Indoor powered FM antennas

[markfx]

Just to be clear, because there always seems to be a lot of interest in FM antennae...


The main reason that outdoor TV antennae seem to work for the FM broadcast band is because they are outside and up in the air.


Indoors or outdoors, there is no substitute for full sized antennae that are resonant at the frequencies of interest.

Wow, amazingly educational post, thanks!

(took the liberty of abridging the quote)

 

[JBL GUY]

markfx

Thanks for the compliment.

I am glad you found it helpful.

 

[slow_jazz]

There's always the Bic Beam Box!!

 

[JBL GUY]

There's always the Bic Beam Box!!

I am interested in your experience with the BIC Beam Box.

 

[epifanatic]

I live on the outskirts of town (very hilly) and had trouble pulling in the PBS station that is located downtown as well as the college station over in C.B. on the other side of the river. I found this Parsec LS-4 at a thrift for $10.00 and it works great.

 

[FauxHall]

I have on of those Parsec antenna also. Nice small footprint and variable gain.

Still, the RadioShack unit I posted earlier in the thread is better.

As to noise from an amplified antenna, Mr. Beezley's experience and analysis seems to indicate that it is less of an issue than one would suppose:

http://ham-radio.com/k6sti/preamps.htm

 

[fixtillbroke]

Wow, amazingly educational post, thanks!

(took the liberty of abridging the quote)

One small point to make. Not all of us have their own house to attach the antenna to. Those of us in multi unit apartments and condos have to comply with restrictions on exposed wires or metal reception equipment. Without an attic or crawl space there's just no alternative to these table top substitutions.

 

[KiM3Ce]

I have an antenna in my attic from 30 years ago when TV was still UHF and it is fine. If you can't go outdoors, consider your attic if you can.

Not a cheap solution but Magnum Dynalab does make a "Signal Sleuth" that is an adjustable amplifier/attenuator with a tuned filter. I see one on sale now for $550. Lots of test reports online. Maybe a dealer will let you try one at home. Good luck!

 

[DesertRatt]

For a broadcast "radio signal" there is no substitute for having the pickup antenna as HIGH AS POSSIBLE ABOVE GROUND. Even basic dipole improves dramatically if you can raise it up say - to the ceiling.

Height, Height, Height!

The powered indoor FM antennas are essentially just amplifiers. They try to make up for a lack of height by just amplifying the hell out of what little signal they get.

 

[El Rubio]

antenna height is ideal, but not always practical. A good LNA can improve reception by amplifying the signal without adding additional noise. Now, if you are in an RF noisy environment where there is strong adjacent frequency transmissions, the LNA can get saturated or overloaded and produce undesired IMD. This happens in the mixer of your receiver too. You end up with a high noisefloor and not enough received signal above that level.

The Magnum Dynalab suggested is an ideal LNA because it includes a preselector filter that is narrow and tunable. Plus an adjustable gain LNA. The filter is first in the signal path after the antenna. This blocks any strong out of band signals from overloading the LNA input. Without the filter, the LNA is prone to IMD and once those distortions are present, they may be within the passband of the receiver and make reception worse. This is probably what happens when some people claim LNA’s amplify noise and aren’t an improvement. It depends what the noise source is. A tunable filter on the input is a major game changer. I don’t know the specifics, bit this sounds like an awesome filter/amp and a must have for anyone into FM DX’ing.
A cheaper LNA can be helpful in most situations, ideally with adjustable gain.