Transmitters That Don't Cover All 70cm

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Seven-Delta-FortyOne

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First, I apologize for the lack of an intro, but I don't see an introduction forum.

I'm scheduled to take my Tech and General exams in mid-July, so I've been radio shopping. I notice that alot of the imported radios, HT's and mobile's, from Yaesu, Icom, Alinco, etc., only cover from 430-450 MHZ, not 420-450 MHZ.

Is this because of a difference in Ham bands between the United States and Asia, or is it for another reason? I did notice, when reviewing band plans, that 420-430 is mostly organized for ATV. Could that be the reason?

Thanks.




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nd5y

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The 70 cm band varies in different countries. In the US it is 420-450 (remember that for your exam). In Canada it is 430-450. Many other countries only have 430-440 which is the international allocation.

The Japanese manufacturers make different radio versions for different markets.
I have never seen an explaination why they don't make US market radios that cover the full 420-450 US band out of the box.

The 420-430 part of the US band isn't strictly for ATV.
 

ko6jw_2

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If you look at the ARRL band plan for 420-440 you will see a variety of uses and modes. The HT's and mobiles operate only with FM modulation and not CW, SSB, ATV etc. Thus, their use in the 420-440 range could interfere with other users. That said there are some FM links that operate in that range, but they are fixed point to point. You would not normally need to transmit on these frequencies with an HT or mobile. It is also important to remember that amateur radio is a secondary user of the 420-450 band. The primary users are military radio location services.
 

mm

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additionally within ~ 50 miles of the US border of some states and Canada the lower end of 420 to 430MHz is not allowed for amateur use as this is a Canadian Public safety allocation.
 

Seven-Delta-FortyOne

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Thanks for the replies.

I did not know that Amateur was a secondary user of 70cm. I read nothing about that in any study materials. I knew about sections of 1.25m, though.




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The tuned circuits in a receiver and transmitter are only perfectly tuned at one frequency. The performance will be acceptable over a range of frequencies centered on that tuned frequency. Outside of that range, the performance falls off.

420 to 450 MHz is a range of 30 MHz. That's probably wider than the bandwidth of acceptable performance for most consumer or hobby-grade radios. Even commercial LMR radios for UHF have limited bandwidths.

Since the range over which FM is typically used in most countries is limited, I believe that the manufacturers of FM radios limit them to that range to make it easier for them to guarantee performance.
 

zz0468

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The tuned circuits in a receiver and transmitter are only perfectly tuned at one frequency...

...420 to 450 MHz is a range of 30 MHz. That's probably wider than the bandwidth of acceptable performance for most consumer or hobby-grade radios.
Getting excellent wideband performance across a large chunk of spectrum is almost trivial these days. The frequency limitations in amateur transceivers is not due to an inability to provide consistent performance over the entire 420-450 range. It's because there's little purpose to cover beyond 440-450.
 

kayn1n32008

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additionally within ~ 50 miles of the US border of some states and Canada the lower end of 420 to 430MHz is not allowed for amateur use as this is a Canadian Public safety allocation.

While there is some public safety between 420-430, the vast majority of LMR users is for commercial use. Here in Alberta I would say that the majority of use of 420-430, out side of the big cities, is SCADA for the gas/oil industry.

In Canada, is not 'PS' only frequencies or business use only frequencies.


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zz0468

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Why is that? Most of the repeaters are in the 440-450 range?
Yes, but make that all, not "most". In places that have access to the rest of the band, it's used for TV, links, and ssb/cw weak signal stuff... all of which requires a different sort of radio.
 

n9mxq

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ko6jw_2

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Limitations on the use of 420-450 are not just along the Canadian border. Here in California some repeaters in the Bay Area have had severe imitations placed on them by the Air Force for alleged or potential interference with PAVE PAWS radar.

It is also worth mentioning for a new ham that many or most 440 repeaters in California are closed. In other words their use is limited to a group of operators who own and maintain the repeaters. This is perfectly legal. In choosing a first radio, 2 meters is probably a better choice. If you want to use 440, get to know some hams in your area. I belong to a "closed" repeater group, but we are always open to new members. Some are not so friendly. If you try to use a closed repeater you may be warned off or they just won't talk to you.
 

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I would suggest finding out what part/portion of any band is allowed in your country. They all are not the same. If/when you know that, then pick a radio that covers the allowed frequencies. It's still up to you to determine where you are allowed to be, and to stay in that portion of the band. Going out of that allowed portion is a waste of iime because you won't find anyone to talk to, right? Oh well. Anything odd about that? Nope. That's about as normal as it gets.
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Seven-Delta-FortyOne

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I would suggest finding out what part/portion of any band is allowed in your country. They all are not the same. If/when you know that, then pick a radio that covers the allowed frequencies. It's still up to you to determine where you are allowed to be, and to stay in that portion of the band. Going out of that allowed portion is a waste of iime because you won't find anyone to talk to, right? Oh well. Anything odd about that? Nope. That's about as normal as it gets.
- 'Doc
:blink:

I know what portion of 70cm I'll be able to operate in. It's 420MHZ-450MHZ. That's the 70cm Amateur band in Los Estados Unidos, where I live.

My question was why the radios targeted for the US market, don't cover that entire band. Pretty simple.

But thanks for trying to help, anyway.







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LtDoc

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Why don't you have privileges in ALL the band instead of just part of it? Beats me, ask the FCC. That's how it s though so take it of leave it. A lot of bands are shared', amateurs don't have exclusive use. Basically that means that you have to not use portions of a band. I wish it were different too, but it's not, oh well. If you can't live with that, then I have to say you are in the wrong hob by. Sorry 'bout that.
- 'Doc
 

Seven-Delta-FortyOne

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Why don't you have privileges in ALL the band instead of just part of it? Beats me, ask the FCC. That's how it s though so take it of leave it. A lot of bands are shared', amateurs don't have exclusive use. Basically that means that you have to not use portions of a band. I wish it were different too, but it's not, oh well. If you can't live with that, then I have to say you are in the wrong hob by. Sorry 'bout that.
- 'Doc
Havn't a clue what you're taking about, Hoss.

Didn't say anything about priviledges. Amatuer Operators have priviledges from 420-450. In 70 cm. Period.

Some radios cover 430-450. In 70 cm.

Not sure what's so hard to understand about this.






Delta
 
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