RCA ANT751 How is it on VHF?

G

Guest

Guest
#41
If you extend the longest element another 18" on each side, the channels that use the lowest frequency will come in beautifully.
Antenna out of the box will hardly receive signals from 40 to 88 Mhz.
 
G

Guest

Guest
#42
This is good to know. I have two RCA751R's to put on outside poll. I am experimenting in attic now. The issue is I have a channel 5 (NBC) west at 9 miles (72-82MHz). The rest of the channels are North (mostly UHF and one Hi-VHF on Ch13), and one (PBS) on UHF East-SouthEast. I am getting it, but my Channel Master recorded programs sometimes have interruptions (in good weather). My plan is to have one pointed 751 WEST and one pointed North East, and try and get all the other channels. The 751 may not be tuned for Low VHF but from my calculations it is almost 1/4 wave. So it does work. However I had the idea of adding length to the elements in the VHF section. Since it is an odd ball Yagi and Log Periodical Dipole hybrid I am a not sure. So I will do a test set up and use my older Sony TV or my hauppauge tv tuner in my old PC (I made into a DVR) and measure the signal and errors and experiment with element lengths. If I want half wave it will be roughly double for channel 5. So now a stock 751 I recall has 39" rear element dipole, it will need to be 69". Since I will have a good signal I am sure outside with a mast preamp (RCA with separate VHF and UHF inputs) I will be fine. I may however can the second 751 and look for a dedicated low VHF. They had several great models in the past, all discontinued.
 

Fringe Reception

Super Moderator, Chief Content Editor
Staff member
#44
Guest,

Glad to see you are experimenting and please share your progress with us. You may not need the RCA pre-amplifier and depending on your situation, it may do more harm than good. You can combine your antennas (without amplification) for UHF and high-band VHF using a UVSJ (UHF-VHF-Signal-Joiner) but I'm not certain it would pass Channel-5 / low-band VHF.

Jim
 
M

Mike OH

Guest
#45
If you look at the RCA ANT751 you will see that the 2 (slightly different width) VHF High elements on the top of the boom are fed in a log-yagi configuration.

That is 2, not only driven elements but interconnected in a log periodic formulation which also increases gain.

From what I can tell ofthe Winegard 7000R, it has at least one driven element the 100" wingspan on the back, and perhaps the second longest element in front of it on the top of the boom as well.

I have the RCA ANT751 right here with me.

Back elements are 34" total and 16" each plus gap.
Next forward driven log yagi element is 29" total and 14" each side plus gap.

The directors in front of that on the bottom of the boom are...

26" (rear) adn 25" (front) and are not electrically seperated from the boom.


Everything from the 2 directors behind the UHF folded dipole forward looks the same on these antennas.
You are more knowledgeable than I am so I must ask: If I wanted to optimize the ANT751 for RF 8, should I trim that back element? If so, to what length?
 

Fringe Reception

Super Moderator, Chief Content Editor
Staff member
#46
You are more knowledgeable than I am so I must ask: If I wanted to optimize the ANT751 for RF 8, should I trim that back element? If so, to what length?
Mike,

You cannot optimize a Yagi-style antenna for one channel by altering the length of only one element, including the reflector. As with most TV antennas, the ANT-751 is a compromised design intended to receive many channels including those on high-band VHF.
 
J

Jim Navotney

Guest
#47
Fringe as usual is spot on

Those antennas were designed by Winegard engineers to work together as one unit so any change to any element length will cause it to degrade performance.

If you need a RF 7-36 directional antenna that has better gain on channel 8 then an antenna like the Winegard 7694 may be a better choice.
 
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