A Scanner System That Really Works!
This page was last updated on Tuesday, May 17, 2005 12:19:38 PM
One of the most frustrating aspects of railfanning is not knowing exactly when a train is in the area. In the past, I would either wait aimlessly by the tracks wasting time waiting for the "non-existent" train to arrive or leave the trackside only to have a train arrive just as I left. The main problem I had was my scanner!
Your normal hand held scanner with the rubber ducky antenna has a range of 5 miles at maximum and normally just a couple of miles. After becoming completely disgusted with my scanner's performance I decided to take action and investigate how to get a scanner system that really works!
Shown in the photo below is the final product of many discussions with PAR Electronics. What I discovered was that I needed:
1. A tuned antenna
2. Filters to eliminate interference
3. A good amplifier
4. An LNA
To get maximum performance from this scanner system, all components except the LNA are absolutely necessary to make it work properly (although the LNA increased the performance significantly). The tuned antenna (1 in photo below) was purchased from Railcomm. This antenna is tuned specifically to the 160 - 161 mhz frequencies that almost all railroads operate on.
However, along with the increased range comes increased noise, especially from high powered pagers and channel skipping. The high powered pagers combine with other signals causing severe interference due to their high signal strength. This is called intermod. You can also see intermod due to signals from nearby channels, especially police and fire, skipping onto the railroad frequencies. I found that the intermod in certain locations made my scanner useless.
Thus, there is a need to buy intermod filters if you purchase the tuned Railcomm antenna. The intermod filters (2-5 in photo below) work by filtering out the frequencies that most commonly cause intermod on your scanner. These frequencies are 153mhz and 158 mhz (most common frequencies for high powered pagers) and 155mhz (fire and police frequencies that causes intermod).
In addition to intermod, all of these high powered frequencies enter the "front end" of the scanner, overloading it's ability to receive signals and thus reducing your range. The more filters you add to your scanner system, the better your range will get!
With the intermod filters in place it is then possible to amplify the signal without causing intermod. There are basically two ways to amplify signal. The first is by using a GRE Super Amplifier (6 in photo below) available from Grove Enterprises. This amplifier will amplify ALL signals entering your antenna. The second way is to use an LNA (not shown in photo but resides in position 7), which is an amplifier that will amplify only the desired signal. In my system I use both but you can only use one LNA and one GRE Super Amplifier without overloading the front end of the scanner, which is thus the maximum limit for range for the scanner I am using which is a Radio Shack Pro-91 scanner (8).
With this scanner system I can hear in my car clearly and consistently within a 25 mile radius of wherever I am and maximally to a 30 mile range fainter signals. Now I can railfan with confidence knowing when trains are in the area thus being able to plan where and when I will get photo's and when the line is "dead", wasting little time waiting for the "non-existent" train to come. The price is a little steep and but in the end well worth the money!
Bill of Materials
1. MaxRad Tuned 3/4 wave antenna - (901-755-1514) - $69.95
2. 155mhz intermod filter (special order) - PAR Electronics - $79.95
3. FM trap intermod filter - Grove Enterprises - $69.95
4. 153mhz intermod filter - Grove Enterprises - $69.95
5. 158mhz intermod filter - Grove Enterprises - $69.95
6. GRE Super Amplifier - Grove Enterprises - $59.95
7. LNA (special order) - PAR Electronics - $199.99
8. Radio Shack Pro 91 Scanner - $99.99
Total (minus scanner) - $619.69