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Railfan Technology > Yet Another Antenna Question


Date: 04/14/19 09:44
Yet Another Antenna Question
Author: philippe

So I purchased a RH77CA for my Bearcat 125.  However, the shorty that originally came with the scanner seems to do much much better. Am I missing something.  I'm in the western suburbs (Golden) of Denver and can pick up scans from Leyden to Downtown.  Pick up Brush dispatcher, BN/UP yard chatter, Joint line, KP, Front Range, Limon sub dispatching on the shorty.  Not so much onthe RH77CA.

Thoughts.



Date: 04/14/19 10:02
Re: Yet Another Antenna Question
Author: TCnR

What I see right away is that the RH-77CA is tuned for the HAM Band (144 MHz) and not for the RR Band. I'm surprised the performance is that notable compared to the stock antenna though.

https://www.diamondantenna.net/rh77ca.html

+ Maybe this is a better spec sheet:
https://www.amazon.com/Diamond-Original-RH77CA-Dual-Band-Handheld/dp/B00M1X73EA

Consider checking the antenna againest the Weather Broadcasts, they provide a constant transmit level which is closer to the RR Band, so you can change antennas and compare with a constant test source. It should be more obvious by either hearing more distant weather broadcast transmitters or not, maybe more noise etc.

The Bearcat 125 has a surprisingly good sensitivity in the RR Band:

https://www.universal-radio.com/catalog/scanners/0125spec.html
 



Edited 3 time(s). Last edit at 04/19/19 22:14 by TCnR.



Date: 04/14/19 12:29
Re: Yet Another Antenna Question
Author: cchan006

I have a budget version of the BC75XLT, the BC72XLT. I couldn't hear much outside 5 miles with my rubber ducky antenna. There was considerable improvement with the RH77CA, recommended to me by the local Ham Radio Outlet guys.

My BC72XLT is 10 years old.

It's possible the shorty that came with your 125 is much better than the shorties from the past. For example, maybe there's a loading coil inside to make up for its shortness. I've seen many refinements done by Uniden in the past decade.



Date: 04/16/19 21:10
Re: Yet Another Antenna Question
Author: wa4umr

A quarter wavelength at the railroad frequencies is about 18".  One fact about antennas is that the longer they are, the better they are.  There are some limitations to that statement but for the frequencies we're talking about here, it's fairly accurate.  This assumes that they are tuned close to the frequency you are using them for.  A rubber duckie is a compromise.  It's short and that makes it more convenient to use.  The Diamond antenna (and other similar antennas) are about 17 inches long and that makes them more awkward to use, however, it will perform better.  The RH77 is not tuned exactly for the 161 MHz that the railroads use but it is pretty close.  

Try this.  Put the rubber duck on your radio and search for NOAA weather radio stations.  There are seven frequencies in use.  Most scanners should scan them but if not, they are 162.400, 162.425, 162.450, 162.475, 162.500, 162.525, and 162.550 MHz.  You should receive at least one station and maybe more.  Make sure your squelch is set pretty loose.  Note on the frequencies where you do receive something, the signal quality.  Is it loud and clear or does it have a little noise, or maybe a lot of noise?  Without moving your radio, change to the Diamond antenna and scan again.  You should at least receive the ones that you received with the duckie on the scanner and possibly one or two others.  The signal quality of any weak signals you received originally should improve.  I did this several years ago and initially received 3 stations and when I changed the antenna I received 5 stations.  It's important to keep the radio in a stationary location because, at 161 MHz, the movement of a few inches can change the strength of the signal.

When you try to judge performance with railroad signals, you're dealing with a moving targets with different power levels.  The dispatcher may have a 75 Watt radio while a locomotive might have a 25 Watt radio and the conductor on the ground may have a 5 Watt radio.  Add to that, everything is moving except for the dispatcher.  Using the NOAA weather radio allows you to compare unchanging signal sources. 

John



Date: 04/17/19 08:23
Re: Yet Another Antenna Question
Author: WW

^Good advice from John.  I've used the RH77-CA and I'm not that impressed with it for railfan use.  Going back to my umpteen other posts, my portable antenna recommendation is to try the Smiley Slim Duck tuned to the 160 mHz band, or the Laird EXH-160.  I've had very good results with both with just about any portable that I try them on.   For stock antennas, the BC-125AT stock antenna is not terrible.  On BC-125AT, I often use a stubby 160 mHz antenna of unknown pedigree that I "inherited" in a bunch of scrap radio equipment.  Oddly enough, it works better than the stock antenna and not much worse than the EXH-160.  I wish I knew what make that stubby antenna is, but there are no identifying marks on it.   I know that it's close to 20 years old, based on the junk radios that it was boxed with.



Edited 1 time(s). Last edit at 04/17/19 12:38 by WW.



Date: 04/18/19 22:19
Re: Yet Another Antenna Question
Author: GN_X838

I have this antenna of all my Handheld ham radios and a 125.
Thay have caused a lot of people to change brands.
.........NA7SL.........Swede........Albony,OR....................



Date: 04/19/19 08:15
Re: Yet Another Antenna Question
Author: DMC

I have used the Smiley antennas on all my handhelds for years.  Tried the Diamond and retired it right away.  Not for marine and railroad channels.

DMC



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