Problems with current antenna

[trnbuf]

For the past 10 years I have had an AntennaCraft VHF-HI/UHF Outdoor scanner antenna about 50 ft up with 75 ft of RG6 coaxial cable with a BNC Male To F Female connectionand it worked great for all kinds of frequencies. I also had it connected to a TV amplifier for better reception which I thought seemed to help even more. But recently the wind took it down and I ended up buying a Tram 1410 discone antenna. I am using the coaxial cable and amplifier but now with the railroad transmissions, there is so much static( alot of noise)and I can not pick up as far. I even took it off the amplifier and still no difference thinking that was the problem. But when I scan my weather channels I can pick up 6 different ones perfectly fine, 4 of them are really clear, plus I hear police from all over real good too. So I know my scanner is picking up good reception for that, but my railroad frequencies sound terrible. Do I need to do something different? Do i need a different antenna? Would a J-pole work? Do I need to modify my current antenna? Please help because I provide a railroad feed and I do not want to disappoint my listeners. Thanks so much.

 

[iMONITOR]

If your antenna is mounted at 50 feet, isn't your 25 feet of coax a little short?

 

[trnbuf]

It should say 75 ft, sorry. [emoji16][emoji16][emoji16]

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[iMONITOR]

It should say 75 ft, sorry. [emoji16][emoji16][emoji16]

No problem it's late. What scanner are you using, and nothing else has been changed?

 

[trnbuf]

I am using a radio shack 80 channel Pro 2030. I have not done anything different besides replacing the antenna.

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[iMONITOR]

I am using a radio shack 80 channel Pro 2030. I have not done anything different besides replacing the antenna.

From what I've read the PRO-2030 is very sensitive. It's possible your new discone antenna may be overloading the scanner with intermod from strong radio stations or pager signals. Have you tried the stock antenna indoors?

 

[JoshuaHufford]

If the only thing that has changed is the antenna that I would suspect that your new antenna isn't as good on the Railband than your previous antenna. Only other thing I could thin of is maybe the coax was damaged as well?

Are you scanning other frequencies besides the Railband? If not then something tuned specifically to that range will work much better.

 

[trnbuf]

I am picking up everything else really good except for the railroad frequencies, so I don't believe it's the cable. I'm thinking I need to replace the antenna just for railroads. Are there j-poles just for them?

 

[JoshuaHufford]

There are, with your terrain I would probably go with a SlimJim, they have a lower take off angle which results in more gain. I'm currently using one of these for my feed and it does work well.

VHF Public Safety, MURS, Marine, & Scanner Slim Jim Antenna | KB9VBR J-Pole Antennas

Mine is tuned to the Railband, I think on the sticker it came with it says 160-164MHz, just make sure you make that notation in the notes if/when you order.

Or if you do want the standard J-Pole he has this,

Railroad | KB9VBR J-Pole Antennas

At some point however I do plan on replacing my SlimJim and keeping it in my camper, since it is quite rugged I figure it should survive nicely for that use. Here is what I plan on replacing it with, performance should improve.

https://www.theantennafarm.com/catalog/diamond-f23h-4865

 

[JoshuaHufford]

Also with RG6 you have about 2.6db of signal loss in the coax, not sure how much a TV amp will help with that. Where is the amp located?

If you swap that the coax out for LMR-400 the loss drops to 1.2db. Not cheap but it might help some. You could also put a tuned preamp at the antenna to overcome any loss.

 

[trnbuf]

I replaced the the old rg-6 coaxial with a new 75 ft RG-6 cable today, plus I raised the antenna about another 5 ft or so. It seems to be working a little better. My amp is a 13 dsb amplifier and it is located on the other end of my 75 ft cable. Then from there another 5 ft RG-6 cable to my scanner.

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[Ubbe]

Discone antennas give a high signal level from FM broadcast transmitters. With a 13dB amp it will for sure overload most scanners and will loose sensitivity. Try a FM trap filter. Also the gain of the amplifier are probably too much so get a variable 20dB attenuator, it should be available from the same place as the FM trap filter. The amp should be able to handle the low signal from a discone so set the filter between amp and scanner. Adjust attenuation for best reception.

/Ubbe

 

[trnbuf]

Discone antennas give a high signal level from FM broadcast transmitters. With a 13dB amp it will for sure overload most scanners and will loose sensitivity. Try a FM trap filter. Also the gain of the amplifier are probably too much so get a variable 20dB attenuator, it should be available from the same place as the FM trap filter. The amp should be able to handle the low signal from a discone so set the filter between amp and scanner. Adjust attenuation for best reception.

/Ubbe

What about putting an amp on my AntennaCraft VHF-HI/UHF Outdoor scanner antenna? Would that 13db overload it too? The whole reason for the amplifier is because my cable is so long I feel I am getting signal loss.

What does the FM trap filter accomplish?



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[JoshuaHufford]

From what I understand an FM trap blocks regular FM frequencies, which a discone is very good at receiving, from reaching your scanner and possibly overloading it.

When I use a regular scanner with a preamp it almost continually gets overloaded by weather radio, and sometimes even without a preamp it will still happen. For my feed I switched to a Motorola Radius VHF receiver and all of that intermod went a way and I even started picking up more stuff. If your preamp is giving 13db of gain, 75 Ft. of RG 6 only has 2.6db of loss, so you are still getting about 10db of gain, give or take, which can easily overload your scanner.

I would say either or both the FM trap and variable attenuator may fix the problem, a good quality VHF receiver will likely improve things as well. If you want to go that route I can help you find one that will work and even program it for you.

 

[iMONITOR]

What about putting an amp on my AntennaCraft VHF-HI/UHF Outdoor scanner antenna? Would that 13db overload it too? The whole reason for the amplifier is because my cable is so long I feel I am getting signal loss.

What does the FM trap filter accomplish?

The Antenna Craft antenna is not wide band so it would not gather as much interference from various frequencies.

Strong FM broadcast radio stations can overwhelm your scanner with intermod/interference. The FM notch filter blocks that to a great degree.

 

[hsdtech]

Some of those preamps CAN knock out a few frequencies depending on their quality. I would definitely unhook it. With your antenna at 50 ft. and new coax you should receive 160MHz just fine with a discone. Remember that preamps will also amplify noise/interference as well as signal, especially when it is mounted on the opposite end of the antenna.
One note, are you putting the fittings on your coax yourself or do you buy it with them installed?

 

[JoshuaHufford]

Was curious if you were able to resolve the problem and if so how?