Standard for degraded/unusable frequencies in a radio rx?

If you sold me a radio with only one in a hundred channels usable, you'd find it traveling back to you above the speed of sound.

Do you mean 1% unusable?

Perhaps for commercial rigs, or rigs for sale at retail.

If there's an industry expectation you'll have to find out by talking to folks who use the radios. It's probably different in different markets. So if you're going to sail boats, talk to sailors. If you're going to fly Piper Cubs, talk to your local little FBO. If you're going to fly commercial jets, talk to your local _big_ FBO. Etc.

But there's no fundamental reason why any given chunk of spectrum can't be received cleanly -- just a cost vs. benefit curve that may dictate less than perfect radios for most users.

to

Thanks for your reply, Tim.

Yes, I did mean 1% unusable or degraded. (Sorry, I thought the context would have been sufficient.)

Just to further clarify, I'm interested in an intrinsic effect where the degradation is measurable within an electromagnetically quiet environment (eg, EMC test chamber). End users might have a different expectation as they usually live in a 'noisier' environment where channel unavailability might have nothing to do with the characteristics of any given radio.

The purpose of seeing whether there are any established standards, or credible sources of expectation, is that I'd like to know what I should put in a radio specification.

Regards.

Get a good book on radio receiver design.

One not-too-scientific possibility is the ARRL Handbook. It seems that you're not too familiar with the topic.

At least all the channels on all my aircraft receivers are OK, and both the VHF communication and navigation receivers are using AM.

A simple response to your question: A properly designed and manufactured receiver handles all the channels.

I doubt there's any "industry standard" number such as 1%, but it is true that many radios will have known frequencies where internal interferers noticeably degrade the receiver's sensitivity.

Note that this is a much tougher problem in a wideband receiver than in, e.g., an FRS or CB or WiFi or Bluetooth radio that only cover a (relatively) narrow swath of spectrum.

It really just depends on the industry you're in. With, e.g., ham radio receivers there *aren't* any channels (except on one specific band), so about the only way to build a wideband receiver such that you never run into an interfer is to have really good shielding, bypassing, etc. (which may be costly, although good design techniques help a lot too) and/or be able to change where the interfers are (often somewhere between cheap and free -- many ham radios have a setting to let you change the internal CPU's frequency slightly, so the interfers move to somewhere you're not tuned into).

With a channelized system you can sit down and do a "frequency plan" where you list all the LOs, IFs, other oscillators, etc. in the system and start computing the harmonics, intermods, etc. and see if any land within some frequency you'd like to tune in. Sooner or later *some* intermod frequency will land on top of what you're trying to tune, but if the order is high enough (e.g., 4*LO+5*IF) the amplitude will be low enough that you can ignore it. (This approach is essentially identical to what's known as "mixer spur analysis," which Google has plenty on.)

In complex systems, as far as I'm aware, you typically do end up with some combination of trying to avoid interfers combined with being able to move them around or otherwise actively negate them. For instance, an HP 8753 series network analyzer not only cost roughly what but also weighed roughly what a Citreon 2CV did, yet while signals are routed from one very-well-shielded metal box to another, they also dynamically adjust the numerator and denominator of the fractional-N PLL synthesizer inside so that synthesizer spurs don't end up on a frequency they're trying to measure.

Finally, if you're designing a proprietary system, there's of course nothing to stop you from just not using channels that you know to have degraded sensitivity and not mentioning it -- end users don't except a channel number to directly correlate to frequencies anymore. :-) But this is potentially cheating a bit unless, perhaps, you have very severe cost constraints or something.

---Joel

If so, is there a standard, or industry expectation,

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remember working on bluetooth in a cellphone design many years ago, it took a bit of work to fix the problem that some multiplum of the 16MHz xtal was one of the cellphone frequencies and reduced the sensitivity quite a bit.

-Lasse

Would you care to state the reference that 'led you to believe' this?

Cheers

Ian

"Excognito"

Pretty much all VHF and UHF bands use FM for voice communication with the notable exception of the "air band".

Just what sort of receivers are you crapping on about ??

.... Phil

I recommend starting with FCC part 15 regulations in the US. Similar regulations / standards elsewhere. Specific standards for things like aircraft as well.