Basic Bandwidth Schooling

[kixntuff]

Hello fellas,

I'm really interested in how bandwidth works. I've been reading a lot about it and some goes over me head and some just raises more questions. A brief description of what I'm getting ready to get into. I'm going to be racing the BAJA 1000 on the Baja Peninsula in November and we'll be using radios for coms. All Pit teams, rescue, Score, etc etc will be operating in the business band ranging from151.625Mhz up to 155.???Mhz. The main facilitator will be operating on 151.625Mhz. Race teams choose their frequencies in between those said frequencies mentioned above. It is also instructed by the main facilitator not to choose a frequency in between bands so you don't get bleed over. and that he will not relay to you if you choose a frequency in between bands. I understand what bleed over is and that if you're operating on 151.625Mhz with a band width of 12.5Khz that you can't choose a frequency of 151.634Mhz. I think I'm getting all tripped up because I saw someone's program sheet for a good bunch of the frequencies assigned for a previous race and the facilitator was operating on 151.625Mhz 5Khz bandwidth, others and a good majority where operating at 12.5Khz bandwidth and a couple other at like 25Khz bandwidth. If I could I'd like to use a frequency running around 25Mhz bandwidth for simplex coms between my teams chase vehicles. So this brings me to my 1st question and sorry if these seam silly, but I'm still studying for my amateur license and trying to learn at the same time I'm trying to get coms set up for my team. Also, I understand all the rules and the does and don'ts so lets try and keep it on topic. It's a free for all down in ol Mexico during the time of this race and Score-International has special permissions from the Mexican government for coms during race time.

Is there already a bandwidth assigned to business band 150Mhz to 174Mhz I believe it is. What is that bandwidth?

2nd question, once I know the bandwidth, I should use the step feature in my radio and assign it to the appropriate bandwidth correct? That way when tuning, it will only jump through and scan correct frequencies and not in between bands right?

3rd Sounds like I should also set the radio for wide band instead of narrow band correct? Does it really affect signal strength if one where just to leave there radio set on narrow band?

4th Would choosing a frequency closer to 155Mhz carry better than say closer to 151Mhz?

5th When operating simplex on a particular frequency, can you change your bandwidth on that said frequency? For example, 151.625Mhz, can you change settings in your radio to operate on it sometimes at 5Khz bandwidth and other times at 12.5Khz? I think the only menu settings I've ever seen in a radio allow you to change the step and from wideband to narrowband, not the band frequency. This particular question is where all the confusion is basically and in how bandwidth really works.

Thanks,

Kix

 

[mikewazowski]

Moved to Industry Discussion as this has nothing to do with Amateur Radio.

 

[clbsquared]

Someone please correct me if I'm wrong. Because what I know is worth about two cents when it comes to understanding bandwidth. But I do know the FCC mandated narrow band usage a few years back. In the vhf business band, wideband is illegal to operate. But anyway, the wider the band would seem likely to increase the chance you have for bleedover. Its basically a swing in each direction. The less swing you have in bandwidth, the more frequencies there are available to use.

 

[kayn1n32008]

The op will be in Mexico... the FCC has no jusrisdiction in Mexico.

That said, the op should be asking the mexican government about licensing for tbis race.

 

[jwt873]

Is there already a bandwidth assigned to business band 150Mhz to 174Mhz I believe it is. What is that bandwidth?

If the race is taking place on the Baja Peninsula, it seems that it will be in Mexico. If business band radios are being used, they will be subject to Mexican laws. As kayn1n32008 points out, this is a Mexican issue.

The first thing I'd do would be contact the Mexican version of the FCC and ask what the permissible channel widths are.

The Baja 1000 is a major race. Is there not frequency coordinator tasked with assigning frequencies to the teams to ensure that they don't interfere with each other? Or, is it kind of a wild west, do what you feel like thing and hope for the best?

If it's everyone for themselves, it doesn't really matter about frequencies and bandwidths.

Personally, I'd have everyone using the same bandwidth with suitable channel spacing.

 

[nd5y]

Is there already a bandwidth assigned to business band 150Mhz to 174Mhz I believe it is. What is that bandwidth?

Yes. On most frequencies the banwidth is 11.25 kHz or less. See eCFR — Code of Federal Regulations and eCFR — Code of Federal Regulations
I don't know about Mexico.

2nd question, once I know the bandwidth, I should use the step feature in my radio and assign it to the appropriate bandwidth correct? That way when tuning, it will only jump through and scan correct frequencies and not in between bands right?

Channel spacing and tuning steps are not the same as bandwidth. Setting the tuning steps in the radio does not change the transmit or receive bandwidth.

3rd Sounds like I should also set the radio for wide band instead of narrow band correct? Does it really affect signal strength if one where just to leave there radio set on narrow band?

No. Bandwidth settings on FM don't affect signal strength, only the transmit deviation and receive audio levels. Audio levels on FM don't change with signal strength like on AM.

Setting the radio to "Wide" bandwidth transmits 5 kHz deviation and receiver bandwidth will be at least 16-20 kHz, sometimes up to 30 kHz depending on the radio. "Narrow" bandwidth transmits 2.5 kHz deviation and should have 12.5 kHz or less receiver bandwidth but depending on the type, quality and expense of the radio the receive bandwidth might not change.

Cheap low end low radios don't have two receive IF filter bandwidths (only wide, no narrow) and don't change any receive settings at all when set to narrow.
Some cheap radios increase the receiver audio when set to narrow but don't have a narrow IF filter.
Expensive high quality radios have separate IF filters and audio settings for wide and narrow receive.

4th Would choosing a frequency closer to 155Mhz carry better than say closer to 151Mhz?

No. There would be absolutely no difference.

5th When operating simplex on a particular frequency, can you change your bandwidth on that said frequency?

It depends on the radio. You might have to program all channels twice if you want to switch bandwidth. In the US if you are licensed for narrowband you can't switch to wideband.

 

[mmckenna]

This is a good question.

I agree, this is happening in Mexico, so FCC rules do not apply.

However, its probably a question that needs to be asked, although from what I've read about the guys using these radios on the races they don't know the difference and likely don't care (OP excepted).

The trouble is that all new radios sold in the USA designed for use on the Part 90 spectrum in the VHF high and UHF bands will only do narrow band (with a few very specific exceptions). Any new Part 90 radios purchased in the USA in the last few years are ONLY going to do narrow band on the appropriate frequencies and wide band will not be an option without the key/license/etc. from the manufacturer.

So, I think what you are going to run into is a mix of both wide and narrow band. It'll work, just won't sound ideal.

South of the border you need to do what the Mexican government says followed by what the race organizers say.

North of the border you need to do what the FCC says, which will be narrow band.

You could easily program up a channel for each, depending on where you are located.

 

[ecps92]

That had been suggest before, in the prior threads

The op will be in Mexico... the FCC has no jusrisdiction in Mexico.

That said, the op should be asking the mexican government about licensing for tbis race.

 

[kixntuff]

Score-International has something worked out with the Mexican Government for the week of the race. Not sure what it is. We are instructed not to operate on a frequency in between band, but I don't know what the set bandwidth is. I was going to go off the U.S. FCC rules band width because Most of the team are from the U.S. and operate in the U.S. also. I know from what I said before id that everyone is operating from 151.625 TO 155Mhz. So I'm going to tune all the chase vehicle antennas to 153Mhz and I want to stay around there for operating simplex chase 1 to chase 2 communication. Where I'm tripped up is I saw a program sheet from another racer and the main facilitator is set at 5Khz, others are on 12.5Kz, and a few at 25Khz. So for example if the bandwidth of 12.5Khz is what everyone should be using and I chose a frequency of 153.010Mhz as or simplex frequency, the facilitator will not relay to me because I'm technically in between band right?
Now for my radio, a Yaesu FT-7900r dual band that has been modded, The only thing I can change on it is narrow to wide. 150 to 174 are considered wide band frequencies correct? So If I set it to wide, it will tx on whatever wide bandwidth frequency is set from the factory? Am I saying that right?

 

[mmckenna]

Where I'm tripped up is I saw a program sheet from another racer and the main facilitator is set at 5Khz, others are on 12.5Kz, and a few at 25Khz. So for example if the bandwidth of 12.5Khz is what everyone should be using and I chose a frequency of 153.010Mhz as or simplex frequency, the facilitator will not relay to me because I'm technically in between band right?

Crap, sounds like this is a mess.....

The terminology gets confused, users get confused, and the exact requirements all seem to be in question.

Here's what I can add:
A "25KHz channel" is considered wide band. It uses 5KHz deviation.
A "12.5KHz channel" is considered narrow band. It uses 2.5KHz deviation.

Knowing the differences between these and how to set up your radio is important. If you get it wrong, it'll still work, just won't sound ideal. In a perfect world everyone would be speaking the same language, but sounds like that isn't happening. A good radio tech will understand all this, but expecting off road racers to understand this and get it correct is kind of a stretch.

Now for my radio, a Yaesu FT-7900r dual band that has been modded, The only thing I can change on it is narrow to wide. 150 to 174 are considered wide band frequencies correct? So If I set it to wide, it will tx on whatever wide bandwidth frequency is set from the factory? Am I saying that right?

I won't go into the FCC legality issues with this radio, I'm sure you've heard it before.

-Most- of the amateur radios out there are strictly wide band (25KHz wide channel, 5KHz deviation) since that is the default standard for FM in the amateur bands. Some newer radios -may- be able to transmit in narrow band, but I'm not personally aware of any.
What you are likely seeing on the FT-7900 is it's RECEIVE bandwidth. I used to own the 7800, the earlier version of this radio, and that was the way it worked. It won't transmit narrow, but it'll receive narrow for those amateurs that want to listen in on public safety communications.

150 to 174 are considered wide band frequencies correct?

No, not in the USA, ever since January 01, 2013 -most- of the frequencies in this piece of the VHF band have been required to be narrow band.

 

[nd5y]

The FT-7900R doesn't have narrowband receive so the wide/narrow setting only changes the transmit deviation from 5 to 2.5 kHz.

 

[krokus]

I understand what bleed over is and that if you're operating on 151.625Mhz with a band width of 12.5Khz that you can't choose a frequency of 151.634Mhz. I think I'm getting all tripped up because I saw someone's program sheet for a good bunch of the frequencies assigned for a previous race and the facilitator was operating on 151.625Mhz 5Khz bandwidth, others and a good majority where operating at 12.5Khz bandwidth and a couple other at like 25Khz bandwidth.

The bandwidth is how wide the signal is, including a bit of buffer space between adjacent used frequencies. Part of the supposed benefit of going narrowband, is another narrowband user can be centered on what had been the buffer between the wideband users. That puts three signals in the same space that two had fit, previously.

Is there already a bandwidth assigned to business band 150Mhz to 174Mhz I believe it is. What is that bandwidth?

You would have to find out about the Mexican laws/regulations on that band. (In the US, 12.5 kHz is used in most of that band.)

2nd question, once I know the bandwidth, I should use the step feature in my radio and assign it to the appropriate bandwidth correct? That way when tuning, it will only jump through and scan correct frequencies and not in between bands right?

If you are using commercial radios, you have to program the specific frequencies you want to use, into the memory of the radio. If you are talking about a radio that allows direct input, such as a ham radio in VFO mode, then you are correct. Either way, you need to make certain that the wideband or narrowband are properly selected, too.

3rd Sounds like I should also set the radio for wide band instead of narrow band correct? Does it really affect signal strength if one where just to leave there radio set on narrow band?

If the transmitting radio is set for narrowband, and the receiving radio is set wideband, then the recovered audio will be more quiet than if the bandwidths matched. Wideband can give you more range, but increases the likelihood of interference.

4th Would choosing a frequency closer to 155Mhz carry better than say closer to 151Mhz?

Those frequencies are close enough, that there is no real benefit of one to the other. Pick something that is not being used by anyone else along the course, or near the course.

5th When operating simplex on a particular frequency, can you change your bandwidth on that said frequency? For example, 151.625Mhz, can you change settings in your radio to operate on it sometimes at 5Khz bandwidth and other times at 12.5Khz? I think the only menu settings I've ever seen in a radio allow you to change the step and from wideband to narrowband, not the band frequency. This particular question is where all the confusion is basically and in how bandwidth really works.

There is no 5 kHz bandwidth used on typical FM transmissions. I think you are confusing the tuning step with the bandwidth.

Using a 5 kHz tune step is useful with 2m ham usage; some parts of the US use 20 kHz spacing, and some use 15 kHz spacing. A 5 kHz tune step allows to tune in to all of those frequencies, where as any other tune step will miss some signals.

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[NDRADIONUT]

If all of your radios have narrow fm on both transmit and receive they will work slightly better than being in the wide fm mode.... 11.5k vs 20k

 

[cmdrwill]

If all of your radios have narrow fm on both transmit and receive they will work slightly better than being in the wide fm mode.... 11.5k vs 20k

Baloney...

 

[NDRADIONUT]

Why do you say that ?

 

[kixntuff]

I'm confused now in that MMCKENNA said that 150-174 is narrow band. I thought the bandwidths show in the table here eCFR — Code of Federal Regulations. Would be wideband.

 

[nd5y]

-Most- of the amateur radios out there are strictly wide band (25KHz wide channel, 5KHz deviation) since that is the default standard for FM in the amateur bands. Some newer radios -may- be able to transmit in narrow band, but I'm not personally aware of any.
What you are likely seeing on the FT-7900 is it's RECEIVE bandwidth. I used to own the 7800, the earlier version of this radio, and that was the way it worked. It won't transmit narrow, but it'll receive narrow for those amateurs that want to listen in on public safety communications.

You have that backwards. The FT-7800R and FT-7900R only have wideband receive. Refer to menu 47 in the users manual. It says the wide/narrow setting only affects mic gain and transmit deviation. I have two 7800s and I guarantee you they don't have narrowband receive.

 

[mmckenna]

You have that backwards. The FT-7800R and FT-7900R only have wideband receive. Refer to menu 47 in the users manual. It says the wide/narrow setting only affects mic gain and transmit deviation. I have two 7800s and I guarantee you they don't have narrowband receive.

Thanks for the clarification. I dumped that radio about 7 years ago, so my memory is a bit foggy on it. None the less, the 7800/7900 isn't appropriate for this use for several reasons.

 

[mmckenna]

I'm confused now in that MMCKENNA said that 150-174 is narrow band. I thought the bandwidths show in the table here eCFR — Code of Federal Regulations. Would be wideband.

3Operations using equipment designed to operate with a 25 kHz channel bandwidth will be authorized a 20 kHz bandwidth. Operations using equipment designed to operate with a 12.5 kHz channel bandwidth will be authorized a 11.25 kHz bandwidth. Operations using equipment designed to operate with a 6.25 kHz channel bandwidth will be authorized a 6 kHz bandwidth. All stations must operate on channels with a bandwidth of 12.5 kHz or less beginning January 1, 2013, unless the operations meet the efficiency standard of §90.203(j)(3).

 

[mmckenna]

https://www.fcc.gov/general/narrowbanding-overview