[TenTec] OII V2.044A

Sat Feb 26 17:00:17 PST 2011

I had 3 SX-117's and they were good receivers.  I believe the SX-117 is a
triple conversion receiver.  I am sorry that I gave them away along with 2
HT-44's.  The XYL said get rid of the old stuff!

Fred, AB8AH

-----Original Message-----
From: tentec-bounces at contesting.com [mailto:tentec-bounces at contesting.com]
On Behalf Of kc9cdt at aol.com
Sent: Saturday, February 26, 2011 7:50 PM
To: tentec at contesting.com; geraldj at weather.net
Subject: Re: [TenTec] OII V2.044A

Ray,
In this case it was a pretty weak signal.
I cold not quite copy his call on the OII, I tried everything on the 
OII to get it....RF gain, AGC threshhold, attenuator with/without 
different RF gain, bandwidth, passband tuning, NR, etc.

Then, since I had the Halli SX-117 ad SX-115 on anyway..I switched the 
anyenna to the SX-117 just for grins....I had just a slightly bit 
better S/N or less high frequency sound...really don'y know why, then I 
could copy his call. The best way I can describe it was that the band 
noise was a very low sound...then his signal  just rode above it, 
pretty clear as well.

Anyway, I tried several times A/B OII to Halli...and wound up doing the 
QSO the old way, mute the Halli RX when TX, then back to RCV.

It  made me grin a little, thinking Bill Halligan may be watching me 
from above and maybe he had a grin on his face as well.
If there would have been strong adjacent channel QSO nearby...it would 
have not happened.

73,
Lee, KC9CDT

-----Original Message-----
From: Rsoifer <Rsoifer at aol.com>
To: geraldj <geraldj at weather.net>; tentec <tentec at contesting.com>
Sent: Sat, Feb 26, 2011 1:53 pm
Subject: Re: [TenTec] OII V2.044A

Jerry, Lee, and others,

It may be useful to draw a distinction between digging weak signals out 
of
the noise and improving the SNR on stronger signals so they sound 
better.
As we know, most of the intelligence in (male) human speech is below 
about
2400  Hz.  The human ear is very good at disregarding higher 
frequencies, so
  passing the signal through a low-pass filter will make it sound  
better
but, for most good operators, won't make much of a difference in their
ability  to dig it out of the noise.

73 Ray W2RS

In a message dated 2/26/2011 6:16:09 P.M. GMT Standard Time,
geraldj at weather.net writes:

That's  where I find my passive speaker filter shines. It passes no 
audio
section  noise and no IF noise, an few DSP HF artifacts.

A fundamental of  receiver design is that selectivity works best as 
close
to the antenna as  possible. Unfortunately that ignores the noise
contributions of all the  stages after that. The typical product 
detector
is double sideband so the  IF noise of the image is there along with 
the
signal and the RF noise that  passed through the filter plus the same
sideband noise much wider than the  filter that was up front. Receivers
would benefit from having a SSB filter  at the product detector, but I
know of only one design that way, called  the Hohentweil, a 2m
transverter kit. Then they would benefit from making  the audio output
stage, often essentially a power op amp into an active  low pass filter.

In tube receivers a simple capacitor from audio output  tube plate to
ground combined with the tube and the audio output  transformer to make 
a
rudimentary low pass filter. In the 75S-3B, it was  effective enough to
make using 2125/2975 tones for 850 shift RTTY (and for  all recorded
history, the standard tones for 850 shift RTTY due to an  AT&T 
standard)
difficult until the capacitor was removed from the  circuit.

73, Jerry, K0CQ

On 2/26/2011 11:57 AM, kc9cdt at aol.com  wrote:
> I think one of the reasons the Drake R-4B, Hallicrafters SX-117  and
> many others are beter in a noisy condition is simply they do not  have
> all the high frequency respnse in the audio, or maybe it is the  tube
> amp??. I wish there was a HF cutoff on the OII, full EQ like Bob  Heil
> recommended day one to TT way back may have  helped.
>
> Interestng...last nght, on 40 I was working a really  nice guy in St
> Kitt. There was quite a lot of QRN, He was just above  the noise floor
> I found that if I used the old Hallicrafers SX-117 to  receive
> him...copy was more clear!!!!
>
> OMG, Maybe we  need to go back to the older stuff (I have both) Unless
> of course it  is contesting at a high level...where you need lot of 
speed
>
> I  use the Collins S line&  KWM-2
> Drake C line (all Sherwood  mods)
> Halli SX-117/HT-44
> Halli SX-115/HT-32B
>
>  Along with the OII of course.....
> 73,
>  Lee
>
_______________________________________________
TenTec  mailing  list
TenTec at contesting.com
http://lists.contesting.com/mailman/listinfo/tentec

_______________________________________________
TenTec mailing list
TenTec at contesting.com
http://lists.contesting.com/mailman/listinfo/tentec

_______________________________________________
TenTec mailing list
TenTec at contesting.com
http://lists.contesting.com/mailman/listinfo/tentec