An unexpected sensitivity experience - I'd like some comments...

Quaxo

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May 1, 2007
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Hello,
I've always been into air band listening (not much interested in other bands) and I've always tried to obtain related equipment, since I was a child.
My very first air band radio was an "International 877T" - you can see it here even though the model name is different on that site.
With that radio, and its telescopic antenna, I was able to receive perfectly clearly all the transmissions from my local international airport (LIRF, Rome Fiumicino) - I could hear the planes AND the ground transmissions - Approach, departure, VOLMET, radar, and so on.The reception was good even if I don't have a line-of-sight view of the airport. I'm about 30 miles away from the airport (line of sight distance).
I had fun with that radio even if it was a nightmare to tune, but then I misplaced it, and so I bought a Uniden UBC30XLT, but I didn't love it especially for the lack of alpha tags, and no direct frequency entry. So I bought a Uniden UBC3500XLT, which later was run over by a car, and then a UBC125XLT. And a Radio Shack Pro-82 just because it was cheap at a flea market. I use them with the Watson W-901 antenna, and with the Watson Super-gainer (both bought from a respectable UK seller, so should be genuine) and with a magnetic-mount Air-band-specific antenna whose brand I forgot. The latter is the best performer of all.

Well, with all these scanners, I've never been able to receive any ground station at all. On any frequency. Occasionally something from a smaller airport that's closer to me, but never LIRF, which I used to hear well with that ancient analog radio. I honestly assumed they had reduced their transmit power, maybe because the receivers onboard airplanes had gotten better in these 20 years.
Fast forward to a couple of days ago, and during a house move, I found my old analog radio. I put fresh batteries in, and after applying some contact cleaner spray on the switches and pots, I was able to get it running... and imagine my surprise when after fiddling with the tuning pot, I heard loud and clear all the ground transmissions from LIRF.
So it appears that a very old, analog-only, battered radio receiver with its flimsy fixed telescopic antenna receives much better than my new, much more expensive, scanners connected to an outside antenna that is supposedly meant for air band. And now I'm puzzled and would like some advice.
I honestly need to hear the ground part of the conversation. Air band is rather boring without it. So what should I do? Is it conceivable that my scanners are so deaf compared to the old radio? Should I buy a much better antenna, and if so, which one? I have some space under my (concrete and tiles) roof where I could install an antenna as long as it's shorter than 2m more or less. That would be about 20 ft above ground. Or I could put it on the roof but I would be a bit worried about lightning.
I don't need stellar performance, I just need to hear what I could hear 20 years ago.
I'm prepared to buy a new scanner, possibly handheld but also a desk unit would do. I really don't need a transceiver but I could go that way if needed. Or maybe just a new antenna could do? But this would still not explain why my older radio would get those signals with an indoors stick antenna.
I've heard about the Yupiteru MVT-7100 scanner, supposedly very seneitive, but I would really like to have alpha tags.
Ah, scanning is pretty important too, so I'd rather avoid "pure receivers" that don't scan.
My total budget (radio + antenna if needed) could be about 400 euro or slightly more, but I would be much more happy if I could spend 250 or so.

The "bigger" Unidens both also have a Squelch issue, in that level 1 always stays open, and level 2 is too strong - i.e. it blocks some perfectly usable signals. But that's not the point of this post.

Well... that's about it. Thank you for reading this, and for any advice...
Cristian

EDIT: I thought I might add that with my newer scanners, the farthest I ever heard an intelligible transmission from an airplane, was about 130 miles away. With the older analog radio, I heard - faintly but clearly - an aircraft that was almost 200 miles away.
 
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RFI-EMI-GUY

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Hard to say given the limited information you provide. But 30 years ago the VHF noise floor was probably a lot lower. You should evaluate your antenna location and the noise sources around it. If possible an antenna with a balanced feed would be optimium to reduce common mode noise from the shack getting into your antenna. Your antenna is grounded? An antenna should be as high up and unobstructed as possible.

Handheld scanners have poor antennas. They are usually helical design and lossy. Plus the radios radiate a noise floor of their own making them innefective for sensitive reception. You can connect an outside antenna, but sometime the receivers will get blown away from high power paging and broadcast signals when connected to a REAL antenna. .

As far as receivers, I suggest ICOM's base station type receivers. I have an ICR-9000 which was pricey, but ICOM made a slew of receivers from the ICR-7000, ICR-8500, etc which were all fine and had analog squelch controls and AGC, features you won't find on the "scanner" type receivers. The ICOM's will scan just fine, but they are targeted for more active manual signal tuning. They also have better receiver circuits.
 
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mmckenna

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Well, considering you have the old radio back and it still works better, I think the issue is that many scanners are just not very good performers across the entire spectrum they cover.

A radio that is designed to cover one portion of the spectrum often can outperform a scanner that is designed to cover a much larger portion of the radio spectrum. Reason is it's easier to design filtering that works effectively in a smaller portion of frequencies.

For the scanners, there could be a some stronger signals that are outside the air band that is partially deafening the receiver. Not uncommon.
Could also be that the type of circuit they use to get the audio out of the RF signal is better in your older radio.

Might be worth trying a dedicated air band radio. You can sometimes find VHF AM Air band portable radios fairly cheap. Might work better than a scanner.
 

RFI-EMI-GUY

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That old radio you have appears to have a manually tuned dial. It means it was a simpler design and has no inherent noisy digital circuits. It also means it can be tuned directly on frequency. Modern scanners tune in steps like 5, 12.5 and 25 KHz. In Europe, some channels are in 8.33 KHz steps, meaning some older radios will be off frequency on certain channels. If you buy a modern receiver, be sure it tunes 8.33 KHz step for airband or can be tuned in 100 Hz or smaller steps.
 

Ubbe

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Older recievers from 40 years ago can have good selectivity but usually bad sensitivity. An old scanner like Radio-Shack Pro2006 have a sensitivity like 0,5uV and modern scanners are almost twice as good but with less selectivity and almost any modern scanner needs a FM trap filter to reduce FM broadcast transmissions when monitoring VHF air band. A manually tuned receiver could use several capacitors that are ganged on the same axel when you tune the frequency to control both the oscillator frequency and the front-end filter. Modern scanners has fixed filters that pass a whole frequency band from the antenna to the receiver.

Some people say that Pro2006 are the most sensitive scanner they have when it in fact it probably has the worst sensitity of their scanners but its selectivity and capability to handle strong signals without loosing sensitivity are much better than their other scanners.

In the old days there wasn't much knowledge about filters and overload issues and probably wasn't needed either as receivers where designed differently. Now scanners are made to impress with good sensitivity figures in the sales blurbs and that's what many people go by when they look for a new scanner to buy. There are few scanners that have both great sensitivty and good strong signal handling. Even in professional 2-way radios like Motorola you can in some of them program the receiver for city use or suburban use as it can't handle both types of signal enviroments at the same time. The city mode doesn't have as good sensitivity but it handles strong signals without loosing the sensitivity it has.

/Ubbe
 

cbehr91

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Older recievers from 40 years ago can have good selectivity but usually bad sensitivity. An old scanner like Radio-Shack Pro2006 have a sensitivity like 0,5uV and modern scanners are almost twice as good but with less selectivity and almost any modern scanner needs a FM trap filter to reduce FM broadcast transmissions when monitoring VHF air band. A manually tuned receiver could use several capacitors that are ganged on the same axel when you tune the frequency to control both the oscillator frequency and the front-end filter. Modern scanners has fixed filters that pass a whole frequency band from the antenna to the receiver.

Some people say that Pro2006 are the most sensitive scanner they have when it in fact it probably has the worst sensitity of their scanners but its selectivity and capability to handle strong signals without loosing sensitivity are much better than their other scanners.

In the old days there wasn't much knowledge about filters and overload issues and probably wasn't needed either as receivers where designed differently. Now scanners are made to impress with good sensitivity figures in the sales blurbs and that's what many people go by when they look for a new scanner to buy. There are few scanners that have both great sensitivty and good strong signal handling. Even in professional 2-way radios like Motorola you can in some of them program the receiver for city use or suburban use as it can't handle both types of signal enviroments at the same time. The city mode doesn't have as good sensitivity but it handles strong signals without loosing the sensitivity it has.

/Ubbe
I can agree with that to a degree. My experience lies more with rail monitoring (160-161mHz), but I do a fair bit of AM air band monitoring as well.

Anyway, I've used a Pro-2006 in the past for both and thought it was rather deaf compared to either the slew of 2m transceivers I have/had. On the airband as I recall it had some birdies. I wonder if others had the same experience?

However, for the rails the Regency HX1000/1200/1500 from the 1980s blows pretty much every scanner away and their receive performance is on par with a commercial railroad radio, but the rated sensitivity in the manual is something like 0.4uV while a modern Kenwood or Icom is usually .2-.3uV. I'm not sure what the rated sensitivity was of "classics" like the Moto HT1000 or different Spectras. The selectivity on the old Regencies isn't as good, but that's only an issue if you're near a big city (in my experience, anyway).

The best air band receiver I've tried is a Yupiteru MVT-7100. A Regency HX1200 will match it, but the audio won't be as clear.
 

spacellamaman

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Hello,
I've always been into air band listening (not much interested in other bands) and I've always tried to obtain related equipment, since I was a child.
My very first air band radio was an "International 877T" - you can see it here even though the model name is different on that site.
With that radio, and its telescopic antenna, I was able to receive perfectly clearly all the transmissions from my local international airport (LIRF, Rome Fiumicino) - I could hear the planes AND the ground transmissions - Approach, departure, VOLMET, radar, and so on.The reception was good even if I don't have a line-of-sight view of the airport. I'm about 30 miles away from the airport (line of sight distance).
I had fun with that radio even if it was a nightmare to tune, but then I misplaced it, and so I bought a Uniden UBC30XLT, but I didn't love it especially for the lack of alpha tags, and no direct frequency entry. So I bought a Uniden UBC3500XLT, which later was run over by a car, and then a UBC125XLT. And a Radio Shack Pro-82 just because it was cheap at a flea market. I use them with the Watson W-901 antenna, and with the Watson Super-gainer (both bought from a respectable UK seller, so should be genuine) and with a magnetic-mount Air-band-specific antenna whose brand I forgot. The latter is the best performer of all.

Well, with all these scanners, I've never been able to receive any ground station at all. On any frequency. Occasionally something from a smaller airport that's closer to me, but never LIRF, which I used to hear well with that ancient analog radio. I honestly assumed they had reduced their transmit power, maybe because the receivers onboard airplanes had gotten better in these 20 years.
Fast forward to a couple of days ago, and during a house move, I found my old analog radio. I put fresh batteries in, and after applying some contact cleaner spray on the switches and pots, I was able to get it running... and imagine my surprise when after fiddling with the tuning pot, I heard loud and clear all the ground transmissions from LIRF.
So it appears that a very old, analog-only, battered radio receiver with its flimsy fixed telescopic antenna receives much better than my new, much more expensive, scanners connected to an outside antenna that is supposedly meant for air band. And now I'm puzzled and would like some advice.
I honestly need to hear the ground part of the conversation. Air band is rather boring without it. So what should I do? Is it conceivable that my scanners are so deaf compared to the old radio? Should I buy a much better antenna, and if so, which one? I have some space under my (concrete and tiles) roof where I could install an antenna as long as it's shorter than 2m more or less. That would be about 20 ft above ground. Or I could put it on the roof but I would be a bit worried about lightning.
I don't need stellar performance, I just need to hear what I could hear 20 years ago.
I'm prepared to buy a new scanner, possibly handheld but also a desk unit would do. I really don't need a transceiver but I could go that way if needed. Or maybe just a new antenna could do? But this would still not explain why my older radio would get those signals with an indoors stick antenna.
I've heard about the Yupiteru MVT-7100 scanner, supposedly very seneitive, but I would really like to have alpha tags.
Ah, scanning is pretty important too, so I'd rather avoid "pure receivers" that don't scan.
My total budget (radio + antenna if needed) could be about 400 euro or slightly more, but I would be much more happy if I could spend 250 or so.

The "bigger" Unidens both also have a Squelch issue, in that level 1 always stays open, and level 2 is too strong - i.e. it blocks some perfectly usable signals. But that's not the point of this post.

Well... that's about it. Thank you for reading this, and for any advice...
Cristian

EDIT: I thought I might add that with my newer scanners, the farthest I ever heard an intelligible transmission from an airplane, was about 130 miles away. With the older analog radio, I heard - faintly but clearly - an aircraft that was almost 200 miles away.
i appreciate you bringing this up as i have collected some similar models over the years but never found a good use for them, as being in proximity to other scanners causes other problems. i never thought about how well they could work regarding range though, which could be useful for me.

The "bigger" Unidens both also have a Squelch issue, in that level 1 always stays open, and level 2 is too strong - i.e. it blocks some perfectly usable signals. But that's not the point of this post.
yeah im glad im not the only one perturbed by this. what really bugs me is a couple of models that require level 4 lest we have to lock out half the spectrum doing a search.

So I bought a Uniden UBC3500XLT, which later was run over by a car,
its amazing how easy that is to do. RIP BC346XT, you deserved better than an 18 wheeler, my trusty friend.
 

popnokick

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a magnetic-mount Air-band-specific antenna whose brand I forgot. The latter is the best performer of all.
Where is this "best performer" antenna mounted and how have you confirmed the proper operation of the antenna, cable, and mount (e.g. an analyzer, simple ohmmeter checks on the cable, etc.)? You wrote that you have a concrete and tile roof... what is the magnetic mount base for the antenna using to hold it in place and act as an RF ground / counterpoise?
 

majoco

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I have a Signal Communications Corp R-532 airband receiver that out-performs the scanners that I have except an Icom R7000 - which is not really a scanner anyway! IMHO a dedicated receiver for a particular band will always be more sensitive and have better filtering by design than anything that does DC-to-daylight.
 

RFI-EMI-GUY

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I have a Signal Communications Corp R-532 airband receiver that out-performs the scanners that I have except an Icom R7000 - which is not really a scanner anyway! IMHO a dedicated receiver for a particular band will always be more sensitive and have better filtering by design than anything that does DC-to-daylight.
I have had my eyes out for one of those. It looks like a nice radio for its day. The R-535 is a newer version with LCD.
 
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Ubbe

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I have a Signal Communications Corp R-532 airband receiver that out-performs the scanners that I have except an Icom R7000 - which is not really a scanner anyway!
The R7000 are sensitivive but have reportedly bad strong signal capability and overloads and goes into intermod easily. But in New Zeeland you probably don't have to worry about that and can use high sensitive receivers without any problems.
IMHO a dedicated receiver for a particular band will always be more sensitive and have better filtering by design than anything that does DC-to-daylight.
Yes, they can use the space and money to focus on one good filter. But a multiband receiver could be just as good if they made more and narrower filters but that are more costly and needs more space in a receiver. They only make scanners good enough to satisfy most users and not the best they can do.

/Ubbe
 

Quaxo

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Thank you everyone for your replies. It's more complicated than I thought... I just wanted a good quality air band scanner, didn't think it would be so complicated... You know, like "Shut up and take my money!" :)
I might try the Yupiteru 7100, though I would have liked the alpha tags. We'll see if that one is as good as the old analog radio. I'll also look for the R-532.

Where is this "best performer" antenna mounted and how have you confirmed the proper operation of the antenna, cable, and mount (e.g. an analyzer, simple ohmmeter checks on the cable, etc.)? You wrote that you have a concrete and tile roof... what is the magnetic mount base for the antenna using to hold it in place and act as an RF ground / counterpoise?
It's a movable antenna, I just it put it up whenever I want to listen, and wherever I am. I usually just put it on the metal railing of my balcony.
In the best conditions, the Uniden scanner with that antenna, performs almost as good as the older radio. The older radio though is much much better when compared "apples to apples", i.e. when on the modern scanners I use small antennas comparable to the telescopic one on the old radio (i.e. the W901).
Maybe before buying a new scanner, I'll try building an antenna. For self-built, attic-mounted antenna, what would be better? Ground plane or dipole? These seem easy enough to build. That would be my first self-built antenna, by the way.
If I were to install the antenna on the roof, to get even better reception... how worried should I be of lightning? We don't get many lightning here, but we get some; and I wouldn't be too upset if a bolt damaged my antenna, but I wouldn't want it to hurt someone who happened to be in the house, near the cable...

Hard to say given the limited information you provide. But 30 years ago the VHF noise floor was probably a lot lower. You should evaluate your antenna location and the noise sources around it.
Yeah but as others said... the older radio is still outperforming the others *now*, so it can't be increased noise. And it outperforms them when used side-by-side, with a comparable antenna, so it can't be the location... It has to be the actual receiver.
A very good antenna on my modern scanner will probably give me a good result... but imagine what the good antenna would do with the older radio... :) That's why I would like a better modern scanner: then I wouldn't constantly think that I could hear more with a better receiver.

its amazing how easy that is to do. RIP BC346XT, you deserved better than an 18 wheeler, my trusty friend.
Yeah, I was just stupid... I had my Uniden on the passenger seat of my car - I had been listening to the aircraft my wife was coming home with - but then I had to put my child's seat in, and I moved the scanner to the roof of the car... and forgot it there. I noticed it was missing when I got back home. Went back to look for it... It had resisted on the roof for a few km, then ultimately fell on the highway. I found it still inside its pouch. I picked the pouch up, and it rattled a lot. Inside the pouch... it was not a pretty sight. Must have been run over by dozens of cars and trucks.

Cristian
 

w0fg

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You might consider one of the Yaesu or Icom dedicated aircraft handhelds. The basic COM only models are no more expensive than many scanners, running in the $200-250US range. When it comes to scanners, my ancient RadioShack PRO-2045 does a far better job on aircraft than either of my Uniden digital models.
 

Quaxo

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You might consider one of the Yaesu or Icom dedicated aircraft handhelds. The basic COM only models are no more expensive than many scanners, running in the $200-250US range. When it comes to scanners, my ancient RadioShack PRO-2045 does a far better job on aircraft than either of my Uniden digital models.
By "dedicated aircraft handhelds" do you mean transceivers? The price is OK for me, but I would prefer receiver-only to avoid the added legal risks. And I couldn't easily justify being found around an airport carrying a transmitter... :)
I had a look online at the Pro-2045... Seems like a nice radio, but the reported sensitivity on Airband is 1.5uV... Much worse (on paper) than Uniden's... Is that because the specs are totally unrealistic, or is the sensitivity just a not-so-significant figure?
 

Quaxo

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You might consider one of the Yaesu or Icom dedicated aircraft handhelds. The basic COM only models are no more expensive than many scanners, running in the $200-250US range. When it comes to scanners, my ancient RadioShack PRO-2045 does a far better job on aircraft than either of my Uniden digital models.
Another question... I can't find the 2045 right now. Are the other RadioShack (Realistic) scanners any good? For example the PRO-2042, I found one that's pretty good looking... Is it good?

Cristian
 

spacellamaman

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Yeah, I was just stupid... I had my Uniden on the passenger seat of my car - I had been listening to the aircraft my wife was coming home with - but then I had to put my child's seat in, and I moved the scanner to the roof of the car... and forgot it there. I noticed it was missing when I got back home. Went back to look for it... It had resisted on the roof for a few km, then ultimately fell on the highway. I found it still inside its pouch. I picked the pouch up, and it rattled a lot. Inside the pouch... it was not a pretty sight. Must have been run over by dozens of cars and trucks.

Cristian
virtually the same story. still light outside, put scanner on roof of car, so i would see it and not forget it. got tied up, therefore running late, back outside rush to the car in the darkness. sped down the driveway, got to the highway and floored it to get ahead of an 18 wheeler. and heard a funny bump, ba-bump. the rest of the story tells itself. i found virtually all of it, but it took about a half hour looking even though it was tethered to a non-standard flip down carry case. i was sick. alas, life is so short.

PSA: Don't leave your kids in the car in the summer or your scanner on the roof in winter.
 

Ubbe

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For example the PRO-2042, I found one that's pretty good looking... Is it good?
No. A BCT15 are way better. The Pro-2042 isn't as sensitive in FM VHF/UHF as Unidens BCT15 and absolutly not as good when it comes to overload issues. It also lacks proper narrow FM mode and some step sizes and the delay time are often not long enough.

In the VHF airband I have the 2042 connected to the same splitter as the BCT15 and I use amplifier and FM broadcast trapfilter and I adjust the signal level from the amplifier, as it might desense even at lower levels, but cannot improve reception of the 2042. The BCT15 are superior to it also in VHF air.

Remember that scanners work differently at different locations and one guy migh say that one scanner have best reception as it has good strong signal handling but could have the worst sensitivity of his scanners, but at another place you only need good sensitivity and strong signal handling are not needed. It's the same with antennas that each location will be unique. If one scanner and one antenna always where the best one for everyone then we would all get only those and forget about all the others. It's almost impossible to give advice about scanners and antennas. You probably have to try yourself what combination are the best for your unique location.

/Ubbe
 

Quaxo

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No. A BCT15 are way better. The Pro-2042 isn't as sensitive in FM VHF/UHF as Unidens BCT15 and absolutly not as good when it comes to overload issues. It also lacks proper narrow FM mode and some step sizes and the delay time are often not long enough.
Thank you. I'm looking into the BCT-15, and I see it's discontinued and replaced by the BCT-15X. Is it as good as the old one?
And, do you know how it compares to the Yupiteru MVT-7100, which I heard is particularly good?

Thanks again
Cristian
 

Ubbe

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Thank you. I'm looking into the BCT-15, and I see it's discontinued and replaced by the BCT-15X. Is it as good as the old one?
As I understand it is only software that are changed in the X model to add features that where missing from the BCT15.
And, do you know how it compares to the Yupiteru MVT-7100, which I heard is particularly good?
I have no experiance of it other than people said it was good 20 years ago. It seems to drift up to 4KHz in frequency and needs to be retuned so often that one guy drilled a hole to access the trimmer from outside. The plastic at the antenna connector flex so that the soldering might crack at the circuit board if you use a heavy antenna like a telescope type. You can read the reviews at eham.net

/Ubbe
 

p1879

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RadioShack PRO-2045 seems to me a great scanner for Mil-air, and lowband vhf dx. Does have step-size and NB issues in VHF FM though, but can still hear distant USFS stations on the "rounded off' frequency it resorts to in some cases. Found one at the Flea for 35$. It always trounced my 2 BC780's on sensitivity, to my ears.
 
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