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Author Topic: High End Transceivers and RX Design  (Read 469 times)
KC8QVO
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Posts: 62




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« on: November 21, 2009, 06:47:58 PM »

I am not sure which category to put this in so I figured I would ask here and see what happens.

My question is related to all receivers really. I am interested in why the higher end radios, like the IC-7800 and FTdx-9000, have such "good" receivers, yet they are still up-converstion designs.

I notice the IC-7800 is a two-stage IF and the FTdx-9000 is a three-stage, both up-conversion superhet's.

When you look at the K3 and the TT O2 they are both down conversion, and I am assuming they are superhet's also.

One advantage I see that the K3 and O2 have over the IC-7800 and FTdx-9000 is the ability to have very narrow, in comparison, roofing filters - a product of the down conversion design vs. the up conversion.

How is it that the FTdx-9000 and IC-7800 still have such excellent performance while not being able to close down the front end to keep junk out? is it just that they are "that hot" of RX'es? I am curious as to what really makes them that good.

On the same token - the Elecraft KX1 has a fantastic RX in it. I know, I have used one before. In fact, I compared it to my TS-2000 here in the shack and I could work people on the KX1 that I couldn't detect on the TS-2000 - if I didn't know the stations were in there on the KX1 I would never have found them on the TS-2000. Granted, the TS-2000 is a 4 stage IF up-conversion rig with a 15kHz front end. The DSP filtering doesn't come in until the 4th stage, so signals have all the previous 3 stages to go through before getting narrowed down. By that time it's too late. Though, the KX1 is such a simple, in comparison, design the performance is a world of difference. Why is that?

What is it with big name companies and the radios that are over a thousand dollars and the fact that they can't be built to be "great" in RX performance (like my TS-2000, at the time I got it I paid $1950 out the door)? Even radios like the FT-2000 and IC-756proIII aren't "that" great. One has to spend a LOT of money to get a quality feel radio like the IC-7800 and FTdx-9000 that also has the receive performance that is possible. With the radios like the K3 and the TT O2 you get great receive performance but a lack of quality feel.

If a KX1 has such a hot RX, why can't regular base station radios that are what people are going to use every day?

Steve, KC8QVO
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KC8QVO
Member

Posts: 62




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« Reply #1 on: November 21, 2009, 06:49:45 PM »

Reply to the next one, this got re-posted by accident.

Steve, KC8QVO
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