Yagi Or Log Periodic For 156-162 MHz ?

[BOBRR]

Hi,

Have done a fairly exhaustive search, but have come up empty, so I thought I'd ask here if anyone might suggest something.

I would like to pick up Marine Frequencies from the Harbor, but am just a bit too far away, apparently, at about 25 miles or so. My antenna (a Scantenna) is as high as I can get it in my attic; outside is just not practical.

Seems like a Yagi or a Log-Periodic is what I want, as a very directional antenna with lots of gain would be worth trying. LOS from my place to the harbor isn't going to change, so a highly directional would be just fine.

The marine frequencies I would be interested in are from 156 thru 162 MHz.

Anyone know of a Yagi or Log Periodic that covers this freq. range with "lots of" Gain over this Full band ? (the 161-162 is important to me, as I want to try AIS reception)

The problem seems to be that the 6 MHz range I am looking to cover is just too broad for a Yagi or Log-Periodic from looking at all the on line data sheets.

Any thoughts on ?

Thanks,
Bob

 

[SkipSanders]

If you have weak signals now, a yagi would help. If you have NO signals now, it probably won't.

Marine stations are at low antenna heights, say, 5-30 feet. Your antenna is probably around 30 feet up. That's 11 miles highly reliable, 22 miles 'barely', for the highest ship antennas. If there's anything between you and the harbor, like a hill, or a lot of buildings, you may be out of luck.

 

[DaveH]

A yagi antenna should be able to handle 6MHz bandwidth at VHF highband.
Log periodics are designed to handle very wide frequency ranges (several
octaves, factors of two) and are more complex/expensive and overkill.

Some ham-band yagis might only cover say 144-148MHz on transmit with
certain VSWR i.e. below 2:1 but I would not worry a bit for receiving.
There are broadband yagis availiable, which use folded dipole drivers,
for commercial use, but they'll cost you (Sinclabs etc.).

You could find a yagi specifically for the marine band, or get a 144-148
version and trim the elements; you'd need to get the info from the vendor,
or use basic design principles. I can't suggest a specific source of info,
it's all over the internet.

Check amateur radio and scanner outlets first. You should find something
suitable

Dave

 

[nycrich]

You might want to build a J-pole antenna. It has a small bandwidth(tuned to the marine band) to fit your need, simple to build, and cheap( since indoors, cheaper materials). At least you would not have to commit large amounts of money that logs/yagi cost and if it does not work out you did not loose that much.
I believe there is plans in the Wiki forum and the internet.

 

[prcguy]

You might consider a 4-bay dipole array in a offset pattern. These have 9dB gain over a dipole, upwards of 20MHz BW and a fairly wide horizontal beamwidth of 140deg or more. Compare this to a 5 element yagi with about the same gain and maybe 50-60deg of horizontal beamwidth and only a few MHz of BW at best. Height is everything at VHF/UHF and a VHF dipole array is about 21ft tall by itself. I use several dipole arrays on VHF and UHF and highly recommend them for the max gain possible for a given length antenna in omni mode. On the J-pole idea, in actual use a simple ground plane made with #12 house wire soldered to an SO-239 connector usually outperforms a J-pole and the ground plane is much easier to make. There is lots of data on the web that shows measured gain comparisons between the two to support this. I suspect a J-pole would not perform any better than your Scantenna on VHF anyway.
prcguy

 

[trooperdude]

I would like to pick up Marine Frequencies from the Harbor, but am just a bit too far away, apparently, at about 25 miles or so. My antenna (a Scantenna) is as high as I can get it in my attic; outside is just not practical.

STOP !

You can't break the laws of physics with regard to radio horizon.

Here is a calculator to figure out your radio horizon
http://www.vwlowen.co.uk/java/horizon.htm

How high is your attic ? What's the roof made out of ?

You may be attenuating 1/2 your signal (3db) just by having it in the attic behind
roofing materials.

Sorry, but for 25watt marine radios, simplex at 25 miles, even a yagi isn't going
to help you if it's in your attic.

You HAVE to go high and outside.
Here is a good read on radio horizon:
http://www.chem.hawaii.edu/uham/horizon.html

Seems like a Yagi or a Log-Periodic is what I want, as a very directional antenna with lots of gain would be worth trying.

Save your $$$ It's not going to help in your application.

The ONLY way to reach your goal is a gain antenna at elevation and quality coax.

I have the same issue with fireground communications on VHF.

I had to go with a Yagi at 60Ft. to hear low-power fireground comms that are 15 miles away.
(couldn't go dipole because I had to be able to steer the beamwidth in an 180 degree arc depending
on where the fire is)

 

[k9rzz]

Yeah, 25 miles is a stretch, but I would think he could hear the stronger transmitters. Depends greatly on the terrain involved inbetween.

If you're inclined to build a yagi, I did a similar project for the VHF weather band by scaling 2m lengths to 162mhz. It worked quite well. I posted the whole project here (pics included!):

http://radioreference.com/forums/showthread.php?t=46494

Maybe it will give you some ideas for your setup.

 

[mancow]

I have an ELK dual band log periodic and it works great. I think it would probably a good choice for what you are looking at doing.

 

[trooperdude]

I have an ELK dual band log periodic and it works great. I think it would probably a good choice for what you are looking at doing.

In the attic ?

:lol: :lol: