1/4 wave or 1/2 wave?

does one recieve better than the other? what about a full wave? how long should each be? i have a mobile with a 17 inch magnet mount that works good but have noticed the csx maintenance trucks have a longer antenna. would something like that work better?

The longer antennas you are seeing are probably 5/8th wave antennas. If there is a cylindrical coil at the base of the antenna, I would say that is what you are seeing. A 5/8th wave antenna will give about 3 db gain over a quarter wave antenna. At least that is the way it works with ham antennas for the two-meter band (144-148 mHz) which would make them a few inches longer than the 161 mHz rail antennas. I have found that my two meter mobile antenna works fine on the rail frequencies, but certainly not as well as an antenna cut specifically for 161 mHz. Your 17 inch quarter wave sounds about right for 161 mHz. The 2-meter ham quarter wave is about 19-20 inches.

just wondering what i can do to get the best reception possible.

Getting a 5/8th wave for the rail frequencies would probably be rather expensive. The reason being that the coil would have to be matched for the rail frequency (161 mHz). I am sure these are available, but you would probably have to obtain it from a professional two-way dealer and that will cost $$$. 5/8th wave antennas for the ham bands are more expensive than 1/4 wave antennas, but not prohibitively so. You will have to deal with a commercial provider for a 5/8th antenna cut and tuned for the rail frequencies. I will try to research this and get back to you.

Here is a rather technical site which explains why 5/8th wave antennas (and many other antennas) have more gain, but honestly, this is way toooooo technical for this forum.

http://www.w8ji.com/mobile_and_loaded_antenna.htm

I was unable to quickly find anyone in the U.S. selling 5/8th wave antennas specifically designed for the rail frequencies. I did find a dealer in England selling marine 5/8th wave antennas for boats (156-160 mHz) which use frequencies very close to railroads. These antennas started at about $200 US. You can also find lots of dealers selling 5/8th wave mobile antennas for hams (144-148 mHz), but these are too far away in frequency from 161 mHz to give great rail performance.

If you are determined to get "the BEST" antenna for mobile rail monitoring at any price, you should contact your local two-way radio dealers who could help you (for a price!).

Antennas with even more gain than 5/8th wave models also exist. One type is called a co-linear antenna. If you are interested, you can do a Google on these (and other) antennas to get all sorts of technical info.

But this is all getting way too technical for 99.9% of those using this site.
And, it boils down to how much money do you have?

IMHO, a properly cut (in length) quarter wave using quality coax cable will perform adequately in nearly all railfan cases.

read the "antennas for handhelds" thread on "railfan.net"... we beat this topic to death, then we kicked it around some more.. Ed k2lck

well, thanks for the help but i wasnt looking to spend a small fortune. what i have is the magnet mount scanner antenna from radio shack with just the top piece of the three sections trimed to 17 inches. it works good for me but wasnt sure if there was a secret to better reception is all.

If you know a ham who is getting rid of a two meter 5/8 wave mag mount, you'll do well to obtain it. Tuned to 144 MHz, this will be close enough to rail frequencies. I used a Larsen 5/8 wave chasing BN through the Marias Pass region and had outstanding reception, better than subsequent trips with 1/4 wave dual-banders!

va3ori wrote:If you know a ham who is getting rid of a two meter 5/8 wave mag mount, you'll do well to obtain it. Tuned to 144 MHz, this will be close enough to rail frequencies. I used a Larsen 5/8 wave chasing BN through the Marias Pass region and had outstanding reception, better than subsequent trips with 1/4 wave dual-banders!

Or for the purists, take the two meter antenna, check the length chart and cut off the correct amount (in the range of several inches) and it will be a perfect match for 160MHz RR.

Virtually all 5/8 wave antennas are usable between 144 and 174 MHz simply by cutting to the proper length. The extra cost of one specifically for railroad frequencies is paying someone several $10s for 5 minutes of work cutting the whip to length with a hacksaw.

MY speeder's antenna is a Larsen commercial/ham version with wideband coil and I cut it to the middle between 151 and 161 MHz which gives a good match on the NARCOA frequency on the the low end and the railroad frequencies (rarely used on a run for transmit but useful to receive) at the high end.

The other advantage of a 5/8 over 1/4 wave is the 5/8 results in less mobile flutter on weaker signals when one or both ends of the conversation is moving.

73, Ken W2KB