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Televes active antennas do not have any insertion loss when used in active mode with the amplifier receiving power and working (which is how they are designed to be used) other than an around 0.5dB loss due to the input saw LTE filter. The passive pass-through does incur significant insertion loss and it is intended as an "auxiliary mode" of sorts only, when the available signals are so strong that said insertion loss is irrelevant, or more importantly in the event power fails to reach the preamp for any reason so that the antenna continues to work, albeit at a lowered performance level. Other active antennas do not do this and just fail to work when power fails, this behavior is also better than the alternative of a mast mounted amplifier failing to receive power and interrupting signal flow altogether.

Therefore any spectrum analyzer screenshots, parameter values, and/or conclusions drawn with a DAT LR or any other Televes amplified antenna used in passive mode with the addition of an external third party preamp will show a very significantly diminished performance due to the C/N degradation incurred in that set up. Conclusions, measurements and graph representations derived from such an exercise are apples-to-oranges, uninformed, inaccurate, and in summary, just plain wrong.
That is conveniently left out of all the sales information. The take-away when reading the brochure at Solid Signal is the antenna used with the preamp unpowered is the same as no preamp at all.

Somewhere I read that an external preamp can be used instead of the built-in preamp with no mention of loss through the unpowered preamp. Or maybe that was just an incorrect assumption made along the way somewhere.

Thank-you for clarifying that.


The NF values posted by this individual are also way off, probably because the error is being carried over and the methodology is flawed. It is also unknown how those supposed insertion losses are being measured, since the dipole input where the preamp resides is adapted to the antenna impedance of around 300 ohm balanced (depending on the particular antenna) and not at 50 or 75 ohms, so measuring at the input of the amplifier with a 50 ohm unbalanced meter will not provide any real valuable information.
Thanks for confirming the 300 ohms. I used one of my calibrated 4:1 coax baluns to take a more careful look at the preamp. I am NOT just sticking a 50 ohm noise source on a 300 ohm preamp. I'm using a TPX-75-4 50:75 ohm transformer (0.4 dB insertion loss) and the 4:1 coax balun (~0.2 dB insertion loss) to reduce the ENR of the Ailtech noise source. This produced an improved noise figure of 4-5 dB on UHF. I still consider that to be poor though for a preamp claimed to be <2 dB. If you have any other measurement tips I'd be happy to hear them.

What's going on with VHF is not clear at all. The driven element is a simple dipole which is 75 ohms. I tried both 75 ohm and 300 ohm feed baluns on the preamp and the results were terrible. The noise figure using the 75 ohm balun was 10-11 dB and even worse with the 300 ohm balun. I have a separate high VHF 4:1 balun from another antenna. I'm using the same test setup I've used many times in the past with no issues on high VHF.


I would encourage any interested readers to disregard this misinformation and reach out to Televes directly with any doubts, concerns or for accurate feedback. The RED (radio equipment directive) specifies the FoM (figure of merit) for the characterization of active antennas. The exercise of comparing noise floors to measure NF is incorrect and leads to wrong conclusions. The FoM is related to the antenna gain, the noise power and the NF of the amplifier. Televes active antennas are RED compliant and have been characterized and tested by the most prestigious laboratory in the industry, PKM in Germany.
I'm not sure what you're talking about when you say "comparing noise floors to measure NF." I think you may be conflating NF measurement with comparing antenna gain by equalizing noise floors for antennas with different preamps and coax runs.

RED

"The EU’s Radio Equipment Directive (RED) was introduced in 2016 to establish manufacturing standards for radio products relating to their health and safety, electromagnetic compatibility (EMC) and efficient use of the radio spectrum."

Can you provide a link to the applicable section of the directive so we can understand exactly what this is talking about? Being an EU thing, few in the US are familiar with it. I'm particularly interested in what goes into the FoM to see how applicable it is to the discussion at hand.

To reiterate, the posted values and graphs by this poster in this and several other threads in this forum are wrong. They do not represent the real performance of a DAT LR antenna when used as intended and, although the time and dedication are very much appreciated, they portrait a very misleading picture of the product -probably unintended- and are to be deemed completely irrelevant.
I'd like to point out to readers that the poster is the head sales rep for Televes in North America so he'll never say anything negative about Televes products. He has a strong incentive (keeping his job :) ) in emphasizing the positive and ignoring the negative and every incentive to discredit me as someone who doesn't know what he's doing. I'm just an old retired test engineer with no financial incentive one way or the other to recommend or not recommend any product. My only incentive is the fun of testing these things and hoping someone will get a little bit better TV reception.
 

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I found it!

Harmonized European Standard

Amplifiers and active antennas for TV broadcast reception in domestic premises; Harmonised Standard covering the essential requirements of article 3.2 of Directive 2014/53/EU


Section 4 seems to be of primary interest. Paragraph 4.5 is where the specifications are and 4.5.7 is the Figure of Merit.

Paragraph 5.3.2 describes measuring Noise Figure using a spectrum analyzer. Figure 6b is my test setup. It looks like part of their procedure calculates 2nd stage noise figure and subtracts this out of the calculation. A high 2nd stage NF will make the NF of the AAUT higher than it really is. I take a slightly different approach to this. I use an optional amplifier with 30 dB of gain to override the poor NF of the analyzer. My 2nd stage NF is typically around 0.05dB which is a tiny addition to the final number. I'm more concerned about the accuracy of the Noise Source ENR.

Looks like I'm using the approved RED method to measure Noise Figure.

Chuck
 

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Any changes in test results I presented here came about from improved information from Televes. Finding out that the DAT BOSS was 300 ohms feed impedance resulted in an improved technique lowering the Noise Figure a bit. When the manufacturer doesn't supply complete information assumptions have to be made and occasionally a wrong one is made. When I discover something like this I correct it. All manufacturers give incomplete information so assumptions have to be made or nothing could ever be tested. Any new "angles" are simply me thinking up different ways to test something.

If Televes had come to me and said "I think your numbers are wrong. Can we discuss your test methods and see if we agree on the methods and go from there?" But no, the approach was "Your results are wrong and you probably don't know what you're doing." How is any average person going to react to that?

I have no opinion on any Televes equipment I have not tested, only this one antenna and preamp. As things stand with the information I have, this antenna/preamp doesn't meet my expectations based on claims made for it. My homemade VHF/UHF antennas work better. The preamp doesn't have a good noise figure on UHF and it's downright bad on high VHF.

I've run noise figure on many preamps and published the results of a few. Most of them have performed as expected. A few have not. Unfortunately the Televes is one of the few that did not. Unless new information comes to light, I've ran all the tests I can. Should new information come to light and the NF result is much improved, then I'll share that and explain what happened. At this point I'm at a dead end.

Chuck
 

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Sounding good! Volume consistent with surrounding channels. (y)
Hi Ray,
Thanks for being a viewer! I worked with KMMC-LD and the FCC to change KMMC-LD's virtual channel from 40 to 30. Some people were complaining about there being a conflict with Sacramento 40. I updated the encoder just now.
3073059

Blessings,
Keith
 

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I also flipped 30.1 from being 480i to being 480p. It looks better to me, but I'd like to hear other comments, too.
 

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It is unclear what may be going on with those noise figure tests that are being posted for that DAT LR antenna. Maybe a mismatch issue in the testing setup that's affecting the value or the way the connection to the circuit is being made. The values posted are still not correct.

With regards to the noise figures that have been posted on the Televes 560483 preamplifier, it is very important to understand this is a dual input broadband preamp and most of the contribution to the values that are being brought up is due to the broadband combination of two incoming RF feeds, which is unavoidable physics in such setup. Not an apples-to-apples comparison when put side by side with single input preamplifiers. The Televes 560383 should be considered in that situation, which is lower NF than most of units mentioned while still providing the needed out of band filtering some of the lowest NF models are lacking. The dual is a great tool for many applications, but in a very fringe situation a more optimal solution would be to use individual preamplifiers per feed and combine after the preamps, provided the makeup of the two different RF feeds allows for it. In some situations individual filtering of RF carriers per feed will be needed as well for a proper combination that is not detrimental. Tools exist for such a system.

Readers need to be conscious that there are many other considerations that are as important as the noise figure when comparing preamplifiers which are never brought up in this forum, such as the capability of properly filtering interfering signals, flatness, gain regulation, RF immunity, consumption, build quality, etc. The sole focus on the noise figure is by no means a full picture analysis and/or review of these products, and provides just a very partial view of their performance that leads to wrong conclusions in our opinion. In particular when non-equivalent products are compared, such as a single input fixed gain no filtering amplifiers as opposed to multi-input units with several band filters and gain controls. It is not complicated to design a basic preamplifier that filters no interfering signals and minimizes the measured NF in the circuit, but in the real world there are many aspects that influence the performance of an antenna system in the long run way more significantly than a dB up or down in NF test bench values.

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Chuck,

A thought about your readings. The Televes preamp (unlike nearly all other consumer preamps) has a built in AGC and no way to disable that to my knowledge. It sounds like you are feeding it a very strong signal for your testing. Is it possible that the AGC action is throwing off your readings?

Les
 

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Hi Ray,
Thanks for being a viewer! I worked with KMMC-LD and the FCC to change KMMC-LD's virtual channel from 40 to 30. Some people were complaining about there being a conflict with Sacramento 40. I updated the encoder just now.
View attachment 3073059
Blessings,
Keith
Another channel scan? Well, maybe I'll get lucky and get rid of the extra 7.1-3 that I picked up on the last scan! Will do it this afternoon and let you know.
 

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OK, new world's record for channels acquired at 113. 30.1-4 are live, look and sound good (.5 and .6 still awaiting programming). Can't comment on the 480i to 480p change.

* Duplicate 7.1-3 still there. Reception excellent today.

EDIT: Channel scan missed ch 36. Slight antenna adjustment and manual scan ... now up to 118 channels!
 

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Chuck,

A thought about your readings. The Televes preamp (unlike nearly all other consumer preamps) has a built in AGC and no way to disable that to my knowledge. It sounds like you are feeding it a very strong signal for your testing. Is it possible that the AGC action is throwing off your readings?

Les
Thanks for the idea. I took a brief look at that earlier and I don't think that's the case. Here's another look.

I measured the maximum output on the amp at -15 dBm, the AGC threshold. The attached spectrum analyzer display shows around -50 dBm with the noise source on. That's not what the preamp actually sees. You have to consider Total Noise Power. The preamp has a bandpass of roughly 600 MHz and the analyzer display is using a 100 KHz filter. The Total Noise Power the preamp sees is about 38 dB higher. But I use a 35 dB amp between the preamp and the spectrum analyzer so the preamp total output power is roughly (-50 dBm - 35 dB + 38 dB) = -47 dBm. That's a comfortable 30 dB below where the AGC begins to reduce the gain.

The test setup is: Noise Source --> Preamp --> 35 dB amp --> Spectrum Analyzer

The only additional signal the preamp sees is the Noise Source ENR of 14 dB.

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If anyone has an idea of how to make a better connection of a 300 ohm balun to this preamp with terminals about 1.5" apart, please let me know. I'll give it a try.

3073363
 

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Here's a Noise Figure test on KT-200 preamp I ran today a few minutes after I ran after the Televes NF test shown a couple of posts above. The Noise Figure is <1.0 dB. The test setup is identical except for the 300 ohm balun (<=0.4 dB insertion loss). This is the same balun I've used on my pair of XG91s to reduce balun loss for a decade.

Noise Figure measurement isn't that complicated until you try to get a highly accurate reading. I'm not trying for that here. I'm sure I'm better than 1 dB and probably more like 0.5 dB. Maybe the preamp I have is defective and we're arguing over nothing. The dual input preamp mentioned above that I tested came in very close to the numbers for gain and NF printed on the case.

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Hi Ben,
Can you pick up KQRO-LD 45 again? I came out to the site just now. The preamplifier and receiver had died. So, I bypassed the preamp and swapped receivers.

Blessings,
Keith
Yes & No
I see the signal is back on the air, however I need to do some outside antenna work to know for sure. It's not pointed to San Jose.

Plus, I'm sure all these christmas lights near the antenna don't help with that matter.
So we'll find out later.

Not heard from Larry Kenney in over a few months on this forum. If he reads this maybe he can chime in. His antenna has a rotor.
So he can instantly tell if it works.

This & that
RF-3 from Mt. Tam still won't lock in.
Even though RF-4 does. It has a weak signal that seems to navigate omnidirectional from here. Weird.
Plus Mt. Tam is line of sight from here.

New channels, 15, 30, 40, 52
See no EPG for current programs.
40 still works... unless you do a new scan.
No auto program guide forcing it to move to 30.

Happy new year.
 

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Chuck,

Thanks for the new data and your analysis. Very few consumers have the equipment and knowledge to run these measurements at home. Assuming your figures accurately reflect performance, does it mean that for very weak signals the Televes preamp would add some noise that could obscure reception of the signal - but for signals above that level it would have no adverse effect? Thanks. Les
 

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Les,

Yes, you have it correct. In many cases a very low noise figure may be of no help at all because of noise or other interference in high RF environments like the Bay Area and San Francisco in particular.

I am fully aware that Noise Figure is not the only factor to consider. Most people are not going to be able to tell the difference between a preamp with a 1 dB NF and a 4 dB NF. In lots of cases in the Bay Area I recommend no preamp at all because the signals are plenty strong and a preamp can just cause problems. Even in my fringe area I have only one station that requires the lowest noise preamp, having just a 4 dB noise margin using a KT-200 preamp. All my other stations have noise margins of 15-30 dB. It doesn't really matter what antenna/preamp combination I use for those stations.

I measure preamp gain because it's important to know when calculating the optimum gain for someone's setup. Gain affects System Noise Figure.

I measure Noise Figure because it is the limiting factor when there are no other issues preventing reception.

Sometimes I measure broadband gain to see what the filtering looks like. FM filtering and LTE filtering are often of interest.

Finally, in reference to comments above, I completely disagree that a dual input preamp is a special entity that should be considered separately from other preamps because it has a passive power splitter on the input. If you want a lower noise figure, then design each input with its own amp and combine them.

Chuck
 

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To reiterate, the dual input amplifier mentioned in this thread is a tool for an application. It could certainly be designed differently by making it effectively a double amplifier, which is not the case in the current offering, as one could use two single units in that case. If one was really interested in an apples-to-apples comparison, one would of course use the single input version, which is functionally equivalent to other units mentioned from that perspective, has lower NF than most single input competing units, much better out of band rejection characteristics and gain regulation.

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In a real life installation many other factors mentioned earlier are in actuality more important than a marginal difference in NF, when two comparable units are being evaluated side by side. When within' reason, it is not the sole end and be all parameter by which an amplifier is to be judged, in particular when digital signals are concerned. Adequate filtering of interfering signals and overload avoidance are very often a lot more beneficial in the long run.

A few illustrative responses follow below:

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Hey everyone--new to the forum, and appreciate the valuable information here as I ditched Comcast last month after patiently waiting many years for AT&T to drop fiber in my 'hood (now I'll wait a few more years for Sonic) and am looking for the best solution for my TV needs.

I am less than 20 mi from Sutro and Mt. San Bruno, but I'm in the canyon leading into the west entrance to Caldecott bore 4, so it's not your usual "suburban setup":

Rabbit Ears Study

The Terk HDTVA I've had in the closet over the years obviously won't cut it, but I was able to move it around on the balcony and get decent UHF, although less so for KGO and KNTV on VHF hi.

Additional constraint: I have a stucco house and warrantied membrane roof, so drilling into either is pretty much a no go.

I figured I'd start simple so I'm going with a Clearstream 4V on a Rohn nonpenetrating roof mount with a 5 ft/1.5 in o.d. mast and just under 300 lbs of ballast. The 4V just beat out the CM ultra 80 due to cost and size; my hunch is that it should be fine for UHF, but I may need to compensate for VHF and from what I've read here it sounds like the Stella 30-2475 would be the next step up.

One question: is there an "affordable" coax antenna signal meter anyone could recommend? In case I need to up to a directional antenna it would definitely make placement easier than "trial and error" off my Tablo tuner.
 
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