combo antennas which all experience a slight roll-off with frequency,
resulting in a variation of 2-3 dB. So on CH9, CM4228 has 4-10 dB less gain than purpose built
VHF/UHF Combos and is actually within +/- 2 dB, just like the Combos...

Note that the CM4228 is maintaining good energy across CH9, rather than rolling off like the VHF/UHF Combos.
An adaptive equalizer can overcome freq response irregularities much easier than trying to recover energy that is no longer there.

================================================
In NTSC, the audio carrier should be about 8-15 dB below the visual carrier:
http://www.sencore.com/newsletter/No...files/HDTV.htm
However, each station can chose a specific setting and what you see on a spectrum analyzer depends on
the bandwidth and integration time settings.
Hence overall, it appears that most NTSC channels are displayed with the audio carrier about 10 dB below the visual.

On NTSC CH11 and CH13, let's look at the relative strengths for the triple peaks (visual, chroma, audio).

On CH11, the three best VHF/UHF Combo antennas have about the same gain as the CM4228 for the visual carrier,
however the Combos also experience perhaps 6-8 dB EXCESS of gain for the audio carrier, the worst being the CM3671.
The CM4228 seems to be experiencing a gradual frequency rolloff, increasing to perhaps 6-8 dB for the audio carrier.

On CH13 the CM4228 APPEARS to be matching the gain of the best VHF/UHF Combos on the visual and audio carriers.
However, if you download and blow up the chart, you'll see that the CM4228 is providing 3-4 dB less gain than the combos.
This overall gain loss of 3-4 dB is also seen across the mid-channel frequencies, illustrating a generally flat response for the CM4228 on CH13.

So on CH11 and 13, the best VHF/UHF Combo antennas only provide a few dB more gain than the CM4228
and on CH11 experienced frequency flatness issues that are on the same order as the CM4228.

=================================================
BTW: STATIC, SMOOTH frequency response irregularities on the order of a few dB can be readily accommodated in an ATSC receiver's adaptive equalizer.
DYNAMIC and/or NOTCHED frequency response irregularities displayed on a spectrum analyzer are evidence of underlying multipath problems.

==================================================
YMMV: Anytime you measure antenna gain in a real-world location, the results will also reflect current multipath signal conditions. The nature of multipath can cause signal nulls and peaks that vary with location, meaning that one antenna may
experience a frequency response problem differently than the others.

Also, the Ground-Bounce reflection can cause as much as a 3 dB increase in measured gain at certain frequencies,
including those reported by Kerry Cozad using an outdoor antenna range. Reflections from nearby buildings can also inflate the measured gain.....
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post #4903 of 16297 Old 06-15-2006, 06:46 PM
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Quote:
Originally Posted by holl_ands View Post

...the SS-1000 Square-Shooter... still claims to be a "VHF/UHF" antenna.

And I claim that my paper clip is a VHF/UHF antenna. Winegard wants to sell Square Shooters (about $100 each, retail). They can sell more by calling it a combo antenna than by calling it UHF only. Most buyers who also wanted VHF capability may keep it even if it does not meet their expectations because of the investment they have in its installation, as well as the fact that it usually meets their UHF needs.

In fact, in many markets, like mine, the VHF highband final assignments aren't being used yet, so if anyone in this market bought one for that eventuality, he presently doesn't know if the Square Shooter will fail to meet his needs.


Quote:


In NTSC, the audio carrier should be about 8-15 dB below the visual carrier:... However, each station can chose a specific setting and what you see on a spectrum analyzer depends on the bandwidth and integration time settings. Hence overall, it appears that most NTSC channels are displayed with the audio carrier about 10 dB below the visual.

I install antennas on tall buildings with clear, line of sight paths to about 16 full-powered analog transmitters ranging from three miles to about forty miles away. I usually use Blonder Tongue BTY-BBs or BTY cut-to-channel antennas for the VHF channels, and Winegard HA9065s or Channel Master CM-4228s for UHF. I don't go out of my way to check to compare the relative strengths of the visual and aural carriers, but I am virtually certain that they all consistently have a differential of 5 to 6dB, with the only possible exception being WMPT 22 analog from Annapolis.

The recommendation that the aural carrier be as low as 15dB below the visual carrier is the recommendation for relative levels of processed signals that are being mixed into an adjacent channel distribution system AFTER they have been faithfully received by the antenna. Strip amplifiers and channel processors typically include an analog tunable notch filter that is used to attenuate the aural carrier so as to minimize visual interference on the upper adjacent channel.

When you properly notch an aural carrier, you do not affect the chroma portion of the NTSC signal, but if you have an antenna that shows 10dB or more of differential between the aural and visual carriers, then it probably has about three dB or more of excessive attenuation of the chroma burst. I would consider that to be indicative of sucky antenna performance


Quote:


YMMV: Anytime you measure antenna gain in a real-world location, the results will also reflect current multipath signal conditions. The nature of multipath can cause signal nulls and peaks that vary with location, meaning that one antenna may experience a frequency response problem differently than the others...

Also, the Ground-Bounce reflection can cause as much as a 3 dB increase in measured gain at certain frequencies,including those reported by Kerry Cozad using an outdoor antenna range. Reflections from nearby buildings can also inflate the measured gain.....

If a ground bounce were equal in strength to the desired signal AND if it hits the dipole exactly in phase with the desired signal AND if the antenna gain in the elevation of the bounced signal was as efficient as the gain in the horizontal plane, THEN, there would be a three dB increase in signal strength. You'd have to have a real world topography of a giant roller skating rink to even make that approach a physical possibility. Maybe, across Bonneville Salt Flat, you might be able to approach a three dB boost...

Quote:


So on CH11 and 13, the best VHF/UHF Combo antennas only provide a few dB more gain than the CM4228 and on CH11 experienced frequency flatness issues that are on the same order as the CM4228...

It also would be interesting to see how the gain changes as the CM4228 is rotated, since the max VHF gain isn't always aligned with the UHF beam direction....

This Saturday, I'm going to be on the rooftop of a building in DC that has a BTY-BB pointed at analog channels 7 and 9, four miles away, another pointed at 11 and 13 maybe 35 miles away, and a couple of CM 4228s and HA9065s. It will be fairly easy for me to do some performance comparisons, and I'll also be able to visually compare the pictures of analog 11 and 13 coming off the BTY-BB and a CM 4228 on the 25" test TV in the mechanical room. Unfortunately, I am not outfitted to produce any kind of a screen capture, so I will be resigned to describing the picture quality as faithfully as I can.

I'll also compare the A/V ratio of analog channel 22 from WMPT from each type of UHF antenna used, to see if the 10dB differential I have measured in Arlington is local to that installation or if that might reflect the real carrier power differential.
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post #4904 of 16297 Old 06-15-2006, 07:35 PM
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The relative levels of the visual and aural carriers depends on how you measure them.
I didn't immediately see what bandwidth Bob Chase used for these measurements,
but it must be much less than a MHz in order to resolve the individual visual/chroma/aural carriers.
If you are using specialized TV test equipment, the bandwidths of the separate visual and aural filters
are wide enough to include energy in the sidebands and hence will yield different ratios.

Looking at Bob Chase's charts for the UHF band, I see 3 and 6 dB minimum values and 11 db (twice) as the maximum values.
Discarding these anomalous extremes (might be antenna related), the remaining values are 10, 10, 8, 9, 9, 7 and 8
which averages to about 8.7 dB...so my first eyeball guess of 10 dB might be just a tiny bit high.

For low-band CH2, combo antennas have visual/aural ratio of about 4-6 dB and the CM4228 is about 8 dB....only minor roll-off.

In the high-VHF band, CH8 has a ratio of 6 or 7 dB for the Combo antennas....and CM4228 is 9 dB....only minor roll-off.

CH11 ratio is only about 4 dB per VHF/UHF combo antennas...and CM4228 is about 17 dB....significant roll-off. [But is it due to irregular antenna response or an artifact of multipath????]

CH13 is 8 dB per CM3671, 8 dB per Scala....and 7 dB for CM4228....essentially the same.

Moving the antenna up and down, back and forth, can easily change the frequency and location of multipath null patterns, easily resulting in variation in these values by more than a few dB....so don't try to read too much into a 2 dB difference:
http://www.hdtvprimer.com/ANTENNAS/siting.html
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post #4905 of 16297 Old 06-15-2006, 07:51 PM
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[quote=pclement]Does anyone know why there aren't any Channel Master 7777 Pre-amplifiers available? None of the stores (brick and mortar or e-tail) seem to have them in stock. Lighting took out my amplifier last week and I can not find another one.

[quote]

I don't know myself but mine has been on backorder since 5/2/06. When I called Warren Electronics, they tell me that Channel Master keeps pushing back the shipping date.

May be due to SMD shortage from oversea supplier.
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post #4906 of 16297 Old 06-15-2006, 10:37 PM
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Quote:
Originally Posted by holl_ands View Post

The relative levels of the visual and aural carriers depends on how you measure them.
I didn't immediately see what bandwidth Bob Chase used for these measurements,
but it must be much less than a MHz in order to resolve the individual visual/chroma/aural carriers.
If you are using specialized TV test equipment, the bandwidths of the separate visual and aural filters
are wide enough to include energy in the sidebands and hence will yield different ratios.

Looking at Bob Chase's charts for the UHF band, I see 3 and 6 dB minimum values and 11 db (twice) as the maximum values.
Discarding these anomalous extremes (might be antenna related), the remaining values are 10, 10, 8, 9, 9, 7 and 8
which averages to about 8.7 dB...so my first eyeball guess of 10 dB might be just a tiny bit high.

In the VHF band, CH6 has a ratio of 5, 7 or 9 dB, depending on which antenna you look at.
CH11 is 4 dB per the highest gain (CM3671) VHF/UHF antenna and 7 dB per CM5646 VHF/UHF antenna.
CH13 is 8 dB per CM3671 and 8 dB per Scala.

Holl_ands & AltAntMike
Back then I would have been using 100 kHz RBW with the display set to max (peak hold). I use 4001 data points for the sweep so that I am not skipping over frequencies on that large of a span with that narrow of an RBW. (The default is 401 data points.) Averaging would have been set to off.

If I leave the SA in max for 3 minutes or more, I will usually get all of the sync pulses captured from all the stations before I write the data file. Modern (common mode) transmitters always have some video on their audio carriers, so peak hold gives a slightly higher (1 or 2 dB) reading than what the real (average) aural power level is.

Typically, NTSC transmitters are set up for a 10% Aural to Visual power ratio. The FCC maximum licensed aural power is 20% of visual power and not all stations are licensed for that much. But even way back when we had separate aural & visual transmitters most UHF folks didn't run that high of aural power because of the electric bill. Some modern (common mode) transmitters have to be run down at 5% aural to make intermod specs. (I know of one station in Dallas that runs 3% aural.)

Quote:


And I claim that my paper clip is a VHF/UHF antenna.

On a lighter note, I actually got some of them in the mail from a vendor. The clips were in little plastic bags labeled "Precision low-gain HDTV antenna" on one side and had "Installation Instructions" on the other. Gota love those marketing types.

Bob

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post #4907 of 16297 Old 06-16-2006, 10:48 AM
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SRO Dave:

You understand what I was saying about their availability. However, I ordered one from Solid Signal and it is being delivered to my home today (UPS Tracker). Solid Signal may not have any more as they had previously put mine on backorder and said that they were only getting a few units is. Availability is very hit or miss with the e-merchants. I let you know how it works.
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post #4908 of 16297 Old 06-16-2006, 02:52 PM
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With 4600 posts it's kinda impossible to read through them all.

For the TV engineers here (and I see a few), I would like to purchase a Spectrum Analyzer. The use it would have concerning this forum is to tune single UHF channel traps (filters if you prefer). Of course this is not the only reason, nor would it be the only time it would be used. Please don't waste any time telling me of a cheaper route to do this since this is a long term investment, mostly being used to the 2- way radio spectrum (and TV).

From what I have read, RBW is a important issue, but it also seems to take me out of the price range I want to stay in. Some have suggested RBW as low as 100 Hz or even 10 Hz, but that really seems overkill. Of the two units below only the Instek is a real RTSA and it has a RBW of 3kHz which seems ok to me. They do have a LCD version with 2.5 GHz coverage, but it is almost 2x the price.

Here are the links for the GPS-810 ($1750) from Instek and the Protek 3290 ($1900) which is only a "Field Strength" Analyzer, but it gives me 2.9 GHz coverage which the Instek doesn't.

http://www.instek.com/GSP-810.htm

http://www.protektest.com/ProdInfo.asp?prodId=3290

I also looked at the Avcom PSA-37XP ($3200) w/ 2.5GHz coverage, a LCD display, but at a much higher price tag and the RBW is only 75 kHz. The B&K 2630 ($1900) gives you a tracking generator, but the RBW is only 20 kHz if I read specs correctly;

http://www.avcomofva.com/products/de...p?page=psa37xp

http://www.bkprecision.com/www/np_specs.asp?m=2630

It was also suggested to look at the used market which I did, but I'm not into 'boat anchors' especially considering the weight of some of these (60 lbs). While it doesn't have to be a handheld unit, I need some type of portability. Also, those $30k units from 20 years ago are way to much machine for me even though the prices are sometimes good if you can find someone that has them and can align them (I have and he was trying to sell me a Aglient 8650 or something close to that for around $3k).

Hope most of that made sense.

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post #4909 of 16297 Old 06-18-2006, 05:36 PM
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Someone who has an Avcom "37" of some variety posted in another forum that Avcom wanted about $1,000 to fix it, and he was hoping that some member could point him to an independent repair company, which no one did. If that is a representative Avcom. out-of-warranty repair charge, then I'd say if any comparison between buying an Avcom product and a competing one is anywhere near close, I'd go with the other brand.
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post #4910 of 16297 Old 06-18-2006, 06:42 PM
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Purchased house with existing antennae, didn't get all local UHF channels, but we were able to get sporadic Digital signal on our HDTV set, so we decided to purchase new Yagi style Antenna (43XG) from Antennas Direct. Once it was set up things were worse then before.

Debating on whether to go back to Cable, but aren't ready to get hit with the huge bill.

If anyone has any suggestions please advise.

-AA


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Please post your experiences with antennas, preamps, all related equipment, and installation experiences. Indoor & outdoor. To include mounting, cabling, connectors, rotors, etc.

- Be specific; brands, models, sources, prices, etc.

- What works, what doesn't, and why?

- Tricks of the trade, and unique solutions.

Thanks in advance for your participation. AVS is only as good as it's members, and our members are the best.

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post #4911 of 16297 Old 06-19-2006, 06:55 AM
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Quote:
Originally Posted by Anti-ant View Post

Purchased house with existing antennae, didn't get all local UHF channels, but we were able to get sporadic Digital signal on our HDTV set, so we decided to purchase new Yagi style Antenna (43XG) from Antennas Direct. Once it was set up things were worse then before.

Debating on whether to go back to Cable, but aren't ready to get hit with the huge bill.

If anyone has any suggestions please advise.

-AA

Start with antennaweb.org so you'll know the direction and distances of broadcast towers in your area. Then you'll have to decide which stations you want to get which will determine the antenna you need. A lot of times all you need to do is reposition the antenna to get most if not all the stations you want.
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post #4912 of 16297 Old 06-19-2006, 07:37 AM
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AntAltMike; $1k to repair a $3k unit isn't really outlandish depending on what's wrong with the unit. With something that specialized I wouldn't be surprised that few if any would or even couild repair it. I doubt I would even consider sending to anywhere other than back to the manufacture.

Other than that, where are all the TV engineers in this thread with all that in depth topic discussion??

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post #4913 of 16297 Old 06-19-2006, 09:03 AM
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Quote:
Originally Posted by Anti-ant View Post

If anyone has any suggestions please advise.

Well, your alias doesn't make me optimistic, but here's some advice for you.

First, if you want help on this forum we need more information than just what antenna you're using. Distances to the stations, frequencies (real, not virtual) of the digital signals, call letters of the stations you're having trouble with (as not all are broadcasting at high power or from tall towers yet), and what relative analog signals look like. A brief summary of terrain (trees, buildings, hills) between you and the transmitters would also be helpful. You should also include information on what, if anything, is connected between the antenna and your tuner (multiplexers, splitters, etc.) age of coaxial cable and connectors, and tuner model.

Once we have that, it should be easy to determine what the problem is and help you fix it, or tell you the problem can't be easily fixed.
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post #4914 of 16297 Old 06-19-2006, 12:16 PM
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AntAltMike writes:

> Unfortunately, I am not outfitted to produce any kind of a screen capture

There's always the old fashioned method: point a camera at the screen.

videobruce writes:

} With 4600 posts it's kinda impossible to read through them all.

I did. It takes awhile. You didn't miss a thrilling discussion on spectrum analysers.

} Some have suggested RBW as low as 100 Hz or even 10 Hz

I could see 10 Hz or even lower for audio, but it certainly sounds
like overkill for RF.

What RF application needs 10 Hz?

How are you going to display it?

A HD display at 1920x1080 would only give you a 19,200 Hz wide display.
A Apple/Dell $$$$ 30" 2560x1600 display will give a 25,600 Hz wide display.
A 1200 dpi laser printer with 14" paper gives at most a 168,000 Hz wide display.

} It was also suggested to look at the used market which I did, but
} I'm not into 'boat anchors' especially considering the weight of
} some of these (60 lbs).

} While it doesn't have to be a handheld unit, I need some type of
} portability.

Portable means it has a handle and fits through a submarine hatch. :-)

I've also been looking at spectrum analysers. For those of us who only
require submarine hatch level portability, does anyone have thoughts on
the Tektronix 7000 series SA plugins? I already have the mainframe.

Has anyone found a SA that connects to a computer? (e.g. a "plugin"
except using a computer for display instead of a scope/analyser mainframe)

At the very low end, there is the Digiair, available from solidsignal.com.
But at 1 pixel per channel, it doesn't look very useful. (It's really a
signal level meter with an extremely wimpy SA mode thrown in.)

I guess the real question that both videobruce and I have, is:
what is the least expensive SA that will get the job done?
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post #4915 of 16297 Old 06-20-2006, 05:27 AM
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I don't understand your paragraph on video display resolution for HD or computer monitors as is has NOTHING to do with the subject.

The 100 & 10 Hz for Resolution BandWidth was a recomendation I have seen a couple of time for tuning filters, but I suspect they were talking about if filters at the board component level. Something I doubt I would ever do.

I have the option of the Protek 3201 or the Instek 810 at around $1700 for either with return privileges.

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post #4916 of 16297 Old 06-20-2006, 08:18 AM
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I use a 100Khz bandwidth filter resolution when adjusting FM equalization notches in master antenna systems in which the FM is to be deliberately incorporated, but must not contribute to the overload of the distribution amplifiers. And in the instance of someone needing to attenuate the aural carrier of an NTSC channel where there is an ATSC channel immediately above it, like a channel 2 NTSC aural carrier at 59.75Mhz, without damaging the channel 3 NTSC pilot at 60.9 Mhz, a grade of resolution a little finer than 100 Khz would be helpful but not essential.
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post #4917 of 16297 Old 06-20-2006, 09:35 AM
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Ok, Mike any anyone else, why are these other guys saying 100Hz and even 10Hz for a RBW??
Where would one need something that tight??

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post #4918 of 16297 Old 06-20-2006, 10:22 AM
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Quote:
Originally Posted by videobruce View Post

...why are these other guys saying 100Hz and even 10Hz for a RBW??

So it won't seem out of place alongside their Lamborghinis. Or their 1080p TVs.

They may also prefer Monster Cable test leads.
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post #4919 of 16297 Old 06-20-2006, 11:34 AM
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Not in these forums, I was referring to articles I have read from various sources.

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post #4920 of 16297 Old 06-20-2006, 05:18 PM
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> I don't understand your paragraph on video display resolution
> for HD or computer monitors as is has NOTHING to do with the subject.

My point is that there will be so much data that there is no way
to display it.

A standard TV channel in the US is 6 MHz wide.

If you want a spectrum analyser to show you a graph that is 6 MHz wide
and resolve down to 10 Hz, you need a display with 600,000 pixel
horizontal resolution. I don't know of any display that has anywhere
near that resolution, whether CRT, LCD, plasma, DLP, or paper.

A CRT might be 100 dpi. A laser printer might be 1200 dpi.
At 1200 dpi you would need a piece of paper 41.6 feet (12.7 meters) wide.
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