DE11 kinda pricey . .

http://cgi.ebay.com.au/DEGEN-REDSUN-...QQcmdZViewItem

I think the price of the DE11 is too high based on what it gives you. The Tecsun PL200 is full-featured, receiving all of the 3-30 mhz shortwave spectrum, but it is a single-conversion radio.

The Degen 1102 and 1103 are near the price of the Tecsun PL200. The 1102 and 1103 include dual-conversion reception (to eliminate wrong-frequency images), and ssb (to decode amateur, utility, and various other broadcast modes). To learn more about some of these radios, see the reviews section at www.radiointel.com .

On Tue, 26 Sep 2006 03:55:29 UTC, weatherall
wrote:


Wrote:
DE11 kinda pricey . .

http://tinyurl.com/rl6n2

I think the price of the DE11 is too high based on what it gives you.
The Tecsun PL200 is full-featured, receiving all of the 3-30 mhz
shortwave spectrum, but it is a single-conversion radio.
Damn, you would think in 2006 that single-conversion radios were not
even being made! I have an old S-38 and an HE-10, both single
conversions, but they were made in the '40's and '50's! They still
pull in great DX on the BCB though and the tubes keep my room warm in
the winter!


The Degen 1102 and 1103 are near the price of the Tecsun PL200. The
1102 and 1103 include dual-conversion reception (to eliminate
wrong-frequency images), and ssb (to decode amateur, utility, and
various other broadcast modes). To learn more about some of these
radios, see the reviews section at www.radiointel.com .






--
"What do you mean there's no movie?"

In article g40vCXBzNU8x-pn2-Q82zQcWLtrec@localhost,
"Count Floyd" CountFloyd@MonsterChillerHorrorTheater wrote:

On Tue, 26 Sep 2006 03:55:29 UTC, weatherall
wrote:


Wrote:
DE11 kinda pricey . .

http://tinyurl.com/rl6n2

I think the price of the DE11 is too high based on what it gives you.
The Tecsun PL200 is full-featured, receiving all of the 3-30 mhz
shortwave spectrum, but it is a single-conversion radio.
Damn, you would think in 2006 that single-conversion radios were not
even being made! I have an old S-38 and an HE-10, both single
conversions, but they were made in the '40's and '50's! They still
pull in great DX on the BCB though and the tubes keep my room warm in
the winter!

Snip

That's because the age of the design has nothing to do with whether it
is 1, 2, or 3 conversion. There were double and triple conversion
receivers back then.

What determines the number of conversions is cost.

--
Telamon
Ventura, California

"Count Floyd" CountFloyd@MonsterChillerHorrorTheater wrote in message
news:g40vCXBzNU8x-pn2-Q82zQcWLtrec@localhost...

Damn, you would think in 2006 that single-conversion radios were not
even being made! I have an old S-38 and an HE-10, both single
conversions, but they were made in the '40's and '50's! They still
pull in great DX on the BCB though and the tubes keep my room warm in
the winter!



Why shouldn't single conversion receivers still be made? They still work
well enough for people to buy them.

The only real problem with single conversion is image rejection, and older
higher quality single conversion radios obtained increased image rejection
with additional tuned RF circuits. Hallicrafter's top of the line radio for
1947, the $275.00 SX-42, was single coversion (tuned antenna and two tuned
RF stages) with an IF of 455 kc through 30 Mc. The second in line, the dual
conversion (on six meters) SX-43 (tuned antenna and one tuned RF stage),
cost $169.50. The S-38 (tuned antenna stage only) cost only $47.50. As a
comparision in complexity, the SX-42 used a 10 wafer bandswitch, as long as
the radio, to switch the oscillator and RF coils in and out. The S-38 used
a stubby 2 wafer bandswitch.

Here's an article about the restoration of a SX-42, with a particular
emphasis on the bandswitch:

http://antiqueradio.org/halli07.htm


For the same image rejection at high frequencies, a high IF converted to a
lower IF will be cheaper than that lower IF with multiple tuned RF stages.
However, conversion stages are noisier and potentially less linear than
amplifier stages. I suspect Hallicrafters went with the more expensive
single conversion scheme in order to sell an amateur radio with low noise,
low distortion high fidelity ability all the way from the AM broadcast band,
through SW, low VHF to the FM broadcast band. Hallicrafters soon replaced
the 42 with more specialized amateur receivers, and reskinned it as the
SX-62 (still expensive!) single conversion SWL radio. The SX-62 was around
'till 1965.

If anyone ever manages to design an inexpensive narrow bandwidth filter with
an excellent shape factor at 45 Mhz or so, we can pretty much say goodby to
the multiple conversion radio. Skip all those troublesome conversion
stages! Exept there might still be a few radios with extra conversion
stages. If so, there will surely be somebody saying "I can't believe
they're still using that old 20th century technology!!" Of course, the
manufacturer might be doing it to distribute gain at different frequencies
in order to avoid oscillation. But that's whole 'nother bit of radio design
trivia.

Frank Dresser

"Telamon" wrote in message
...

That's because the age of the design has nothing to do with whether it
is 1, 2, or 3 conversion. There were double and triple conversion
receivers back then.

Yes, but back then, multiple conversion was just downconversion. After the
crystal controlled synthizers got cheap enough, the current popular
up/downconversion scheme became practical. This way is particularly
inexpensive, because the images can be attenuated with a low pass or
bandpass filter.


What determines the number of conversions is cost.

And it's cheaper to hit a particular image rejection target across a wide
band with multiple conversion.

Frank Dresser

On Wed, 27 Sep 2006 04:13:19 GMT, Telamon
wrote:

In article g40vCXBzNU8x-pn2-Q82zQcWLtrec@localhost,
"Count Floyd" CountFloyd@MonsterChillerHorrorTheater wrote:

On Tue, 26 Sep 2006 03:55:29 UTC, weatherall
wrote:


Wrote:
DE11 kinda pricey . .

http://tinyurl.com/rl6n2

I think the price of the DE11 is too high based on what it gives you.
The Tecsun PL200 is full-featured, receiving all of the 3-30 mhz
shortwave spectrum, but it is a single-conversion radio.
Damn, you would think in 2006 that single-conversion radios were not
even being made! I have an old S-38 and an HE-10, both single
conversions, but they were made in the '40's and '50's! They still
pull in great DX on the BCB though and the tubes keep my room warm in
the winter!

Snip

That's because the age of the design has nothing to do with whether it
is 1, 2, or 3 conversion. There were double and triple conversion
receivers back then.

What determines the number of conversions is cost.
You can make a fairly respectable single conversion receiver, but
there are a couple things you need to do to get reasonable image
rejection, and selectivity. Raise the IF frequency to several Mhz, and
put a tuned rf amp in front of the mixer. That usually required a
crystal filter for good shape characteristics and good selectivity.

Triple conversion is more about being able to put the final IF down
low enough that you can get very sharp skirts, and narrow passbands
without an especially high Q filter. I.E. a bandwidth filter with a Q
of 100 gives you a 10Khz passband at a 1Mhz IF, but at 50Khz, it is
only 500Hz wide, very suitable for CW, and an L/C filter costs a lot
less than a real multipole crystal filter.

"matt weber" wrote in message
...

You can make a fairly respectable single conversion receiver, but
there are a couple things you need to do to get reasonable image
rejection, and selectivity. Raise the IF frequency to several Mhz, and
put a tuned rf amp in front of the mixer. That usually required a
crystal filter for good shape characteristics and good selectivity.


But if the IF is in the middle of the range of a wide coverage receiver, the
low bands will track backwards with respect to the oscillator frequency.
This can be dealt with by manually tuning the RF amp seperately or by
beating the tuning oscillator against a seperate oscillator and taking the
difference, which will track in the right direction.

Making single conversion radios with good image rejection is certainly
possible, but it isn't simple.


[snip]

Frank Dresser