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The Official AVS Antenna and Related Hardware Topic! - Page 524

post #15691 of 16086
Measuring Some Preamps

There's a lot of discussion about preamps here with much quoting of specifications but not very much hard data. I've managed to acquire the test equipment necessary to perform the critical measurements that we want to see. In the next few posts I'll present data I've taken on some preamps. I'd consider performing measurements on more preamps and posting them here but I'm not going to buy them all. If you like what you see here and have a preamp you can part with for a week or two consider sending me a PM and maybe we can arrange for you to send it here for measurement. I think I'm up to speed on my own preamps and it won't take long to measure others.

I've run the following tests:

1) Gain - Including showing any built in filters such as bandpass or FM traps
2) Isolation - Input to Output signal leakage when the power is removed
3) Noise Figure
4) Input and Output Return Loss - Can be converted to VSWR
5) 1 dB Gain Compression

The only other test I can think is 3rd order intermods and I don't have two signal generators to do that one.

I use the following test equipment:

Rigol DSA 815 - Spectrum analyzer with tracking generator
Agilent 68207A 75 ohm directional coupler
Murray Microwave/Ailtech 7618E Noise Source
Q-Bit 35 dB Gain/3dB NF amplifier (500MHz, works past 700 MHz with reduced gain)
75 to 50 ohm transformers
28V Power Supply
Misc Pads, adapters and cables.

A few notes on measurements...

I don't have any officially calibrated test equipment. I'm not concerned about that for most of the tests. Gain, isolation and return are only comparing two values. Gain compression does require an absolute power measurement so errors in that will make the measurement wrong.

I was most concerned about noise figure. My noise source was last checked for calibration 10 years ago plus it is 50 ohm device and preamps are 75 ohms. I used a JFW 75 to 50 transformer and subtracted out the average loss of the transformer in the frequency range of the measurement from the ENR in the table on the noise source. As you will see this has produced values close to what the manufacturers claim.

I used the spectrum analyzer method of measuring noise figure which is to take the difference in noise power between noise source on and off. The Q-Bit amplifier was used to boost the noise out of the preamps to raise to it into the middle range of the spectrum analyzer.

For those interested, the formula to calculate noise figure is:

NF = 10*Log(((ENR/10)^10)/((Noise Diff/10)^10-1))

Calaveras
post #15692 of 16086
Winegard HDP269 Preamp

This preamp is advertised as low gain, average noise figure and overload tolerant.

Gain



The markers are set to the band edges. The big notch is above the FM band so I don't know what it is there for. It certainly has low gain running 10-13 dB.


Isolation



Power off means your signals are attenuated by 20 dB. Might be an interesting feature if you think you're still getting overload.


Noise Figure



I calculated noise figure for each analyzer display division representing low and high VHF and UHF. Winegard says the NF averages 3 dB and it looks to meet that. You can see external signal ingress on the noise source off trace. In UHF you can see channels 18, 21 and 25. You can see the FM band in low VHF.


Input/Output Return Loss (VSWR)



I calculated VSWR for the lowest return loss. I'm surprised at how poor it is. Seems like you'd want a better match to you antenna. A poor match means lost signal.


1dB Gain Compression

No graphs, I just measured it at the center of each band:

Low VHF - +13.5 dBm
High VHF - +15 dBm
UHF - +15 dBm

Calaveras
post #15693 of 16086
Winegard AP8700 Preamp

This preamp had considerably more to measure than the HDP269. Originally I tested all 3 bands separately but decided to combine some to reduce the number of images in this post.


Gain



This is the gain display with the FM trap turned off and the variable FM notch set to out of the band. The markers are set to the TV band edges. I have a schematic of the preamp and from looking at that I think what looks like bandpass filters are only simple notch filters. Not sure how they get the gain on high VHF to be lower than low VHF or UHF. That small notch on the first slope above low VHF is where the variable FM notch is tuned to.


Isolation



The markers are set to the TV band edges.


FM Filters



The first image shows the Fixed FM Trap with my markings added to show the FM band. The second image shows the range of the tunable notch filter with the fixed trap off. I think you'd want one or the other not both. It would be very hard to set the tunable filter without a spectrum analyzer. I'll bet it's rarely used.


Noise Figure



Here's a detailed look at noise figure. The spec is 2.8 dB and it mostly meets that. Lots of signal ingress though. I don't know what all those spikes on high VHF are. The noise figure goes up at the top end of low VHF because the FM Trap was in during the measurement.


Input/Output Return Loss - Low VHF



I calculated VSWR for the lowest return loss. Turns out the FM trap changes the return loss so I took curves for the trap in and out.


Input/Output Return Loss - High VHF



Again the FM trap changes the return loss.


Input/Output Return Loss - UHF



The FM trap had no affect on the UHF return loss. I continue to be amazed at the poor return loss though.



1 dB Gain Compression

Low VHF - +17 dBm
High VHF - +10 dBm
UHF - +9 dBm

Calaveras
Edited by Calaveras - 12/21/13 at 8:30pm
post #15694 of 16086
TinLee MA-25U-77A UHF Preamp


Gain



The built in high pass filter is shown as part of the gain graph. Gain spec is 30 dB.


Isolation



Great isolation with this preamp.


Noise Figure



Noise figure spec is 2.0 dB. I was told by the engineer that it typically makes 1.5 dB. Looks like it makes that! No signal ingress at all.


Input/Output Return Loss



Best I've seen yet but not amazing. At least it's better than 2:1 in most places.


1dB Gain Compression

UHF - +20 dBm

This is the only high gain preamp that I found to work with my 525' cable run that didn't overload on my strong local channel 18. Now I know why. I still have to use a channel 18 filter to keep the TV from overloading.

TinLee is much more expensive but I guess you get what you pay for.

Calaveras
post #15695 of 16086
Looks like the Tinlee performed the best. But did the Tinlee preamp give you better signal strength measurements than the Winegards? And did it receive any weak channels that the Winegards did not? And since these older model Winegard preamps are now being discontinued, it might be of interest to compare the AP-8700 with the new LNA-200 XT Boost version. It claims better signal isolation and a lower noise figure around 1.5db. And is the Tinlee version still available for purchase, and where?
post #15696 of 16086
Quote:
Originally Posted by tylerSC View Post

Looks like the Tinlee performed the best. But did the Tinlee preamp give you better signal strength measurements than the Winegards? And did it receive any weak channels that the Winegards did not?

This is sort of a loaded question. First it is not possible for me to do an A/B comparison as it takes me 1/2 day to swap out preamps on top of the tower and conditions change too much over time. Second, when you make incremental improvements to the hardware you get incremental improvements in reception. For example, if I upgrade a preamp with a lower noise version, replace a lossy balun with a lower loss one and raise the antennas 10' I might now receive a station 90% of the time that previously was 75% of the time. Unless you go from an indoor antenna to a good outdoor antenna it's unlikely you'll ever see a station go from no reception to 100% reception.

Quote:
And since these older model Winegard preamps are now being discontinued, it might be of interest to compare the AP-8700 with the new LNA-200 XT Boost version. It claims better signal isolation and a lower noise figure around 1.5db. And is the Tinlee version still available for purchase, and where?

I don't think the AP8700 or the HDP269 are discontinued but who knows, it could happen any time.

I'd be happy to measure an LNA-200 if someone wants to send me one. ADTech did some measurements sometime back on that model:

http://www.avsforum.com/t/381623/the-official-avs-antenna-and-related-hardware-topic/15480#post_23636098

Yes, you can purchase Tinlee preamps and other devices.

http://www.tinlee.com/MATV_headend.php?active=4#ANTENNAPREAMP
post #15697 of 16086
Hello all. I hope this is the right place to post this question. Can anyone recommend a vhf only (lo and high band) yagi antenna with a fairly high gain. My plan is to install in the attic. The channels I'm trying to get are 6 and 12 and hopefully 8 off the back side. I have a winegard 8200u outside now which specs say has 6db gain on channel 6 which works great for channel 6.

Apparently I'm in a difficult reception area and the broadcast towers are geographically all over the place. My goal is to get a good bank of channels (at least one of each network) without having to rotate an antenna. We use media center to dvr so if the antenna is in the wrong spot we miss dr oz.

Here is my tvfool: http://www.tvfool.com/?option=com_wrapper&Itemid=29&q=id%3d46aed98b2c4c67

My plan is to point the vhf at philly to get 6, 12 and 2 (that's new), and hopefully get 8 off the back side. Use a 91xg to get uhf from philly (which is a different angle due to hills). I'll combine them with a cm7777 pre-amp and then combine with a uhf pointed west. Any lessons learned on combining the two directions would be appreciated as well.
post #15698 of 16086
could someone help me to find the best antenna for my location in Forest, Mississippi. Here is my TV fool report: http://www.tvfool.com/?option=com_wrapper&Itemid=29&q=id%3d46ae20ae1498d6.
post #15699 of 16086
For individual antenna assistance, find an existing thread in the Local Reception area (index is at the top) and ask there. If there is no local or nearby thread, return here and follow the instructions at the top of the section (sticky note 2, in red).

That being said..

Richard: You're probably going to need a deep-fringe UHF-VHF-Hi combo, roof mounted with a rotor and a pre-amp. It's pretty hilly where you are IRRC

Zirkelad: If 2 is a priority, then you're going to need some serious aluminum in that attic. And different antennas pointed in different directions in the same attic and fed into a combiner could be a multipath and interference nightmare. Consider an A/B switch should the combiner fail. I really would do outdoor with a rotor were I you. Here's the beast I had in my attic in Kentucky to pick up both Cincinnati and Dayton, though not all of the Dayton signals would reach me. Advantage: I was on the top of a hill.
post #15700 of 16086
Quote:
Originally Posted by zirkelad View Post

Hello all. I hope this is the right place to post this question. Can anyone recommend a vhf only (lo and high band) yagi antenna with a fairly high gain. My plan is to install in the attic. The channels I'm trying to get are 6 and 12 and hopefully 8 off the back side. I have a winegard 8200u outside now which specs say has 6db gain on channel 6 which works great for channel 6.

Apparently I'm in a difficult reception area and the broadcast towers are geographically all over the place. My goal is to get a good bank of channels (at least one of each network) without having to rotate an antenna. We use media center to dvr so if the antenna is in the wrong spot we miss dr oz.

Here is my tvfool: http://www.tvfool.com/?option=com_wrapper&Itemid=29&q=id%3d46aed98b2c4c67

My plan is to point the vhf at philly to get 6, 12 and 2 (that's new), and hopefully get 8 off the back side. Use a 91xg to get uhf from philly (which is a different angle due to hills). I'll combine them with a cm7777 pre-amp and then combine with a uhf pointed west. Any lessons learned on combining the two directions would be appreciated as well.

I would be amazed if you could receive all the stations you want with an attic antenna. I't more likely you'll need something outside high enough to clear the local trees and buildings. Even your strongest stations aren't very strong. With mostly 2 edge paths you're almost guaranteed to have dropouts under some weather conditions even if you do everything perfectly. You won't be able to receive 8 off the back of an antenna. Don't even bother to think about combining two antennas that cover the same band on one piece of cable. The only way to really do that is to isolate one channel with a bandpass filter on one antenna and notch it out with another filter on the other antenna and then combine them. It's very expensive and largely impractical for multiple channels.

I agree with DrDon that an outdoor antenna and rotor is the most practical way to go. The alternative would be two outdoor antennas, one pointed at 109 degrees and one pointed at about 260 degrees and use an A/B switch.
post #15701 of 16086
Quote:
Originally Posted by Richard Lewis View Post

could someone help me to find the best antenna for my location in Forest, Mississippi. Here is my TV fool report: http://www.tvfool.com/?option=com_wrapper&Itemid=29&q=id%3d46ae20ae1498d6.

You have a similar situation to zirkelad, two groups of stations in very different directions. Your terrain plots don't look as bad as his though. One antenna with a rotor or two antennas with an A/B switch mounted high enough to clear the local ground clutter and it should work. I see a caution flag on the preamp because you have two very strong local stations. You'll probably be okay though since you won't be pointing at them. Use a lower gain preamp around 15 dB to minimize overload issues. The new Winegard LNA-200 claims it handle large signals.
post #15702 of 16086
Quote:
Originally Posted by tylerSC View Post

Looks like the Tinlee performed the best. But did the Tinlee preamp give you better signal strength measurements than the Winegards? And did it receive any weak channels that the Winegards did not? And since these older model Winegard preamps are now being discontinued, it might be of interest to compare the AP-8700 with the new LNA-200 XT Boost version. It claims better signal isolation and a lower noise figure around 1.5db. And is the Tinlee version still available for purchase, and where?
While on the subject of preamps, last weekend I switched out a Kitztech 200 and replaced it with a new Channel Master 3410 dist amp used as a preamp with remote power supply. Almost identical performance, and slightly better numbers on some weaker signals with the 3410. A very good performing amp. Although the Kitztech is very low noise, it is probably too much power at 24db because I have strong local signals nearby. Possible overload. The CM-3410 has more moderate gain at 15db and is more resistant to overload and distortion. And a respectable noise figure of 2.7db. I get the same signal strength on most channels, but some of the weaker ones are indeed better with the Channel Master. And a great deal at $23.99 when purchased. I recommend the Channel Master distribution amps as a good product where a high gain preamp is too powerful or unnecessary.
post #15703 of 16086
Thanks, TylerSC. Maybe I'll have to try one. Do you think it'll handle 1 megawatt signals from 3/4 mile away?

Larry
SF
post #15704 of 16086
Quote:
Originally Posted by tylerSC View Post

While on the subject of preamps, last weekend I switched out a Kitztech 200 and replaced it with a new Channel Master 3410 dist amp used as a preamp with remote power supply. Almost identical performance, and slightly better numbers on some weaker signals with the 3410. A very good performing amp. Although the Kitztech is very low noise, it is probably too much power at 24db because I have strong local signals nearby. Possible overload. The CM-3410 has more moderate gain at 15db and is more resistant to overload and distortion. And a respectable noise figure of 2.7db. I get the same signal strength on most channels, but some of the weaker ones are indeed better with the Channel Master. And a great deal at $23.99 when purchased. I recommend the Channel Master distribution amps as a good product where a high gain preamp is too powerful or unnecessary.

I assume that when you say "signal strength" that you mean "signal quality" since with 9 dB less gain all the signals will be 9 dB weaker. This is a good illustration as to how it is so difficult to tell the difference in a couple dB of noise figure in the real world. Any signal that is strong enough to give you an SNR in the mid 20's is unlikely to improve with a lower noise figure preamp. Very weak signals that are received only part time may improve a little with a lower noise figure if there are no other issues.

The problem with the Kitztech is that it is unfiltered and can become overloaded easily even if it has a high 1dB compression point. It only takes one very strong signal to do that. If that happens then it will negatively impact all the weak signals. I've seen a situation with my own setup where a preamp made the weak stations disappear. The solution was a one channel filter.

I have a Kitztech on high VHF but I carefully evaluated my RF environment before installing it. I have no very strong DTV stations on high VHF and the public service transmitters below 174 MHz aren't that strong either. The antennas themselves act as a filter out side of high VHF TV to reduce out of band strong signals. I also added a nearly lossless coaxial power combiner for my two antennas. With both those improvements (2-3 dB) and evaluation over time I'd say reception of my weakest station improved from 75% to 90%. The station is 110 miles away over a mountain and there is no practical antenna I can put up to get that last 10%.

I plan in the near future to lower the tower and run a set of tests on the Kitztech.
post #15705 of 16086
Quote:
Originally Posted by Larry Kenney View Post

Thanks, TylerSC. Maybe I'll have to try one. Do you think it'll handle 1 megawatt signals from 3/4 mile away?

Larry
SF

It would be very interesting to use a spectrum analyzer to look at your out of the area stations to see just how strong (or weak) they actually are. It's hard to imagine that the Sutro stations are not impacting the weaker stations in some manner. It would be very interesting to place a one channel bandpass filter on a station like KMAX and see if the SNR went way up when you reduced everything else.

Another point..... At only 3/4 mile from Sutro Tower I assume that the DTV antennas are at least 1000' higher than you are. That would mean you have a fairly substantial angle to look up at the tower, at least 14 degrees. The elevation pattern of the transmitter antennas show that the ERP at 14 degrees down is about 5% of the main lobe. That means instead of 1 MW ERP you get about 50KW ERP. Still that's an immense signal at only 3/4 mile.

Considering the problems I have with just one 50KW ERP station 14 miles LOS, I can only imagine the issues a tower with 10 or more of them causes at 3/4 mile. eek.gif
post #15706 of 16086
Those strong signals are ALSO reflecting BACK from houses IN the beam, which F/B Ratio might not be protecting against....
Don't even THINK about using a Preamp within about 10-15 miles of Sutro Towers....
post #15707 of 16086
If you are in a fringe area, the Kitztech may indeed perform better with more power and lower noise. But in an area with both weak and strong signals, the 3410 may indeed be a better choice. And perhaps a better choice than the Winegard 269 which is a bit noisier. But to use the CM-3410 as a preamp, you will need to purchase a separate power supply.
post #15708 of 16086
Quote:
Originally Posted by Calaveras View Post

It would be very interesting to use a spectrum analyzer to look at your out of the area stations to see just how strong (or weak) they actually are. It's hard to imagine that the Sutro stations are not impacting the weaker stations in some manner. It would be very interesting to place a one channel bandpass filter on a station like KMAX and see if the SNR went way up when you reduced everything else.

Another point..... At only 3/4 mile from Sutro Tower I assume that the DTV antennas are at least 1000' higher than you are.

Sometime when you're going to be down in this area with a little free time, let me know. Bring along your spectrum analyzer and we'll have some fun!

The Sutro antennas are all 1300 to 1600 feet above my antennas, which are at about 350 above sea level, so they're up at about a 22 degree angle.

There are only two adjacent channels on Sutro for distant stations I receive: 34 - 35 and 45 - 46, as you're aware, so that could be a help for me.

Larry
SF
post #15709 of 16086
Quote:
Originally Posted by holl_ands View Post

Those strong signals are ALSO reflecting BACK from houses IN the beam, which F/B Ratio might not be protecting against....
Don't even THINK about using a Preamp within about 10-15 miles of Sutro Towers....

At 3/4 mile, every preamp I've tried has definitely failed. I should probably give up. smile.gif

Larry
SF
post #15710 of 16086
Kitztech KT-200 Broadband Preamplifier


Gain



Not as flat as I expected.


Isolation





Noise Figure



As expected, this preamp has superior noise figure. The problem of course is fairly high gain and no filtering. It's hard to get very accurate numbers with such low values and tiny changes in connector losses and ENR affect the noise figure. Looks to me that the average is around 0.5 dB. No signal ingress here.



Input/Output Return Loss






1 dB Gain Compression

Low VHF - +17 dBm
High VHF - +18 dBm
UHF - +15 dBm
Edited by Calaveras - 12/29/13 at 3:16pm
post #15711 of 16086
I was unaware that there was SOOOOOOOO much to antennae selection!

Some background, recently purchased new home, haven't sold last home yet, so, $ is tighter than two coats of paint.

But, I also vowed to leave the likes of CommunistCast behind me. My zip code is 20659 and the websites call for a "medium directional" antennae. My home has a roofline that points nearly true north, so, I'm thinking that a good antennae in my attic, on the north end, oriented at about 335 degrees would work. My home is alone on a large flat piece of farmland, where there is little obstruction from trees, no obstruction from buildings, but, subject to some hellacious winds.

My hope is to put the antenna indoors, mostly due to appearance, and some just from the weather issues. The home was built in 2006, and the north face of the home is osb sheathed, and then most likely fanfold insulation or house wrap, that I am unsure of, and vinyl sided. So, the antennae would be receiving through vinyl siding, not asphalt shingles.

The roof has a steep pitch, so the trusses have steep angles to the support legs, so, a long (8 foot or so) antennae may be impossible to attempt to install and aim for good reception. In my antennae ignorance searches, I was leaning towards the CM4228 antennae with the CM7777 amp. I would hook the antennae to the prewired RG59 that the house has running to the main patch panel under the stairs.

So, if any of you have suggestions, questions, etc, please fire away, the access to the attic is not easy, but then again, not difficult, just takes planning. I'd rather not purchase and return three antennas to find the one that works, but, am prepared to do so, should that be required. I just don't care to fund the cable companies any more.

Thanks in advance, Happy New Year to you all.
post #15712 of 16086
DaveinMaryland... The CM4228 is great for UHF, but only so-so for VHF channels. Do you have stations that transmit on VHF in your area? It would be best if you could post the TV Fool report for your address that you get at www.tvfool.com. That way all of us could see what stations are available on what channels, from what distances and from what directions. Then we can give you a lot better suggestion.

Larry
SF
post #15713 of 16086
A generic TVFool report based on zip code only shows a couple of high VHF stations with all signals having noise margins in the 20's. An attic antenna might be good enough but you'll need a VHF antenna to go along with the CM4228. An indoor antenna is doubtful and it wouldn't surprise me if it turned out an outdoor antenna was required. A preamp could be helpful in this situation where there are no really strong locals.

An indoor antenna at 10' shows all 1 and 2 edge stations. The situation improves a lot with an outdoor antenna at 30' with mostly LOS stations.
post #15714 of 16086
Hello all - looking for a recommendation on an antenna and preamp if required. Moving into a new house soon. Here are my tvfool results:

http://www.tvfool.com/?option=com_wrapper&Itemid=29&q=id%3d46aefb158d3cd4

Thanks

David
post #15715 of 16086
Thanks for your patience, I hope this pastes correctly.

http://www.tvfool.com/?option=com_wrapper&Itemid=29&q=id%3d46ae5a3810d975

Thanks again.
post #15716 of 16086
Quote:
Originally Posted by dlbeck View Post

Hello all - looking for a recommendation on an antenna and preamp if required. Moving into a new house soon. Here are my tvfool results:

http://www.tvfool.com/?option=com_wrapper&Itemid=29&q=id%3d46aefb158d3cd4

Thanks

David


A small, all-channel combo like the AntennaCraft AC9 should work well. Aim it to the north-west. No amplifiers!
post #15717 of 16086
Quote:
Originally Posted by daveinmaryland View Post

Thanks for your patience, I hope this pastes correctly.

http://www.tvfool.com/?option=com_wrapper&Itemid=29&q=id%3d46ae5a3810d975

Thanks again.

Since attic space is tight, that rules out a 10-12' antenna like you probably need.

Therefore, use two antennas that can be independently positioned. I'd suggest the DB4e for UHF and an AntennaCraft Y5713 (if space permits). If you don't have space for the Y5713, then substitute the ClearStream 5 as it's much more compact. Use an RCA TVPRAMP1R to combine and amplify the signals at the antenna location. Skip the high-gain CM preamplifier, you don't need it based on your stated requirements.
post #15718 of 16086
Hello all,
Can someone offer me some antenna recommendations on what I might need for an attic mount to receive all the major networks here as posted in my tvfool results?
I do receive most of these stations with a very simple indoor antenna near the tv, except CBS.
However I have a lot of tv's but I have a nice wiring system in the house where one antenna would feed all my sets.

I have one of those Channelplus(?) cable tv amps that splits off into 8 feeds that I used for basic cable, but since everything is now scrambled, I was thinking of an antenna in the attic to regain all those free OTA stations.

The attic is fairly roomy, very high pitched roof lines with asphalt shingles, and decent access on a two story house.
Any help would be appreciated.

http://www.tvfool.com/?option=com_wrapper&Itemid=29&q=id%3d46aed0b99c65ea
post #15719 of 16086
slapshot - You have lots of strong stations and all LOS so it should be easy. An attic antenna ought to do the job. Make sure you get something with both VHF and UHF. Maybe your current indoor antenna doesn't have VHF and that would be the reason you don't get CBS. High VHF is a bit harder to get indoors than UHF. I'd suggest the Winegard HDP7694 or the Antennacraft equivalent.
post #15720 of 16086
Quote:
Originally Posted by ProjectSHO89 View Post

Since attic space is tight, that rules out a 10-12' antenna like you probably need.

Therefore, use two antennas that can be independently positioned. I'd suggest the DB4e for UHF and an AntennaCraft Y5713 (if space permits). If you don't have space for the Y5713, then substitute the ClearStream 5 as it's much more compact. Use an RCA TVPRAMP1R to combine and amplify the signals at the antenna location. Skip the high-gain CM preamplifier, you don't need it based on your stated requirements.


Thank you ProjectSH089
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