On Sat, 4 Jan 2014 11:14:23 -0500, "Ralph Mowery"
wrote:


Unless I am missing something, seems like a waste of antenna and money.

Nope. Stacking antennas works.

Analysis of the HD-6066P antenna.
http://www.ham-radio.com/k6sti/hd6065p.htm

"You have the CC-7870 hooked up properly. However this coupler is just like
a 2-way splitter hooked up in reverse; in that it will reduce the signal
from each antenna by about 30%. "

Since when do we measure signal levels in percent? Decibels would be
nice.
http://www.solidsignal.com/pview.asp?p=cc7870&d=winegard-cc-7870-2-way-tv-antenna-joiner-coupler-(cc7870)

If it is just a 2 way splitter in reverse, there is usually a 3 db loss and
all you get with 2 antennas is a gain of 3 db, so you gain nothing over a
single antenna with this coupler.

Nope. Let's pretend for a moment that there's no loss in the
splitter/coupler. If you feed a signal into the common (output) port,
the RF power is split equally between the other two (input) ports for
a -3dB loss per port.

However, if you feed a signal into either ONE of the two (input)
ports, all of the signal will appear on the common (output) port.
That's because there's about 20dB of isolation between the two (input)
ports so that no RF is lost going out the other (input) port.

If you have the same signal (in phase) going into both the two (input)
ports, they add, producing a combined signal 3dB higher.

However, reality requires that the combiner has some loss. Usually,
that's about -0.5dB per (input) port for a total loss of 1dB. So,
instead of 3dB gain with the stacking arrangement, you will see about
2dB gain. The -0.5dB loss varies across the band and tends to be
higher at the extreme frequencies, and less in the middle.

To get close to 3 db of gain you need to have a combiner of near zero loss.
This is often done by using an odd number of wavelenghts of feedline of a
differant impedance and hooking them in parallel to keep the impedance the
same. I doubt it would work very well over the while FM band,but may for a
small portion of it.

Yep. That's the problem. The splitter/combiner is a broadband
device, that will work over the entire TV band. 5-1000 MHz is common.
Not so if you remove the splitter/combiner and simply parallel the
phasing lines. That's a narrow band device that works over a narrow
frequency range determined by the length of the phasing lines. That's
not what you would want with a TV antenna.

However, the HD-6065P is a FM band only Yagi, which might work without
the splitter combiner, but as you mention, probably will not work over
the entire FM band.

I don't know how big the antenna is, but you would be beter off with a
single larger antenna, or possiably an amplifier.
Maybe an even beter feedline.

If you use a Yagi antenna, you would need to approximately double the
length of the boom in order to obtain an additional 3dB of gain. The
boom on the HD-6065P is 128 inches long. I would hate to see a
similar antenna with a boom twice as long.

Yagi antennas also tend to be more narrow band than Gray Hoverman
antennas for TV use. For FM band only, gain is more important, so a
Yagi is probably best. For TV, I prefer a Gray Hoverman.

Incidentally, for TV, you can compare the characteristics between both
types for real antennas at:
http://www.hdtvprimer.com/ANTENNAS/types.html
http://www.hdtvprimer.com/ANTENNAS/comparing.html
http://www.hdtvprimer.com/antennas/temporarypage.html


--
Jeff Liebermann
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558