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Old 9-Feb-2017, 7:09 PM   #41
jrgagne99
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Tropospheric propogation?

Lately I've been trying to pull in WFFF (Fox affiliate), which has a NM=-5.8 dB on my Tvfool report (borderline "extreme measures required"). I'm well aware of the difficulties of pulling in a 2+ edge signal 70.5 miles away. Well, this past Saturday in preparation for the Super Bowl, I vertically stacked two SolidSignal HDB8x's, walked the roof to find a "hot-spot", and finally had success!, sort of... I was able to receive WFFF all night Saturday, into the afternoon on Sunday, and then by 2pm, the signal was gone. Bummer, no Superbowl from the comfort of my own living room...

Anyway, I have two questions about this situation:

1) Given that reception lasted for 20+ hours could this have been a "tropospheric" reception phenomenon? I haven't re-established reception since it went out, but it's because the wind blew the antenna out of position on Sunday night and then it snowed later, so I haven't been able to climb up on the roof to re-aim it and secure things better. I am sure that it was not a change in aim that caused LOS on Sunday afternoon.

2) The combined capture area of my two stacked HDB8x's 1728 sq-in. This is exactly the same area as a single DB8e. Do you guys think a single DB8e will perform as well (or maybe even better) than my stacked HDB8X setup?

Thanks in advance, as always.

Last edited by jrgagne99; 9-Feb-2017 at 7:27 PM.
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Old 10-Feb-2017, 1:21 AM   #42
rabbit73
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The signal path for WFFF is very similar to the WCAX signal path, but WFFF is running much less power and its antenna is a little lower on a separate tower.





You are on the extreme fringe of coverage for WFFF



A closeup of WFFF coverage; purple is very weak, no color is dead zone



Quote:
1) Given that reception lasted for 20+ hours could this have been a "tropospheric" reception phenomenon?
Yes, very possible. You can track changes in tropospheric events here:
http://www.dxinfocentre.com/tropo.html

Other local changes in atmospheric conditions can also affect reception of WFFF.

Quote:
I vertically stacked two SolidSignal HDB8x's,
An 8-bay antenna has a horizontal beamwidth that is more narrow than a 4-bay, but its vertical beamwidth is the same as the 4-bay.

When you have a vertical stack of two 8-bays, the vertical beamwidth is even more narrow than one 8-bay. This means the azimuth aim AND the elevation aim are very critical. It might be necessary to tilt the top of the antenna back to aim slightly above horizontal for peak signal.

One of my antenna test locations has a clear path across water, but I found it necessary to tilt my 4-bay for max signal.

Attached Images
File Type: png jrgagne99TVFp1WFFFp1.png (23.8 KB, 351 views)
File Type: png jrgagne99TVFp1WCAX.png (23.7 KB, 364 views)
File Type: jpg jrgagne99TVFcovWFFF.JPG (105.2 KB, 359 views)
File Type: jpg jrgagne99TVFcovWFFFcu.JPG (58.6 KB, 344 views)
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Last edited by rabbit73; 10-Feb-2017 at 2:42 AM.
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Old 10-Feb-2017, 12:27 PM   #43
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Thanks very much Rabbit for the dxinfo URL.

How about 2xHDB8x vs. 1xDB8e? Thinking in terms of the capture area. I ordered a DB8e on sale, with VHF dipole (maybe it'll pick up WVNY) for $160, free shipping.
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Old 11-Feb-2017, 1:22 AM   #44
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Two 8-bay antennas will have a larger capture area, but that doesn't guarantee signal increase, as I mentioned in post #9. The larger capture area theory assumes that the wave front is uniform across the whole antenna; that is rarely true especially with weak 2Edge signals that have been scattered by terrain interference.

The DB8e has been optimized for the latest 14-51 band. I have no idea about the actual gain of the HDB8X based on range tests.





In this case, a smaller capture gives a stronger signal:

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Last edited by rabbit73; 11-Feb-2017 at 1:36 AM.
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Old 20-Jun-2017, 12:43 PM   #45
jrgagne99
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In my latest experiment, I combined a Stellar Labs 30-2476 VHF yagi with a DB8e 8-bay using a UVSJ combiner (Stellar labs 33-2230 UVSJ). Real channel 25 (WNNE) is strong enough that it is separately received by both antennas, even though I point them 90-degrees off from the Real-25 tower to pick up Burlington stations. I confirmed this by separately removing UHF and VHF feeds to the UVSJ, and I receive Real-25 in both cases. Strangely, when both feeds to the UVSJ are populated, the UVSJ does not allow Real-25 to pass through to the output.

Any thoughts on what might be going on here? Is this some form of destructive interference where some very low amplitude CH-25 signal passes through the VHF-pass filter and destructively interferes with the CH-25 coming through the UHF-pass section?

Is this an example of UVSJ's "not always doing what they're supposed to" and why I've seen several people on this forum recommend using separate coax runs and an A/B switch for UHF and VHF instead of using a UVSJ combiner?

Last edited by jrgagne99; 20-Jun-2017 at 12:47 PM.
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Old 20-Jun-2017, 4:43 PM   #46
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The UVSJ you used is an unknown quantity. I've not made nor have I ever seen a detailed analysis of its performance.
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Old 20-Jun-2017, 5:45 PM   #47
jrgagne99
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Which UVSJ one would you recommend ADTech?
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Old 20-Jun-2017, 5:53 PM   #48
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Quote:
Originally Posted by jrgagne99 View Post
In my latest experiment, I combined a Stellar Labs 30-2476 VHF yagi with a DB8e 8-bay using a UVSJ combiner (Stellar labs 33-2230 UVSJ). Real channel 25 (WNNE) is strong enough that it is separately received by both antennas, even though I point them 90-degrees off from the Real-25 tower to pick up Burlington stations. I confirmed this by separately removing UHF and VHF feeds to the UVSJ, and I receive Real-25 in both cases. Strangely, when both feeds to the UVSJ are populated, the UVSJ does not allow Real-25 to pass through to the output.

Any thoughts on what might be going on here? Is this some form of destructive interference where some very low amplitude CH-25 signal passes through the VHF-pass filter and destructively interferes with the CH-25 coming through the UHF-pass section?

Is this an example of UVSJ's "not always doing what they're supposed to" and why I've seen several people on this forum recommend using separate coax runs and an A/B switch for UHF and VHF instead of using a UVSJ combiner?
Thank You for so eloquently describing what I have experienced in
the field so many, many times.... In theory, a good UVSJ should
work under all conditions but in practice, that is not so. That is why
I always recommend keeping separate coax runs and using an A/B
switch.....
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Old 20-Jun-2017, 6:38 PM   #49
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Quote:
Which UVSJ one would you recommend ADTech?
Given the limited availability since so many ones from the past are NLA, ours is the only one currently on the market that I have current performance data on. I tested a number of them 5-6 years ago but haven't revisited them since most of them have been discontinued.

Quote:
Thank You for so eloquently describing what I have experienced in
the field so many, many times.... In theory, a good UVSJ should
work under all conditions but in practice, that is not so. That is why
I always recommend keeping separate coax runs and using an A/B
switch.....
Remember to old TV commercial that said "If it doesn't say Sunkist, you don't know what you're getting""? (https://www.youtube.com/watch?v=5jP09HFiRD0) When importers like MCM bring is stuff from China without any performance data provided, there's no telling what you're buying.

:shrug:

Quote:
Strangely, when both feeds to the UVSJ are populated, the UVSJ does not allow Real-25 to pass through to the output.
Sounds more like there's simply excessive insertion loss in the UHF high pass filter and the signal was simply lost due to an inefficient device.
Quote:
Is this some form of destructive interference where some very low amplitude CH-25 signal passes through the VHF-pass filter and destructively interferes with the CH-25 coming through the UHF-pass section?
Unlikely, see previous.

I don't recall, but are you using a preamp with this arrangement. Have you tried amplifying only the UHF signals? IIRC, your combiner has a switch that allows pass-through on the UHF-only port and, if implemented, that would overcome insertion loss of the combiner's UHF port.
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Last edited by ADTech; 20-Jun-2017 at 6:57 PM.
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Old 20-Jun-2017, 8:06 PM   #50
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Quote:
Originally Posted by jrgagne99 View Post
In my latest experiment, I combined a Stellar Labs 30-2476 VHF yagi with a DB8e 8-bay using a UVSJ combiner (Stellar labs 33-2230 UVSJ). Real channel 25 (WNNE) is strong enough that it is separately received by both antennas, even though I point them 90-degrees off from the Real-25 tower to pick up Burlington stations. I confirmed this by separately removing UHF and VHF feeds to the UVSJ, and I receive Real-25 in both cases. Strangely, when both feeds to the UVSJ are populated, the UVSJ does not allow Real-25 to pass through to the output.
You are expecting too much and not giving even the best UVSJ a chance. When you aim your DB8e at Burlington, you are placing WNNE perfectly in the antenna null, making it much weaker. That is what you would do if you wanted to reject WNNE, not receive it.



As ADTech said, their UVSJ is the only one currently available with known performance.





There are a few Radio Shack 15-2586 UVSJs still left; the last one I measured did well.





I opened up the MCM 33-2230 and wasn't impressed, but haven't measured it yet. They are using an all purpose board modified for use as a UVSJ, with a lot of empty pads for components.





Attached Images
File Type: jpg jrgagne99nullWNNE.jpg (158.5 KB, 224 views)
File Type: jpg ADEU385CS-1Sfront.jpg (157.8 KB, 215 views)
File Type: jpg RS 15-2586previous.jpg (144.6 KB, 218 views)
File Type: jpg RS_15-2586_UVSJinside.jpg (216.2 KB, 217 views)
File Type: jpg MCM33-2230UVSJ.jpg (145.1 KB, 211 views)
File Type: jpg MCM33-2230boardtop.jpg (167.3 KB, 214 views)
File Type: jpg MCM33-2230boardbottom.jpg (174.2 KB, 211 views)
File Type: jpg ADEU385CF-1Sinside.jpg (172.8 KB, 202 views)
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Last edited by rabbit73; 21-Jun-2017 at 12:26 AM.
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Old 20-Jun-2017, 8:58 PM   #51
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Quote:
Originally Posted by jrgagne99 View Post
Any thoughts on what might be going on here? Is this some form of destructive interference where some very low amplitude CH-25 signal passes through the VHF-pass filter and destructively interferes with the CH-25 coming through the UHF-pass section?
I think it is possible. You have a very weak CH-25 signal coming from BOTH antennas.
Quote:
Is this an example of UVSJ's "not always doing what they're supposed to" ?
It's an example of trying to make a UVSJ do what it was never designed to do.
Quote:
and why I've seen several people on this forum recommend using separate coax runs and an A/B switch for UHF and VHF instead of using a UVSJ combiner?
That can work well if the antennas are aimed at the transmitters.

If you want reliable reception of WNNE, the antenna must be aimed at WNNE.
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Old 20-Jun-2017, 10:27 PM   #52
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Ad Tech and Rabbit,

The current ambient outdoor temperature at 5,600 feet
is almost 100f. In the lower deserts, the ambient temperature
is over 120f. Now, take a small, enclosed case, filled with
rather delicate electronics...... See how long they hold up.....
I've seen melted circuit boards, melted plastics, and melted
and burned electronic components. Know matter how good
the quality, heat is the enemy of electronics. That is why
auto manufacturers have moved the most expensive and most
delicate electronics inside the car, usually under a seat, where
the heat impact is lessened......
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Old 20-Jun-2017, 10:55 PM   #53
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A car alternator is designed to run with a case temperature of 200F, according to a GM tech in Detroit that I consulted. He had done many measurements on car and truck alternators using thermocouples attached with thermal epoxy. I measured car alternators with a Fluke thermocouple probe when I was installing transmitters in cars to find out how much extra current could be drawn by the transmitter without damaging the alternator. For every 10 degrees C rise in temperature above 212F (100C), the life of the alternator is cut in half. The insulation on the wires starts to soften at about 120C, depending upon the insulation Class. The diodes get pretty hot, too.

And your point is, for the current topic?
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Last edited by rabbit73; 21-Jun-2017 at 12:24 AM.
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Old 21-Jun-2017, 12:58 AM   #54
JoeAZ
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Quote:
Originally Posted by rabbit73 View Post
A car alternator is designed to run with a case temperature of 200F, according to a GM tech in Detroit that I consulted. He had done many measurements on car and truck alternators using thermocouples attached with thermal epoxy. I measured car alternators with a Fluke thermocouple probe when I was installing transmitters in cars to find out how much extra current could be drawn by the transmitter without damaging the alternator. For every 10 degrees C rise in temperature above 212F (100C), the life of the alternator is cut in half. The insulation on the wires starts to soften at about 120C, depending upon the insulation Class. The diodes get pretty hot, too.

And your point is, for the current topic?
"Now, take a small, enclosed case, filled with
rather delicate electronics...... See how long they hold up.....
I've seen melted circuit boards, melted plastics, and melted
and burned electronic components. Know matter how good
the quality, heat is the enemy of electronics."

My point is that electrical components like USVJ's, are the
most likely to fail and the most problematic......

And when would you possibly see a 200f under hood temperature
in a modern car???? None I know of.... and certainly not when
the ambient temperature is above 120f.... That is why we
see so many car fires these days...........
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Old 21-Jun-2017, 1:27 AM   #55
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Quote:
200f under hood temperature
Read it again, Joe; I said alternator case (the metal housing of the alternator) temperature, not ambient temperature under the hood.
Quote:
My point is that electrical components like USVJ's, are the
most likely to fail and the most problematic......
Your point that electrical components will fail above a certain temperature is valid, but UVSJs can tolerate higher temperatures than a preamp out in the sun because they do not have any active components, just wire inductors and ceramic capacitors.

I consider the UVSJ one of the most reliable components in an antenna system.

It is so rare for a UVSJ to fail that I have never heard of it, but many preamps do fail.

I can imagine any antenna system component can fail from a lightning strike, but they are not expected to survive a strike.

Even coax will fail outside when it gets old or corroded from water entry.

Just exactly how, in detail, do you think the OP should set up his system using an A/B switch; which antennas aimed where, to get what he wants?

What happens when the viewer at TV #1 wants the switch set to "A", but the viewer at TV #2 wants the switch set to "B"?

A system with an A/B switch IS very reliable (until the switch fails), but if the TV tuners are not able to add a channel after scan, then it is necessary to rescan after switching to the other antenna. User convenience is just as important as reliability.
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Last edited by rabbit73; 21-Jun-2017 at 2:11 AM.
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Old 21-Jun-2017, 2:45 AM   #56
jrgagne99
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I did some more tests this evening, (all in the last 30 minutes before sunset, for what it's worth). It seems that the 33-2230 UVSJ is greatly attenuating my UHF signals. I was using my Solid Signal HDB91X UHF yagi mounted at 30 feet AGL, with a CM-7778 pre-amp at the mast. In Configuration#1, I sent the HDB91X signal directly to the pre-amp (no UVSJ). In Configuration #2, I combined the HDB91X with the StellarLabs 30-2476 VHF yagi using the UVSJ, and then fed that to the pre-amp. Here are the SNRs as reported by my Sony Bravia (typically need SNR>14 to receive channel):

Real Ch____Config#1 (no UVSJ)___Config#2 (with UVSJ + VHF yagi)
13___________0 (no VHF ant)________18
14___________20__________________15
22___________19__________________6
24___________24__________________9
25___________21__________________8
32___________18__________________10
50___________29__________________17


I repeated configuration #1 a second time and confirmed this wasn't a temporal effect. I also did configuration #2 again, but left the VHF input to the UVSJ empty. The results were the same as with the 30-2476 VHF yagi feeding the UVSJ (except of course no Real 13 reception). Leaving the UVSJ out of the picture (HDB91X and pre-amp only) and signal strengths seem to be unchanged as i write this, even though it is now over 1 hour after sunset. One thing I didn't try was to see how Real13 is affected by the UVSJ. It comes in with the UVSJ (SNR=18), but I didn't measure the signal strength if I use the VHF yagi directly, with no UVSJ. Maybe it would be a fair bit higher. Also, FWIW, there is about 100 feet of RG-6 between my mast mounted pre-amp and the power inserter.

It would seem that I should try a different brand of UVSJ. I would rather like to avoid two lines and an A/B switch.

Last edited by jrgagne99; 21-Jun-2017 at 2:51 AM. Reason: tried to improve table formatting
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Old 21-Jun-2017, 3:11 AM   #57
rabbit73
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Thanks for the test results.
Quote:
It seems that the 33-2230 UVSJ is greatly attenuating my UHF signals.
It looks that way to me, too.

has weatherproof housing

https://www.antennasdirect.com/store...Combiners.html

no housing

https://www.radioshack.com/products/...itter-combiner

maybe try both?
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Last edited by rabbit73; 21-Jun-2017 at 3:23 AM.
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Old 21-Jun-2017, 2:48 PM   #58
jrgagne99
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What about the RCA TVPRAMP1Z Preamp, instead of a new UVSJ?

www.amazon.com/RCA-TVPRAMP1Z-Preamplifier-...

This preamp serves dual purpose, replacing the UVSJ and my CM-7778 pre-amp.

Generally speaking, are folks having good experiences with these?
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Old 21-Jun-2017, 3:05 PM   #59
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The RCA TVPRAMP1R does have dual inputs and is inexpensive. It seems to do well; I'm using one with a GE 34792 Attic Indoor antenna.

There are reports about QC problems, in particular about the combined/separate switch not making good contact with the VHF antenna with the switch in the separate position. The fix is to set the switch to combined and use a UVSJ, which brings you back to where you started.

There is also a review by an installer (Robert Hughes) on Amazon who likes the RCA preamp, and has bought many of them as Amazon Warehouse Deals. The power inserters have a high DOA rate, probably because they were returns that were never tested.

I'm seeing a similar pattern with Duracell batteries on Amazon. Amazon is shipping them in plain packaging instead of the original packaging; many batteries are old, DOA, or leaking.

I suggest you try the RCA preamp, but order from Walmart instead of Amazon.

I'm still confident about the AD and RS UVSJs, but not the MCM. Maybe I'll make some tests of the MCM to see how it compares with your results.
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Last edited by rabbit73; 21-Jun-2017 at 3:18 PM.
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Old 21-Jun-2017, 3:57 PM   #60
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If you buy the RCA preamp, buy two of them and keep your receipts.... Just saying.
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