Correct and the accepted definition of Dual Conversion in the world of
Superhetrodyne receiver design would be a radio with two distinct RF
frequency IF's before detection or demodulation to audio.
Cecil
K5DL
----- Original Message -----
From: "Carl Moreschi" <n4py2@earthlink.net>
To: "Discussion of Ten-Tec Equipment" <tentec@contesting.com>
Sent: Saturday, April 14, 2012 6:23 AM
Subject: Re: [TenTec] DUAL CONVERSION
> Actually, converting directly from RF to AF is called Direct Conversion
> and that is what Flex radio does. This was also done in the Tentec
> Century 21 and 22, and the Heath HW7 and HW8. But the Flex radio scheme
> uses a DSP phasing method to remove the audio image so that signals are
> only heard on one side of zero beat. The older schemes in the Century
> 21, 22, HW7, and HW8 had an audio image so that you heard each station
> on both sides of zero beat.
>
> Carl Moreschi N4PY
> 121 Little Bell Dr.
> Hays, NC 28635
> www.n4py.com
>
> On 4/14/2012 5:19 AM, Rick - DJ0IP / NJ0IP wrote:
>> Barbara, this is actually a trick question.
>>
>> I assume you mean dual "IF" conversion vs. single "IF" conversion.
>>
>> However now that FlexRadio is on the scene, their definition of single
>> conversion is RF straight to AF.
>> BTW, this is also the original definition!
>>
>> For the past 40 years or so, when we said single conversion, we were
>> referring to a radio like the original Omni or Argonaut which had a
>> single 9
>> MHz IF. We called it single conversion, but actually by definition it is
>> dual conversion because the RF is converted to the IF frequency (which is
>> actually still RF) and then converted to audio.
>>
>> Thus dual conversion (as referred to in the past 40 years) and as seen in
>> the Omni VI, with 9MHz and 5MHz IF frequencies, was actually triple
>> conversion, because the signal still gets converted to audio.
>>
>> None of this would be worth discussing if Flex had not come out with a
>> new
>> version of an old design.
>>
>>
>> So when I read your email, I don't know if you are referring to single
>> conversion as used by Flex or single conversion as used by Ten-Tec in the
>> Corsair.
>>
>> If you mean dual-IF-conversion (like Omni VI), there are a couple of
>> advantages:
>>
>> - you need two IF frequencies with small filters (typically crystal) to
>> be
>> able to have passband tuning. For instance, the K2 with its single 9MHz
>> IF
>> has no passband tuning.
>> - good quality filters with maybe 80dB of ultimate attenuation, when
>> used
>> in a single conversion rig, will typically have only 60dB of ultimate
>> attenuation, due to signal leakage around the filter. If you add a
>> second,
>> similar filter with the same IF frequency in series, you get maybe 90 dB,
>> but if the second filter is on a different IF frequency, you can get as
>> much
>> as 120dB of ultimate attenuation. THESE ARE BALLPARK NUMBERS, but your
>> get
>> the idea.
>> - dual conversion using a higher "FIRST" IF (above 30 MHz) has the
>> advantage that you have fewer birdies which fall inside the ham bands
>> (usually none). Radios with single conversion or dual conversion with
>> their
>> first conversion on lower frequencies (5MHz or 9MHz) typically have
>> birdies
>> which fall within the ham bands... BUT...
>> - IF filters at higher frequencies are not nearly of as good of quality
>> as
>> those at lower frequencies (due to a thing called fractional bandwidth),
>> so
>> you don't have the ultimate attenuation that you have with IF's at lower
>> frequencies. This usually deteriorates the close-in DR3 significantly,
>> which kills us in contests.
>>
>> You pays your money and you takes your choice.
>> Do you want a good general coverage radio with no birdies in the 0 to 30
>> MHz
>> range, but lesser performance on the ham bands, or do you want a radio
>> with
>> much better performance on the ham bands but maybe 2 or 3 birdies (albeit
>> usually only S5 or less) within some ham bands?
>>
>> I WILL GO WITH THE BETTER PERFORMING RIG ANY TIME.
>>
>> 73
>> Rick, DJ0IP
>>
>> On 08/20/2010 10:37 AM, Barbara wrote:
>>> Please tell me some of the improvements dual conversi9on vx. single
>> conversion receiver? thanks jjdavis
>>
>>
>>
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