[Elecraft] K3 Digital Voice Mode - our future?

brian alsopb at nc.rr.com
Fri Sep 18 04:18:21 EDT 2015


Comparisons with single signal stations seems irrelevant.

Is anybody addressing the issue of QRM from other stations?   I suspect 
digital will fold -- especially when one is trying to detect one out of 
many or a station immersed in splatter from one or more stations.

The ability of the mind to pull out an individual station in the analog 
QRMed world would seem to be lost.  This is best illustrated by people 
being able to decode one voice of many at a party.

Here the switch to digital TV has been frustrating.  Stations which had 
previously been received acceptably are spotty.   The digital cliff 
effects are a killer.   The one station we really like to watch (PBS 55 
miles away, two edge diffraction reception) is greatly effected by 
day/night, the seasons and weather conditions. Admittedly some of 
degradation is due to the move from VHF to UHF. However I suspect that 
an analog transmission on the same frequencies would still be 
watchable.   Part of the problem at UHF is enhancement of multipath 
effects.  (Also DTV apparently is transmitting with 6db less power which 
is supposed to be made up by the digital decoding at the reception end. 
)  One sees this with a highly directional high gain antenna.   A 
station will drop out and if you bump the antenna a few degrees, it will 
return and then drop out.  It is a dance between the rotor to try to 
keep a station locked.    If these multipath effects are so significant 
for digital, single signal one might expect the problem to exist in 
spades on HF.  Anybody who has looked at WWV carrier transmissions on a 
high resolution FFT display can see several distinct signals due to 
multipath shifted by up to 2 Hz at times.   The strongest of the bunch 
moves from FFT bin to bin.  As a side note, those HDTV stations who 
stayed on low VHF channels have had no end of problems.

Apples and oranges perhaps.....

73 de Brian/K3KO
On 9/18/2015 2:16 AM, Gary wrote:
> Don,
>
> Absolutely spot on sir.
>
> Gary
>
> -----Original Message-----
> From: "Don Wilhelm" <w3fpr at embarqmail.com>
> Sent: ‎18/‎09/‎2015 11:30 AM
> To: "elecraft at mailman.qth.net" <elecraft at mailman.qth.net>
> Subject: Re: [Elecraft] K3 Digital Voice Mode - our future?
>
> You have listed 3 digital voice modes that do not talk to each other.
> Furthermore, I recall that these are proprietary coding schemes.
> That is not "Ham Radio" in my mind.  Ham Radio is "everyone can talk to
> everyone else", and those digital voice systems where you can only talk
> to those hams who have purchased the same brand of equipment as you have
> selected is more like commercial circuits where you want to shut out
> those who do not 'speak the same language that you do'.
>
> I don't think proprietary protocols belong on the ham bands - just my
> not so humble opinion.  Yes, I am also opposed to proprietary data modes.
>
> 73,
> Don W3FPR
>
> On 9/17/2015 9:03 PM, Robert Nobis wrote:
>> Take a look at the digital voice modes that are being used on the VHF and UHF bands: DMR, D-STAR and Fusion.
>>
>>
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