Yagi Question: Freq. Coverage Range
 

Hello,

Is the freq range of 156 to 163 MHz (receive only) too much to probably
consider a yagi for ?

If so, any suggestions for type(s) that have intrinsic Gain ?

Can, and probably should be, be very directional.

Thanks,
Bob

Yagi Question: Freq. Coverage Range
 

On Mon, 18 Jun 2007 17:23:53 -0400, "Robert11"
wrote:
If so, any suggestions for type(s) that have intrinsic Gain ?

Log Periodic Dipole Array

73's
Richard Clark, KB7QHC

Yagi Question: Freq. Coverage Range
 

Hello,

Is the freq range of 156 to 163 MHz (receive only) too much to probably
consider a yagi for ?

That's less than 5% width, so it's probably reasonable. Yagi antenna
design involves a bunch of tradeoffs - Yagis which are optimized for
the highest gain at a specific frequency (or for the greatest
front-to-back ratio) may tend to be more narrow-band than a Yagi of
similar boom length which has a somewhat lower gain or F/B ratio.

There have been some interesting developments over the past few years
with OWB (optimized wide-band) Yagis... I gather that it's now
possible to put together a Yagi which can cover the whole 144-148 MHz
spectrum (and beyond) with very decent performance over the full range.

Yagi behavior tends to deteriorate more rapidly at the upper end of
the frequency range, if I recall correctly, so you'd probably want a
Yagi which is optimized for somewhere around 162 MHz.

If so, any suggestions for type(s) that have intrinsic Gain ?

Can, and probably should be, be very directional.

Log-periodic antennas are known for having a wide SWR bandwidth, and
decent gain and directional characteristics. Depending on the number,
spacing, and taper schedule, it's not difficult to cover a frequency
range of 3:1 with decent gain and with an SWR of no worse than 2:1.
Log-periodics are often used as TV/FM antennas, precisely because this
application requires decent directionality and a wide frequency
coverage.

It's possible that a commercial TV/FM antenna might do the trick for
you. A full-sized VHF-TV-plus-FM antenna would work from 45-88 MHz
(VHF TV low-band), 88-109 or so (FM), and 174-216 MHz (VHF TV
high-band). It's not uncommon for such antennas to use the longer
elements in two modes - they resonate on their fundamental frequencies
for VHF low-band, and on their third harmonic for VHF high-band. If
you see a TV antennas whose longest elements are "swept forward" (with
their tips aimed at an angle in the direction that the antenna is
pointing) then it's likely that the antenna is using this particular
trick.

If so, then there's a fairly good chance that it would cover the
marine-band frequencies as well, since those also fall within the
range of the third harmonic of the VHF low-band frequencies.

So - you could buy yourself a VHF TV antenna, log-periodic type, which
has swept-forward elements, and just rotate it into a vertical
orientation (i.e. mount it sideways on the mast, held out some
distance from the mast so that the mast doesn't de-tune it).


--
Dave Platt AE6EO
Friends of Jade Warrior home page: http://www.radagast.org/jade-warrior
I do _not_ wish to receive unsolicited commercial email, and I will
boycott any company which has the gall to send me such ads!

Yagi Question: Freq. Coverage Range
 

On 18 Jun, 14:23, "Robert11" wrote:
Hello,

Is the freq range of 156 to 163 MHz (receive only) too much to probably
consider a yagi for ?

If so, any suggestions for type(s) that have intrinsic Gain ?

Can, and probably should be, be very directional.

Thanks,
Bob

Since you are using it for receive only I don't see why a yagi
would not suffice. A log periodic could give constant gain
over the frequency range but it will be a LOW gain compared
to a good yagi.
Art

Yagi Question: Freq. Coverage Range
 

On 18 Jun, 16:03, (Dave Platt) wrote:
Hello,

snip.

There have been some interesting developments over the past few years
with OWB (optimized wide-band) Yagis... I gather that it's now
possible to put together a Yagi which can cover the whole 144-148 MHz
spectrum (and beyond) with very decent performance over the full range.

I never knew that this was a problem.
I would like to tackle that.
What would be the specs that would provide a
decent performance over the full range? I don't use
frequencies higher than 30 Mhz so I will be starting
from scratch but it will be an interesting challenge.
If it works out then the poster will get the help he
is looking for
Many thanks
Art


snip

--
Dave Platt AE6EO
Friends of Jade Warrior home page: http://www.radagast.org/jade-warrior
I do _not_ wish to receive unsolicited commercial email, and I will
boycott any company which has the gall to send me such ads!

Yagi Question: Freq. Coverage Range
 

Bob, do you ever acknowledge or thank others that answer your questions
and/or send you info ?

Answering your indentical question posted in another group, I sent you a
link for a VHF antenna that is perfect for what you asked for in your OP,
but you have never commented or acknowledged receipt of it. I sent it
again in this group when you posted the exact question here, but got the
same non-response.

James

Yagi Question: Freq. Coverage Range
 

"Robert11" wrote in message
. ..
Hello,

Is the freq range of 156 to 163 MHz (receive only) too much to probably
consider a yagi for ?

If so, any suggestions for type(s) that have intrinsic Gain ?

Can, and probably should be, be very directional.

Thanks,
Bob

I would say - try a quad instead. and use copper tubing to help make it
broad-band.