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

[balm]

im trying to receive a weak, 2nd edge channel VHF-Hi #13 (NM=4.6), im using an 11 db DIY yagi with f/b >25 db, and the Kitztech-200 coax preamp (nF= .4 db)


so far i have no reliability, sometimes its a lock, another moment it disappears, WHEN the signal is there, the preamp appears to bring it from 50% to 60 % (which is a lock) on the TV signal meter

also seems better reception when co-channel analog #13 (NM=-.5 db) from opposite direction fades. Im not sure about adjacent channel analog #12 interference.

I also need to have a variable 20 db attenuator at the max setting for the signal to appraoch a lock (i assume its needed because of the co-channel interference)


is there another preamp option which may work out better specifically for VHF?

thanks

[bigblueguy]

I recently picked up a Philips SWS2083W/17 pre-amp. I was wondering if anyone had any experience using it with a CM4228HD? What mods were done to the antenna to get it connected? The amp has 300 Ohm terminals to connect it to the antenna and 300 Ohm as well as the F-type connector for the connection to the amplifier. The amplifier also has 300 Ohms and F Type connectors for the connection to the pre-amp and the connection to the TV. See the link provided.

http://www.p4c.philips.com/files/s/s...17_pss_aen.pdf

[rabbit73]

Without seeing your tvfool report, I don't think another preamp is the answer. If you need to insert 20 dB of attenuation to eliminate interference from another signal, then you are also attenuating your desired CH13 signal. I think you would be better off with a CH13 single-channel bandpass filter, either the CH13 bandpass section of a Join-tenna or a custom CH13 bandpass filter from TinLee.

If the interference is from an adjacent channel signal, then the bandpass filter will help. If the interference is from a co-channel signal, then it will not help. What you would need is greater F to B/R ratio from a yagi designed for max rejection from the rear, like the K6STI yagi or one with a corner reflector. Two CH13 yagis that are staggered would give even better rear rejection at the design freq.

If your yagi really has a F/B of 25 dB and your co-channel NM is -0.5 dB, then I doubt that is the problem.

When you attenuate your desired signal, then you are not only making it weaker, but you have lost the ability of the AGC to compensate for changes in signal strength because the AGC is then running at max gain.

[majortom]

in this post there is a link to where a guy describes a project using two like antennas, a balun, a couple variable resistors, and a couple capacitors to phase shift/cancel out an interfering co-channel signal. Two antennas are used, one aimed right at the interferer, the other aimed at the distant desired station. Scroll about 1/2 way down the page for the circuit diagram.

http://www.digitalhome.ca/forum/show...77&postcount=9

[balm]

thank you rabbit73,

i agree the preamp may not be the issue

here is my fool (desired is #13 WVNY):

http://www.tvfool.com/?option=com_wr...03d98eba129270

unfortunately I cannot locate a jointenna#13 up here, since they are not available anymore, and tin-lee is very expensive considering it may not solve the problem

I do believe it is more an issue of 2nd edge reception

regarding the custom yagi, the one i designed is f/b=29 dbi, im not sure what other single yagi i can design


but i will look into stacking


thank you

[Jake]

Hey I went to Princess Auto as well last week.

There are no mods required. The antenna twin lead or coax is wired into the top of the booster. They suggest about 3' from the antenna. If you use coax then you will need to strip the coax back to expose the conductor and shield. Coax goes out the bottom to inside you home. The amplifier inside is just coax in and coax out to TV.

[wilspin]

Problem is you have 2 13's. I dont see a solution for that. CTV on the back side

[rabbit73]

balm:

Thanks for the tvfool report; I have a better understanding of your problem.

I see WVNY at 119 degrees true, co-channel CJOH at 290 degrees true, and adjacent channel CFCF on CH12 at 56 degrees, that is about 22 dB stronger than WVNY.

The channelmasterstore.com site (under Amplifiers & Distribution) lists the Channel Master CM 0583 Join-Tenna CH 13 (CM0583) for a very reasonable price. They also list the CH6 version for people having trouble with FM interference.

EDIT by stampeder: See Post #551 in the Stacking and Ganging thread for info from rabbit73 on "Stagger Stacking"

[hoopitup2000]

With only 7kw's @ 87 miles out, I can't imagine RF 13 would ever be reliable enough for regular viewing.

[wilspin]

And an analogue torch on the back door, I am skeptical of any results also

[rabbit73]

Yes, it is a difficult problem, with no guarantee of success.

[balm]

thank you all for your input

i was somewhat hopeful, because sometimes its watchable for a couple of hours, then not, but the signal is almost always CLOSE to locking (50-60%)

i would have assumed that the other #13 is nulled by the f/b = 29.5 dbi. in august, when undesired #13 goes digital, its power will drop a bit.

as for channel 12, that can be dealt with.

i probably shouldnt waste more time on higher gain antenna, since it probably wont make the difference in this case.

nearly all my channels are edge channels

I guess these last few posts could be subject for a new thread.

[rabbit73]

Yes, it is off-topic, but you did ask it here, thinking that a different preamp might help.

What would stampeder call it, Problem with reception of WVNY CH 13?

i was somewhat hopeful, because sometimes its watchable for a couple of hours, then not, but the signal is almost always CLOSE to locking (50-60%)

That would give me hope too. Some tuners are more sensitive than others.

i probably shouldnt waste more time on higher gain antenna, since it probably wont make the difference in this case.

I agree.

nearly all my channels are edge channels

Very challenging.

[intravino]

is there another preamp option which may work out better specifically for VHF?

Yes, the Winegard AP 3700 VHF. I compared it to the Kitz, CM7777 and RC 9260. The AP3700 was better then the others for VHF only. Also, It has a better FM trap then the CM7777. The only problem is that the preamp is hard to get, I got mine at an online retailer.

[balm]

intravino,

thank you, i received your messages

where did you post VHF results for the preamp testing you did, i was previously so keen on the Kitztech (200) due to its ultra low noise?