Band Splits

[compuruss]

I have a question that I have been wondering about for awhile. If someone wouldn't mind enlightening me, I'd appreciate it. My RS Pro-97 can receive transmissions on most frequencies. However, my Rescue Squad's Minitor pagers and their handheld radios that can Tx have narrow band splits that they can't be used outside. Why does it work this way?

 

[Grog]

my Rescue Squad's Minitor pagers and their handheld radios that can Tx have narrow band splits that they can't be used outside. Why does it work this way?

What? Do you mean the frequencies cannot be entered excactly into the pro97? I knwo it does some narrowband freqs but likely not all of them. If you can program the frequency as close to what you use it should work ok, maybe not as well but you can always try.

 

[compuruss]

Clarification

I am sorry. I didn't phrase the question well; allow me to clarify. What I meant to ask was how can the Pro-97 receive on so many frequencies, but the other radios can only receive and/or transmit on such a small number, comparatively speaking?

 

[EFjohnsonVHF]

I think it's because most transmit radios are usually capable of just one band, Some are capable of more, But that makes them a lot more expensive, Such as the 700/800MHz Motorola XTS radios.......Hope that helps.

 

[compuruss]

Exactly what I'm getting at...Why does the Minitor need so many band splits; why can't they just make one for all VHF, one for all UHF, and one for all Low Band, or even one that does them all? The Pro-97 shows that a receiver can be made economically that does all three!

 

[EFjohnsonVHF]

It's probably the way that the computer chips inside the newer minitors (3's, 4's, & 5's) work (Someone please correct me if I'm wrong). But the more they make it do, The more it will cost to produce (and the more it will cost you, the consumer) and those things are already expensive enough as it is, With stored voice and all that in some of the minitor models

 

[Don_Burke]

Transmitters are less forgiving on frequency, so most manufacturers go for better performance by going relatively narrow.

On the receive side, the same wide range on the Pro-97 that lets me listen all over the place also lets it get torn up by pager transmitters and desensed by FM broadcasting. The manufacturers of commercial radios put more emphasis on the frequencies that the user needs and have less problem with interference.

It is a tradeoff.

 

[EFjohnsonVHF]

It is a tradeoff.

Just like the "Good/Fast/Cheap you can only get two thing, you have to trade something to get something.

 

[gmclam]

The title of this thread doesn't match what you're now asking. But if I understand the question correctly, here's my $0.02. Generally speaking, each band requires circuitry. For the PRO-97, there are a lot of components in the front end just there to selectively "filter" (band pass) the desired frequency. Any transceiver would have to replicate something like this for its receiver, and then would have to deal with the transmitting side. Transmitters are a little less forgiving than receivers in this regard.

Overall I think it comes down to only desiging a product to do what is NEEDED. The device you use as an example does not NEED to be a transceiver across the wide frequency range covered by a PRO-97. OK, so it does need to perform in sections of each band, but that's different. Designing a transmitter to cover the entire range would either increase complexity, cost, weight or a combination of all 3. So the designer chose to make the thing with "modules" for each range.

I hope that answers your question.