re: Hoverman mods - Page 2 - Canadian TV, Computing and Home Theatre Forums

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post #16 of 31 (permalink) Old 2017-06-15, 09:55 AM
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I don't want my Mom to lose stations she may be watching while I rotate towards ION.
OK, I get it now; you aren't able to aim directly at ION for the best reception.
Quote:
I also have a Winegard AP-8780 preamp as well as the Channel Master 7775. Is the Winegard less prone to overload compared to the Channel Master?
I haven't compared them, so I can't give you a good answer. I did compare the CM3410 with the original CM7777. The original CM7777 UHF section is identical to the 7775. The 3410 had better overload resistance than the 7777. But, that's just the first hurdle; the tuner can also overload, even if the preamp doesn't.
AP-8780
Gain
VHF 17dB
UHF 28 dB

Noise Figure
VHF 2.9dB
UHF 2.8dB

The Noise Figure looks good, but a 28 dB gain preamp will overload more easily than a medium gain preamp.

Quote:
I have been very lucky to pickup up two Winegard Model # U-620K corner reflector uhf antennas. The reflectors don't look like the usual type with the V shaped reflector, but have a more rounded "C" type shape.
Very interesting. That antenna sounds like the antenna described in the Winegard patent 3518693.



Quote:
I have the original documents for these Winegard uhf antennas.
I would very much like to see a photo of that Winegard antenna and also the documents.
Quote:
The driven element is a loop type with connections on the top
and bottom with instructions to attach the vhf antenna lead to
one set & the down lead to the other.
John Winegard calls that a Tetrapole in his patent.


If you can not measure it, you can not improve it.
Lord Kelvin, 1883

Last edited by rabbit73; 2017-06-15 at 02:00 PM.
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post #17 of 31 (permalink) Old 2017-06-15, 02:11 PM
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The curved reflector is used in the GE Attic Mount Antenna, which performs quite well on UHF.



It has a REAL UVSJ instead of 1/4 wave shorting stubs:





GE also makes an outdoor version:



When I was through testing the GE 29884 antenna, I started to put it away, but my wife said, "Don't do that, I want to look at it. I like the curve of the reflector."



Never underestimate the importance of the WAF (Wife Acceptance/Approval Factor).

If you can not measure it, you can not improve it.
Lord Kelvin, 1883

Last edited by rabbit73; 2017-06-15 at 02:27 PM.
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post #18 of 31 (permalink) Old 2017-06-15, 04:41 PM
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What we know re CM7775 (UHF Only part of OLD CM7777):
Specs: UHF Gain = 26 dB, NF=2.0. [See PREAMP OVERLOAD CALCULATOR Spread Sheet for Overload Specs.]
Per SPECS, I calculated UHF Max Input of -35.8 dBm for Two Strong Signals and Max SFDR = 55.0 dB
CM7775 + OLD CM7777 NOT tested by either Calaveras or ADTech for Overload.

What we know re AP8780 (UHF Only part of AP4800):
Specs UHF Gain = 28 dB, NF=2.7. [See PREAMP OVERLOAD CALCULATOR Spread Sheet for Overload Specs.]
Per SPECS, I calculated UHF Max Input of -28.8 dBm for Two Strong Signals and Max SFDR = 62.0 dB
AP8780 + AP4800 NOT tested by either Calaveras or ADTech for Overload.

So, PER THE SPECS, AP8780 has 5 dB Wider SFDR and can Tolerate a 7 dB Higher Max Input Signal Strength.

PS: Spurious Free Dynamic Range = Difference between Strongest Carrier Level and Thermal Noise Floor when Input Level is Adjusted for Max Dynamic Range wherein the InterMod Distortion Noise is just barely BELOW the Thermal Noise Floor (about -106 dBm). Note that some INPUT ATTENUATION may be required in severe Overload situations in order to bring the signals within the Max Input Signal Level, since IMD is reduced by 3 dB for each 1 dB of Input Loss, hence 6 dB Input Loss reduces IMB by 18 dB, a NET Improvement of 12 dB.

BTW: NEITHER of these comes even close to the Overload Resistance of fol. Mast Mounted Preamps: A-D Juice (SFDR=82.5 dB) and HDP-269 (SFDR=85.7 dB, Spec Calcs claim 71.3 dB, only 15 dB Gain only suitable for LOW LOSS Systems) or the fol. inexpensive DistroAmp: CM3410 (SFDR=81.9 dB)....where the extra Input Coax Loss MIGHT actually be HELPING to reduce InterMod Noise Levels.

Calaveras Comparisons of MEASUREMENTS:
http://photos.imageevent.com/holl_an...028Nov2015.jpg

Comparisons of OLD PREAMP Specs: [I added last two columns, re-normalized for TWO Strong Input Signals.]
http://photos.imageevent.com/holl_an...20RevB.doc.pdf

My OLD PREAMP OVERLOAD CALCULATOR SPREAD SHEET: [Pick *.PDF if you only want to LOOK at it.]
XLS 9 of 25, OTA Reception Files

Note that in the Overload Calculator S/S, I advise keeping Input to Tuner (Sih) less than -10 dBm and preferable less than -15 dBm....a educated guesstimate, since Tuner mfr's NEVER divulge this important piece of information. And NOTE that the + 5 dBm SINGLE SIGNAL Overload Number found in CECB Requirements Spec is DIFFERENT, measuring when the Amp goes into SATURATION, no longer passing ANY Signals....whereas we are far more interested in the INTERMOD Interference, which is a TWO or THREE Strong Input Signal Test that DEGRADES Sensitivity for Reception of WEAK Signals.

Antenna Simulations, Overload Calculations, etc: http://imageevent.com/holl_ands

Last edited by holl_ands; 2017-06-15 at 05:29 PM.
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post #19 of 31 (permalink) Old 2017-06-15, 06:14 PM
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holl_ands:

For reference, this is his latest updated tvfool report. If you click on pending, you will see CBLT with a signal power of -24.7 dBm, giving a total of 4 very strong signals. The input to the preamp would be that, plus the antenna gain. How much is too much in terms of IMD and SFDR for the preamp and tuner?
TV Fool

His weakest desired signal is WPXJ, a Tropo signal with a NM of -22.3 dB.

If you can not measure it, you can not improve it.
Lord Kelvin, 1883
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post #20 of 31 (permalink) Old 2017-06-15, 09:49 PM Thread Starter
 
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Hi: rabbit73.

Hey, that's them.

I never found any info online about the Winegard corner reflector.

Thanks so much for posting it.

I have two brand new ones in my garage.

If I could do the rotator thing, I would stack the two Winegard
antennas & I'm sure they would kick ass.

Bruce.
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post #21 of 31 (permalink) Old 2017-06-15, 10:01 PM Thread Starter
 
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Hi: rabbit73.

I feel like such a dumb ass but I forgot how to post pics on here.

If you want to meet up sometime I would be happy to give you
a copy of the Winegard documents.

Or send me an email & I will email them to you.

bruce1965@bell.net
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post #22 of 31 (permalink) Old 2017-06-16, 02:46 PM
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First of all, we need to look at Specs and calculated SFDR for each selected Preamp. Max SFDR is the Maximum Signal to NOISE FLOOR Level, so subtract 15.2 dB [ATSC's Min SNR Requirement] to find the below calculated SIGNAL DYNAMIC RANGE (SDR). In order to PROVIDE this Max SFDR, an Input Attenuator is needed to bring the INPUT signals to within the Calculated Max Input Signal. Where we need to account for the difference between the number of STRONG Signals (6 in this case, the first 3 significantly stronger than the next 3) and the calculated 2 Input Signal Max Input...."multiple signal derating". I'm going to eyeball it as equivalent to (roughly) two -20 dBm signals, which is close to what AP8780, Juice and CM3410 need to provide MAX SFDR if 0 dBi Antenna Gain [so need Input Attenuator db = Antenna Gain dBi]...although 1-2 dB MORE MIGHT be needed to Tweak it. And CM7775 needs about 15 dB MORE Input Attenuation that THAT....illustrating what we have been saying for MANY years....ONLY use CM7777/CM7775 in a RURAL Location, well away from ANY Towers. And when you have -20 dBm Input Signals with ANY of the Other Preamps, you are ALREADY in severe Overload and need to either Attenuate the Input Signals.....or TRY IT with NO Preamp:

CM7775 Specs: UHF Gain = 26 dB, NF=2.0; SFDR=55.0 dB, SDR=39.8 dB.
AP8780 Specs: UHF Gain = 28 dB, NF=2.7; SFDR=62.0 dB, SDR=46.8 dB.
AD Juice Specs: UHF Gain = 26 dB, NF=2.0; SFDR=82.5 dB, SDR=67.3 dB.
CM3410 Specs: UHF Gain = 26 dB, NF=2.0; SFDR=85.7 dB, SDR=70.5 dB.

Clearly the CM3410 would be the BEST (and least expensive choice)....and per C-M/PCT is water resistant.
The WEAKEST (average) Input Signal Level would be -25.3 dBm - 70.4 dB = -95.8 dBm.
This explains why WDTB (-96.7 dBm) is in TVFool's GREY Zone....ain't gonna happen.
And the RED Zone stations may or may NOT be possible, esp. if they experience severe Multipath Fading.

If AP8780 is used with an Input Attenuator (about Equal to Antenna Gain) to avoid OVERLOAD,
the WEAKEST (average) Input Signal Level would be -25.3 dBm - 46.8 dB = -72.1 dBm.
This means the BEST it would MAYBE Receive is WKBW (ABC) with Rx(dBm) = -71 dBm (before Attenuation).
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post #23 of 31 (permalink) Old 2017-06-16, 06:09 PM
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Thanks for the analysis.

If you can not measure it, you can not improve it.
Lord Kelvin, 1883
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post #24 of 31 (permalink) Old 2017-06-17, 02:03 AM Thread Starter
 
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Thanks for the additional info about he preamps.

So I guess it's safe to say if I do a vertical stack with the 2 RS Hoverman's
I should have sufficient gain & should not use a preamp.

The only reason I was even thinking of the preamp in the first place
was due to splitting the signal for 3 tv sets & I wanted to make sure
I had sufficient signal for each set.

I know indoor preamps pretty much suck, so this is why I was thinking about
an outdoor one.

What would happen if I connected the two Hoverman's with 300 ohm twin lead & connected
a single balun to the lower one or alternately rigged up a new insulator between the upper
and lower antenna & connected the balun to the center point ?

Any thoughts since I was advised not to use two baluns & a two way splitter backwards
to connect the two antennas.

Thanks again guys.
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post #25 of 31 (permalink) Old 2017-06-17, 03:51 AM
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You are probably right about CHEAP Indoor Amps being of low quality.

HOWEVER, Drop Amps QUALIFIED for CATV Use [such as CM/PCT CM3410 with Passive RETURN Channel, whose performance speaks for itself] mean they were Designed to MEET a whole BUNCH of Distortion Specs and undergo regular QUALITY CONTROL Test Processes mandated by the CATV Systems....which also means that they have a more sophisticated PUSH-PULL Amplifier Design which SUPPRESSES all EVEN Harmonics [for less degradation of FM on Hi-VHF Stations], unlike single Transistor Preamp Designs, which do NOT.

CATV Spec Descriptions...prob. not the latest version, but gets the point across:
http://www.keysight.com/upload/cmc_u...?&cc=US&lc=eng

Antenna Simulations, Overload Calculations, etc: http://imageevent.com/holl_ands
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post #26 of 31 (permalink) Old 2017-06-17, 11:07 AM
 
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@holl_ands ,

In post 22 you mention the CM3410 with a UHF gain of 26 db.

The CM spec sheet lists the gain as 15db across the entire VHF/UHF bands.

Did you measure the 26 db gain?

FTA, Openbox S9, 33” dish, Avenger PLL LNBF. Stab 90HH.
OTA, CM4221HD, 3410 amp, 4 way split, HW-150 PVR
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post #27 of 31 (permalink) Old 2017-06-17, 03:50 PM
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Thanks for catching my Copy/Paste Error....I forgot to change the Gain Spec from the preceding line.
Yes, CM3410 UHF Gain = 15 dB....all other numbers are correct:
https://www.channelmaster.com/Antenn..._p/cm-3410.htm

Antenna Simulations, Overload Calculations, etc: http://imageevent.com/holl_ands
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post #28 of 31 (permalink) Old 2017-06-17, 11:11 PM
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Juice UHF Gain 19 dB
https://www.antennasdirect.com/store/JUICE.html

If you can not measure it, you can not improve it.
Lord Kelvin, 1883
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post #29 of 31 (permalink) Old 2017-06-18, 02:20 AM Thread Starter
 
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@holl_ands

Thanks for the info about the CM-3410.

It seems like a top grade preamp for sure.

I hope to get my two Hoverman's up
sometime during my next week off in July
and I will let you know what results I get.

I seen a post where someone had two 8 bay Hoverman
antennas stacked & they had the phasing bars.

They hook to the bottom side of the upper & lower
Hoverman & connect in the middle as the feed-point.

I will try to replicate that setup with my 2 single bay Hoverman's
and also try the two balun & 2 way backward splitter to see the
results.

I will also try the 300 ohm twin lead connect as well to
connect the two antennas for my vertical stack.


Bruce.
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post #30 of 31 (permalink) Old 2017-06-22, 02:22 PM
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I'm getting closer to UPLOAD time, Comparison Charts are nearly done....waiting for a couple last minute Re-Runs to finish up.

One last question: You said Distance between "Rivets" at Feedpoint were 2-1/16 inches apart. Although it won't make much difference, what is the nearest Metal-to-Metal Distance for each of the three BLUE Spacers???? [IN my BLACK Spacers, they're all about 1.5-in.]

BTW: Our R-S Hovermans are 2-3 dB WORSE than the OTHER R-S Hoverman versions.....I've done some "Sensitivity Studies", varying just one parameter at a time to determine WHICH Parameter made the most difference....but there was hardly ANY change varying either Feedpoint Separation, Overall WIDTH SCALE or Overall HEIGHT SCALE....so I'm a bit baffled as to WHY they're degraded...after all, all except the Outer Zig-Zags are all 7-in. [And the Vertical Spikes in the Center, as well as the 1-in "Hooks" on the outer ends are superfluous.] OTOH, reusing the three Spacers (Blue or Black in my case) with larger, Re-Optimized Zig-Zag's, results in performance approaching that of nikiml's Optimized SBGH [GH0 and GH4 with 4 Reflector Rod Pairs]. Next step is to do a run to determine OPTIMIUM HVH Dimensions.

Antenna Simulations, Overload Calculations, etc: http://imageevent.com/holl_ands
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