[Elecraft] Neat K3 Video!

[Ian White GM3SEK]

Joe Subich, W4TV, wrote:
> However, all three changes could have been incorporated in the K3 for 
>pennies in parts instead of requiring user modifications or "add on" 
>boxes with just a little "market research" beyond the tight-knit group 
>of insiders who do not push the operating envelope.

While I agree with Joe's technical analysis, the problem wasn't really 
about a group of field testers who "do not push the operating envelope". 
On the contrary, many of them do, in various areas. The problem was 
simply that, on the issue of compatibility with existing technical 
standards in the market, nobody picked up the ball.

This is another symptom of the paradigm shift that the company is having 
to go through, from its origins serving the QRP community to becoming a 
supplier in a much wider market. Many of these new customers will be 
integrating the K3 into existing stations, and will not be pleased by 
the incompatibilities of the ACC interface.

1. Reverse polarity on the ALC input. The industry standard is a 
negative-going voltage because that made perfect sense in the era of 
tube rigs when it was first introduced. Most solid-state transceivers 
convert the ALC input to a positive-going signal for internal use, but 
they don't attempt to buck the negative-going interface standard.

In the K3, the ALC input appears to connect through to the input of an 
ADC, whose data sheet specifies an absolute maximum of 0.3V in the 
negative direction. If someone connects a normal negative-going ALC 
signal to this input, there is a risk of internal damage.

2. Reverse logic for the TX inhibit input. The standard here was set by 
Yaesu (TTL or open-collector input to the transceiver, logic 1 to 
inhibit TX, logic 0 to enable). Originally this facility was provided as 
an the interface to Yaesu's own-brand amplifiers; but third-party 
providers have adopted it too, which is how such standards come to 
exist.

In the K3, this incompatibility could be easily fixed by a config 
option.

3. Reverse logic in the band data output. Again, this 4-bit encoding was 
originated by Yaesu, and has since been adopted and extended by a range 
of third-party providers. The standard band data output is TTL, logic 1 
= 5V, logic 0 = 0V.

The K3 uses industry-standard band encoding, but the output interface is 
not standard. Use of open-drain pulldowns in the K3 means that existing 
non-Elecraft band data  interfaces will not work without some 
modifications and a user-provided positive supply rail.


Whether or not any of those interface facilities is "really needed" is a 
side issue. Those interfaces exist in the K3, so the relevant discussion 
is about compatibility with users' existing stations.


At the technical level, these are all fairly trivial problems. My 
holiday project was already going to be a breakout box for the 15-way 
cable from the ACC connector, where the interfaces with several 
different parts of the station can be patched in. The inverters and 
level shifters that will be needed to give the K3 an industry-standard 
interface to the outside world can go in there. It's just a little more 
work than anyone would really have wanted.





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73 from Ian GM3SEK