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GRE Scanners - A forum for the discussion of all GRE branded scanning radios and receivers. Whistler branded scanners belong in the Whistler forum.

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Old 08-29-2016, 1:46 PM
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Question Improving Reception On PSR-600

My PSR-600 seems to have problems with intermod here in the Denver area. I primarily listen to aircraft and railroads, very little public safety. I ran across a FM Band Trap and put it into the antenna feed line and found the intermod was reduced...

Anyone else found this to be true? I'm just wondering if I stumbled on to something or am I just having a good day in the neighborhood. Thanks!
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Old 08-29-2016, 2:12 PM
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Hello,

GRE/Whistler scanners prior to the TRX-1/TRX-2 have a history of signal overload problems on VHF-High Band. I have to use the attenuator when I use an external antenna. I am close to several high power FM Broadcast transmitters. The FM Band Trap is a common solution for this problem.

It is reported that the new TRX-1/TRX-2 has a redesigned RF front end and does not suffer from the signal overload problem.

73 Eric
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Old 08-29-2016, 2:17 PM
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Default PSR-600 Intermod

That's good news... Thank you! I did try the global attenuate but it didn't seem to make a difference.
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Old 08-29-2016, 3:53 PM
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Quote:
Originally Posted by Mojaveflyer View Post
That's good news... Thank you! I did try the global attenuate but it didn't seem to make a difference.
What are you using for a antenna? In high rf rich areas, sometime a Less efficient antenna does the trick. No preamps, or gain antennas, sometimes even a indoor antenna will decrease the intermod. 73, n9zas
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Old 08-29-2016, 4:44 PM
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Default PSR-600 Intermod

The radio is mounted in a vehicle using a hole mount, 1/4 wave VHF antenna. I will occasionally use a 1/2 wave VHF antenna when I'm on the road.
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Old 08-29-2016, 5:48 PM
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Quote:
Originally Posted by Mojaveflyer View Post
My PSR-600 seems to have problems with intermod here in the Denver area. I primarily listen to aircraft and railroads, very little public safety. I ran across a FM Band Trap and put it into the antenna feed line and found the intermod was reduced...

Anyone else found this to be true? I'm just wondering if I stumbled on to something or am I just having a good day in the neighborhood. Thanks!
I second that. An FM Band Trap should be in the toolbox if not in the antenna cable of any scanner user who is even miles from an FM broadcast station. Even if you do not hear interference, the radio will often be desensed by the FM station and the user will not even know it.
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Old 09-12-2016, 9:25 AM
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Is there a place that is reliable and way under 100 dollars for a fm band trap??
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Old 09-12-2016, 9:43 AM
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Quote:
Originally Posted by Mojaveflyer View Post
My PSR-600 seems to have problems with intermod here in the Denver area. I primarily listen to aircraft and railroads, very little public safety. I ran across a FM Band Trap and put it into the antenna feed line and found the intermod was reduced...

Anyone else found this to be true? I'm just wondering if I stumbled on to something or am I just having a good day in the neighborhood. Thanks!
. Because GRE's have such a sensitive front end, this is pretty common in a high rf environment. I don't have this issue since I'm in sort of a suburb, but If I did I would try using my ATT (attenuator) on objects which are programmed that very high signals and probably my FM trap as well. You can Also try a indoor antenna to decrease the amount of signal you're getting. Do you know you have a Attenuator on your 600 ? 73, n9zas
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Old 09-12-2016, 9:47 AM
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Is there a place that is reliable and way under 100 dollars for a fm band trap??
If you still have a radio shack near you, they may have one. Its less than $20. 73, n9zas
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Old 09-12-2016, 1:59 PM
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Default FM Trap

FM Trap is available on Amazon.com, Radio Shack part # 15-577 for under $20. I use the attenuator but it seems to do little to help with the overload on my radio. Good luck! You need adapters to go from the "F" type connectors to the BNC connectors on your radio.
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Old 09-12-2016, 2:22 PM
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Thanks for the suggestions.
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Old 03-08-2017, 4:11 PM
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Quote:
Originally Posted by Mojaveflyer View Post
My PSR-600 seems to have problems with intermod here in the Denver area. I primarily listen to aircraft and railroads, very little public safety. I ran across a FM Band Trap and put it into the antenna feed line and found the intermod was reduced...

Anyone else found this to be true? I'm just wondering if I stumbled on to something or am I just having a good day in the neighborhood. Thanks!
Yes, yes! The interference is being caused by one of the towers atop Lookout Mountain. At first, I thought it was one of the towers itself creating noise across the band however that was ruled out as it does not affect all receivers (only GRE PSR-600 type scanners). I tried one of the FM traps on my PSR-600 and it did not help at all or very, very little. Attenuation also does not help.

There is something different going on in Denver with the PSR-600 than simple overload as the interference begins to break the squelch South of Platteville, CO and gets steadily worse as I approach Lookout Mountain. As I am driving from Platteville to Denver, anything that gets in the way of the towers atop Lookout Mountain (a passing semi-truck, a tall hill, another mountain, tall buildings, etc.) drastically reduces or entirely eliminates the interference.

I experimented up in Golden with this exact problem. Heading West on Highway 58 into Golden approaching Highway 6 (with the Lookout Towers in clear sight), the interference across the VHF band (esp. 160-173 MHz) is S5 even with attenuation turned on and a FM trap installed making the band entirely useless. This was while using a 2-meter roof mounted antenna. However, if you continue driving just another 1/2 mile or so West past Highway 6 a mountain blocks the view of the Lookout towers and the interference vanishes completely!!

Now what is really fascinating about this issue is that the interference being caused by the Lookout towers begins to break the squelch on frequencies in the 170 MHz range just south of the city of Platteville, CO which is over 40 miles away!! How can that be explained?? The squelch has to be progressively turned up higher and higher (esp. on freq.'s in the 160-173 MHz range) as one drives further South from Platteville toward the Lookout towers.

Digital television stations these days just sound like white noise when tuned in on a scanner. I've pondered whether digital white noise from one of the television stations is entering the scanner and then not being filtered out properly prior to the mixing sections of the circuit. If the cause of the problem is a signal near the 1st IF mixer frequency of 380.8 MHz (television station frequency range) then the digital television white noise could affect every frequency across the band as it would get mixed into every frequency.

I do not experience any problems anywhere else (Loveland, Fort Collins, Greeley, Cheyenne, etc.) only from the Lookout towers West of Denver and it starts over 40 miles away from the towers!

I ordered one of the new Whistler TRX-2 units due to this very problem in the Denver area. The TRX-2 is touted not to have the same issues the PSR-500/600 scanners have with desense, open squelch, unwanted noise across bands, etc. The TRX-2 has some issues of its own (does not power on when vehicle turned on, long power on times {30 seconds to one minute}, have to press scan when finally turns on, missing STAT option in multi-site settings, etc.) however if it fixes the problem with all the noise across the upper part of the VHF band it may be worth it. If you are interested, I will report back on my findings of how the TRX-2 performs compared to the PSR-600 type scanners in the Denver area.

Shawn

Last edited by ScannerSK; 03-08-2017 at 4:16 PM..
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Old 03-08-2017, 10:07 PM
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Thumbs up Intermod With PSR-500/600

Wow, most interesting response... I've pondered purchasing a TRX-2 but have held off for several reasons. Please let me know if you do get one and what your results are. Thanks!
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Old 03-08-2017, 10:50 PM
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The TRX-2 should be here Saturday. Possibly this Sunday I will have a chance to take it for a test drive to see how it performs interference wise and also test it here in Weld on the simulcast system. I'll let you know the results.

Shawn
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Old 03-16-2017, 1:16 AM
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Quote:
Originally Posted by Mojaveflyer View Post
Wow, most interesting response... I've pondered purchasing a TRX-2 but have held off for several reasons. Please let me know if you do get one and what your results are. Thanks!
The TRX-2 arrived 3/15. I should be able to test it out in Denver tomorrow 3/16. It was a bit of a learning curve getting Whistler's unsigned driver to function on my Windows 8.1 machine which requires signed drivers as a default. A few issues with the TRX-2 are that it will not power on when the vehicle powers on; it has to be manually powered on each time. The amplifier is kept hot (high gain) inside the receiver so there is some unnecessary white noise between words while stopped on a channel/talkgroup. It has somewhat of a long power up (around 30 seconds). I kept running into issues with the computer software program freezing and with "waiting on the main unit" errors on the TRX-2 display which I had to look up on how to correct. I think there are too many issues for me to keep one around personally.

The Uniden BCD996P2 works very well without any noticeable VHF interference so prevalent in the PSR-600 scanner in the Denver area. I plan to test out the TRX-2 with regards to interference and report back tomorrow.

I have also been reviewing the 108-225 MHz band pass filter built into the PSR-600 scanner which consists of 16 parts. I have a couple of ideas to try which may fix the issues with this scanner.

One thought that keeps going through my mind is that TV Channel 9 is on Lookout Mountain and spans the 186-192 MHz frequency range. The second harmonic of this range is 372-384 MHz which just happens to cover the 1st I.F. mixer frequency (380.65-380.86875 MHz). I'm thinking the digital TV noise from channel 9 (which sounds just like white noise) is getting through the 108-225 MHz band pass filter and then mixed into the 1st mixer then to appear as white noise across the VHF frequencies. Possibly just reducing the amount of signal allowed to pass through this filter will allow it to function more efficiently/properly.

I hope to have results soon for those interested.

Shawn

Last edited by ScannerSK; 03-16-2017 at 1:21 AM..
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Old 03-16-2017, 11:38 PM
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Quote:
Originally Posted by ScannerSK View Post
The Uniden BCD996P2 works very well without any noticeable VHF interference so prevalent in the PSR-600 scanner in the Denver area. I plan to test out the TRX-2 with regards to interference and report back tomorrow.
Well, I had a chance to test out the TRX-2 in the Denver area (specifically near Lookout Mountain). My conclusions are that it receives signals equally as well or just slightly better in the VHF band than the PSR-600 when prone to strong interference. The TRX-2 still displays S5 noise across the entire band from 108-174 MHz. It appears the main advantage of the TRX-2 over the PSR-600 (with regards to VHF interference issues) is with how the squelch functions. The squelch now stays closed even in areas of S5 noise (due to nearby interference/overload) while on the PSR-600 the squelch opens. Possibly they adjusted the squelch circuit to sample a higher frequency range to operate more efficiently.

The Uniden BCD996P2 did a much better job receiving signals in the presence of strong interference than either the TRX-2 or the PSR-600.

Quote:
Originally Posted by ScannerSK View Post
I have also been reviewing the 108-225 MHz band pass filter built into the PSR-600 scanner which consists of 16 parts. I have a couple of ideas to try which may fix the issues with this scanner.
Wow, this project is not for the faint in heart. Removing the epoxy from off the solder joints around the two shielded antenna circuit enclosures was a challenge. This took maybe 30 minutes or so plus an additional 30-45 minutes to desolder the metal shielding boxes. A slip of the hand scraped off a trace which took some additional time to repair.

Overall, nothing I attempted helped to receive desired signals in the presence of strong interference on the PSR-600 even though several professional radios I own work rather well at the same location.

Quote:
Originally Posted by ScannerSK View Post
One thought that keeps going through my mind is that TV Channel 9 is on Lookout Mountain and spans the 186-192 MHz frequency range. The second harmonic of this range is 372-384 MHz which just happens to cover the 1st I.F. mixer frequency (380.65-380.86875 MHz). I'm thinking the digital TV noise from channel 9 (which sounds just like white noise) is getting through the 108-225 MHz band pass filter and then mixed into the 1st mixer then to appear as white noise across the VHF frequencies. Possibly just reducing the amount of signal allowed to pass through this filter will allow it to function more efficiently/properly.
Scrub the above. I scanned the frequency range from 370-390 MHz and there is nothing unusually strong in that frequency range so the second harmonic idea does not pan out.

I attempted to reduce the amount of signal allowed to pass through the VHF band pass filter and that did not help either.

So, I still have the same old PSR-600 with its interference issues however plan on keeping it due to its multi-site STAT / Check All CCs Yes/No functions which are important features in my set up.

Shawn
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