TRX-2: Internal vs external attenuation on TRX-2

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alabamarailfan

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Hey Folks,
Like many of you, I have run in to cases where my TRX-2 goes completely deaf in an RF dense area. In fact, most of the time, VHF-High and UHF shows between 4 and 5 bars of signal all the time (see attached). I am using a 1/4 wave VHF whip on the truck, not a gain antenna.

Anyway, the last time it went deaf, turning on the internal attenuation didn't seem to help. Would external attenuation work better? I have been thinking about maybe a 3dB or 6dB attenuator but wasn't sure if those were decent values to use.

Anyone tried this and would it work any better than the internal attenuation? "Out in the country" this radio picks up great but quickly gets overwhelmed in the city, especially bigger ones. This is one of my few disappointments with this radio.

Thanks in advance!
-- John

61616d1510623857-no-nxdn-audio-20171108_184138-0-.jpg
 

Ubbe

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Go to tune mode, Fn+0 and enter the frequency. Set squelch to min and use left/right arrows to tune around that frequency. Listen to the audio.

If you hear a mix of different signals the scanner is overloaded by a strong signal. If you hear white noise that is the same you hear when you open squelch on any frequency, the scanner are probably trying to cope with a strong signal on an adjacent frequency, and will be noticed when you tune around.

You wrote that using the attenuator didn't help. Did the signal strenght go down at all? If not, it must be a birdie in the scanner from an oscillator or something. Then you probably don't monitor this frequency when your are outside town as it should always interfere whatever location you are at.

/Ubbe
 

Swipesy

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It has been a long know fact by Railfans that GRE/Whistler scanners, starting with the PSR-500, PRO-106 forward were very poor devices for monitoring train radio traffic. I used to run the 500 next to a Yaesu VX170 and a Uniden BC125AT. The 500 only picked up 35% of train transmissions in comparison to the Yaesu and Uniden, using the same antennas. The PSR-800 was even worse. Your TRX-2 is the same family so no surprises you are not hearing much.
 

Ubbe

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My TRX-2 have excellent reception of 155MHz and 166MHz but not so good in the 420MHz band.
Someone wrote that Whistler fixed the poor performance in the TRX-1 and 2.
I haven't tested the 160MHz strong signal performance as I first have to make a cig plug adapter for my car to be able to drive close to transmitters.
Whistler forgot to include that cable with their scanners.
But it would be interersting to have the result of the min squelch test and adjacent frequency monitoring.

/Ubbe
 

alabamarailfan

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Thank you for the responses! I believe (I will need to check this) that I am only experiencing this in a city about 75 miles away so I can't run out and test it easily. I forgot to mention that I brought a Motorola Maxtrac with me last time and it continued to pick up just fine when the TRX-2 "went deaf".

I was driving on the Interstate and did not have a bunch of time to check all the possibilities but I will go back and do that. I couldn't tell if the signal bars went down when I turned on global attenuation but I did notice that the Maxtrac continued to receive even though the TRX-2 did not.

I monitor the same channels whether "in the country" or in the city. The image of the signal strength bars at 4-5 is actually here in the smaller town where I live. Here, when I turn on ATT, it drops to about 1-3 bars. I do monitoring other stuff but when out of town, especially if I am railfanning, I only monitor the railfan band.

Swipesy, I had a PSR-500 and got rid of it for just that reason. Overall the TRX-2 works pretty well but since I noticed it going deaf in the larger city, it has me starting to wonder if I am missing other stuff and I don't realize it.

I will post more info when I get another chance to go down and test it in the "big city". I have the Motorola as a backup but it scans soooooooo slowly and is large and bulky. I hate to have to buy something like another professional radio (Kenwood, most likely) just to monitor the railroad band in larger cities.
 

Ubbe

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Have you tried a FM trap filter? Or it's more likely to be a super strong weather channel on 162MHz interfering with your 160MHz channel. Then you could try a 1/4 coax stub filter to notch out the weather channel. Coax stub filters are made of a piece of coax and involves no costs to try.

/Ubbe
 

alabamarailfan

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Hello Again and thank you for the responses! I haven't tried anything yet, that was kind of the purpose for this post, was to get some ideas. I am indeed seeing the radio has a hot front end but I don't think I am seeing the deafness where I live and monitor everyday.

I was hoping to get some ideas for when I go back to Birmingham (AL) and can test the radio a bit more. It wasn't until the last visit when I had the Motorola with me that I realized that the TRX-2 was going deaf. Indeed the area is a dense downtown area and there is a relatively large mountain close to downtown with both TV and FM on it.

One thing I plan to try is a 160 MHz pre-selector/filter (see image). I found this part number called out in a document related to CSX radio installs and was lucky enough to grab a few of them (Sti-Co FILT-NB-MIL-U). I am going to see how that helps. When I am in Birmingham, I am mostly interested in railroad anyway and won't mind losing other stuff. It is too broad to help if the problem is a weather channel but we'll see...

I will let you guys know how it works next time I get down there!
 

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yeg_scan

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I live in a very RF dense area and my WS-1095 is mostly useless and I had to pull it from my vehicle cause it would not work at all (totally overwhelmed) even with external attenuation added and almost no antenna (1/4 wave inside a vehicle). The issue .. cellular signals. It was not bothered by WX stations or FM broadcast stations.

Learned that the cellular sites have an ERP of about 400 watts and really are just about everywhere, thus the issues while mobile. Adding filtering did not help at all and eventually I gave up so the radio is indoors with a duckie.

But the worst radio I have .. the Uniden 536HP and in my testing the TRX-1 was actually very good in this regard, though I have not tested a TRX-2.
 

nanZor

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Not sure if this is relevant as I have tested both external and the internal 20db attenuators on my 1040 and 1065 in rf-dense areas...

Seems like the external attenuator (same value as internal - 20db) does a better job than the internal attenuator at attenuating. Makes me wonder if there is some sort of leakage in the internal attenuator's path.

Also wonder if we are dealing with a real honest attenuator at all, or is Whistler just lowering the gain of the first stage?

I think it's worth a try to use an actual external attenuator vs the internal and see if there is much of a difference. Of course an external attenuator is a global thing, but worth a test anyway.
 
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