Well, there are a few issues here.

First of all, most decent radios are superhets. This means that there must
be an intermediate frequency. Selecting an intermediate frequency, or two,
gets to be more of a problem the more frequencies you need to cover. Many
DC to daylight rigs are full coverage, which makes the problem a lot harder
than a ham band only radio, and adding more coverage obviously complicates
the problem.

Secondly, as you go up in frequency, the problem changes. Component layout
gets to be a bigger deal, and it is harder to get the gain you need. Many
HF only radios have only marginal performance at 10 meters. If you are
going to cover frequencies higher than 30 MHz, then you can't really fudge
the 10 meter performance because you need to go beyond it.

At 50 MHz, you are sort of in a no man's land. You can use HF techniques or
VHF techniques, but go firmly into VHF and you essentially are building
another radio for the frequencies above 50 MHz or so. The techniques and
parts are a lot different, even the problem you need to solve is different.
At HF, it is easy to get more gain than you can actually use. As you go up
in frequency, you need more gain but it gets harder to come by. Worse
still, at HF the relatively low gain requirement is caused by noise in the
atmosphere. Increase the gain and you get more noise, so it really doesn't
buy you anything. That atmsopheric noise becomes less of an issue as you go
up in frequency, but the noise in your circuitry becomes greater. As you
get to VHF and beyond, you are concerned with noise figure, something that
really doesn't matter at HF because it is orders of magnitude below the
atmospheric noise.

As far as transceivers vs. receivers, well, there is a little cost
differential, but perhaps not as much as you would expect. Part of that is
because a lot of the transmitter circuitry is shared with the receiver. In
particular, the expensive, critical parts are shared. The other dimension
is that there is only a tiny market for high-end receivers. There are lots
of SWLs out there, but very few SWLs who are willing to spend on a high end
receiver. On the other hand, hams need a lot out of a receiver for it to be
even useable, and they are more likely to buy a transceiver than a separate
transmitter and receiver, so the size of the market starts to come into
play.

Hope this sheds some light

...


"ShutterMan" wrote in message
ps.com...
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). An AM/FM stereo
radio is cheaper in many cases than a similar radio with SW bands.
But you'd think that VHF reception would be slightly more expensive to
manufacture than AM's nearby neighbor SW. Confuses me.

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.

Thanks for your responses.