[Elecraft] Re： OT: QST's review of the Yaesu FTDX5000MP

[Johnny Siu]

Hello Don,

Very true indeed.  Downward conversion is a good cost Vs performance solution 
for radio targeting at ham band.

Elecraft's selection of downward conversation is clever because both K2 and K3 
are targeting ham operators.
 cheers, 


Johnny VR2XMC 



----- 郵件原件 ----
寄件人﹕ Don Wilhelm <w3fpr at embarqmail.com>
收件人﹕ Elecraft at mailman.qth.net
傳送日期﹕ 2010/11/17 (三) 7:47:07 AM
主題： Re: [Elecraft] OT: QST's review of the Yaesu FTDX5000MP

  Actually, the 9 MHz IF got started and gained momentum from the first 
SSB phasing generators.  Some of the first SSB transmitters were phasing 
types with the 9 MHz IF - using a 5.0 to 5.5 MHz VFO, one could cover 
3.5 to 4.0 MHz and also 14.0 to 14.5 MHz with the same 9 MHz generator.  
Transceivers were only a dream at that time.  Receivers did not normally 
use a phasing approach.

Then McCoy came out with a reasonably priced 9 MHz crystal filter that 
made filter SSB transmitters possible with the same 9 MHz IF.  
Transceivers were now possible with that filter, and there were several 
homebrew designs as well as some commercial implementations of 
transmitters and receivers and transceivers using a 9 MHz IF.

Another observation - sideband suppression and top-notch performance 
were difficult using analog phasing methods (although Rick Campbell KK7B 
does have some very good analog designs), the DSP algorithms are a 
perfection of the phasing method of SSB generation and reception, so we 
have come "full circle" with the advent of DSP implementations.

As far as the advantages of "down conversion" - that was very 
successfully implemented in the K2, although there were other homebrew 
implementations.  The single conversion down-conversion receiver in the 
K2 proved its worthiness to many operators while the rest of the world 
was using up-conversion to obtain full 0.1 to 30 kHz continuous coverage 
and few 'birdies'.  Birdies are inevitable with a down-conversion 
scheme, and the challenge is to keep them out of the ham bands.

73,
Don W3FPR

On 11/16/2010 6:11 PM, Ron D'Eau Claire wrote:
> Sometime in the 1960's or early 70's one company started offering a 9 MHz
> filter at a decent price that was widely used by homebrewers back then and
> the subject of many QST and ARRL handbook designs as well as a number of
> "commercial" rigs.
>
> Obviously, those rigs up-converted the lower MF frequency bands and
> down-converted the higher MF frequency bands.
>
> Early M.F./H.F. superhetrodyne receivers all "down converted" to an I.F. in
> the low MF range (usually 455 kHz) but designing input filters for the M.F.
> range that would adequately reject the image response at 2X the I.F. became
> very difficult. Filter technology limited the selectivity available at
> higher frequencies, forcing designers to use a low frequency I.F., but the
> press was on from the beginning for better I.F. filters at higher
> frequencies.
>
> Like all designs, it's always a compromise. The best designers are those who
> make the best compromises using the components available at an acceptable
> price.
>
> Ron AC7AC
>
>
> -----Original Message-----
> There is a serious misconception by some true believers that Elecraft
> "invented" down-conversion (or at least conversion) to an i-f in the 8 to 9
> MHz range.
>
> Nothing could be further from the truth, and I know that the folks at
> Elecraft would never claim as much.  I had a Henry Radio Tempo-1 (Yaesu
> FT-200) back when radios warmed up the shack.  It was a 9 MHz i-f
> transceiver.
>
> Wes Stewart,  N7WS
>
> --- On Tue, 11/16/10, Benny Aumala<benny.aumala at gmail.com>  wrote:
>
>> When K3 came I told this RX architecture will soon be a
>> standard
>> (as Rob Sherwood told long time ago).
>
> ______________________________________________________________
> Elecraft mailing list
> Home: http://mailman.qth.net/mailman/listinfo/elecraft
> Help: http://mailman.qth.net/mmfaq.htm
> Post: mailto:Elecraft at mailman.qth.net
>
> This list hosted by: http://www.qsl.net
> Please help support this email list: http://www.qsl.net/donate.html
>
______________________________________________________________
Elecraft mailing list
Home: http://mailman.qth.net/mailman/listinfo/elecraft
Help: http://mailman.qth.net/mmfaq.htm
Post: mailto:Elecraft at mailman.qth.net

This list hosted by: http://www.qsl.net
Please help support this email list: http://www.qsl.net/donate.html