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Old 1-Apr-2021, 6:28 PM   #4
rabbit73
Retired A/V Tech
 
Join Date: Aug 2012
Location: S.E. VA
Posts: 2,747
Quote:
Originally Posted by beebo89 View Post
The info I have found seems to indicate that a folded dipole like you mentioned works better than what I made, but I am having trouble finding small aluminum tubing.
You could try small diameter copper tubing, or bare 8 gauge solid copper ground wire from Lowes or Home Depot.

I have a GE 29884 antenna in my window that has a VHF aluminum folded dipole, but that might not have quite enough gain for your location. The folded dipole is about 29" long. I use it for Channel 11:



The signal looks pretty good on my SDR, in spite of the high noise level on VHF at my location:







I made a folded dipole for channel 3 using yardsticks and THHN 14 gauge insulated solid copper wire.





Quote:
If I would go that route, is the length of a folded dipole the same as a simple dipole?
Yes. I use this formula:
5540/freq in MHz
Channel 10 is 192 to 198 MHz, center freq is 195 MHz
5540/195 = 28.4 inches
Quote:
What is the distance between the top part of the element and the bottom part? What is the gap where the balun ties in? This would all be for channel 10, which if I understand correctly is 195 MHz.
Just go by the diagram as a starting point for experimentation. If you want precise answers, the antenna would have to be modeled by computer modeling, which I don't do because it is too tedious. I would rather do antenna performance measurements using TV SNR, my signal level meter, and SDR images.
Quote:
The reception I am getting now is just under where it needs to be, I am wondering if my problems would be solved with a preamp? The limited info I have found so far is that a really powerful preamp can be too strong if you are fairly close to the stations. I am guessing I need a low to mid level preamp? Can you, or anyone else, please recommend one?
The Channel Master Titan 2 Medium Gain Preamplifier (Version 3) CM7778V3 might be suitable.
https://www.channelmaster.com/collec...on-3-cm-7778v3

A less expensive alternative is the CM3410 distribution amp (15 dB).

I use the more expensive CM7777HD Amplify, which has low and high gain settings, for my test setups.

It is possible to just amplify the weaker Channel 10 signal before the UVSJ. Connect the output of the power inserter to the VHF input of the UVSJ.
Attached Images
File Type: jpg CH11GE29884left_1.jpg (153.9 KB, 4456 views)
File Type: jpg CH11GE29884left2_3.jpg (180.6 KB, 4416 views)
File Type: jpg CH3rcvFDant2.jpg (131.9 KB, 4450 views)
File Type: jpg CH3 Indoor Folded Dipole5_1.jpg (165.4 KB, 4421 views)
File Type: jpg 3AntennasInRoom.jpg (185.5 KB, 4467 views)
File Type: jpg 1-10-21 VHF-Hi test2 29884 near window10in_3.jpg (133.8 KB, 4437 views)
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Last edited by rabbit73; 1-Apr-2021 at 11:00 PM.
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