On Fri, 16 Oct 1998 10:03:40 -0400 "D. C. O'Connor" <k8do@enc-1.com>
writes:
>>something not noticed in the din of HF operating.
>
>Well, it has been noticed by me over the years...
Me too but I did not want to get vy deep into this issue on the AMPS
reflector. Living in the middle of contestings Kilowatt Alley has brought
that fact home too many times.
During a major HF
>contest, usually after the halfway mark when the stations begin to
>thin out
>and you can find a hole that doesn't have a big signal immediately on
>each
>side, and just listen to the noise with the widest filter you can
>use...
>Tape record or remember what it sounds like and write down the s-meter
>reading... Then about ten minutes after the contest do the same test
>on the
>same frequency... If you have not done this before be prepared for a
>revelation...
>The rigs and amps we use are dirty... White noise spreading out on
>each
>side of the main signal (pick your color if you don't like white)...
It will become intolerable on 10M IMO as F2 progresses, the band noise is
low enough to make the rig noise really stand out. The degradation will
usually become less offensive as the frequency decreases just due to
atmospheric noise and splatter....the white noise is something very few
hams recognize.
As I hope we all realize is that as carriers within the RX passsband
increase, they eventually take on the white noise characteristics. I
learned this back around 1981 when at Wang Labs and we were the first
large company to use CATV type technology for data, video, voice, etc in
closed systems. Prior to that I thought infinity was the limit!
>Buckshot up and down the band, often over a 100kc away when I finally
>find
>the perpetrator... Big guns (calls withheld to protect the guilty)
>which
>have hard keying, carefully and deliberately adjusted so that you
>cannot
>get within 800-1000 cycles and hear anyone else... Just a steady roar
>the
>full width of the band, often times S8 or S9 in level... We should be
>doing
>better than this...
The stock TS-940 can barely make -70dB in broadband TX noise ...just
keyed and no audio, etc..., changing to PIN diodes in many circuits can
improve that about 25dB. If you look at QST reviews you note that even
expensive current rigs are not much better and on VHF they are much
worse.
BTW, I just bought another TS-830 today for a VHF IF platform!
>
>This is made worse (imo) by the current generation of receiver
>technology
>which lets 500kc(+) of solid noise and signals through the front end
>band
>pass filters and into the rf amps and mixers and depends upon the if
>filters to lay a mask over this bubbling brew and only leave a tiny
>window
>open... You can brag all you want about our high imd preamps and
>mixers,
>but when you present that much wideband, high level rf to the active
>rf
>devices they are going to mix it... testing imd and spurious in the
>lab
>with just two hi purity input signals does not show what happens in
>the
>real world... A return to tracking of tuned circuits in the front end
>of a
>high-dollar, no-holds-barred, contesting transceiver will give an
>intrepid
>manufacturer a bigger niche of the market
I have been thru various great receivers of the past, including 7360 mod
75A4's, loaded R4C's etc. I dont WANT to go back to hollow state for top
performance in the new millenium. The advances in SS technology say that
superb performance is possible...its just that the Japs cant read English
( build to the lowest common denominator) and the few remaining US
companies are hamstrung by internal ineptitude, etc.
... Ten-Tec / Collins /
>Drake, are
>you guys awake?.... Serious contestors will drop $5K on a rig if it
>gives
>them an edge...
I almost suspect that a PC based rig will be the future of performance
rigs. The Kachina is far from performance but it is a start.
Digital processing will progress up in frequency and IMO that is the real
future.
73 Carl KM1H
>
>Denny
>
>
>
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