Signal Amplifiers (Amps, Preamps, Distro Amps) - See Chart in Post #1

[flavoie]

Great, thanks majortom & ADTech !

majortom, I think you meant the 22 miles vs 70 miles transmitters at 35 and 152 degrees with 117 degrees separation in between? The local channels with local news are at 35 degrees and are priority. I guess there's no reason why I couldn't try pointing at 152 degrees if there's enough margin for off the back reception. But from my own experience, the cm4228hd off the back reception is limited, and the ANT751 back reception is unknown to me.

[ProjectSHO89]

Has anyone ever modeled the ANT-751? I haven't run across anything yet.

[majortom]

eek, yes, that is what I meant. must be getting dyslexic...
would still try it though before I left, for curiousity sake if nothing else.
if it could still pull in the stronger stations from the behind with the preamp added, there would definitely never be any risk of overloading the preamp.

Thx Adtech, have you done any two tone IM tests on that PA-18 preamp?
Got any IM test results / specs you can share?

[holl_ands]

Originally Posted by ProjectSHO89

Has anyone ever modeled the ANT-751? I haven't run across anything yet.

I took a shot at it, using several modeling approaches, from a simplified all-tubular
model with TL Cards & No Boom....all the way up to a detailed Boom and Feedlines.
But the SWR was all over the place and only improved when I assumed unrealistically
low Impedances for the Feedlines. The VHF Gain curve was fairly stable, but UHF was not.

I don't think NEC2 has enough accuracy, cuz I saw same problems trying to model YA-1713....

From what I've seen, it's probably close to the W-G HD7000, from which it was derived,
using the SAME UHF front end with shortened long elements to eliminate Ch2-6 coverage:
http://www.winegarddirect.com/pdf/HD7000R.pdf

[ADTech]

Adtech, have you done any two tone IM tests on that PA-18 preamp?

I haven't as I don't have quite enough test equipment in-house, but there are some two-tone graphs somewhere around here from a couple of years ago that our contract design engineer produced during his evaluation of some PA18 and CPA19 samples. I'll see if I can locate them and get permission to post them. The difference is pretty dramatic between the two amps.

As I recall, the 3rd order products were down around 20-25 db from the input tones on the PA18. On the CPA19, they were almost 50 dB down.

[rick5127]

. I live in a northern Detroit suburb so have quite a few strong signals. My GH6N3 is probably fine for any and all that I need.
TV Fool info http://www.tvfool.com/?option=com_wr...ec12e0e0b61c2f

Now for the question. I found an amp the other day, a Winegard model AP-8700, that I had laying around the house. I am considering using this preamp on this antenna. I don't think the antenna really needs it but with it up about 30 feet high, plus rg6 from the room inside where I control all wiring then to the living room TV. I figure is going to be close to 100 feet. So... am wondering if I should just put this preamp inline to help get the signal there nice and strong. Amp specs are 17db UHF, 14db VHF, with NF of 2.8

I only am going to get one chance at this so once it goes up it is going to stay there till next spring. So the question is... do I put on the preamp or not?
__________________

[kc2cbd]

rick5127 give it a try. I have the AP- 8780 and it works well with no overload.
With close to 100 ft of coax I would put it on if it were me.
I would try without and see what you get then install it and make sure you don't lose anything, you should gain.
Your TV fool doesn't exist.

[rick5127]

Well thats kind of the point. I got one shot at this as I will get her up next week or so and then after that I have bad weather till spring. So trying my best guess for the first shot.

[majortom]

I think this is Rick's TVFOOL. The llink was probably inadvertantly corrupted when his post was moved here, to the correct thread. Had it in my browser history from last nite. Rick, is there something in your TVFool that u "must have" that isn't reliable now?.
I've had decent luck with the AP-8700 here in Buffalo, suburban environment. But there's really only 4 or 5 distant stations I really need it for, mostly Canadian stations.


http://www.tvfool.com/?option=com_wr...ec12e0e0b61c2f

[holl_ands]

You have FIVE very strong UHF stations (ch39-45) plus strong Ch14 and Ch21.

"DTV Preamp Signal Overload Calculator" sez your Spurious Free Dynamic Range
is going to be limited, with InterMod Noise blocking reception of affected weak channels.

"DTV Interference Calculator - Rev G" sez the five strongest stations will generate
InterMod Noise on ALL channels from Ch33 to Ch51. And strong Ch14 & Ch21 will
help to generate InterMod Noise on ALL of the lower channels under Ch33.
[see GENERIC-5 - Ex 7 & 8] :
http://imageevent.com/holl_ands/files/ota

If you want to try the AP8700, I would recommend inserting 3-4 dB of attenuation
PRIOR to the Preamp...and then try a 6-8 dB attenuator. For every 1 dB of attenuation,
the InterMod Noise is reduced 3 dB, hence 3 dB Loss reduces IMD by 9 dB and 6 dB
Loss reduces IMD by 18 dB.

[Michael DeAbreu]

I added an Antennas Direct CPA-19 pre-amp to an Clearstream 4 in my attic. TV Fool report
The nearby stations didn't seem to overload the pre-amp but it sure as shootin' overloaded the Hauppauge 2250 tuners in my HTPC. I lost every channel. The TV had no problem and I got respectable signal strength on some distant Seattle stations. I tried aiming off-axis, adding splitters to attenuate the signal and a couple of really silly experiments with an old UHF bowtie. In the end I yanked the pre-amp.

[majortom]

pretty slick holl_ands, I like it, thanks.
Have ya ever played with this one?
a windows app, but works under wine for linux users

http://www3.telus.net/PassiveRF/

Here's a generic report I had it generate for Downtown Toronto
just a quick hack as example output, no real thought in to it (bogus lat long info)
grabbing just some of the channels I think are on the air there
9,19,20,41,44,47,51, and using a rcv window 170 -> 700 MHz

http://dl.dropbox.com/u/44636646/Toronto.txt

[kc2cbd]

Correct me if I'm wrong but wouldn't rick5127 be better off with some sort of omni or bidirectional antenna?

[rick5127]

You have FIVE very strong UHF stations (ch39-45) plus strong Ch14 and Ch21.

Interesting. I don't presently get any channels in the 39-45 range, nor channels 14 or 21. Oops I was looking at virtual not real channels. I DO get the above channels with my present antenna. Actually I get real channels 39, 43, 45, 44, 41, 7, 21, 14, 8, and 31. 31 is right on the edge of dropping out now and then and some days does not come in. Why I don't get those others in between is probably a direction thingy.

"DTV Preamp Signal Overload Calculator" sez your Spurious Free Dynamic Range
is going to be limited, with InterMod Noise blocking reception of affected weak channels.

"DTV Interference Calculator - Rev G" sez the five strongest stations will generate
InterMod Noise on ALL channels from Ch33 to Ch51. And strong Ch14 & Ch21 will
help to generate InterMod Noise on ALL of the lower channels under Ch33.
[see GENERIC-5 - Ex 7 & 8] :
http://imageevent.com/holl_ands/files/ota

If you want to try the AP8700, I would recommend inserting 3-4 dB of attenuation
PRIOR to the Preamp...and then try a 6-8 dB attenuator. For every 1 dB of attenuation,
the InterMod Noise is reduced 3 dB, hence 3 dB Loss reduces IMD by 9 dB and 6 dB
Loss reduces IMD by 18 dB.

To be honest the above is very confusing to me. But from what I can understand my best bet would be to leave the preamp off. Like I said I am only going to get one shot at this. Any further testing will have to be in the spring.

[Michael DeAbreu]

Yeah, I'm a bit confused too about adding an attenuator prior to the pre-amp. In that case, why not put the amp at the end of the cable run and let line-losses attenuate the signal?