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Old 2010-11-22, 02:26 PM   #2251
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Thanks for suggestions about DIY pre-amps (esp. to make a low gain, high overload, lightning resistant) unit. As I said, just doesn't seem feasible.

Long ago, poor but earnest audiiophiles could make a twin-tee filter for about $2 and, by filtering out the filter frequency 60 dB (even without caring exactly what that happened to be), see how much distortion an audio amp was adding.

I struggle to find an equivalent DIY cheap approach to making a properly tuned quarter-wave balun, let alone a pre-amp. Now, I have signal generators (called "stations") and I have tunable RF meters (called "tuners" with signal strength meters)... so what else do I need?
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Old 2010-12-05, 03:55 PM   #2252
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Default Terminate distribution amps?

I got a 4-way distribution amp from Home Depot. I stuck it up in the attic space before taking a peak in side. Do you still use terminators on unused outputs? Don't know if they just stick a splitter on the output or put each out put on a separate output transistor.
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Old 2010-12-05, 04:38 PM   #2253
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Yes, always.
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Old 2010-12-05, 04:59 PM   #2254
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Yes, a splitter requires proper termination on all ports to maintain specified impedance.
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Old 2010-12-07, 05:34 PM   #2255
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Default Pre Amps vs. Drop Amps

I was in the cabling thread and talked about shortening the coax to get a better signal, from this it was suggested that I should "drop" the drop amp and use a pre-amp. I tried this before and got less channels, but that was before I got the ch. 11 trap. So now I tried comparing the drop amp to a hdp-269 when using the trap.

Lo and be hold, the pre-amp worked pretty good even though it was 50 odd feet from the antenna. But the best set-up is using both. Multiple antennas feed into a joiner, then preamp, then drop amp- quite the mess of cables/amps/power insertors/traps/grounding block in my set-up. It didn't get me a lock on my edge channel- WNYO, but it got a better lock on my other finicky channel - Global -65.1, and other channels have seen a bump in strength.

I will still shorten up the coax inside the house, and I might try using a lower noise amp- CM 7778, hopefully the tuner won't be overloaded.

It's funny how the pre-amp can still work even though it's not right underneath the antenna.
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Old 2010-12-07, 07:18 PM   #2256
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A pre-amp doesn't have to be right at the antenna in order to be helpful. However, that location allows for the minimum of signal insertion loss before the signal gets amplified. Moving the amplifier "downstream" away from the antenna has the same effect as increasing the noise margin of the pre-amp by the amount of insertion loss of the intervening cable. Therefore, unless there is a concern about strong signal overload, the pre-amp will be always be MOST beneficial as close to the antenna as possible should a pre-amp be called for.

I use a pre-amp in my basement as a distribution amp because I had an extra pre-amp on hand and was too cheap to go buy a 4-way distribution amp to finish off my system. It feeds a 4-way splitter and does the job I gave it to do.
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Old 2010-12-07, 09:17 PM   #2257
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Paulo, about your question in the cable thread regarding shortening your coax as well (sounds very similar to goforit) I forgot to mention there's no reason you can't move a preamp closest to the antenna and remove your current distribution amp. You seemed to think you need a power source close to the preamp to power it, but you don't need one.

The power is fed through the same coax cable as the image/sound is passing.

You'd remove the amp close to your TV and replace it with a splitter. Then you'd install a preamp closest to your antenna as possible. Your preamp comes with 2 parts - 1=preamp, located close to the antenna, 2-power inserter, located in your case just before your splitter would be.
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Old 2010-12-08, 01:38 PM   #2258
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Hi flavoie, I actually did shorten my 60' run to 40' on my TV2 downstairs and I did notice a very small increase in signal strength (3-5%) on my TVs signal meter. I understand what you are saying about the preamp, any recommendations on a good pre-amp?

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Old 2010-12-08, 10:28 PM   #2259
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check the preamp chart attached at the start of this thread. You'll find many low-noise preamps. The 7777 is extremely popular for mast mounting, it also has 2 inputs in case you were to hook up 2 antennas (1 UHF, 1 VHF). There are also KitzTech preamps. If you need to use a Kitz outside, you'd need the coax powered version AND make your own weatherproof enclosure. But beware of the lower noise figure. In my area, people need to put an FM trap in front of need, and this can negate the noise figure difference between a Kitz and a Channel Master preamp. In my personal case, even though I had a Kitz already, when it was time to bring it on the roof I decided to use a CM7777 instead for better (I hope) reliability. Check this thread for more info about past experiences.

On the top of your shopping list, I'd consider, in this order, the Channel Master 7777, Channel Master 7778, Kitztech KT200 coax powered.
If you can put the preamp right under your antenna you would gain some noise margin. Just keep the existing cable going to your antenna as the preamp output, then add a short, new cable between the antenna and the preamp input. The CM preamps are ready-to-install on a mast outdoors.
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Old 2010-12-08, 11:30 PM   #2260
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Default 7777 vs. 7778

I've had some success in using the hdp-269- jump in signal strength on most digitals, and clearer analog. Now I was thinking of going with a CM pre-amp.

I am very close to the CHCH tower, but have a 11.0 trap- it works well with the distribution amp and the hdp-269 pre-amp.

What would be better- 7777 or 7778?

I was thinking of going with the 7778- less chance of overload since the CHCH tower has 2 other analog channels (CITS and SUN 2), but the noise figure is slightly higher, 2.2 vs. 2.0 for the 7777, but both are lower than the noise of the hdp-269 which has a noise value of 3.0.

Am I splitting hairs over the .2 difference between the 7777 and the 7778, or is that a significant difference in getting a better lock on weak stations?
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Old 2010-12-09, 01:30 PM   #2261
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Thanks goforit & flavoie, I may just go with the 7777 as you guys mentioned.......funny I called Solid Signal, just to get their advice/opinion on swapping the CM 3412 distribution amp with this 7777 or 7778 and they were very hesitant in recommending this to me.

Any thoughts..... I mean I will probably go ahead anyway, I am just wondering if I/we overlooked something.

Thanks

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Old 2010-12-09, 04:11 PM   #2262
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Paulo, i'd say upgrade to a preamp only if you're committed to bring it right under a few feet of your antenna. This way you should expect some better results than if you just swapped your distribution amp with a preamp. I'm saying this because the noise figure difference between your amp and a future preamp will be small, but being able to move the preamp nearest to the antenna will bring in more SNR difference, this where your preamp would be a better value for the money spent. Otherwise, i'd say skip it for now and check what types of tuners you have to see if an upgrade is possible or worth it there.
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Old 2010-12-09, 04:20 PM   #2263
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Overall the edge goes to the 7777. I like mine.
The 7777 is dual input so it you wanted (in the future or now) to ever use a VHF and UHF antenna, it is a nice feature which the 7778 does not have.
Otherwise, they both have a selectable FM trap but they have different gains, and the edge in the noise figure going to the 7777.

The only reason you'd want to select the 7778 was if you thought the 7777 had too strong a gain for your situation.
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Old 2010-12-10, 10:20 AM   #2264
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Quote:
Originally Posted by flavoie View Post
Overall the edge goes to the 7777. I like mine.
The 7777 is dual input so it you wanted (in the future or now) to ever use a VHF and UHF antenna, it is a nice feature which the 7778 does not have.
Otherwise, they both have a selectable FM trap but they have different gains, and the edge in the noise figure going to the 7777.

The only reason you'd want to select the 7778 was if you thought the 7777 had too strong a gain for your situation.
Thanks flavoie, I will most certainly bring the 7777 pre-amp right under the antenna. Since my antenna is in the attic is a 1' distance from antenna to the 7777 pre-amp ok or should it be 2' or 3'.... or does it matter at such small distances?

PS. I don't really have a place to tie down the pre-amp, since the antenna is suspended at its top ends on the roof beams. Can it just "hang" down on the RG6 cable? Also doe this thing get hot (temperature wise) ?

Thanks

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Old 2010-12-10, 11:10 AM   #2265
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Quote:
Originally Posted by Paulo View Post
Thanks flavoie, I will most certainly bring the 7777 pre-amp right under the antenna. Since my antenna is in the attic is a 1' distance from antenna to the 7777 pre-amp ok or should it be 2' or 3'.... or does it matter at such small distances?
It doesn't really matter with such short cable lengths. The key is to minimize the amount of signal loss in the cable before the pre-amp, but not much signal will be lost in a few feet of good quality cable.

Quote:
PS. I don't really have a place to tie down the pre-amp, since the antenna is suspended at its top ends on the roof beams. Can it just "hang" down on the RG6 cable?
I wouldn't recommend letting it hang as it could put stress on the RG6 over time. Try attaching it to a truss or make a little support stand to keep the cables loose.

Quote:
Also doe this thing get hot (temperature wise) ?
No, it shouldn't get very hot.
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