Whistler Fake News

[hiegtx]

I would have to disagree with this but not in the reception part, in the trunking part.
I monitor a connect plus system and because the 436 handles trunking so much better i never miss a call or tone out (medical helo) but on the 1080 i often miss parts of calls. From what i have gathered the whistler units dont actually trunk track but rather scan the channels for the active TG. But i could be wrong.

That's my experience as well. On a not-too-busy system, my TRX-1 works reasonably well. But on a busy system (I monitor the same one as you), you can miss more than you realize.

I've pretty much relegated the TRX to the two NXDN systems in my part of the county, and monitor DMR mostly with the Uniden scanners.

 

[radio3353]

My 1080 and 1095 are fantastic on 700mhz P25 Phase II, actually I can't imagine it could get any better. All just a matter of location and the system that is being monitored.

The bold italics are mine. I take it you are talking about simulcast systems. That can be a pretty big problem (mobile usage, having to move the scanner to the closet or basement, etc) for 90% of listeners as we have seen many times here. Shouldn't be trivialized.

 

[Ed6698]

The bold italics are mine. I take it you are talking about simulcast systems. That can be a pretty big problem (mobile usage, having to move the scanner to the closet or basement, etc) for 90% of listeners as we have seen many times here. Shouldn't be trivialized.

I can be anywhere in my home and monitor this simulcast system. All I use is a basic rubber duck or the 800mhz RS antenna. Like I said it is all a matter of location. I don't take my scanners mobile as it is illegal to in Indiana, unless a person is a licensed ham.

 

[wbswetnam]

....unless a person is a licensed ham.

What's stopping you? The Tech license is ridiculously easy.

 

[nanZor]

As an old Pro-2006 owner, quickly hacked up with Cheek's mods, I too am saddened by the deterioration of build quality over the decades. Even participated in the classic (but often misunderstood "ocfd" antenna) with him back then, but that is a different sub-forum.

But, in Cheek-fashion, here we go....

Tip: 800/900 mhz reception - do NOT use mag-mounts. Physically they stick, but the "ground" is non-existent for the most part. That makes the common-mode of your feedline in a mobile the ground. Basically a 16 foot or so random wire hanging off your scanner. And very poor radiation / reception angles. Mostly straight up. Sorry, but at these high freqs, you really must drill that hole to get the ground you need.

By the same token, has anyone tried using ferrite chokes near the feedpoint, like Type 43 which are 30-300mhz coverage, around their feedlines, even mobile? Mobile noise sources traveling from the interior up the roof feedpoint, and then back down into the radio are reduced. Same kind of thing with fixed base installations.

Sure, we *shouldn't* have to do these things, but for now, has anyone tried this - with common mode being very hard to filter with all the cpu's, dsp's, etc. My early Uniden BC125AT seemed to have this issue - only type 43 chokes fixed it until Uniden did an upgrade very very soon thereafter.

 

[Ed6698]

What's stopping you? The Tech license is ridiculously easy.

Getting a license never really interested me for some reason. There are enough distractions in driving already, keeping a eye out for the other guy, a scanner in the car would probably be distracting to me.

 

[Ubbe]

With higher frequencies the requirements for a large ground plane is less. The mag in itself are a sufficient groundplane at 900MHz. At VHF the groundplane is large but a car roof is big enough. There is never any electrical contact from a magnet mount to the roof. Sometimes that is a positive effect when a radio is bolted to the chassi and its negative power terminal goes to the battery, which also are grounded in chassi, and could cause irritating ground loop problems when the antenna is grounded to chassi and the coax goes from one ground at the roof to another ground at the radio.

/Ubbe

 

[ScannerSK]

Some additional testing yesterday on a PRO-197 did indicate the VHF overload is occurring at either Q7 (2SC4094) or in the mixing stages as noted above. Possibly, a different transistor other than the 2SC4094 would correct the issue? In areas with strong RF overload, the PRO-197 can actually work better with Q7 (25-512 MHz) and Q3 (2SC4094)/Q4 (2SC4226) (764-1300 MHz) disabled. I figure it's an issue either with the transistors or cheap ceramic filters presently.

Shawn

There is one issue that really perplexes me with regard to the GRE type scanners (particularly the mobile unit {PSR-600} with an external antenna mounted on my truck). As I make my drive from Platteville, CO (about 30 miles North of Denver) toward Denver, white noise across the VHF band (particularly noticeable between 170-174 MHz) steadily increases in signal strength (as noted by the signal strength indicator in the scanner's LCD display). This affects every VHF frequency however is particularly noticeable between 170-174 MHz. What could possibly explain this?

As I am driving toward Denver (along the 30-mile stretch), semi-trucks that pass me so as to block my view of Lookout Mountain (where there is a large antenna farm for television and FM radio stations) block and eliminate the wide-band white noise (as noted by the signal strength indicator in the LCD display dropping to zero). Semi-trucks which pass on the other side of me and which do not block my view of Lookout Mountain have no effect upon the signal strength of this white noise.

At first, I thought the source of this wide-band white noise was actually being transmitted by a faulty radio tower from atop Lookout Mountain however further tests using commercial grade receivers do not experience the same issue. So, the wide-band white noise is not being transmitted from a faulty radio tower but is being generated internally somehow within the PSR-600 scanner starting at a distance of over 30 miles from the Lookout Mountain towers where the noise just barely begins to show an S1 signal strength in the display!

What could possibly explain increasing strength wide-band white noise (esp. between 170-173 MHz) as one drives over a 30 mile stretch toward Denver? The signal strength of this wide-band noise slowly and steadily increases the closer one gets toward Denver until it reaches S5 in strength. In Golden, CO, where the Lookout Mountain towers are in plain sight, the problem is so bad all VHF frequencies have S5 noise which makes the scanner deaf in the VHF band. Driving just 1/2 mile down the road where a mountain blocks the towers causes all the wide-band white noise to completely disappear.

The reason I am intrigued by this is that it may provide a clue as to what is wrong in the design of the PSR-600 scanner and provide a clue as to how to repair it to correct this issue. Whistler's new TRX-2 scanner also has this same problem. They just fixed the squelch on the TRX-2 so it does not open as readily to this same internally generated noise.

A cellphone tower located within about 1/2 mile of my sister's house creates the same issue (wide-band white noise) across the 800-MHz band which is somewhat understandable due to the close proximity to the towers. Uniden scanners however at this site work just fine in the 800's while the PSR-500/600 is almost deaf at this location.

But the real question is why would radio towers over 30 miles away begin to create wide-band white noise in a scanner which increases slowly and gradually in signal strength as one drives along a 30 mile stretch toward a specific group of radio towers? This just does not make sense and I fail to find an explanation. Any ideas? The part that really puzzles me is why this issue starts over 30 miles distant from the towers?

Shawn

 

[Machria]

ScanSK,
I had an office in Arvada, just south of where your talking about, and often stayed at one of the hotels next to the "Flatiron" area and shopping mall. There is small airport behind there (to the south east of the mall) up on the hill. They could possible have some VOR navigation equipment transmitting..... ? Just a guess...

 

[RFI-EMI-GUY]

There is one issue that really perplexes me with regard to the GRE type scanners (particularly the mobile unit {PSR-600} with an external antenna mounted on my truck). As I make my drive from Platteville, CO (about 30 miles North of Denver) toward Denver, white noise across the VHF band (particularly noticeable between 170-174 MHz) steadily increases in signal strength (as noted by the signal strength indicator in the scanner's LCD display). This affects every VHF frequency however is particularly noticeable between 170-174 MHz. What could possibly explain this?

As I am driving toward Denver (along the 30-mile stretch), semi-trucks that pass me so as to block my view of Lookout Mountain (where there is a large antenna farm for television and FM radio stations) block and eliminate the wide-band white noise (as noted by the signal strength indicator in the LCD display dropping to zero). Semi-trucks which pass on the other side of me and which do not block my view of Lookout Mountain have no effect upon the signal strength of this white noise.

At first, I thought the source of this wide-band white noise was actually being transmitted by a faulty radio tower from atop Lookout Mountain however further tests using commercial grade receivers do not experience the same issue. So, the wide-band white noise is not being transmitted from a faulty radio tower but is being generated internally somehow within the PSR-600 scanner starting at a distance of over 30 miles from the Lookout Mountain towers where the noise just barely begins to show an S1 signal strength in the display!

What could possibly explain increasing strength wide-band white noise (esp. between 170-173 MHz) as one drives over a 30 mile stretch toward Denver? The signal strength of this wide-band noise slowly and steadily increases the closer one gets toward Denver until it reaches S5 in strength. In Golden, CO, where the Lookout Mountain towers are in plain sight, the problem is so bad all VHF frequencies have S5 noise which makes the scanner deaf in the VHF band. Driving just 1/2 mile down the road where a mountain blocks the towers causes all the wide-band white noise to completely disappear.

The reason I am intrigued by this is that it may provide a clue as to what is wrong in the design of the PSR-600 scanner and provide a clue as to how to repair it to correct this issue. Whistler's new TRX-2 scanner also has this same problem. They just fixed the squelch on the TRX-2 so it does not open as readily to this same internally generated noise.

A cellphone tower located within about 1/2 mile of my sister's house creates the same issue (wide-band white noise) across the 800-MHz band which is somewhat understandable due to the close proximity to the towers. Uniden scanners however at this site work just fine in the 800's while the PSR-500/600 is almost deaf at this location.

But the real question is why would radio towers over 30 miles away begin to create wide-band white noise in a scanner which increases slowly and gradually in signal strength as one drives along a 30 mile stretch toward a specific group of radio towers? This just does not make sense and I fail to find an explanation. Any ideas? The part that really puzzles me is why this issue starts over 30 miles distant from the towers?

Shawn

My guess is that the scanner has poor out of band spurious image response and that the transmitters on lookout mountain are entering the receiver mixer and creating a rise in the noise floor. These could be HDTV transmitters on frequencies far removed from the 170 to 174 MHz band, yet mathematically related to the local oscillator and IF frequencies the scanner uses when tuned to that band.

In the past, I would blame NOAA radio transmitters for desensitization and Intermodulation responses as those were common problems with scanners. But now, with the rise in noise floor I would consider HDTV transmitters.

The fact that the problem noise rise is slow and gradual is indicative of the fact that you are mostly in line of sight with Lookout Mountain and that free space loss is the only mitigating factor until a truck shadows the site. Free space loss is surprisingly a small effect on signal paths.

An easy fix is to put a VHF bandpass filter in the antenna line and see if that eliminates the problem. It probably will, yet it is not a practical solution for a scanner. If you can determine the IF and LO frequencies of your specific scanner , I can run a calculator to determine possible transmitters. A notch filter might be a solution.

Being that the signal is confined to a 4 MHz swath, implies that one HDTV channel or other broadband carrier is the cukprit.

Sent from my SM-T350 using Tapatalk

 

[ScannerSK]

My guess is that the scanner has poor out of band spurious image response and that the transmitters on lookout mountain are entering the receiver mixer and creating a rise in the noise floor. These could be HDTV transmitters on frequencies far removed from the 170 to 174 MHz band, yet mathematically related to the local oscillator and IF frequencies the scanner uses when tuned to that band.

In the past, I would blame NOAA radio transmitters for desensitization and Intermodulation responses as those were common problems with scanners. But now, with the rise in noise floor I would consider HDTV transmitters.

The fact that the problem noise rise is slow and gradual is indicative of the fact that you are mostly in line of sight with Lookout Mountain and that free space loss is the only mitigating factor until a truck shadows the site. Free space loss is surprisingly a small effect on signal paths.

An easy fix is to put a VHF bandpass filter in the antenna line and see if that eliminates the problem. It probably will, yet it is not a practical solution for a scanner. If you can determine the IF and LO frequencies of your specific scanner , I can run a calculator to determine possible transmitters. A notch filter might be a solution.

Being that the signal is confined to a 4 MHz swath, implies that one HDTV channel or other broadband carrier is the cukprit.

Sent from my SM-T350 using Tapatalk

I was thinking down the same line at one time: that the issue may be related to HDTV signals interacting with the oscillator/mixing circuit(s). The 1st IF is noted as 380.8 MHz (380.650-380.86875 MHz) and utilizes a saw crystal filter, the 2nd IF is noted as 21.4 MHz and utilizes a crystal filter, and the 3rd IF is noted as 455 kHz and uses apparently two ceramic filters. I noticed the 2nd harmonic of TV channel 9 (190.4 MHz) in our area is 380.8 MHz so this is one possibility.

The owner's manual also states the following should it be helpful:
1st IF 380.8 MHz (The 1st LO uses high side of receive frequency range for VHF and UHF Low/T, and low side of receive frequency range for >512 MHz)
2nd IF 21.4 MHz (The second LO uses low side of 1st IF)
3rd IF 455 kHz (The 3rd LO uses the low side of the 2nd IF)

The problem occurs across the entire VHF band however gets progressively worse with rising frequency so that 174 MHz is the worst in the VHF band. Higher in frequency, 216 MHz is better than 174 MHz and testing upward in frequency from 216 MHz the issue gets progressively better until around 400 MHz it is hardly noticeable. This would seem to indicate the source of the interference is somewhere between 174-216 MHz which is not capable of being received on this scanner.

Some cellphone towers also generate the same wide-band white noise in this scanner however in the roughly 800-950 MHz frequency range. At each respective location where I experience issues, the opposite bands are just fine (where the VHF band is good in one area the 800 MHz band is bad in that same area and vice versa) which leads me to a second thought below.

There are two front-end RF transistors used in these scanners both of which are 2SC4094. One amplifies the frequencies from 25-512 MHz and the second amplifies the frequencies from 764-1300 MHz. This specific transistor uses a "new proprietary DNP process" to make these transistors however I doubt that would play into the picture, although I have pondered whether the 2SC4094 transistor itself could be the culprit as typically only one band or the other (either 25-512 MHz or 764-1300 MHz) is affected each of which is amplified by a separate 2SC4094 transistor.

Do you think the problem could be related to simply cheap saw/crystal/ceramic filters?

Just thoughts on this end...

Shawn

 

[RFI-EMI-GUY]

Without looking at the schematic, I hesitate to say whether upgrading those parts would help. You might find a part that is 6 dB better, but if you have a 20 dB overload situation, I can't see that helping much.

Certainly an RF transistor with higher intercept point will help somewhat. But keeping the unwanted signal out of the receiver will be more effective. It does sound like a component is being driven into non linearity, but keep in mind that the first mixer normally operates in nonlinear mode and it precedes the saw filter.

If it were mine, I would start with using a spectrum analyzer to see what is out there and the relative signal strengths. Scanners are notoriously awful with respect to out of band spurious response. Some receivers like the ICOM IC-R7000 employed varactor tuned filters in the front end to give some semblance of RF selectivity. I don't know how the Pro 197 is configured, if it has varactor tuning, which I doubt, it may be possible to tweak it a bit narrow the bandwidth.

Have you tried another scanner or commercial radio in this environment?

 

[ScannerSK]

Without looking at the schematic, I hesitate to say whether upgrading those parts would help. You might find a part that is 6 dB better, but if you have a 20 dB overload situation, I can't see that helping much.

Certainly an RF transistor with higher intercept point will help somewhat. But keeping the unwanted signal out of the receiver will be more effective. It does sound like a component is being driven into non linearity, but keep in mind that the first mixer normally operates in nonlinear mode and it precedes the saw filter.

If it were mine, I would start with using a spectrum analyzer to see what is out there and the relative signal strengths. Scanners are notoriously awful with respect to out of band spurious response. Some receivers like the ICOM IC-R7000 employed varactor tuned filters in the front end to give some semblance of RF selectivity. I don't know how the Pro 197 is configured, if it has varactor tuning, which I doubt, it may be possible to tweak it a bit narrow the bandwidth.

Have you tried another scanner or commercial radio in this environment?

I tried an HTX-202 ham radio and a Motorola HT1000 and they do not have any problems with reception or stuck open squelch as does the GRE type line of scanners at the same locations.

I sent an e-mail your way in case you would like to review the schematic.

Shawn

 

[RFI-EMI-GUY]

I tried an HTX-202 ham radio and a Motorola HT1000 and they do not have any problems with reception or stuck open squelch as does the GRE type line of scanners at the same locations.

I sent an e-mail your way in case you would like to review the schematic.

Shawn

The filter for the 108 to 225 MHz band is fixed, no track tuning. It probably has a 3 dB point extending an additional 5 MHz above and below the band. The way this receiver works is that each filter is switched with PIN diodes (D15 and D16, biased via R19, R17 and R18 for this section). There is no protection from strong out of band signals into the active stages



By comparison the ICOM R-7000 receiver has individually tuned preselectors for each band, the equivalent filter in the ICOM is a 90 to 250 MHz filter tuned with varactor tuning diodes and also has a tune-able notch for FM broadcast frequencies. For more information read Page 3-1 Block Diagram RF Unit BPF2 90-250 MHz, Page 4-1 Section 4-1-3 RF Amplifier Unit (RF UNIT), also Section (b) BPF2, also Section 4-1-9 TUNED CONTROL CIRCUIT (RF UNIT). Schematic is in the circuit Description tab, or page 106 of the document.

http://www.radiomanual.info/schemi/IC-R7000_serv.pdf

You could replace the components Q7, IC2 and XF1 with parts exhibiting better Output Intercept Point, but you would have to consider increasing biasing voltages (and it still may be no better)

I would check the spectrum, determine what frequency the offending carrier is on and then see if it can be notched effectively using a custom filter from PAR or a home made coaxial stub. A VHF bandpass preselector might help, though you will probably have to yield some sensitivity on the end of the band near the offending signal.

What antenna are you using? If it is more than a 1/4 wave VHF whip, that may be hurting you. That said, your solution could be a coaxial switch to select a 1/4 wave UHF whip or 1/4 VHF whip depending upon need to attenuate OOB signals versus ideal reception.

http://www.parelectronics.com/scanner.php

 

[yeg_scan]

Just wanted to comment .. my original post was due to the inability to receive an 800 MHz system. It was unable to be monitored from my vehicle.

I tried a couple of bandpass filters and lab grade external attenuation and nothing helped. The radio was simply overwhelmed when it was near a cellular site (which around here is like every few blocks and transmitting at about 300-400 watts).

I now use the 1095 inside *with a custom 1/4 wave duckie .. monitoring the same system and sitting on one talkgroup as overall it is pretty useless to do much else.

 

[ScannerSK]

It's unfortunate the PSR-500/600, PRO-651/652 and WS1040/1065 all have this type of issue. And the new TRX-2 appears to suffer from the same problem however the squelch was fixed to no longer open on the white noise however it is still present desensing the receiver.

It sounds worse than anticipated in the sense of there being no really easy fix (swapping a transistor or one filter, etc.) I have looked into the PAR filters (somewhat expensive) in the past and would likely purchase one if I lived in Denver. Maybe the Uniden scanner I recently purchased will shed some light on the offending frequency which is almost certainly an HDTV signal in the 174-216 MHz range. The trick may be finding different locations in which something blocks the view to different towers (depending upon my location) which may assist in narrowing down the offending tower and specific frequency involved in generating the wide-band noise.

40 miles North of Denver at my sister’s house, it is the same problem however in the 800’s. In essence, I may require a bag of filters depending upon my location. Some have stated strong broadcast FM radio station towers create issues as well and I appear to experience greatly reduced scanner sensitivity in one location I frequent just several blocks from a FM radio station. Reluctantly, I will most likely make the switch over to a Uniden handheld permanently. This was likely coming anyway as we are on a P25 phase two system however only currently using phase 1. I really prefer GRE’s programming software (with its ability to assign individual talk groups and conventional channels from all systems radio wide and place them into a single scan list) however having a scanner capable of receiving radio traffic trumps the programming preference. This was probably the dying cry of my GRE radios.

Outside of actual filters, I found that a pot in series with the incoming signal and a shunting pot between the ground and the scanner side of the first pot works amazingly well. I assume this method lowers the signal enough for the scanner to obtain a little more control over things however the desired signals are still weaker than if the radio simply worked properly with correct filtering in place. I’m not sure what Uniden did different in the design of their scanners however their scanners do not appear to experience any problems at the same locations from tests I performed in the past.

The antenna is just a standard 1/4 wavelength VHF whip. This problem even effects the handheld PSR500 using a rubber duck antenna at a distance of ten or fifteen miles from the towers however only S2 or S3 noise if I remember correctly.

Thank you for taking a look at the schematic. This is certainly a wake-up call for Whistler to revamp their next line of scanners with better front-end filtering before releasing them onto the market.

Shawn

 

[WhistlerWendy]

The real deal would be if Donald J would tweet about his wonderful new Whistler scanner. I think Whistler Wendy should send him a free one (just not a 1095) so we get him into the hobby and we can make a thread about it.

Now that would be the *fake news* of the day!