In article om,
ShutterMan wrote:

Hey folks,

A lurking SWL listener here. Was wondering something about receivers
in general. Why is it that all-band receivers are generally more
expensive than HF-only receivers? I know there are other circuits in
there, but in essence, aren't all receiver circuits basically the
same, just with the ability to tune to different frequencies?

I suppose another way of asking is this: a simple AM radio tank
circuit could be modified by adjusting the coil turns and/or variable
capacitor in order to pick up other frequencies. Why does this
(rather oversimplified) simple change cause the cost of the receiver
to go up nearly 50% in cost? (comparing a simple handheld AM radio
with one that includes a shortwave band or two).

Well, there's cost, and then there's price. They aren't the same thing.

The cost may go up because:

- The general-coverage receiver may need additional "preselector"
stages in its RF front end (one per band), and

- The differences in the local oscillator stage may be more
involved than you think, in order to get an LO which tunes
reliably, smoothly, and stably over a very wide range of
frequencies, and

- The general-coverage receiver may need more sensitivity, as well
as a higher IP3 (i.e. ability to handle strong signals without
overloading) because it has to handle both local signals (which
are usually quite strong) as well as weak DX signals that are down
near the band's noise floor, and

- The general-coverage receiver may require multiple IF frequencies,
switching between them on a band-to-band basis, in order to ensure
that the IF, and the harmonics of the local-oscillator frequency
don't wipe out the signal you're trying to receive.

Then, there's price. Price is as much a marketing and perception
issue as it is a cost issue. The market for general-coverage radios
is smaller, there are fewer models made, there's less competition
between sellers, and the perceived value (the set of features or
capabilities) is greater. All of these contribute to the supply-and-
demand equation, and tend to cause the price to settle at a higher
level.

I also notice that HF transceivers can cost roughly the same as HF
receivers - you'd think a receiver WITH transmitter would be much more
expensive, but from what I can see its not. Something isn't
registering in my mind as to why all these cost differences.

That's partly because the receiver actually does incorporate most of
the signal-chain components present in the transmitter - power supply,
local oscillator and tuning electronics and mechanicals, case, front
panel, etc. - in many transceiver designs these are shared between the
transmit and receive pathways. There's some savings when you
eliminate the transmitter components, but less than you might imagine
(especially in today's highly-integrated designs).

It's also likely that receivers sold as receivers, may have a somewhat
more sophisticated receiver design (and better performance) than the
receiver stages built into all-in-one transceivers, and thus may
actually cost more to build.

Then, add the smaller-marketplace and this-is-a-special-purpose-box
issues, and the market price floats up.

--
Dave Platt AE6EO
Friends of Jade Warrior home page: http://www.radagast.org/jade-warrior
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