A couple years ago I reduced power from 1200w to 50 watts to thin a gigantic
pileup of Europeans on 160. Rate went way up after about five minutes. I
think even without that situation occurring you would have to increase the
times for each power to 10 minutes or more to see the impact. Every other
minute won’t tell you anything in my opinion. Those who have gone to great
effort to gain another dB or so over what they had know, intuitively, that it
makes a significant difference.
Stan, K5GO/ZF9CW
Sent from my iPhone
> On May 20, 2022, at 5:43 PM, Michael Tope <W4EF@dellroy.com> wrote:
> If you use a differencing method that inserts and removes the 1dB transmit
> attenuator in a way that is not known to the operator and that ensures the
> operators spends an equal amount of time at each power level, then the impact
> of the 1dB "psych out" would presumably get spread equally between the two
> power levels. The key is engineering the attenuator control so that the
> system doesn't give off subtle clues that it has changed state (e.g. change
> in VSWR, change in plate or drain current, sound of vacuum relays clicking,
> etc). Of course, as N5OP suggests, getting volunteers who are representative
> (i.e. highly competitive individuals) who are willing to subject themselves
> to being at a small power disadvantage 50% of the time, might be a challenge.
> 😉
>
> 73, Mike W4EF....................
>
> On 5/19/2022 4:24 PM, David Hachadorian wrote:
>> Just knowing that you are wasting 21% of your output power in an unnecessary
>> 1 dB of feed line loss will play with your head and cause you to perform
>> sub-optimally.
>>
>> Dave Hachadorian, K6LL
>> Yuma, AZ
>>
>>
>> On 5/19/2022 3:01 PM, Lux, Jim wrote:
>>> On 5/19/22 11:38 AM, Jim Brown wrote:
>>>> On 5/19/2022 6:23 AM, Lux, Jim wrote:
>>>>> I'm not so sure that it's out of reach. yes, trying to implement it with
>>>>> gear from 1980 would be challenging. But with more modern equipment,
>>>>> where the "radio" is a black box controlled by a "front panel" or
>>>>> "computer" it gets easier.
>>>> The Elecraft K3 with second RX that is the same as the main RX, and which
>>>> can be synced with the main, allows diversity reception, and I've been
>>>> using it since 2008.
>>>> Diversity requires an antenna for each RX, spaced as widely as practical
>>>> from each other. It was invented in the earliest days of radio to counter
>>>> the effect of selective fading, which is the the cancellation of two or
>>>> more arrivals of the wavefront from the same TX that have followed
>>>> different paths, arriving at different times. The time differences cause
>>>> the arrivals to have a variable phase relationship with each other,
>>>> combining algebraically to cancel or add, depending on the resulting phase
>>>> relationships. Diversity works best when the antennas have the greatest
>>>> spacing, so that when cancellation is occurring at one antenna, it is less
>>>> likely to do so, or even to increase, at the other.
>>>>> And the diversity combining - doing it in analog is hard, but in the
>>>>> digital domain it's much easier, and for the most part it can be done at
>>>>> audio (or post down conversion to baseband or low IF).
>>>> As diversity has been practiced since the beginning, combination is done
>>>> in the brain of the operator, with audio from the two receivers in
>>>> opposing ears. That's how it's done in the K3. The result is a sort of
>>>> spatiality to the sound, a bit like the true stereo image produced by a
>>>> spaced pair of microphones dedicated to left and right loudspeakers.
>>>> Combining the outputs of the two receivers to a single (mono) channel is
>>>> problematic, because the phase relationships at audio have a good chance
>>>> of cancelling.
>>> For SSB, yes - a simple summing won't work. But it's widely used in other
>>> systems where there's some processing or where the baseband phase is
>>> reliable - For instance, on AM or FM, the instantaneous audio phase will
>>> match, so you coherently combine - typically modern diversity receive does
>>> some sort of weighting on the basis of SNR - the stronger signal gets a
>>> heavier weight, and when there's fading, it smoothly changes.
>>> I will say that there are *bad* implementations - I had a car radio that
>>> did diversity on FM, but the two paths were noticeably different time delay
>>> (as in milliseconds) so you could hear an apparent "echo" as it switched
>>> from one to the other.
>
> _______________________________________________
>
>
>
> _______________________________________________
> TowerTalk mailing list
> TowerTalk@contesting.com
> http://lists.contesting.com/mailman/listinfo/towertalk
_______________________________________________
_______________________________________________
TowerTalk mailing list
TowerTalk@contesting.com
http://lists.contesting.com/mailman/listinfo/towertalk
|