Hi Paul, I also noticed that the Tecsun radios disappeared from the XHDATA website a couple of weeks ago. I was quite disappointed by that, as I use them often to order my radios. Best price by far! But, the good news is the Tecsun radios appear to be back, since yesterday, 16 March.

I've seen mention elsewhere of a design change in the Siduadon-brand version of the D-808 which has a USB-C charging port.

On Mon, Mar 20, 2023 at 06:02 AM, Michael Schuster wrote:

I've seen mention elsewhere of a design change in the Siduadon-brand version of the D-808 which has a USB-C charging port.

Michael, Paul and All,

There has been a major redesign in new D-808 models, which I first noticed while doing a loopstick transplant on a new Sihuadon D-808 model two weeks ago.

In addition to the USB cable plug change, the RF boards in the old and new D-808 models are entirely different (see photos). The biggest change is a major drop off in the audio amplifier power in the new models, which negatively affects reception of very weak AM-DX stations. Maxing out the volume control in the new models results in significantly lower volume than in the the original D-808 models. In addition, you must short-press the Power switch to turn the new models on or off, unlike in the original D-808 models. If you press the Power switch on the new models and hold it down, the radio will beep, but nothing happens. I have personally verified that the Si4735 DSP chip is still used in the new D-808 models, so RF reception is still unchanged-- only the audio amp is weaker. There are probably other changes in the new models, which will be discovered after further investigation.

What isn't clear at this point is whether this new D-808 version will only be for Sihuadon D-808 models, or for all D-808 models from now on. My strong impression is that all D-808's will made this way from now on, since the circuit boards in the new version are stamped "D-808," and don't mention "Sihuadon," or "XHDATA." I have ordered a new XHDATA D-808 to find this out, and should receive it within a week. As for the weaker audio amp in new D-808 models, XHDATA certainly won't mention anything about this, so bear this in mind if you are an AM-DXer who typically searches for very weak DX stations.

73 and Good DX,
Gary DeBock (in Puyallup, WA, USA)

Qué bueno que lo mencionas Gary. pensaba comprar uno de esos pero en esas nuevas condiciones ya no lo haré. Generalmente cuando cambian algo en el diseño de un aparato es para empeorarlo no para mejorarlo 

On Mon, Mar 20, 2023 at 03:07 PM, <chevargasluis@...> wrote:

Qué bueno que lo mencionas Gary. pensaba comprar uno de esos pero en esas nuevas condiciones ya no lo haré. Generalmente cuando cambian algo en el diseño de un aparato es para empeorarlo no para mejorarlo 

Gracias Chevargasluis,

You are correct. Many of the Chinese companies make equipment changes to increase profits, but they never tell customers about the negative changes that they make.

73, Gary DeBock (in Puyallup, WA, USA)

Op 20/03/2023 om 23:20 schreef Gary DeBock via groups.io:

Many of the Chinese companies ...

We haven't heard that of the far west?

Many of the Chinese companies make equipment changes to increase

profits, but they never tell customers about the negative changes that they make.


Marc
--
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On Mon, Mar 20, 2023 at 04:47 PM, Gary DeBock wrote:

In addition to the USB cable plug change, the RF boards in the old and new D-808 models are entirely different (see photos). The biggest change is a major drop off in the audio amplifier power in the new models, which negatively affects reception of very weak AM-DX stations. Maxing out the volume control in the new models results in significantly lower volume than in the the original D-808 models.

Thanks Gary!


This group will recall that the original hardware of this family of "808" radios (XHDATA/Sihuadon/Deshibo/Digitech) all suffer from a high background audio noise floor, most apparent at low volume.
It is also impedance-dependent, so the problem will be more or less apparent depending on what headphones you attach.

The underlying cause is the omission of an audio preamp (necessary to match the relatively low DSP output).
To compensate they were running the audio amp at an extremely high gain setting where its SNR is poor - hence the background noise.
Unfortunately it would appear that, in a counterproductive attempt to fix that cheaply, they simply turned down the gain!

--mike

On Tue, Mar 21, 2023 at 05:13 AM, Michael Schuster wrote:

The underlying cause is the omission of an audio preamp (necessary to match the relatively low DSP output).
To compensate they were running the audio amp at an extremely high gain setting where its SNR is poor - hence the background noise.
Unfortunately it would appear that, in a counterproductive attempt to fix that cheaply, they simply turned down the gain!

--mike

Thanks Mike,

I think you are exactly right about this. A "new model" D-808 seems to retain the background noise while reducing the overall gain of the audio amplifier, thereby making the model much less effective in chasing very weak AM-DX stations. Especially for weak-signal DXers, that sort of change is a major drawback.

It's also worth remembering that most of XHDATA's consumer market in China probably doesn't care much about weak signal DXing, so it's unrealistic to always expect them to prioritize our wishes. A bright spot for DXers is the new XHDATA D-109 model, which seems to have improvements in the SNR as well as the full range of DSP filtering options, a powerful speaker and a decent audio amp.

73, Gary DeBock (in Puyallup, WA, USA)