AM Airband

[ludek-brno]

My SDS200 shows very poor performance of AM modulation on Airband from base stations (Tower / APP / ATIS).
After 2 seconds of the session, the voice is unintelligible.
Ground and airborne aircraft are demodulated correctly.
Many intermodulation hatches between air AM channels from base stations were not on BCD436 / 536HP
Airband AM modulation is the weakest side of the SDS200 scanner for me.

 

[jjbond]

Welcome to owning an SDS radio, all but useless a lot have found on anything other than 700/800 trunking systems.

 

[jaspence]

For around $100, the Uniden BC125AT is a good way to fill in the air band and other analog coverage.

 

[phask]

I find my SDS to receive Air very much the same as a 996P2 and a 536, no discernible difference between any of them.

I am in a fairly low RF environment (excepting cell ).

 

[mule1075]

Welcome to owning an SDS radio, all but useless a lot have found on anything other than 700/800 trunking systems.

Not true at all works quite well on 150mhz and 450mhz simulcast systems. It has been stated many times over that if you don't have simulcast issues you could probably stick with what you have unless you want the latest and greatest. With all that being said with the addition of the filters the analog performance on my sds100 that I sold and now my 200 is on par with my 15x.

 

[MisterLongwire]

Mine works quite well....ATIS......departure control...very surprised with the stock antenna reception

 

[R0am3r]

Welcome to owning an SDS radio, all but useless a lot have found on anything other than 700/800 trunking systems.

Do you own a SDS radio? My SDS200 works great and has a fantastic receiver. I can hear every law enforcement agency and fire/EMS team in my home county [Oneida County NY] as well as four of the surrounding counties. I typically listen to analog and P25 systems between 150 MHz and 470 MHz. My SDS is indeed quite useful.

 

[jjbond]

Do you own a SDS radio? My SDS200 works great and has a fantastic receiver. I can hear every law enforcement agency and fire/EMS team in my home county [Oneida County NY] as well as four of the surrounding counties. I typically listen to analog and P25 systems between 150 MHz and 470 MHz. My SDS is indeed quite useful.

Yes, the Phoenix area is terrible on them, lots of front end de-sense. So would not be surprised if yours was fine.

 

[R0am3r]

Ah, now I understand your post. I live in the country so I don't have problems with front end desense issues. I am blessed with a noise-free environment from the AM broadcast band on up. When I tune into the Airband with my SDS, I hear lots of overhead aircraft chatting with the regional ATC centers (Boston, Cleveland, and New York) with no noticeable signal degradation or performance issues.

 

[TailGator911]

I am in a mid-sized city just a mile from the main gate of a major Air Force base, and I have zero intermod or interference issues on my SDS scanners. I can almost hit a cell tower with a rock out my back door. People should reference that 'MY SDS' has issues without an unfair generalization that 'ALL' SDS have the said issue. There are way too many satisfied owners that would disagree with such a negative remark. It's tough that some have these issues, but they are definitely in the minority, as the majority of us are happy campers without their issues. To generalize that all SDS scanners have these same problems is just an unfair and biased assumption. I recently bought a new LG UHD UK6190 70" Tv and it was delivered, unboxed, and did not work. I did the customer service hoop jumps for the better part of a month before a new TV was sent. It would be very immature and hateful act for me to go online and declare that ALL LG TVs suck, even tho I was told my TV was one of quite a few with the same repair issue. Luck of the draw. My replacement is absolutely awesome.

JD
kf4anc

 

[W5JCK]

As far as AM aircraft band issues from ground based transmitters go: Well, they are ground based and thus subject to a lot of terrain and objects that can mess up the propagation of those radio waves. After all, ground based AM aircraft transmissions are used to communicate with aircraft in the air or very near as in on the airport property or at least very near it. They were not set up to communicate long distances between other ground based systems. AM, or other modes too, work best when there is a direct line of sight between the two stations that are trying to communicate with one another. Put an airplane a few miles up in the air and line of sight can become dozens if not hundreds of miles. Put two stations on the ground, and line of sight can dropped to mere feet, or at best a few miles. The radio waves will propagate across the land for a few miles bending downward a bit more quickly than the curvature of the Earth. Depending on height of antenna, frequency range, mode, etc. ground to ground radio wave propagation is generally a matter of a few miles unless you can bounce those waves off of the upper layers of the atmosphere (called skip). Skip can work okay, though it is not very controllable, with HF and below frequencies as long as they do not exceed the MUF (maximum usable frequency). Aircraft AM VHF/UHF band frequencies are much too high for skywave propagation in most cases. So you are only going to see a few miles of propagation from them before the terrain and the curvature of the Earth dissipate them. So your location is very important. The closer you are to the ground based transmission antenna the better. Even better is if you have a direct line of sight to it, which most probably don't have. You probably do have a direct line of sight to many of the aircraft nearby that are airborne though, so they should be much easier to receive.

Line of sight for VHF and UHF does make a huge difference. Try talking on 20-50 watt radio like ham radios when both are ground based and you can perhaps get a 5 to 10 mile range when using FM simplex. Try talking to or listening to a satellite station like the one on the ISS which is a few hundred miles above you and if you have direct line of sight you can get very good propagation with just a few watts. Your GPS unit in your car easily receives satellite communications from GPS satellites located more than 22,000 miles away as long as there is a clear line of site. Place some pesky trees, buildings, terrain in the way and you can have problems.

So if you are having trouble receiving the ground based aircraft band transmissions, try raising your exterior antenna higher. Or try using a directional beam antenna with a lot more gain and pointing it toward the antenna you want to monitor.

 

[kc2kth]

For around $100, the Uniden BC125AT is a good way to fill in the air band and other analog coverage.

I wouldn't respond except that I just received a new BC125AT on Friday and had the weekend to play with it. I specifically bought it for air/milair (yes, I know it has a bit of a gap, but couldn't find a EU 126 around cheap). After how many years of trunking and digital scanners, it's really a joy to use a simple analog scanner again. The 125 is a bit more than that though since it does allow programming via computer which makes it much easier to assign names to various channels (yes, it's a true bank/channel type scanner too). Anyhow, really enjoying having a simple portable again. I've had my PRO-2005 on my office desk for a while and it was what made me want something simple again for around the rest of the house. Great buy, and performs very well for air as well.

 

[majoco]

My SDS200 shows very poor performance of AM modulation on Airband from base stations (Tower / APP / ATIS).
Ground and airborne aircraft are demodulated correctly.

ATIS, approach and ground control are usually from antennas on top of the tower. Aircraft on the ground may give greater signal strength due to their position on the airfield. You need to take your radio to another site and see if the responce is the same, I'm guessing you are shielded in some way from the tower at your current location - what antenna are you using and where is it sited - it is possible that you may be in a position of low signal strength for those particular frequencies from the tower or getting multi-path phase cancellation.

 

[ludek-brno]

I have an SDS200 as a base scanner.
My Based antenna is Sirio GP145.
Problem with degradation of AM modulation only at base stations.
Mobile and on-board aircraft stations are demodulated without degrading AM modulation on the scanner.
Using ATT will improve base station reception, but I will not hear ground stations
Other services in the NFM are fine with the W-Normal filter.

Ludek

 

[AI7PM]

ATIS, approach and ground control are usually from antennas on top of the towe..........

Approach freqs are rarely atop the tower. In some cases, even the transmitters and receivers are on separate towers located on or near the airfield. At larger facilities like DFW, Atlanta, Chicago, etc., the facility will have radio facilities located miles away from the primary airport.

 

[mortoma61]

My SDS200 shows very poor performance of AM modulation on Airband from base stations (Tower / APP / ATIS).
After 2 seconds of the session, the voice is unintelligible.
Ground and airborne aircraft are demodulated correctly.
Many intermodulation hatches between air AM channels from base stations were not on BCD436 / 536HP
Airband AM modulation is the weakest side of the SDS200 scanner for me.

I have had no problem with my SDS200 on aircraft band. I also have a BC125AT and the 200 is slightly better overall on aircraft and that means a lot since the BC125AT is a superior aircraft scanner. And now that just about every place is going to trunking for Police/Fire/EMS that's about all the BC125AT is good for. Both the 200 and BC are almost as good as my old AOR AR1500 was on aircraft band and that says a lot. I get ATIS from Salt Lake City International about the same on both scanners, which is weak but intelligible.

Since all aircraft comms are either from the ground or from the air I don't know what you mean. You talk about the "tower/APP/ATIS" and say it's no good but then you turn around and say you are okay on "ground and airbourne". There is no in between. The Tower/APP/ATIS are all ground. If a transmitter is high on a tower it would still be considered a ground station. Even if it was up on a hill or a mountain, still a ground station. You can't have it both ways, either ground or airbourne. It can't be bad on ground and good on ground at the same time. Please elaborate in a more understandable way.

 

[TailGator911]

I have done side-by-side airband comparisons with my SDS100 and my BC125AT and I have to say the 125 was the winner, but not by much. The BC125AT is a great airband scanner and has a rep for it, while the SDS100 has gotten some bad reviews in that category. I found the 100 to be almost neck and neck with the 125. Everything local was on par, but when listening to Columbus airport (approx. 75 mi) the 125 pulled in those towers with no problem while the SDS100 was hit and miss with them. If I want to monitor the air bands I go to the BC125AT. That's actually what I bought it for, my QTH being very close to the Wright-Patterson AFB. Just my observations.

JD
kf4anc

 

[iMONITOR]

I have an SDS200 as a base scanner.
My Based antenna is Sirio GP145.
Problem with degradation of AM modulation only at base stations.
Mobile and on-board aircraft stations are demodulated without degrading AM modulation on the scanner.
Using ATT will improve base station reception, but I will not hear ground stations
Other services in the NFM are fine with the W-Normal filter.

Ludek

I don't think the GP 145 (145-175MHz) was a good choice if your intended use was for aircraft communications. A better choice would have been the Sirio GP 108-136 LB/N (108-136MHz).

 

[KR7CQ]

After all of the testing I have done, in my situation, sensitivity is not the problem with the SDS200 + outdoor antenna combination. The problem for some including myself, is interference from nearby frequencies. This applies to AM air, but also to everything else. It even happens with 700/800 MHz digital systems, you just don't hear the results there. In fact, you might just not hear anything because the control channel can't even be decoded properly due to interference, or you may have sporadic reception, depending on whether or not a nearby frequency is transmitting. If you don't have a Unication G4/5 or a Moto radio around for a control, you might not ever know what all your are missing, or not missing.

If you don't have issues with interference in your situation, you will likely be quite happy with the SDS200 in all bands. The problems caused by interference are most noticeable on AM air, where a station transmitting on a nearby frequency can cause major issues on your target frequency's reception. Issues can include noise, apparent weak reception, and worst of all, audio bleed-over with AM air. I can be listening to air to air chatter and it sounds pretty darn good...until a nearby frequency transmits and I can hear audio from both frequencies at once along with noise, or in some cases I just get greatly diminished reception. The root cause can be easily verified by monitoring a second scanner for transmissions on nearby frequencies. This is a problem I never saw with my good heterodyne receivers. As others have stated, the hardware filtering used with the SDR chip in the SDS scanners doesn't do very well at preventing interference from transmissions on nearby frequencies. It's just the nature of the hardware. Filters introduced in firmware have helped, as can IFX and attenuation, but degrees of success using these counter-measures varies by user / situation.

Adding more antenna gain may not help, and could make matters worse. You might actually find that lowering that antenna will yield better results. I'm about ready to put up a dedicated SDS200 antenna mounted lower than my primary discone. Recent testing showed that this will likely work better for me in a few important areas. Once I do more thorough testing I will share the results.

The SDS's are the best digital scanners ever made, and the only LSM-capable scanner ever made. As a bonus, they can monitor VHF / UHF analog stuff. I think that makes them pretty darn cool devices, regardless of everything else that I said in this post. Some will say they are perfect and amazing (in their situation), and a few like myself say the are imperfect and amazing (in our situations). Some hate them enough to return them. This will vary by person / their needs / situation. Personally I don't do any serious analog with the SDS's. I recommend keeping a BCT15X around for base analog, and a BC125AT for when you are on the go. I know that some bristle at this idea, but serious hobbyists have been using multiple scanners together forever and this is nothing new to them. It's an expensive hobby full of challenges, and conquering those challenges is part of the fun. Enjoy.

 

[TailGator911]

I know that some bristle at this idea, but serious hobbyists have been using multiple scanners together forever and this is nothing new to them. It's an expensive hobby full of challenges, and conquering those challenges is part of the fun. Enjoy.

You said a mouthful right there. It's all about getting to know your radios and their limitations, where each one shines, where others don't, and assigning them accordingly. Once you get to know your radios - and each one is as individualistic as its owner - you know which one to turn to for a specific task. Using multiple scanners to monitor your locale is a science of sorts. Once you get if figured out, your listening post will be a fine tuned and optimal machine.

JD
kf4anc