[Elecraft] Advice needed: Remote Station Enhancement

[Don Wilhelm]

Joe,

You do admit that many amateur products do not conform to typical 
communications standards in the digital world. My experience does go 
back to my design and evaluation of IBM terminal communication between a 
DCE and a DTE device.  Although this was not necessarily RS-232 levels, 
the same thing is true.  The drivers provide the low and high levels to 
the line (an open circuit or a ground) while the receiver at the far end 
of the line provides the logic high level.  All other receivers will not 
provide voltage, but can listen in on the communication.  This is not 
consistent with amateur products with one providing pullup resistors ath 
the driver location and some receive locations requiring the opposite 
I.E, those providing pullup resistors to +12 volts.
THe point is that the two do not work together.  It is not a systems 
approach.

73,
Don W3FPR.


On 2/27/2018 10:09 PM, Joe Subich, W4TV wrote:
>
> You're dealing with a "standard" that was originally developed for use
> only within one company's products - much like Elecraft's Aux Bus.
>
> As such, any "industry standard" is moot.  The design is for active
> high/voltage source (to +12V originally) and was not intended for any
> purpose than providing band switching for the FL-700 then the Quadra.
> It would seem to me that any product that claims to inter-operate with
> the Yaesu "Band Data" would emulate or at least be compatible with
> that behavior - including the ability to *source* sufficient current
> at +12V.
>
> These devices are not operating in the "communications (non-ham) world",
> they are strictly amateur products.
>
> 73,
>
>    ... Joe, W4TV
>
>
> On 2/27/2018 9:28 PM, Don Wilhelm wrote:
>> The problem is that most devices (in the ham world) expect the driver 
>> device to provide voltage.
>> In the communications (non-ham) world, the expectation is that the 
>> driver device produces either a logic low (short to common) or a 
>> logic high ( open circuit).
>>
>> Look at the data sheets for "line drivers" and "line receivers" to 
>> check out what I am saying.
>>
>> Open collector or open emitter does not make a difference in 
>> function, it is only a circuit design decision.  Yes, open Collector 
>> (or open drain) is commonly use in logic where the active state is 
>> zero volts (transistor or FET conducting to ground).
>> The open emitter design is the opposite.  A conducting device will 
>> provide a voltage on the line (or signal) being driven.
>>
>> The point is that in a properly designed communications system, the 
>> drivers provide either conduction to ground or an essentially open 
>> circuit to the communications line (think of a relay being either 
>> open or closed).  The receiver provides the voltage to detect whether 
>> the driver is in an open circuit or closed circuit state.
>> If there are multiple receivers in the system, only one can be 
>> "boss", and that one determines the open circuit voltage and contains 
>> the pullup resistors for the system.  Other receivers work in listen 
>> mode and will contain no pullup resistors or active drivers.
>>
>> This whole situation goes back to the "one driver, one receiver" 
>> condition.
>> Only one driver can exist on a communications system without conflict.
>> Multiple receivers are possible, but only one (at the far end of the 
>> line) should provide the pullup resistors.  All other receivers must 
>> be only in the listen mode.
>>
>> 73,
>> Don W3FPR
>>
>> On 2/27/2018 8:06 PM, Joe Subich, W4TV wrote:
>>>
>>>  > But many (most) ham devices do not do it that way, they expect the
>>>  > pullup resistors will be provided by the driver gear.
>>>
>>> Actually, most devices that use BCD "band data" expect an open
>>> emitter driver not an open collector driver.  Open emitter will
>>> *source* voltage for logic high and be open circuit for logic
>>> low.  This is the convention from the early Yaesu rigs which
>>> were the first devices to support "band data" (it is the way
>>> the FL-7000 and Quadra amplifiers operate).
>>>
>>> You will find the W9XT BCD10/BCD14 decoders with their opto-isolator
>>> inputs work just fine with the "open emitter" drivers.  Other devices
>>> designed with Yaesu transceivers in mind have appropriate current
>>> limiting (series) on the input lines and "pull down" (parallel)
>>> resistors on the logic gates.  Some "standard" devices (Top Ten
>>> BD-Y and the original microHAM Band Decoder) will provide both
>>> current limiting resistors and internal pull-ups but I have not
>>> seen any amateur product with series diodes in the band data lines.
>>>
>>> 73,
>>>
>>>     ... Joe, W4TV
>>>
>>>
>>> On 2/27/2018 4:17 PM, Don Wilhelm wrote:
>>>> Knut,
>>>>
>>>> That is the way it *should* be, and was that way in the K3 originally.
>>>> But many (most) ham devices do not do it that way, they expect the 
>>>> pullup resistors will be provided by the driver gear.
>>>> So, because of that, Elecraft added pullup resistors to the band 
>>>> data outputs of the K3 long ago.
>>>> So yes, we are left with a situation that often requires steering 
>>>> diodes.
>>>>
>>>>
>>>> 73,
>>>> Don W3FPR
>>>>
>>>> On 2/27/2018 3:48 PM, ab2tc wrote:
>>>>> Hi Don and all,
>>>>>
>>>>> Hear,hear, Don. The receivers should have the pullup resistor to 
>>>>> whatever
>>>>> the appropriate voltage needed (within reason) *and* a steering 
>>>>> diode in
>>>>> series with the input. This will prevent another device with a higher
>>>>> voltage from feeding current back into the device which could damage
>>>>> semiconductors. Without the steering diode all receivers must use 
>>>>> the same
>>>>> pullup voltage. Of course a single receiver is not a problem either.
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>>
>