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.

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.

http://forum.tvfool.com/attachment.p...1&d=1486689565

http://forum.tvfool.com/attachment.p...1&d=1486689565

You are on the extreme fringe of coverage for WFFF

http://forum.tvfool.com/attachment.p...1&d=1486692691

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

http://forum.tvfool.com/attachment.p...1&d=1486692691

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.

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.

http://forum.tvfool.com/attachment.p...3&d=1477409166

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.

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.

http://forum.tvfool.com/attachment.p...5&d=1466633825

http://forum.tvfool.com/attachment.p...6&d=1446858514

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

http://forum.tvfool.com/attachment.p...1&d=1475692853

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?

The UVSJ you used is an unknown quantity. I've not made nor have I ever seen a detailed analysis of its performance.

Which UVSJ one would you recommend ADTech?

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.....

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.

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:

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.
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.

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.

http://forum.tvfool.com/attachment.p...1&d=1497985402

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

http://forum.tvfool.com/attachment.p...1&d=1497986210

http://forum.tvfool.com/attachment.p...1&d=1497990764

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

http://forum.tvfool.com/attachment.p...1&d=1497987107

http://forum.tvfool.com/attachment.p...1&d=1497987107

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.

http://forum.tvfool.com/attachment.p...1&d=1497987508

http://forum.tvfool.com/attachment.p...1&d=1497987508

http://forum.tvfool.com/attachment.p...1&d=1497987508

I think it is possible. You have a very weak CH-25 signal coming from BOTH antennas.
It's an example of trying to make a UVSJ do what it was never designed to do.
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.

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......

A car alternator is designed to run with a case temperature of 200°F, 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 212°F (100°C), the life of the alternator is cut in half. The insulation on the wires starts to soften at about 120°C, 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...........

Read it again, Joe; I said alternator case (the metal housing of the alternator) temperature, not ambient temperature under the hood.
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.

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.

Thanks for the test results.
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?

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?

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.

If you buy the RCA preamp, buy two of them and keep your receipts.... Just saying.

Thanks for the feedback. I just bought both the RCA combiner/preamp from Walmart and the Antennas Direct UVSJ from Amazon. I will test both setups and keep you posted on my results.

What's the consensus on a dedicated deep fringe VHF-Hi antenna?

My Stellar Labs 30-2476 yagi works for WVNY, but DW thinks it is too big. What are the odds a Clearstream 5 VHF rig would work? $139 each is kind of steep to gamble on....

The simulation's math suggests it will work. However, my practical experience with the predicted vs actual signal levels suggests that the calculations for 2-edge paths is often highly variable. I've had instances where Fool indicated a +10 dB margin and no signals were in the air above the noise floor and others where Fool predicted -20 dB margin and reception was 24/7 reliable. At 70 miles away and with less than 10 kW ERP, I'm surprised their signal is even making the trip to your location.

If you try it out, but it from someplace that offers an easy return policy and then watch your return dates. Amazon, for example, only offers 30 days and, if you're a Prime member, quick shipping and pre-paid returns (usually). If you order directly from us, we offer 90 days to return, slow-boat "free" shipping, and you pay the postage if it gets sent back. Other retailers will have something somewhere in the middle.

That got me curious, so I made some measurements to compare four UVSJs:

MCM 33-2230
Radio Shack 15-2586
Antennas Direct EU385CF-1S
Macom (Old)

For the first measurements, I used a Blonder Tongue HAVM-1UA Frequency Agile Modulator as a stable signal source, and a Sadelco DisplayMax 800 Signal Level Meter. The modulator puts out an analog signal; I used the video carrier for each channel. The Sadelco meter has 0.1 dB resolution.

http://forum.tvfool.com/attachment.p...9&d=1498349912

I was having a problem getting consistent measurements. The Sadelco meter has a built-in calibration reference and at certain intervals will correct its readings. This was difficult for me to deal with when making 0.1 dB resolution measurements, so I switched to my Sadelco 719E meter that has a panel meter with wide 1 dB divisions in the center of the scale that allows me to interpolate to the nearest 0.1 dB.

The Sadelco 719E is on the left; the DisplayMax 800 on the right:

http://forum.tvfool.com/attachment.p...1&d=1440873529

I used the red divisions and the second scale -10 to +20 dBmV.

http://forum.tvfool.com/attachment.p...7&d=1498343132

I would read that as +2.8 dBmV.

To make a measurement, I first connected the modulator to the meter with an F-81 adapter and took a reading. I then substituted the UVSJ, UHF and common ports, for the adapter for the second reading.

There was an attenuator at the output of the modulator and at the input of the meter to try to keep the line "flat" (low SWR).

The MCM 33-2230 does have a higher insertion loss that might make a difference if your marginal signals are at the "Digital Cliff."

The Macom UVSJ has very low loss because it has fewer components.

http://forum.tvfool.com/attachment.p...1&d=1498430206

http://forum.tvfool.com/attachment.p...1&d=1498430206

L1, C1, and L2 are the lowpass VHF filter; C2, L4, C3, and L3 are the UHF highpass filter.

This UVSJ will pass power to a preamp for the VHF antenna through L1 and L2.

Thanks for the UVSJ test-info Rabbit.

While I was waiting for the RCA TVPRAMP1Z and Antennas Direct mast-mount UVSJ to arrive, I tried another UVSJ that I remembered I had purchased a while back on Amazon- a Blonder-Tongue ZHLSJ. It showed the same wacky UHF attenuation that the MCM 33-2230 did. I was now suspicious that something else in my setup was at play. However, when I plugged in the Antennas Direct UVSJ, it worked swimmingly. No UHF or VHF attenuation! Additionally, the RCA TVPRAMP1Z, with its separate UHF and VHF inputs, worked great as well! Maybe MCM is using Blonder-Tongue components in their parts (or vice-versa) I don't know, but in any case, they both appeared to be defective.

Anyway, for two days now, I've been pulling in WCAX, WPTZ, and WVNY at SNRs all greater than 20 dB, with only very rare pixellations, and no drop-outs. I'm even getting WETK, which is way down at NM=-2.2dB on my report. I'm using the HDB91X for UHF and the MCM 30-2476 for VHF-Hi.

My stretch-goal now is to pull in WFFF (Real Ch 43, NM=-5.8 dB). I have occasionally achieved this before using two vertically stacked HDB8X's positioned in a certain spot on my roof. But that configuration is a real wind-sail, and we live in a especially windy spot. So I'm thinking of stacking two HDB91Xs instead.

Question: What separation distance should I try (to start with) for vertical or horizontal stacking of two HDB91X antennas?

Ditto that. I've had 4 of them, 3 actually worked.

A HLSJ is not the same as a UVSJ. A UVSJ passes UHF and blocks VHF-High and VHF-Low on the high port; it passes VHF-High and VHF-Low on the low port. A HLSJ passes VHF-Low and blocks VHF-High and UHF on the low port; it passes VHF-High and UHF on the high port.

http://forum.tvfool.com/attachment.p...1&d=1494006989

http://forum.tvfool.com/attachment.p...7&d=1473349481

http://forum.tvfool.com/attachment.p...1&d=1498678126

IOW, the crossover for a UVSJ is between VHF-High and UHF; the crossover for a HLSJ is between VHF-Low and VHF-High.

Glad to hear that the AD UVSJ is working well for you.
http://forum.tvfool.com/attachment.p...1&d=1498682526

Even though an HLSJ is a different device than what was needed, it should have no ill effect on UHF pass-through provided the ports were not reversed. Only high-VHF should have been affected (assuming correct connection and no other defects).

Thanks for the info on spacing Rabbit. The chart is slightly confusing, but if I'm reading it right, it looks like the optimum vertical spacing is 0.67*lambda, and the optimum horizontal spacing is 1*lambda, where lambda is the wavelength of the "lower-channel antenna". Since my UHF antennas are obviously both the same, I guess I'll take that to mean the the lowest frequency in the UHF band (Ch14 = 473 MHz), so my lambda is 25-inches. The spacing to optimize reception of WFFF (Real Ch43 = 647 MHz) should be based on lambda=18".

At least those are some ball-park numbers to start with. I'll try vertical stacking first because it is easier to implement. I notice that 0.67*lambda for Ch14 is 16.5". That seems pretty close, but we'll see if it works. The recommended vertical spacing is even closer for Ch43 (0.67*lambda = 12.25").

It seems too close to me also.

This is how seeyabarney stacked his antennas:

http://forum.tvfool.com/attachment.p...3&d=1498789361

his thread:

http://forum.tvfool.com/showthread.php?t=16301

Due to the height of the corner reflectors on the HDB91X, the closest I could space them was about 25". It made maybe a 1 dB improvement in SNR on some channels. Others were unchanged. WFFF might have gone up by 1 dB. Without more sophisticated measurement equipment it is difficult to quantify, especially because in deep-fringe, the SNRs bounce around by 1-2 dB constantly. Even looking at the high-water mark over 30-second intervals, that measurement itself can change by 2-3 dB over a 10-minute period. So it can be difficult to tease out whether the effect is mechanical or temporal.
Multiple repeat measurements at different times of the day are needed to have a better chance at understanding the true impact.

To join the signals, I'm using coax cables of the same length (within 1/4 inch or so), and a combiner scavenged from my HDB8X 8-bay. I'm worried that the combiner losses might be swamping any stacking gains. Can anyone recommend a ultra-low loss combiner I should try?

Most combiners are a splitter used in reverse as a combiner. The insertion loss is very low, average about 0.5 dB. So, the most you can gain by stacking is about 2.5 dB.

However, if the field is non-uniform and one antenna receives a weaker signal, then the gain from stacking can be much less. It's a difficult concept to grasp, but it is possible to end up with less gain from two stacked antennas than what you had with one, even if both antennas are identical, are aimed at the same azimuth, and have feedlines that are the same length.
http://www.hdtvprimer.com/ANTENNAS/merging.html

WFFF will be moving to channel 16, so you will want your antenna to have the highest gain at the low end of UHF, like the DB8E.
http://www.rabbitears.info/market.ph...&callsign=wfff

The only way I know of to combine with a lower loss is to connect both lines together in parallel, giving an impedance of 37.5 ohms, and add a 1/4 wave matching section of 50 ohm coax which transforms the 37.5 ohms to 75 ohms. It would be a custom job. This is what Calaveras did with his two 91XG antennas.
http://www.aa6g.org/DTV/index.html

http://www.aa6g.org/DTV/ABD/Antenna_Block_Diagram.html

http://forum.tvfool.com/attachment.p...1&d=1498854750

Thank-you as always for the info Rabbit. I had no idea that broadcasters were switching channels again. This time it is part of the 2016-2017 FCC incentive auction (per Wikipedia). I called the junior station engineer up on the mountain-top and he said there will be some new transmitter equipment installed as part of the switch. He didn't know if it would be more powerful or less powerful, but I'm going to call the senior engineer Monday night who junior told me will surely know. He's been up there since Elvis died in 1977. :) Hopefully, power levels will go up and coverage will increase...

All other things being equal (i.e. transmitter power), does a move down the band (i.e. WFFF going from Ch43 to Ch16) bode well for deep-fringe reception areas like my house?

I would say yes, if the antenna for Ch16 has at least as much gain as the antenna used for Ch43. I base this on the fact that VHF signals are more frequently used in mountainous areas because they can make it over terrain obstructions more easily. This would seem to apply to UHF low end vs UHF high end signals as well, to a lesser extent.

To summarize, these are the factors to consider when hunting for weak marginal signals:

1. Select an antenna that has the highest gain available for your most desired channel. In your case, it would probably be the AD DB8E after the move to Ch16:

http://forum.tvfool.com/attachment.p...1&d=1489973660

2. Mount the antenna in the best hot spot you can find on your property. That might not be where you want it for the sake of appearance. Often, a single antenna up higher will out perform a stacked pair and will be easier to mount.
3. Keep the coax between the antenna and the preamp input short; every 16 feet of coax is like a 1 dB loss of antenna gain for UHF.
4. Consider switching to a low Noise Figure preamp like the KT-200. They can make the reception of weak signals easier, but are more sensitive to static damage; that's the trade-off.


http://forum.tvfool.com/attachment.p...9&d=1453496093

This is the way it works:

The antenna gain must make the signal strong enough to exceed the Noise Figure of the preamp plus the 15 dB minimum required SNR for the signal. Once the signal reaches that point, the preamp will amplify the signal to overcome the distribution losses. The preamp will also amplify the Thermal Noise Floor which will bury the tuner Noise Figure, making it irrelevant.

The metric for the antenna system performance is called the System Noise Figure; the lower the number, the better. It is primarily determined by the preamp at the beginning of the chain. The System Noise Figure can be calculated using the Friis Noise formula.
https://en.wikipedia.org/wiki/Friis_formulas_for_noise
System Noise Figure calculations for the above Noise Margin diagram:

http://forum.tvfool.com/attachment.p...2&d=1486498735

reducing the balun loss and the preamp NF:

http://forum.tvfool.com/attachment.p...1&d=1489975414

Thanks Rabbit. I had it in the back of my mind that the pre-amp Noise Figure NF is yet another component for me to optimize. Data on the common ones is sometimes hard to find. Here is an effort to condense NF values from commonly (and less-commonly) available pre-amps all into one spot.

CM-7777/7778:
"typically less than 2 dB"
https://www.channelmaster.com/TV_Ant..._p/cm-7777.htm

Winegard LNA-200 "Boost XT"
"1 dB typical"
http://www.winegard.com/amplifiers
but probably overstated according to multiple users

Antennas Direct Juice
"1.5dB on VHF, < 3dB on UHF"
AVS forum post:
http://www.avsforum.com/forum/25-hdt...ce-preamp.html

RCA TVPRAMP1R:
Low VHF - 3.9 dB
High VHF - 3.1 dB NF
UHF - 2.6 dB NF
(from Pete Higgins post, quoting ADTech on this tvfool forum:
https://forum.tvfool.com/showthread.php?t=13530)

KT-200
0.4 dB
http://www.kitztech.com/KT200.html

Research Communications Pre-amps
0.4 dB
configurable for different combinations of VHF-lo, VHF hi, UHF
http://www.researchcomms.com/hdtv.html


It looks to me like the KT-200 might be worth a try for my situation, especially since Research Comms is in the UK. Do you guys have experience with the KT-200s? Is the 0.4 dB NF legit?

The NF is optimistic, but still quite good. That would be the one I would try. Get the coax powered outdoor enclosure version. I can't guarantee that it will improve your reception, but I think it's worth a try.
http://www.kitztech.com/KT200.html

http://www.kitztech.com/standard_coax.html

The LNA-200 isn't as good as when first released. They made some design changes to meet a price point that reduced the performance. Also the shielding isn't adequate. It uses 5V which isn't so good with long coax runs because of the voltage drop. CM made the same mistake with the CM7777hd Amplify preamp.
http://www.highdefforum.com/local-hd...er-7777hd.html

Calaveras on AVS tested a whole bunch. His results in the attachment.

My current setup:

Recently I've been using a single HDB91X at 30 feet agl and a MCM-30-2476 at 28.5 feet agl. Both aimed at 342 degrees, combined with the RCA-TVPRAMP1R preamp/diplexer at the mast, then 100 feet of RG-6 then 50 feet of RG-59. I get good reception of all the 342-degree stations except WFFF which is too far down in the weeds for me i guess.

Observations:

1) My wife didn't like the look of the 4-element planar reflector on the 30-2476, so I modified it down to a single element reflector. After making the change, I lost about 3 dB of SNR on WVNY (real-13), as reported by my Sony Bravia. I was not surprised by this. The SNR is still reliably at 22+, so it is a non-issue (minimum of 14 dB required for reception). So i thought.

2) I installed a generic splitter to try reception on 2 TVs last night. With the secondary TV off, signal strength on the main TV#1 (the Sony) was unchanged across all channels, compared to my original no-splitter setup. But when I turned on TV#2, the signal strength reported by the Sony for WVNY dropped by another 3 dB. The effect was very repeatable, and no other station showed a change in signal strength on TV#1. Last night was no big deal, but on stormy nights, this could cause a reception problem for WVNY, as I will be approaching the 14 dB minimum.

Any thoughts as to what might be causing this? Would a distribution amplifier help in this case?

Thanks!

One red flag would be the excessively long cable runs.
Another red flag would be mixing RG6 and RG59 in
the same system. Cannot help but wonder if there could
be an impedence mismatch?

Both are 75 ohm impedance. No mismatch there.

Of greater concern is that the RG59 typically has a thinner diameter center conductor. If you connect it to a female F-connector that has previously had RG6 connected to it, you may find that the connector does not make a secure physical and electrical connection. Such a loose connection behaves like a capacitor and can cause a loss of lower frequency (think VHF frequencies) pass-through.

I'm guessing here, but it sounds like the 2nd TV is not terminating the signal when off, sending the current backup the cable to the splitter, which oddly is sending it to the 1st TV. This is the only thing I can think of to allow this turning of the 3db drop on and off like that.

If you try adding another amp, get an adjustable model so you can dial it up and down to find the sweet spot between good signal and overload.

Wineguard makes a model that I've used just in front of a 2 way splitter for a similar situation. I can't remember the model off hand and I'm out of town for the week or I'd look at it. I added it after a long run to 2 TV's close together. The rest of the house did not need an amp so the adjustable one just served these 2 "remote" TVs.