Canadian TV, Computing and Home Theatre Forums banner

Signal Amplifiers (Amps, Preamps, Distro Amps)

1358783 Views 4454 Replies 493 Participants Last post by  dsspredator
This Preamplifier Comparison Chart was modified by holl_ands from an original chart at Solid Signal to show Max Input for two Strong Signals. It was reformatted into PDF form by stampeder with permission of holl_ands for the OTA Forum.

If you have any questions about the data in the chart please post in this thread.

Also see tczernec's Loss Calculator Spreadsheet in this post: To use it, make sure to download it rather than using it online.

Another excellent tool is majortom's Cascaded Noise Figure Spreadsheet:



3341 - 3360 of 4455 Posts
Thanks for all the replies.

I had the TV 4-port amp out of line last week and lost channels at my farthest computer. Probably overkill for FM but so far no signs of overload. Haven't tried with a real TV just Hauppauge HVR-1800 tuner cards. Three FM receivers do seem to work better than they ever have but I was using the same antenna and the VHF side of an old CM 300 ohm VHF/UHF input pre-amp with that setup to get the LA stations. I bought the antenna & CM amp ~20-30 years ago.

Thanks for your detailed posts about your adventures with overload; I found them very interesting. I saw your partial tvfool report link and looked at it to see how strong your local signals are:

KVCR at -15.6 dBm is a challenge to weak signal reception. I have been helping Ynot713 on another forum (not allowed to link to it) with a similar problem. His strongest signal is -10.4 dBm (highlighted in red), and I suggested that a drop amp might work for him as it has for you. I also gave him the link to ADTech's SA images.

Once I’m cleared to post attachments, I’ll attach a drawing of my system.
You are not able to post attachments on this forum unless you are a supporter, but you can include an image (use BB Code) of your diagram in your post, or link to an image host. You mentioned a link to your diagram in post #3334, but I don't see a link.

I looked at your album and saw a thumbnail image, but the fullsize image is missing. That has happened to other forum members too, including me. Are you able to upload the image of your diagram again?

How to create a photo album for use on the Digital Forum

Post Pic or attachments
and in particular

Looking forward to seeing your diagram.
See less See more

I sent you a private message on this forum with my email address & phone number. The full size image shows up in my browser in post 3334 of this forum. If you can send me an email with your email address, I'll be happy to email you the full size .jpg or the VISIO source file if you have VISIO. The amps I'm using are PCT MA2-M's. Channel Master sells the same amps using a CM part number. Since they work with cable systems, I think they will easly handle the -10.4 signal combined with the others.

I deleted and reposted the pictorial. Currently in "Moderated" status.

Thanks for the PM and for uploading the image. I didn't see the image in 3334 at first, but when I used the link in your text box without the IMG brackets in a separate window, I was able to recover the image. After that, it showed in your 3334 post and your album.

After your update, it didn't show in your post or your album, only 7 images as before.

Anyway, I have the image which is, as you said, moderately clear @ 94.9KB(600x777) which is good enough for me to figure out the power feeds for the drop amps which interested me. I have a 3410 and a 3412 and plan to use them with PCT-MPI-1G power inserters if I can find them. If not, maybe a different brand will work.

When I was trying to recover the image, I tried different forum styles with the Quick Style Chooser at the bottom of the frame and it seemed to make a difference. I tried it again, and it didn't; it was just a coincidence that I was doing it at the same time you were in your album.

I'm tempted to post it as an attachment, but I wouldn't do it without your permission. If it shows up full size in your album, that would be sufficient.

I see that you are also a ham; that's why you know what you are doing!

Thanks again for the information about your impressive setup.

Best regards,
See less See more

You are more than welcome to post the pictorial diagram as an attachment, especially if you think it would be beneficial for others to download.

I have run all my PCT drop amps with various power inserters. The first two I bought from Summit Source for $1.98 ea. on 9 July 2012 (tonight they want $3.45 ea.) were ASKA PI-10’s because they were rated @ 60VDC 1 amp with an insertion loss of 0.5dB max. One was shorted when it arrived and they wouldn’t replace it, but the other one worked fine. I have also used the Winegard power inserters and they work fine also. I particularly like the Winegard’s because they have a red power LED so when I look out in the garage I can easily see I have power going to my amp.

73’s KB6YPT

The PCT MA2-M’s are rated @ 15 VDC, 300 ma. They measure 2 ¼” X 3 3/8” and only weigh 4 5/8 oz. They can be powered through the RF output port (via a power inserter) or through a separate power input port (adjacent to the RF IN port). I have two of them mounted directly on the antennas with F-71 M-M barrel connectors.

I have 125’ of RG-6 between my power source and the amps., so I was expecting some voltage drop across the coax. Plus I wanted to combine two antennas with minimal loss and couldn’t find a UVSJ that would pass power on both ports.

I decided to build a couple of power distribution boxes and fit them with fixed +15V, 1.5 amp. 3-terminal 7815 regulators. The regulators are bypassed on the input with 0.33uF caps and on the output with 0.1 uF caps. I used a leftover Laptop power supply that outputs 20 VDC @ 2.5 amps. The regulators and chassis mount ‘F’ connectors are mounted on an aluminum plate inside a plastic box that 22 cartridges came in. Voltage drop across the 125’ of coax is well below the regulation minimum. Hope this helps clarify the small print on the pictorial.
See less See more

I see the full size image in your album now, but it doesn't show in post 3334. The image that I recovered was the old one with pictureid=6018. The new image is pictureid=6098, so I don't think it will show in post 3334. Maybe you can PM the moderator and ask him to edit the link from 6018 to 6098. Or maybe, using 20-20 hindsight, I should have suggested that you ask to have 6018 removed from quarantine.

Thanks for telling me about your experience with alternate power inserters; I'll keep that in mind.

With 125 ft of RG6, I understand why you put the 7815s up by the antennas, expecially if the coax is CCS instead of solid copper. With reduced voltage the amps might not perform as well as far as IM products and NF are concerned.

Yes, I am a ham. I asked the rabbit and he said he didn't want to trade his username for a callsign in a public forum; he's laying low and hiding from the FOX!
He did say I could do this:

Thanks and 73 from
ex-DL4.. US Army radio operator, Germany, 1955
See less See more
Pete's Diagram

Here is a higher resolution file of Pete's diagram that he was kind enough to send to me. I am using my image host because it allows a larger file size and larger image size to see the detail:

If above link fails, you can view the diagram at a lower resolution in Pete Higgins album.

And just for fun, I used Auto Sharpen in Adobe Photoshop Elements 6.0 to make it a little better, but the file size is a little larger. This is the link to that image:
See less See more
Problems in Markham

I have had this discussion on the ganging antennas thread looking for answers. Roger1818 has had some suggestions but none have worked out so I thought I would see if anyone here has some thoughts. I have pasted my description of the problem.

OK guys I appreciate the input. Here is another thing I discovered today. A little history. CFTO reception problems began last summer. I put it down to trees or the change to VHF even though it was ok when the change first happened. The in the late fall I lost all US stations on my upstairs Samsung set. My basement Sony was fine except for CFTO. I discovered if I backed the antenna connector slightly out of the Samsung my US stations came back. I put this down to either a failing tuner or bad connection inside. I purchased another Sony set at Christmas and replaced the Samsung with the Sony from downstairs. Everything was fine except for no CFTO. About 6 weeks ago I lost Fox on both sets. Today I was playing around and decide to try an attenuator. While disconnecting things as I back out the antenna connection on comes Fox at full strength! I attach the attenuator and everything seems fine. NO CFTO. I check downstairs and have lost almost all my stations. Remove the attenuator upstairs and on they all come both upstairs and downstairs. The Fox downstairs starts to fade and backing the connection out slightly brings it back. It would appear I have some sort of fluctuating signal affecting the tuners on both sets and the only thing I can come up with is a failing preamp. OH and also once I fiddle and get Fox I have no sign of CFTO at all. If I tighten things up no Fox but a flickering of CFTO. No lock though. Crazy. I am feeling now the antenna and its aim are not the problem. I am baffled and frustrated to say the least. Any thoughts are much appreciated. Mods feel free to move this if it is in the wrong thread.

I have checked the connections inside and they seem fine. I changed the connection on the power injector that runs to the splitter. While doing this I got the fluctuating signal strength on Fox that I get when I disconnect the antenna at the tv sets. If I unplug the power injector I lose all stations, as you would expect. Plug it back in and everything is fine. EXCEPT CFTO and WUTV.My feeling is this is not an aiming issue as I can get these channels by playing around with the connections, at normal strengths, but they are quickly gone again. Does the fact that CFTO is 9.1 and Fox 14.1 have anything to do with this? ie the higher up you go the less influence whatever problem is going on would have? I will check the voltage at the injector but if it isn't high enough could the pre amp run moderately well but not well enough for these channels? And why would wiggling the connection only affect these 2 channels. I still feel this may well be a preamp problem as it seems to be a powered set of circumstances that cause things. I found a new power injector on line but it is about $45.00 by the time I get it. I wondered if this turns out to be the problem if I should just get a new preamp. If so which one? I know the new CM7778 is not highly thought of and the AD CPA19 doesn't seem to be readily available anymore.

My setup is a chimney mounted original CM4221 and original CM7778.

Thanks for any ideas.
See less See more

Your problem sounds difficult and frustrating. I looked at a few of your previous posts. This might be the proper thread because it sounds like a preamp problem.

I couldn't find a link to your tvfool report. Does it look something like this?

How is you 4221 connected to the 7778?

Is your power supply/power injector the CM 0747?

A diagram of your system would be helpful, showing what is connected to what.
See less See more
A diagram of your system would be helpful, showing what is connected to what.
Agreed. Even if it is a text diagram something like this:

| (3 feet RG6)
| (100 feet RG6)

Include as much detail as you can.
Hi Rabbit/Roger
For some reason TV fool won't accept my address this morning but yes that is fairly representative. The power injecter is the cm 0747. Following is an idea of my set up.

CM4221 chimney mount.
Cm7778 preamp on mast just below CM4221
Cable down chimney to grounding block - 25feet?
Cable to inside basement to power injector-20 feet
Cable out of injector to 2 way splitter-3 feet
Cable to downstairs tv out of splitter-3 feet
Cable to upstairs tv out of splitter- 75 feet

Last night everything ran well with WUTV at almost full strength and CFTO locked at 50%. Other US and Canadian stations as usual. 2 or 3 hours later WUTV starts to drop off and signal strength fluctuates wildly between 0 and 90% CFTO starts to drop. All others normal. It is those 2 stations that are the main issue. The reason I keep going back to the pre amp is, because it happens on both sets I feel it is a common problem. Therefore I think it is either the connection at the antenna,connection at grounding block, splitter ( I just replaced it) or preamp. Because it is ok sometimes and then as time passes starts to fail I am leaning towards the pre amp and maybe a failing power supply. ie it is ok for a while but not for long. I feel all my other stations would be problematic if it was bad connections. What I don't understand is why it seems to only affect those 2 stations. The only thing I could come up with is CFTO broadcasts on 9.1 and WUTV on 14.1 and they are closest to each other. I don't even know if that is a viable reason. Up until the start of all this WUTV would have been one of my most reliable US stations and CFTO was of course a flame thrower. The change to VHF affected CFTO but I had no problems with it until last summer. To be honest I don't remember what my strength reading were after the change but they weren't enough to cause any issues for quite a while. It seems to me CFTO changed to VHF in maybe the summer of 2011? Up until this issue the set up had been quite reliable with only weather related reception issues or the odd minimal tweak in antenna aim. Nothing in the set up has changed since the initial install. Meanwhile I watch on Bell TV until I find this problem or rip it all down in frustration. As much as I like OTA this is the reason I would never cancel my other service. Things do happen.
See less See more

You say your problem builds up as you watch TV for a while. As your pre-amp runs 24/7 it doesn't sound like the pre-amp is problem unless you have the pre-amp plugged into a power bar that you use to turn "everything" on and off with. Is this the case?

If I had to guess, I'd say it sounds more like the TV itself because that's the only component that is warming up and cooling off.

For your sake I hope I'm way off course.
Hi Mapmaker
Thanks for your thoughts but I do not think it is the tv. The one in the basement is brand new at Christmas. The same thing has gone on with the upstairs set plus the original one upstairs that I moved to another room. Highly unlikely all 3 would fail exactly the same way. Also they all work fine on Bell TV. The injector is plugged into a power bar that is always on. This is exactly the way it has been for 6 years so some component in the set up has changed not the set up itself.
For some reason TV fool won't accept my address this morning but yes that is fairly representative.
Using tvfool in Canada can be difficult; coordinates seem to work better. What I did was use the interactive map feature of tvfool:

I entered address of Markham ON. Sometimes I have to use Bing maps to give me coordinates when an approx address doesn't work with tvfool.

The marker on the map was centered on Markham, with the coordinates 43.8561,-79.337019

I moved marker to Bullock and Hwy 48/Markham Rd/Main St as you mentioned in a previous post.

To move the marker, left click on it and hold it down as you move it to the proper location and then release. You will see the coordinates change as you move it. I clicked on Make Radar Plot at top right of map. The short coordinates as shown on your report are 43.88***, -79.26***. I will not give the exact coordinates unless you give me permission.
Some ideas to try


I have just enough (outdated) expertise to be dangerous, plus I am paranoid about signal overload, plus I obviously don’t proficiently speak Canadian… so it took me awhile to figure out what you meant by “CFTO”, but I'll try to help.

As I'm sure you know, your 4221 antenna is a 4-Bay Bow Tie designed for UHF reception. CFTO is broadcast on VHF channel 9 @ only 17.4 kW of power. It also comes from ~43 deg. off bore sight from the Baltimore (Fox) stations. One source of your trouble with CFTO could be that a combination of propagation anomalies and antenna pointing are responsible for your degrading reception over time although I would expect CFTO to appear randomly good or bad. A solution to that would be the addition of a High VHF antenna such as an Antennacraft Y5-7-13 or Y10-7-13 and aiming it towards the Toronto station, then optimizing your 4221 for Baltimore. If your “original” amp has a single RF input, you would also need a UHF-VHF Band Separator/Combiner (UVSJ).

What you describe could also be a milder case of what I experienced with my OTA project. Because of the intermittent nature, I first suspected bad cable connections or parts. I replaced an existing ~30 year old; 125’ run of RG-6 with brand new RG-6, fitted with new Channel Master compression connectors. I substituted both the antenna to pre-amp balum and its jumpers and tried different pre-amps. Sometimes it would work pretty good, at other times it was flaky as all get out.

The 7778 pre-amps are excellent in weak signal environments but lack the “head-room” to tolerate moderate to strong signal environments. Antenna pre-amps are designed to amplify signals within their “linear” range. When input signal strengths exceed that range Inter Modulation Distortion (IMD) products are produced. IMD products are mathematical sums, differences and multiples of the signals involved. If your 7778 is being hit by strong signals causing gain compression or whose IMD products fall on CFTO then that could explain your erratic reception.

To test for this, remove the amplifier and power inserter from your lead-in and see if the CFTO signal can be received reliably (if at all). If it is received but variations still occur then some other mechanism is at work, probably multi-path. 50 years ago we used to get this near Lindberg field as the signals reflected off the arriving & departing airplanes.

If you can’t receive CFTO without a pre-amplifier, try holl_ands trick of using 3 – 6 dB attenuation between the antenna and the pre-amp input. Again, if the degradation is eliminated it is indicative of 7778 overload, if not, it’s some other mechanism.

Obviously, while your making these changes, re-check for loose connections or intermittent cables but they would typically affect all channels.

Partially removing the coax from your TV should reduce the signal strength. One last thought is that your 7778 has to much gain and is slightly over driving your TV tuner. Since most modern tuners are designed to work with relatively strong cable channels, and you've tried two different TV's I doubt that that is the case, but it wouldn't hurt to try your attenuators @ the TV input if my other suggestions don't work.

Please let us know what you find.
See less See more
...they all work fine on Bell TV
I believe OTA and Bell use separate tuners (ATSC and QAM) in your TVs.

I'm glad to agree it wouldn't happen on 3 different sets at the same time after 6 years of trouble free operations but, it seems something is warming up whenever you turn a TV on in order for a problem to occur?

What happens if you turn TV1 on until the problem occurs and then (turn off TV1 or leaveTV1 on) go to TV2? Is the problem immediate? And if the problem only occurs after a warmup period on TV2 does it take another warmup period before it occurs on TV3?

As you must realize, I'm still a believer that it has to be something simple like the proverbial forest that we can't see for all the trees in the way.
Rabbit I can now get my tv fool report so it must have been a website problem. I had looked at it many times before this morning so I was wondering why it hadn't worked. How do I post it to the site?

Pete THANK YOU for your insight. You might be on the right track. I tried a 3 db attenuator upstairs and downstairs with no improvement. However one time by installing it upstairs ALL channels were missing downstairs but removing it upstairs brought them back. I detailed this in the ganging thread when I thought I was dealing with an antenna problem. Are you saying to place an attenuator between the antenna line and input to the power supply? haven't done that. I had thought of bypassing the pre amp so as soon as it warms up here I will go up on the roof and bypass it and check the aim. Thanks for your suggestions. By the way my Fox station is from Buffalo not Baltimore. I would be some impressed if I was getting Baltimore here even with all the drop outs and stuttering. LOL


If the problem isn't there both TVs act the same. Once it surfaces both sets are the same. The only difference is my snr readings on the new downstairs set are approximately 2 to 3 less than upstairs. However it locks at a lower reading than the upstairs one. Interestingly they are both Sonys. I feel it has to be in the system not the TVs but I understand your thoughts re warming up.

Thanks to all of you for your input. I am on a mission to figure this out before my Wife kills me for spending so much time on it. LOL
See less See more
Although I would never tell her that, sometimes a whap upside the head from the SO is the correct business decision for a technical problem.


The idea behind the attunator is to prevent pre-amplifier overload by reducing the signal level to your pre-amplifier. Therefore, it goes between the antenna terminals and the antenna (RF) input on your mast mounted pre-amplifier.

In a like manner, to prevent TV tuner overload it would go in the line that feeds your individual TV tuner -after the power inserter and any splitters.

Normally, you can't put anything on the cable that goes between the power inserter and a mast mounted pre-amplifier. The exception would be something like a splitter that has power passing capability on the ports connecting the power inserter to the pre-amp.
3341 - 3360 of 4455 Posts
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.