ADF reception AGL?

Hi All,

I notice that the Microsoft products disallow reception from ADF stations until one is a few hundred feet above ground level, unless I am very close, such as at the airport where the broadcast station is. I wonder if it is like that in real life. I know that the radio waves with low frequencies used by the ADF transmitters follow the curvature of the Earth in a similar way as AM broadcast stations, but that the former use much less power. That would explain the lack of ground reception at distance, but it is really like that in real life, as pronounced as in FS9 and FS X?

Thanks,

Sean

You are very correct when saying the ADF use far less power for transmitting than the standard AM radio broadcast stations. I will have to do a little more research on their wattage ratings as compared to the AM broadcast power of 50,000 watts. If an ADF tower is placed high enough on a hill top, the range will increase significantly over a ground based tower.

North American NDBs are categorized by power output, with low power rated at less than 50 watts, medium from 50 W to 2,000 W and high being over 2,000 Watts.

You are very correct when saying the ADF use far less power for transmitting than the standard AM radio broadcast stations. I will have to do a little more research on their wattage ratings as compared to the AM broadcast power of 50,000 watts. If an ADF tower is placed high enough on a hill top, the range will increase significantly over a ground based tower.

 

North American NDBs are categorized by power output, with low power rated at less than 50 watts, medium from 50 W to 2,000 W and high being over 2,000 Watts.

An AMBC (AM broadcast) station will typically use daytime powers of 1000, 5000, 10000, or 50000 watts here in the USA. At night the stations that are not on clear channels reduce power at sundown to as low as 5 watts (at least, I saw a transmitter at that level on eBay) but usually 250, 500, 1000, or 5000 watts.

The DF stations often use 40 watts and the lower the frequency, the more disadvantage there is because their antennas are small. I saw a WWII station for the Army that was 800 watts and claimed a 300 miles range, but the ranges claimed in the book will usually only be realized over the ocean on a radio quiet night. The power of the individual stations in my country is easy to look up. Here, this site is a start:

http://www.dxinfocentre.com/ndb.htm

I've never messed much with the NDB in the sim, and I've not tried range checking (especially down low) in real life, but real life NDBs aren't all that good for long distance reception, even in the air. Given that it wouldn't be all that common for an aircraft to be on the ground when using an NDB, it's not normally that important. But since the VORs in the sim are only roughly like real life, I expect that NDBs are the same way.

You can look up "LF propagation" on the web, but NDBs typically don't have their antennas mounted nearly as high as the AM stations or some other LF services, which will also attenuate the "ground wave" signal, especially at lower power.

For those interested , the following instrument is available here from the library ,

it has a signal strength indications .

I built a mini MFD into my autopilot , one of the pages shows tuned radio data if it is within reception parameters .

I find it quite handy when doing ILS as " GS" appears when it is in range and useable .

The problem with ADF is sky skip at evenings and morning due to ionosphere height moving up or down , you see this on your AM radio when you start getting distant radio station reception .

To overcome that you have to positively identify your tuned ADF by listening to the audio Morse Code ID .

With ADF it is possible at night to get hunting where the needle breifly receives a distant ADF and tries to point to it .

You get a similar effect in real life with lightning it will try to point to the lightning bolt , you also hear lightning on you AM radio .

From memory ,

- the 5 watt ADF were small cheap transistorised units often used on farm strips and did not have a backup facility. ( Transistors , now that shows how long ago they came into being )

- the big 2,000 watt units were often placed at coastal locations to support trans oceanic flight in the days before GPS .

Also from memory the high end of the ADF frequency range was used in rugged mountain country due to better propagation .

My own opinion is that Microsoft did a superb job of modelling radio reception for the various radio NAVAIDS .

Cheers

Karol

Name: comgold.zip

Size: 192,888 Date: 03-29-2006 Downloads: 2,058

FS2004 Gauge--ComGold Radio. This state-of-the-art radio contains a full array of digital displays including active and standby frequencies for Com1, Com2, Nav1, Nav2, ADF1, plus transponder code. Frequencies are entered directly into both active and standby memories of all radios using CG's numeric keypad. Values can be entered into the radios or transponder either automatically or manually. ID's of active nav frequencies are displayed if signal strenth is sufficient. Signal strength is animated in an accurate way that is based on numerous attenuation tests. Gauge provides automatic error checking for data entry. Panel or window installation. Uses existing radio icon when replacing default radios. By Glenn Copeland.

For those interested , the following instrument is available here from the library ,

it has a signal strength indications .

 

I built a mini MFD into my autopilot , one of the pages shows tuned radio data if it is within reception parameters .

I find it quite handy when doing ILS as " GS" appears when it is in range and useable .

 

The problem with ADF is sky skip at evenings and morning due to ionosphere height moving up or down , you see this on your AM radio when you start getting distant radio station reception .

To overcome that you have to positively identify your tuned ADF by listening to the audio Morse Code ID .

With ADF it is possible at night to get hunting where the needle breifly receives a distant ADF and tries to point to it .

You get a similar effect in real life with lightning it will try to point to the lightning bolt , you also hear lightning on you AM radio .

 

From memory ,

- the 5 watt ADF were small cheap transistorised units often used on farm strips and did not have a backup facility. ( Transistors , now that shows how long ago they came into being )

- the big 2,000 watt units were often placed at coastal locations to support trans oceanic flight in the days before GPS .

 

Also from memory the high end of the ADF frequency range was used in rugged mountain country due to better propagation .

 

My own opinion is that Microsoft did a superb job of modelling radio reception for the various radio NAVAIDS .

 

Cheers

Karol

Name: comgold.zip

Size: 192,888 Date: 03-29-2006 Downloads: 2,058

 

 

FS2004 Gauge--ComGold Radio. This state-of-the-art radio contains a full array of digital displays including active and standby frequencies for Com1, Com2, Nav1, Nav2, ADF1, plus transponder code. Frequencies are entered directly into both active and standby memories of all radios using CG's numeric keypad. Values can be entered into the radios or transponder either automatically or manually. ID's of active nav frequencies are displayed if signal strenth is sufficient. Signal strength is animated in an accurate way that is based on numerous attenuation tests. Gauge provides automatic error checking for data entry. Panel or window installation. Uses existing radio icon when replacing default radios. By Glenn Copeland.

There is also something called "night effect", which happens on the long wave NDB and medium wave AMBC frequencies. This is where the signal bends back down from the ionosphere at a sideways angle. The effect, when it is happening, is that the needle points at the strongest signal which is coming from different directions, so the needle is pointing different directions while you can hear the ID in your headphones.

I've only read about it for NDBs, but my Mom also has the same problem with her AM radio that she listens to for entertainment.

Someday, I plan to buy an old ADF for use as an entertainment radio, and I'd love to have one with a tuning dial and signal strength meter. If I ever get to playing the simulator with the computer on a desk, I'd like to have a transponder so I can dial in the squawk code and then press the menu item "Acknowledge squawk code" so the change is made in the sim.

I bought a USB radio from an Amazon seller. It is the Saitek unit but it doesn't work. I suspect I might have gotten one that was returned under warranty but that was not fixed.

I have FS9, I"ll install your radio - it looks neat :)

Oh, and one big problem with small range on ADFs is the small receiving antenna. In FS9, the transmitting antenna looks to be 25 or 50 feet high and that is very small for those frequencies. But the receive antennas I see on eBay look to be about the same size as a ferrite bar antenna in an AM radio, a coil perhaps five inches in length. That's pretty small for that power level. But they do work :)

Sean Kelly

W7STK