RF Antenna booster
 

Anyone know of an inexpensive antenna booster for rabbit ears?

I think they're out there. Check on the E-place and enter antenna amplifier.
I don't know what the gain is in DB's. It doesn't say on the amp and I don't have the original paper work. :scratch2:

Just to add my $0.02: With digital signals, I find little difference using rabbit ears with or without my preamp; stations that are unwatchable without it are just less unwatchable with it. If that's what you're looking to do, you might be disappointed.

On the other hand, the amp/ears combo works well when used to receive the output from an agile modulator/dipole I have set up in another part of the house. The picture went from snowy (but still comfortably watchable) to almost perfect.

I'm using an older version of the Rat Shack #15-259. Current price is up to $50, which is on the high side of what I'd consider inexensive for this sort of thing, but I think it's still a fair value.

Like I said, though, that's just my experience and your mileage may vary.

Good luck!

-Steve

Thank you everyone.

Digital TV signals are fussy.

You usually need about -80dBm to the TV with a signal to noise ratio of at least 15 dB.

Anything less and reception is spotty to non-existent.

All RF amplifiers will add noise to the signal and this may be an issue.

There are types of antennae that you can build simply and cheaply that will vastly out perform rabbit ear style antenna.

The Hoverman style antenna is easy to build and performs very well.

The simple basic design will provide 10 dBd or more of gain with out adding any noise to the signal.

Here is a picture of one. The length between the bends is about 7 inches, although there are other designs where some of the lengths between the bends are increased to around 10 inches.

There are a couple of current threads regarding this antenna over on AK.

I have designed modeled and build this style of antenna and it does work very well. As pictured it is bi-directional, but adding a screen reflector behind the elements will increase the gain and make it unidirectional.

I understand that this does not directly answer your question, but it might be a solution for you and others and it may be to large and unsightly for your application.

If you do want to try an RF preamplier, the noise factor rating, (lower is better) is just as important as the gain of the preamplifier.

Does the Hoverman antenna have any gain on the VHF channels? I have 3 channels that actually transmit on high band VHF, these are the most difficult to receive with my present indoor antennas.
jr

Yes it does, depending on the design. It becomes somewhat larger in some designs and various rods are added to the to the ends of the antenna parallel with and inline with the elements. Rods are added behind the elements to act as reflectors to increase the gain and make the antenna uni-directional (gain in one direction only).

For a given size it will not have as much high band VHF gain as it does UHF gain, but some may still have 6 dBd to 8 dBd gain relative to dipole antenna. This is gain with out the noise that an amplifier will add.

This may or may not be enough to help with your issues.

Once again, in case it has been missed I will recommend TV FOOL.

In general you need at least -80 dBm at the antenna terminal of the TV with a carrier to noise ratio of at least 15 dB. This will vary from set to set.

This is where the noise factor of the amplifier comes into play. You may have a signal that is just slightly too weak and just on the threshold of an acceptable carrier to noise ratio. The amplifier will make the signal larger, but it will degrade the carrier to noise ratio.

Using the information in the chart for your location from TV FOOL, you can approximate the amount of gain you may need for the stations that are difficult to receive.

BTW here are a couple of active links on AK, our sister site, discussing the Hoverman style antenna and the fractal style antenna.


Basic antennae


Fractal antennae

It appears that some of the designs of the fractal antenna, such as the Koch Curve fractal geometry antenna work well at UHF frequencies and some have reported operation at VHF frequencies.

It is somewhat difficult to model the various fractal antenna designs as found on the internet, because of the unique manner in which some of the builders interweave the various elements of this the antennae.

I have modeled the Hoverman style antenna in software using this 4nec2 software.

Here is the performance of a Hoverman style antenna at 175 Mhz, the frequency for channel TV channel 7 (first picture). The performance of this version of the Hoverman style antenna if fairly constant with increasing gain and decreasing beam width (more directional) as the frequency increases.

Its performance falls apart below about 150 Mhz and is very poor in the FM broadcast band. See the second picture, the pattern resembles the pattern for a dipole antenna, but with slightly less gain.

In the third picture you can see its performance in the UHF band.

14.6 dBi which is about 12 dBd, that is gain over a dipole antenna.

This is the result of software modeling, but in my case measured performance came close to the modeled results.

Look at the lower right side of the picture, the gain is 9.46 dbi which equals about 7 dBd, gain over a dipole antenna.

I lost some files recently and no longer have the specifics about this antenna.

Because the Fractal antenna is heavily patented, there is very little technical information available from the inventor or his company.

There is some second hand information, but it is not consistent.

The Koch Curve fractal geometry fractal antenna seem to be popular because it is easy to construct, the bends in the wire are basic triangular bends.

The last 2 pictures show the basic form of the Koch Curve fractal geometry fractal antenna. Note there is considerable is variation on the dimensions and the shape of the basic self similar form in the designs.

I can not speak to these designs in terms of hard numbers for VHF TV band operation. As I have mentioned I had computer issues and lost files of information containing the data relative the element for some variations of this antenna. Each of the more complex antennae may have to have several hundred points of data describing the element segments used by the software.

Feel free to experiment and relay your results to us. A little solid copper wire and a form to bend the wire around and you will be good to go.

By the way the impedance of the Hoverman style antenna remains close to 300 Ohms from 175 Mhz through 800 Mhzz

Some of the various designs of the Koch Curve fractal geometry fractal antenna have feed point impedances that vary from the standard 300 Ohms.

Remember RF is the acronym for "Really Fun".

If you have additional questions, I will try to answer them.

Good luck with your quest for perfect reception, and with OTA digital TV reception it must be perfect or all is not good.

My meds are affecting me, I forgot one of the pictures. The last picture, taken from the internet due to my lost files, is how the antenna is modeled starting with a very simple version. Every time the overall shape of the self same iterations is changed, it requires changing the data in the software to model the antenna.

The other antenna performance graphs are from my files.

OK, here is additional information on the 2 Koch Curve fractal geometry fractal antennae pictured in my previous post. The smaller antenna, with the 4 separate elements, may struggle in term of performance in the VHF TV band.

Notice the overall length of the elements from the point of attachment to the end of the elements is not very long. This may limit the low frequency performance of the antenna.

The other antenna has a group of smaller self same iterations at the top of the antenna that one might expect to work well on UHF frequencies.

However, note that the overall length of these elements is longer than in the other picture. This may improve not only the UHF performance, but the VHF performance.

This is just an intuitive observation at this point, as I have neither modeled or measured that particular antenna, but it might be worthy of investigation.